Surely it isn’t true that “Every time you double CO2, you get another 4 Watts per square meter of radiative forcing,” Eventually, the CO2 IR bands are full and adding more CO2 has no effect. The question is, when is “eventually”?
[Response: The CO2 bands may fill up at low levels, but the trick is that there's always a part of the atmosphere tenuous enough that the CO2 bands are unsaturated, and the radiation comes from up there (where it's cold). A complication in thinking about the effect of CO2 on outgoing infrared is that adding CO2 actually tends to make the stratosphere colder, which gives you an additional reduction in OLR (for fixed surface temperature). Long before you get to the point where the stratosphere is optically thick, though, you enter the regime where the weak CO2 bands start to become important, and the radiative forcing per doubling increases -- that's at around 20% CO2 in the atmosphere, which is relevant to the Early Earth, but not to the near (or even far) future. By the way, it takes a whole darn lot of CO2 to saturate all the CO2 bands. Even Venus isn't really saturated. On Earth and other wet planets, the thing that saturates the absorption is the water vapor, which starts to be completely opaque for infrared for saturation vapor pressures corresponding to temperatures around 300K. --raypierre]
Nice post. I too had noticed that he falsely states that as CO2 levels rise, the climate effect reaches a “plateau.” I also noticed that the headline and first several paragraphs give the impression that new results will overturn modern climate theory, but the latter part of the article is much more moderate.
You guys at RC have been busy lately! Thank goodness, because the contrarian forces have been busy too.
I wonder just how much the emergence of the first terrestrial rain forests in the Late Devonian and Carboniferous had a bearing on the glaciations that occured around that time, and that set in with earnest in the late Mississippian (Carboniferous). I am also tempted to think that the switching from primary aragonite and primary calcite marine cements during the Carboniferous may also have a relationship to ocean pH and therefore CO2.
Anyone have any views?
[Response:An excellent point about the rain forests. The albedo feedback and evapotranspiration could be playing a role, but my feeling is that the biggest effect of vegetation in warm rainy areas would be via silicate weathering. Standard wisdom has it that vascular land plants greatly increase silicate weathering, which would draw down CO2, all other things being equal. The effect of varying vegetation on weathering is not yet in the model in our G-cubed paper. Yannick Donnadieu and I are busily trying to learn enough about vegetation modelling that we can put this effect in the geochemical model. --raypierre]
I just had a chance to check last month’s Scientific American out of the library, found a pretty mind-boggling article on the mechanism that now seems likely to have caused most of the big mass extinctions of the past. It starts with unusual volcanic activity raising the atmospheric CO2 level to about 1000 ppm… leading to a sudden change in ocean chemistry, vast anaerobic bacteria blooms that pour H2S into the air, catastrophic ozone depletion (and it’s a miracle anything survives.)
I’m wondering if the total amount of carbon available on the earth’s surface, in forms that could rapidly get into the atmosphere, might have formerly been less (?) Less carbon tied up in methane clathrates in precarious locations, maybe? Then concentrations of CO2 could have remained high for long periods, making for more uniform temperatures, without (often) passing that 1000 ppm overload mark. (?)
And of course I also wonder how this affects recent discussions here of “how much climate change can we afford?” Temperature increases are one constraint, eventual sea level rises another–but how much CO2 ends up in the ocean might put the problem in a whole different worm-can.
The relationship between weathering and vegetation is a tricky one. It is well documented in modern day Sumatra.
In terms of sediment flux- it’s actually semi-arid climates that supply the large sediment fluxes. This is because dense rain forest vegetation binds sediment/regolith and protects it from erosion. Peat is particularly difficult to erode. Also many of the rainforests in the Carboniferous were ombrogenous bogs, with the trees rooted into the underlying peat- not bed rock or sediment.
What is clear is that those Carboniferous rain forests rooted in sandy soils- end up leaching the soil almost to pure qaurtz- giving rise to silcrete palaeosols- known here in Britain as ganisters.
What do you think about the primary aragonite/calcite marine cement flips?.
Very interesting, Ray. Have you gotten in touch with Broad? He is a very professional journalist (a co-recipient of the Pulitzer) and I’m sure would be grateful for constructive criticism. I always hope that when I err in something I write — as we all do — someone would work with me to improve.
[Response: Good point. I like to think that journalists covering climate change are routinely reading RealClimate already, but with time pressure and deadlines and all, that's not a completely safe assumption. I've sent Broad an email pointing out our commentary, in case he hadn't noticed. --raypierre]
“The worst fault of the article, though, is that it leaves the reader with the impression that there is something in the deep time Phanerozoic climate record that fundamentally challenges the physics linking planetary temperature to CO2. This is utterly false, and deeply misleading.”
What would also be misleading would be giving policy makers and the public an impression that we now understand all of the complex, non-linear interactions between all the forcings and feedbacks significantly well to forecast future climate with skill across multi-decadal time. Just because Stefan-Boltzmann and Wein are beyond dispute, the best geological evidence available (most of the last 25% of earths history) tells us that CO2 is not the only game in town. It is the very tricky interaction of CO2 with a number of the other forcings that is really the question. To give one example, the role of aerosols and their associated feedbacks is still incompletely understood, but we know to some extent there is a cooling effect. There might be high aerosols and high CO2 (both can be natural and or man-made), and maybe a cooler than expected climate. What about the feedbacks associated with both? How do they all interact?
[Response: You're not getting the point. All the uncertainties you point are real - but ask yourself whether they can possibly be resolved using data from the early Phanerozoic with (at best) million year sampling? Obviously not - there are many, many more uncertainties in using deep time records than there are in using the relatively well sampled glacial period, or the present. Thus it will always be the case that while deep time may provide tests for our understanding (the PETM, Eocene, snowball earth etc.), it will rarely (if ever) be able to reduce uncertaintites in present climate - and certainly not for changes at the decadal or century scale level. Others might be able to add to this, but I can only think of one thing that deep time has told us that is of directly relevance to reducing uncertainties today, and that is the 100,000 year timescale for the removal of the excess carbon at the PETM. All the other information is more of a 'wow, that's an interesting thing to have happened' kind. Anyone got anything else? - gavin]
[Response: I myself wouldn't go quite so far as Gavin. I'd agree with him that deep time isn't likely to be useful for direct estimates of climate sensitivity in the sense that one teases such estimates out of the Pleistocene. However, the Eocene is the closest thing we have to an example of what a warm world with near-current continental configurations and (probably) high CO2 is like, so the quest to understand it is likely to tell us something about the risks going into a high CO2 world in the future. Its role is to shake loose ideas. For example, if it turns out that polar stratosphericc clouds or enhanced hurricanes are the key to the warm Eocene poles, that gives some additional confidence to our projections about how such things might behave in the future. The way I would put it is that it is unreasonable to demand that we solve all of the grand challenges of climate science (faint young sun, origin of oxygen, snowball Earth, Cretaceous warmth, PETM, warm wet early Mars ...) before the models are deemed an adequate basis for justifying action on CO2 abatement. That would take centuries to sort out, and given the lifetime of CO2 in the atmosphere and the rate of growth of emissions, we don't have the luxury of waiting that long. The examples we have -- the current climate, the past century, the Holocene, the Pleistocene -- provide more than enough checks and confidence in the prediction that the future warming is real and substantial. --raypierre]
Comment #2 above states
“I also noticed that the headline and first several paragraphs give the impression that new results will overturn modern climate theory, but the latter part of the article is much more moderate.”
This raises one of the biggest challenges for writers of all types, but especially science journalists: how to hook the reader in at the beginning, even if your story’s only about an incremental achievement….isn’t it a good thing that climate change gets so much space in the NYT in the first place?! Compare it to the spin on climate in WSJ editorials…
I’m wondering if the total amount of carbon available on the earth’s surface, in forms that could rapidly get into the atmosphere, might have formerly been less (?)
Less than what?
From what I know, deserts and glaciated areas were much smaller in the Paleocene than today, subtropical forests extended as far north as Greenland, and the polar regions were cool and temperate.
To me this implies significant;y *more* carbon in the biosphere.
However, other than tectonic activity, there was nothing bringing the carbon trapped in fossil fuels up to the surface. As to methane clathrates – I guess their modern distribution is not well-characterized, and less is known about their distribution in the Paleocene.
Great post! When I read that NY Times piece the other day, I also felt like the connection to modern issues was being oversold. It brings me back to a couple of years ago when I was hanging out on a message board on the Michael Crichton website and a geologist there was harping on this idea that we don’t understand the climates of hundreds of millions of years ago. I am glad to see that the basic arguments I came up with at the times are the ones you give here (data is not very good, lots of other confounding factors like different continent locations, …).
Another thing I also liked to point out, which you have mentioned but could probably use re-emphasis, is the vast difference in timescales. We are trying to make predictions on timescales on the order of 10^2 years. Do we really need to understand things on timescales of 10^8 or 10^9 years in order to do this? Sure, it would be nice to understand everything. But, it seems sort of ridiculous to say that we can’t make predictions on a timescale of 10^2 years without being able to understand and explain what goes on at timescales 6 orders of magnitude longer than this. It seems impressive enough to me that we now have quite good data and some reasonable understanding (albeit with some gaps) of what goes on at timescales up to 10^6 years.
[Response:Your point about timescales is right on. Yes.--eric]
[Response: The greatest overselling of the link between modern climate change and some vague (and statistically not significant) correlation on the 100-million-year time scale must be this infamous press release by cosmic ray proponent Nir Shaviv. -stefan]
If vegetation reduces sediment flux, then why does the Fly river, which drains mostly PNG rainforest, have such a huge sediment flux? Isn’t total rainfall and terrain relief the dominant factor there (and in other high sediment drainages like the Amazon, Ganges, etc.)?
As for carboniferous forest type, isn’t that a factor of preservation? Obviously subsiding bogs with sedimentary accumulation will preserve their forest much better than eroding hillsides.
[Response: In these discussions of vegetation and sediment flux, please keep in mind that I was talking about chemical weathering (silicate to carbonate, primarily), not physical weathering. Vascular land plants affect chemical weathering by pumping CO2 into the soil, and also by changing the acidity of the soil through humic acids. They probably do a lot of other things to the chemical and microbial environment as well. All of this is different from the sort of thing that determines how much sediment is washed into a river. --raypierre]
> I can only think of one thing that deep time has told us that is of directly relevance to reducing uncertainties today, and that is the 100,000 year timescale for the removal of the excess carbon at the PETM. …Anyone got anything else? – gavin
It seems to show that complex life can survive several thousand ppm CO2. That should counter claims that 600ppm is likely to make humans extinct.
[Response: I was thinking of uncertainties a little more at the forefront of serious research.... - gavin]
[What the record may show is that life can evolve to adapt to pretty large changes, given enough time (hundreds of thousands of years or more). No serious person is predicting "extinction of humans". The question is not whether humanity will "survive", but what we will go through to survive. --eric]
>Response: I was thinking of uncertainties a little more at the forefront of serious research…. – gavin
RealClimate does a good job of presenting clear scientific arguments of why GW is real, but I think countering some of the hysteria of exagerated claims of doom is also important. Judging by some of the comments at RC, it is clearly needed.
[Response: We do spend a fair amount of time countering exaggerated claims of doom. Many of us have tried to set the record staight on the THC/Ice-age catastrophe idea, and I myself have spend much time pointing out why the Earth is not going to succumb to a Venus type runaway greenhouse. Some of you, however, seem to think that any prediction of severe impact is so unpleasant (or has such unpleasant policy implications) that it must, de facto, be an "exaggerated claim of doom." There's not much constructive I can do with that. Very few, if any, scientists are predicting the extinction of human life at 6oo ppm, though once you start messing so much with the whole biosphere, you do have to leave the door open for unanticipated consequences that can be far worse than we think. The predictions of severe impoverishment of the ecosystem and big impacts on the world socioeconomic structure are very legitimate, and in fact are quite legitimate claims of doom. A certain amount of hysteria is justified, indeed encouraged. --raypierre]
I read the article when it came out in the NYT. I was wondering what was big deal. I was going to write a comment on RC and ask about it. You must have read my mind!
From what I learned about climate science and I know about the press, I guessed that it was a minor issue in the scientific community, but the article made it seem like a big drama to get the readers attention. RealClimate confirmed what I thought.
Grant (#2) is right, you guys at RC have been busy lately and its good to see.
[Response: Thanks. It's nice to be appreciated. I've been a bit quiet recently on RC because there's been a huge upsurge of public interest in climate change, and I've been using more of my time on live appearances. --raypierre]
Comment by Joseph O'Sullivan — 9 Nov 2006 @ 10:42 PM
Re-greetings Raypierre, may this be a bad interpretation: CO2 being well mixed throughout the atmosphere can’t have all its molecules saturated at the same time.?? Another question; if there are more molecules of CO2 in the air would this mean more or less OLR in the long run? I am thinking clouds which trap radiation, and tying it with CO2, the problem with clouds is there should be less OLR above them, but with more CO2 the atmosphere should be warmer… Glad I can ask these questions..
[Response: I'm sorry, but I am having trouble understanding your question. Note that when we speak of saturation, we are referring to saturation of the ability to absorb infrared at some wavelength -- once you absorb everything, adding more CO2 doesn't cause any more absorption, since you can't absorb more than everything. Because of a thing called Kirchoff's Law, in this circumstance adding more CO2 also doesn't change emission from the layer, unless you change the temerature. Also, note that when we say CO2 is well mixed, we don't mean that the number density of CO2 is independent of height, but that the mixing ratio (ratio of CO2 molecules to the rest of the air molecules) is constant. For fixed mixing ratio, there are fewer CO2 molecules per unit volume in the tenuous stratosphere than near the surface. To get an idea of how all this interacts with the temperature profile, take a look at Chapter 3 of my Climate Book. --raypierre]
Boy… when I read that article, I immediately wondered what RC would be saying about it.
So… do the people that know what they are talking about now get in touch with this NYT author & let him know?
I have a friend who works for the NYT, in their Technology section… If you need an “in” to voice your dissatisfaction with the article, perhaps I could get the message there. Or maybe just writing the editor would work?
I enjoy this site and learn something new whenever I read all the comments and posts.Everyone who has posted to this site needs to know two things. First, 800 ppm co2 is very possible within the next three hundred years. Second, no one can rule out runaway global warming which will raise the temperature to at least a few hundred degrees F.The unintended consequences of business as usual as we release more and more co2 is completely unpredicatable with current climate models.As the peat moss thaws and polar ice caps melt it is anyone’s guess as to the negative fallout to the climate.A runaway greenhouse effect simply cannot be ruled out given current climate models.End of story.Same with the shutdown of North Altantic current. Anyone who feels confident at estimating the total downside of this event is also sadly mistaken.The fever of a runaway greenhouse effect as relates to the Gaia hypothesis is similar to the human body eliminating a virus or bacterial infection.In this case humanity is the offending virus to Gaia.This has probably taken place on millions of planets in each galaxy. There are approximately 120 billion galaxies, via the Hubble Deep field anaylsis, each with approximately 100 to 300 billion stars.Wherever intelligent life has failed to protect the ecosystem the planet selects against it. Some astronomers, e.g the Drake Equation,think that 95% of planets with intelligent life do not pass this hurdle. Do not think that Earth is exempt from this very common fate for class m planets throughout the Universe which have TEMPORARILY spawned “intelligent” life.
Mark J. Fiore
[Response: Actually, I think a Venus-type runaway greenhouse is one of the few catastrophes one can definitively rule out. See the post that Rasmus and I had on Venus Express some months back. --raypierre]
First, if one sets aside the modern spin issue for the moment, then I think it does do a generally good job of describing what is a significant scientific dispute regarding the Phanerozoic. It is represented by two groups of established scientists publishing in reputable journals. At first glance, it is not unreasonable to think that one could leverage the much larger changes in CO2 and climate that have occured over very long time scales in order to generate an estimate of climate sensitivity. However, the records, to the extent we understand them, suggest that there is not a simple relationship between CO2 and climate. This makes it difficult to know what conclusion, if any, we should draw about climate sensitivity, and that is certainly a legitimate subject for scientific inquiry. Many will say that the Phanerozoic is so long and complicated that we shouldn’t be drawing any conclusion. Some say that the lack of close agreement suggests that the significance of carbon dioxide is less than one might expect. That’s the dispute, and the discussion of that is mostly pretty good.
Some have argued this dispute bears on the modern course of events, which is what makes it sexy and a topic of interest to the public. Though you disagree, as I suspect many climate scientists would, there are a number of published papers arguing that the Phanerozoic data does in fact pose a fundemental challenge to our understanding of the CO2-climate relationship (e.g. Shaviv 2005). However, I suspect that few, if any, scientists have looked at the Phanerozoic evidence and substantially changed their views regarding global warming. I agree with you that it just isn’t firm enough for that.
Returning to the modern issue, I would say that the article does have some spin to it, intentional or not. It suggests that this dispute has or is having an important impact on the scientific community, which isn’t really the case, at least not yet. (Though to be fair it would be hard to discuss the issue at all without suggesting it was important.) My own discussions with Broad did try to draw attention to the views represented by “the evidence of a tie between carbon dioxide and planetary warming over the last few centuries is so compelling that any long-term evidence to the contrary must somehow be tainted”, but obviously it does not play a major role in the resulting text. I also would have preferred that “over geologic time scales” had not been dropped from the front of my quote saying that many factors contribute to climate change.
Ultimately though, I can’t see this as a travesty of science reporting that you apparently do. Its informative and exposes the public to some of the mysteries of deep time and I am glad for that. Does it oversell some things? Yes, but not in a way that I would consider exceptional amongst science reporting. The truth is that as we look back in time there really are many types of climate changes that we simply don’t understand and that does deserve to give us pause, and remember that the sum of all the things we claim to understand is really only a small part of the great variety the Earth has offered us to study. Recognizing that should not be paralyzing though. We have an obligation to move forward based on the undertanding we do have, and take steps to address the likely global warming.
[Response: The article would have been no less interesting if it had simply concentrated on the deep and important mysteries of Phanerozoic climate, without misleading people by drawing out of it all sorts of false lessons regarding future climate. I stick to my assertion that putting the largely discredited arguments of Shaviv and Veizer on the same plane as contributions by scientists like Berner was flat out false balance. The article is not by any means the worst science reporting I've seen, and it has some redeeming features. On the whole, though it gives the reader the wrong take-home message, and that's damaging. --raypierre]
“Standard of excellence in reporting” from the NYT? Really, you must be kidding me.
[Response: I think Ray was referring specifically to their coverage of climate research, which I would agree has generally been very good. Indeed, Andrew Revkin's seems to get things pretty much dead-on most of the time. On other subjects ... I would personally agree that NYT is not particularly a pinnicle of excellence in my book. Having said that, I'm not sure what big newspaper is... --eric ]
[Response:Indeed, it was the science writing I had in mind. I could easily point to spectacular failures of the NYT in the domains of political and national security reporting, but that would risk a flame war that doesn't belong on RealClimate, if anywhere. The NYT has had its share of troubles with unscrupulous reporters in the past, but seems to be making an honest effort to root out such problems. I'm not aware of their ever having had such problems among their science reporting staff, though. --raypierre]
I am a science writer who finds this discussion of phanerozoic climate and its uncertainties, combined with the dissection of Bill Broad’s piece, quite fascinating. I am posting today a link today to the whole thing for other science writers to see at a website established by the Knight Science Journalism Fellowship at MIT. I’d already posted an item on Broad’s article earlier this week, too, but without much commentary on how he tackled the topic.
And thanks for maintaining an informed, civil, and authoritative discussion forum at RealClimate.
The site with the post on your back-and-forth on the Broad story is ksjtracker.mit.edu. If it’s not near the top, just scroll down or use the search function.
An informative review with one caveat re-the geological time scale.
Throughout much of the Phanerozoic Era one cannot sample accurately timescales of less than one million years. Over these extended time periods it is important to know or predict absolute atmospheric pressure. The major gases, oxygen and nitrogen are likely to have varied ca. -/+2 fold from their present compositions. Surface temperatures are exponentially related to absolute pressure. A trip down to the shore of the Dead Sea, 1000ft below sea level,illustrates the enhanced mean temperature increase(1.5Celsius degrees?adiabatic guesstimate). During the earliest Phanerozoic O2 tensions were probably much lower ca. 1% Present Atmospheric level, presumed upon that level of free O2 required by the hydroxyprolinase enzyme to synthesise the essential amino acid hydroxyproline for synthesis of bone connective tissue and collagen; a the main structural protein of bone.
Finally, mean continental elevations of ca. 800m present day will have varied throughout geologicl history. Much lower mean elevations of continents would also enhance mean surface temperatures.
[Response: Let me say upfront that I realize that science writing is hard. I wouldn't call Broad's piece a "travesty," of science reporting; the previous poster who used this word misread my intent. The NYT article is not an instance of the kind of deliberate distortion and disinformation that is common on the Wall Street Journal editorial page, and even (though thankfully somewhat less commonly in recent times) on their news pages. I think it a case of the requirements of accurate reporting getting steamrollered by stylistic considerations -- the desire to make a subject seem important and topical. I think there were ways to make the subject matter seem important and interesting to the reader which would not have risked leaving the reader with the kind of mistaken impression Broad's article engenders. --raypierre]
Comment by Graham Dungworth — 10 Nov 2006 @ 10:36 AM
I’m assuming the up-coming IPCC will come up with better historical CO2 figures for the distant past than is currently believed.
I’m assuming the 3,000 ppm and higher figures from the distant past will be re-estimated lower in the 450 ppm range?
[Response: Note that IPCC does not do original research - IPCC merely summarises and assesses what is found in the peer-reviewed technical literature. So, we (I'm one of the authors of the paleoclimate chapter of the coming IPCC report) obviously cannot come up with something "better" than the scientific state-of-art, we just describe what this state-of-art is. -stefan]
The article would have been fascinating for me as an ordinary reader — had it as Ray says been about deep time. I would very much like to know who else the author talked to and what he read — the web is a good way to present the citations and footnotes that are missing in newsprint.
“I also would have preferred that “over geologic time scales” had not been dropped from the front of my quote saying that many factors contribute to climate change” — Robert Rohde
Well, there’s your smoking editor. Good grief, the whole point of deep time was snipped out, which rather guts the science, leaving the suggestion this applies at current rates of change.
“…. but aside from that, Mrs. Lincoln, how did you enjoy the play?”
RealClimate’s discussion of the Broad piece was noted on a science journalism Web site called the Knight Science Journalism Tracker–http://ksjtracker.mit.edu. Below is a comment I posted on that site:
Clearly, uncertainty remains the thorniest factor in science journalism. How we deal with it makes most of the difference between good science journalism and poor.
But the folks at RealClimate do take a few careless jabs at Broad. For example, they criticise him for allegedly referring to carbon dioxide as ‘blocking sunlight’ when, in fact, it blocks infrared that began as sunlight, was absorbed on Earth and then radiated skyward as IR. What I see in Broad’s story is that CO2 “blocks solar energy”, which is true.
RealClimate also ridicules Broad for, supposedly, referring to CO2 as trapping heat ‘in theory’. They suggest that Broad is ignorant of the fact that this is an established fact. So it is. But that isn’t what Broad was writing about. He was writing about a time in 1958 and said that climate researchers “knew that excess gas could in theory trap more heat from the Sun, warming the planet and providing a new explanation for climate change.” From the context, it seems obvious to me that Broad was using “theory” to refer to the whole sequence of events in that sentence, including the resulting climate change.
I haven’t examined the whole RealClimate debate on this, but those two points near the top of Pierrehumbert’s commentary suggest to me that he’s trying to color the rest of his argument (which may have considerable merit but is more technical) with a couple of easy jabs at Broad’s grasp of the subject. Those seem to have been wild punches.
[Response: Your comment is misplaced. The piece does not 'ridicule' Broad, and the two very minor points you have latched on to are in no way the main thrust of the criticism, are described plainly as 'lesser' details, and come in the 8th paragraph of a 9 paragraph piece - how is that 'near the top'? And CO2 does NOT block solar energy. I would suggest you read and comprehend before you critique - we did. Thanks for the link to the Knight Science-Journalism site - that deserves watching. - gavin]
Re 15 >A certain amount of hysteria is justified, indeed encouraged. –raypierre
That comment appears to be rather irresponsible for a professional scientist and potential fodder for those claiming that many climate scientists are not objective.
[Response: Let's not read more into this comment than I meant. In a properly ordered world, you'd call 911 and calmly report that an intruder is breaking into your house. The folks at 911 would take you seriously, and send help. Yet, there are some documented cases where the calmness of the caller led to the caller NOT being taken seriously, with tragic results. One can argue that we're in a similar situation right now. Hysteria does not mean that the reaction is overblown or unjustified. (the non-medical definition of hysteria involves excessive OR uncontrollable fear, and it's the second aspect I had in mind when saying "some" hysteria is justified) Sometimes, something really truly scary is happening, and this is my considered scientific judgement about the situation with global warming. As I've said before, I'm not alarmist -- just plain alarmed. Now, if you are trying to get out of a dangerous situation, it's far better to stay calm than to panic, so if hysteria can be avoided that's all to the good. Same situation with global warming. If the situation gets so out of hand that people get forced into a panic reaction in 50 years, mistakes are going to be made. All in all, it would be best if the powers that be paid attention to the scientific arguments and acted accordingly. But, when something terrible is coming down the pike and absolutely nothing is being done to stop it, you can hardly blame those who do see it coming from feeling just a BIT hysterical, can you? --raypierre]
Ray doesn’t mention my modeling work also misrepresented by William Broad. I have been looking over the past 20 years at factors affecting the carbon cycle during the Phanerozoic. This is summarized in my book The Phanerozoic Carbon Cycle (Oxford University Press, 2004) There are very many factors affecting CO2 that are not obvious on a human or even Pleistocene time scale. This includes the feedback of global warming on CO2 uptake by increased silicate rock weathering and CO2-induced increased plant productivity as it also affects CO2 uptake by weathering. The rise of vascular land plants during the Paleozoic undoubtedly had a large effect on CO2 uptake via both increased weathering and the accumulation of carbonaceous debris in rocks. Continental drift affects both continental temperatures and river runoff and crude estimates of such factors has been made via GCM modeling The whole long term carbon cycle and its effect on CO2 should not be ignored and replaced by simplistic assumptions for quick calculations of paleo-CO2. Nevertheless, ten million year averages for the many (over 400) independent proxies fall within my estimated error margins, obtained via sensitivity analysis, which are VERY WIDE. A copy of this data is being sent to Ray personally. I couldn’t reproduce it here. Also,the two major extended periods of glaciation (Permo-Carboniferous) and the past 30 million years agree both with modeling and proxy averages. This is crude by modern modelling standards but it is strongly suggestive of a correlation of CO2 with climate. If you don’t like any of this, at least look at my book.
#17 Thanks Raypierre, I don’t have a book store or library here, so will make do with reading RC until I head South again.
As you have imagined, I am very intrigued by CO2 at all levels of the temperature profile. Equally interested with all greenhouse gases for that matter. If I understand you right, there are specific regions above us where
CO2 actually warms the atmosphere, while other
regions with CO2, still bombarded with LR’s not suitable for absorption. Is there
any particular height where absorption is maximized? And also minimized?
[Response: Regarding the book -- until I actually finish the thing and send it to the publisher's, draft in progress is available for free on the web. Go to http://geosci.uchicago.edu/~rtp1/ClimateBook/ClimateBook.html . Chapter 3 is where you want to look, plus the grey gas part of Chapter 4, if you're up to it. --raypierre]
Galileo didn’t have the bandwidth to ask the author to provide the sources and cites and footnotes that didn’t fit on the original printed page, nor to ask the author’s sources whether they were represented correctly.
Rob Rohde has an interesting composite plot of published Phanerozoic CO2 estimates (unfortunately plotted backwards, as palaeo types are want to do). It gives a fair idea of the scatter issue.
BUT, where can we see all this data plotted with some parallel palaeotemperature estimates? Answer seems to be nowhere.
The last couple of decades have seen extraordinary progress in palaeoclimate reconstructions from multiple sources – particularly the ice cores, the ODP and the various Holocene proxies. Mostly real hard data (well, at least semi-hard), not crusty old geological inference. Despite what you say, I think this stuff is highly relevant to any overview of AGW projections, if only to set a context. It deserves to be collated and accessible. Odd, then, that we have to rely on one dedicated Californian PhD student to do the work. And even he is reluctant to cobble it all together (like this), for fear of the obvious criticisms. I hope the 4AR chapter will give us something more to work with…
[Response: One gets into trouble immediately when trying to figure out which "paleotemperature" to plot. It's very difficult to get an estimate of the global mean temperature. Some proxies give land temperature, but the latitudes available change over time. For the more recent parts of the phanerozoic, one can get estimates of tropical and deep-ocean temperature separately. Dan Rothman's paper has a crude comparison with his own CO2 reconstruction, where the climates are crudely categorized as "warm" or "cold". I very highly recommend the paper by Royer, Berner, Montanez, Tabor and Beerling in GSA Today, which is one of the best works available on the issue of CO2 and temperature in deep time. While there are some times when the CO2 and temperature reconstructions are more problematic than at other times, it should particularly be noted in this paper that the association between cooling and a major CO2 drop holds not only for the past 50 million years but also the time around the Carboniferous. This is work I probably should have highlighted explicitly in my write-up, but I assumed it was well-known to our readership though our various discussions of Veizer and Shaviv, since it is one of the main texts rebutting their viewpoint. Required reading, as it were. It's available to the public here . Bob Berner has pointed out to me that this article also raises serious questions about Rothman's reconstruction of CO2. --raypierre]
PS. Are you the same Wayne Davidson that is at the weather office at Resolute ? If so we have met before, I passed through there on my way to Eureka to make O3 measurements in the mid 90′s. We were also both at Eureka for a while in 96 (I think it was).
No. 29 states my original question in re the NYT article: how sure are we that we are not failing to factoring in extremely long-cycle effects, of which we are not aware? do the questions surrounding deep-time suggest the presence of these effects? could human induced changes in GHGs, deforestation, et cetera kick these effects into a higher gear?
[Response: It's not so much the long cycle effects I'm worried about myself. What the puzzles of deep time climate make me worry about are the possibilities of destabilizing feedbacks that kick in in a higher CO2, warmer, world, that we don't yet know about. One could legitimately raise the question of whether further study of the Phanerozoic will reveal stabilizing feedbacks instead (e.g. some kind of cloud fraction thermostat), but on the evidence so far I view that as unlikely. It's hard enough to get the climate to change as much as it did, using the rather energy balance changes due to GHG, continental configurations, and equally well those potentially due to cosmic rays. With any major stabilizing feedback, explaining the Phanerozoic climate variations becomes just about impossible. --raypierre]
#34, What a surprise Dave! You must be in Europe? Can’t meet at a better place though.
Our yellow star overtook my attention I use to give to the red star. Working on something radical which was always in front of us.. Thanks for the link, GHG’s affect the mid troposphere it appears, quite interesting , reading Raypierre’s book will likely confirm. You would not be familiar with the temperatures here, compared to 96-97, which in my memory was the last cold winter. -45 to -50 C for extended periods, I am sure you have not forgot Halebop and other mysteries seen during the very long night.
#34, thanks for that Ray. I guess Royer et al illustrates my point. It’s the failure to do the obvious with the results, like this, that irks. There is a solid story there even using Veizer’s uncorrected interp. It just isn’t presented.
“One gets into trouble immediately when trying to figure out which paleotemperature to plot.” Well, yes – the first of those “obvious criticisms”. But hardly a sound reason to not try, when faced with a matter serious enough to warrant even some “hysteria”? Fact is, there seems to be pretty fair data suggesting that our world hasn’t been as hot as where we’re headed this century for about 15My. And CO2 probably hasn’t been as high as where we’re headed for maybe 20My. That’s seriously important information, even if uncertain and incomplete. It needs to be collated and presented, clearly…
Ray… I looked at the latest draft of the climate book. Very nice work, and I can’t wait for the missing portions to be filled in. I have some caveats, but they’re trivial, e.g., the bolometric Bond albedo of Venus is 0.76 (Taylor 1983), not 0.65, which is a way obsolete figure. You also give the mean global annual surface temperature of the Earth as 285 and 286 K, which is Sellers’s figure from 1965. All the modern estimates I’ve read in the literature have it as either 287 or 288 K (e.g. Henderson-Sellers’s book, Houghton’s, etc.)
“And then, too, the tired old beast of Galactic Cosmic Rays (GCR) raises its hoary head in Broad’s article”
The tone of this comment is odd considering the recent high quality scientific papers which examine how modulation of GCR, by the sun, and changes to the base level of GCR, which occur then the solar system periodically moves through the galactic plane, both affect the earth’s climate.
The GCR hypothesis appears to answer a number of fundamental unresolved puzzles in Paleoclimatology, such as the “100 kyr eccentricity problem” and other orbital forcing related problems, the “faint sun problem”, or the fact that the increase in CO2 levels lags the increase in temperature, at the cycle change from glacial to interglacial.
Shaviv and Veizer’s paper “Celestial driver of Phanerozic Climate?” is certainty not a rehash of an old tired hypothesis.
While I could not find a direct link to that paper, Shavis and Veizer’s response to Rahmstorte et al’s rebuttal of their paper “Celestial driver of Phanerozic Climate?” is a summary of the salient issues.
“We show here why the various criticism raised are either irrelevant or erroneous. Thus the conclusions reached by Shaviv & Veizer (2003) are still valid. In particular, the dominate climate driver on the multi-million year time scale is the variable cosmic-ray flux. CO2 is important, but it likely plays a secondary role in determining the climate.”
“… we fully support the development of alternative energy sources, simply because of real pollution and resource conservation considerations,… ”
“Last, a periodicity in Cosmic Ray Flux (CRF) is predicted by the current astronomical theory. Summing up, we did not use only 20 meteorites to reconstruct the CRF. We used all K-dated meteroites (80 reduced to 50 “heterogenenous” ones) to obtain the most accurate signal possible …”
“The astronomical constraints alone do indicate that the CRF should have been variable, that the period should be 135 25+/- Ma, that the CRF should peak at 31 8+/-yr after the spiral arm passage, that the last passage was at about 50 Ma before present, that the CFR had amplitude variations between a factor of 2 to 10. Clearly they are not trival.”
“We are well aware of these complications, but the available publication space did not permit,… Further, we fail to see how this musing would change the statement that “it is not clear whether CO2 is a driver or is being driven by climate change since the CO2 appears to lag by centuries behind the temperature changes, potentially acting as an amplifier but not as a driver”.
“It remains to be seen whether orbital forcing is the primary driver, since the evidence for correlations with cosmogenic nuclides is accumulating, Sharma, (2002); Christl et al. (2003); Niggermann et al. (2003).
The following is another paper by Shiva “Cosmic Rays and Climate Sensitivity” which I also found interesting.
[Response: The cosmic ray theory isn't all it's cracked up to be, especially with regard to its implications for modern day climate sensitivity. This has been extensively discussed in various earlier RealClimate posts, some of which I linked in the article. --raypierre]
[Response: Here are a few further thoughts concerning your comments on the cosmic ray theory. First, it is not enough to just quote-mine from Veizer's response and miscellaneous papers. Just about every criticism of a published paper gets some kind of response. The fact that there's a response doesn't mean it's a valid rebuttal. You have to look at the actual arguments. The criticisms of the suggested implication for recent climate, and Berner's criticisms of the lack of a pH correction in the reconstruction of earlier Phanerozoic CO2, are compelling. Also, one must recall that when it comes to the effect of CO2 on climate we are not working in a vacuum. There are certain things we know about the effect of CO2 on climate that come from basic established physics; we are not trying to reason entirely from the emipirical record of past climate. The work of the GCR proponents (particularly Veizer) ignores this in trying to shoehorn the whole past into their concept. I wish to make clear that there are hierarchies of ridiculousness, though: the idea that cosmic rays rather than CO2 are mostly responsible for recent climate changes are absolutely ridiculous and should just disappear from the discussion, while the idea that cosmic rays might have played some partial role in earlier climate change is questionable but hard to discount completely, given what we don't know about clouds. The latter deserves further study, but the people doing it have to start trusting the basic physics more if they are going to make progress.
This all raises another question, on the journalistic side, regarding the "false balance" issue. Broad clearly should have known better regarding the inappropriate implication that the cosmic ray theory might have some implications for anthropogenic global warming, but it's somewhat harder to blame him for not getting an accurate read of the scientific community's assessment of CO2 and Phanerozoic climate. After all, even with the weight of the IPCC, it took a long time for reporters to really understand what the consensus is regarding global warming. There hasn't been any analogous consensus document on Phanerozoic climate, and I'd hate to see science go in a direction where such things should be needed for all outstanding problems. Those of us in the trenches of science know that Berner is a towering figure in the field with a reputation for very meticulous work, that Rothman is brilliant but a relative newcomer to geochemistry (using a largely untried CO2 and somewhat speculative reconstruction technique), that Veizer's work is very problematic. To a reporter, looking at a small field where a single vocal figure on the fringe (like Veizer) can make so much noise so repetitively that he wears out the patients of those who need to refute endless permutations of the same wrong arguments, I can see how it can be hard to get a read on who's who, and who to listen to. William Broad was wrong to put Veizer's arguments on the same plane as others, but how was he to know he was wrong? How does a science writer know when balance crosses over into false balance? Of course the ideal thing is for the reporter to actually deeply understand the science, but that may be a bit much to ask for, given the amount of territory reporters need to cover. We aim to help out with this on RealClimate, but I can understand a reporters' being reluctant to lean too much on one blog as a source. It's a sticky problem, and I'd like to hear what both readers and science writers think about this. --raypierre]
Even in Rothman’s reconstruction, during the past 50 milllion years — when the data is best and continents are most like the present — the long term cooling trend leading into the Pleistocene is clearly associated with a long term CO2 decline. This is not our main reason to infer that increasing CO2 will warm the climate in the future, but insofar as the data supports CO2 decline as a main culprit in the long slide from the Cretaceous hothouse climates of 60 million years ago to the cold Pleistocene climate, it also lends weight to the notion that as industrial activity busily restores CO2 to levels approaching those of the Cretaceous, climate is likely to turn the climate clock back 60 million years as well.
How do you jump from “associated with” to “main culprit” ? Correlations are note causations and CO2 trends as well as temperature trends from 50 My BP to Holocene could be (at least partially) the effects of other cause(s). A minima, to define CO2 as the main responsible for T variations of Pleistocene suppose that we know all the forcings, all their sensitivities and so quantify their relative weight. Do we ?
[Response: That's "supports" as in "is consistent with." I'm only addressing the claim that the CO2/climate record is patently inconsistent with CO2 being a dominant control. But as for additional evidence of the cause of the cooling trend, there's the fact that one can get close to this magnitude of cooling with standard models of climate sensitivity to CO2, and so far there isn't any viable competing theory. The GCR idea isn't even close to being quantified well enough to be tested. In that sense, as a theory "it's not even wrong." --raypierre]
My own comment to Broad – timescales, specifically making comparisons twixt distant long and recent short – has been I suspect covered earlier by yr previous commenter/s.
And yes, words-in-the-way viz “blocking” did irritate some, but at first reading your post I was left wondering well, why try take down Wm. Broad who, as far as I know, attempts pitch his stories on actual things, events, disputes etc. As opposed, say, an earlier mistake at the Times with Tierney’s talking points denialist diatribe.?
Not to defend y’understand though likely true to some extent, I’d like to point out that journalism’s publications have their styles. And one thing I find highly pertinent at the NYT is that that considered readerships’ weight is given toward the end of a piece. My own take on this is that prior to this weighted content there is need to draw readership in. Need to be, albeit sedately, provocative. Need to get over, as it were, those holding the accepted science on global warming pov. In order to reach its opponents.. debate arising on and, as I said, real dispute/s. Hopefully widening. Informing..?
The matter of publication date: 7th November. Election day. A let’s get serious day. Tone, in journalism, still exists. Thankfully.
Given the time I could expand on these things, but that’s not the point of RealClimate’s excellent blog and services to interested folks..
[Response: Nobody's trying to "take down" Broad. The point is to discuss what's wrong with the thrust of the article, so Broad and other science writers can do better with this class of issues next time. The point is also to put some more valid information out on the blogosphere, so some of the (probably inadvertent) damage that might be caused by Broad's article can be averted. I wouldn't have written a post based on the lesser quibbles I pointed out; the main problem was Broad's conflation of the general mysteries of Phanerozoic climate with the issue of near-term climate sensitivity. As long as I was writing the article, though, I thought it was worth pointing out the lesser matters as well. --raypierre]
Raypierre, you said: “What the puzzles of deep time climate make me *worry* about are the possibilities of destabilizing feedbacks that kick in a higher CO2, warmer, world, that we don’t yet know about”
What if I said? “What the puzzles of deep time climate make me *curious* about are the possibilities of negative feedbacks causing a cooler world than we might anticipate from simply the radiative forcing of CO2 alone, that we don’t yet know about”
Why do you have license to envoke the “puzzles of deep time climate” to “worry” about a possible catastrophe, but I am chastened for envoking the same “puzzles of deep time climate” to support my “curiosity” about why this catastrophe may not occur? It might appear to some that your statement betrays an “advocacy position”, instead of one of pure scientific endevour. Then again, so might mine.
It is healthy that reporters do not come soley to RC for their information, because at times, the viewpoint expressed here is too narrow.
[Response: I'm not just worrying here idly. The uncertainties in what is going on in the Phanerozoic if anything are specifically suggestive of destabilizing mechanisms we don't know about. CO2 is the only thing we know that moves temperature around enough to come close to explaining the Phan. but it doesn't move the polar temperatures around enough. Mayber there's something else, but so far as quantified physics goes, CO2 and a few other GHG's are the only game in town. So, there I've ponied up my physics. Now you have to pony up yours or fold and quit. Another way of thinking about it is this: What are the consequences if my "worry" is right, vs the conseqences if your "curiosity" is wrong? --raypierre]
The URL directing folks to my commentary on Bill Broad’s piece and broader issues on the Center for Science and Technology Policy weblog is broken. If you’re interested to hear another science and environemtnal reporter’s perspective, go to: http://sciencepolicy.colorado.edu/, and click on the “Prometheus” link at the top right corner of the page.
And by the way, perhaps it is self-serving to say this, but why do you suppose that 68 percent of Americans polled in a recent Pew survey said the federal government should take “immediate action” on climate change? I don’t think Americans arrived at that conclusion by reading Science, Nature, JGR, etc. The vast majority of Americans get their news about issues like climate change from news media. I suppose if you doubt whether climate change deserves immediate action, you might count this as evidence for shoddy coverage of the issue by news media. But I suspect that most readers and contributors to this blog are not in that camp. So if science and environmental reporters have gotten things so very, very badly, as several posts in this thread seem to suggest, then how do you explain the fact that more than two thirds of Americans take climate change seriously, and not only that but believe it is an urgent enough problem to warrant immediate action?
Co-director, Center for Environmental Journalism
University of Colorado at Boulder
[Response: Fixed the link. Sorry about that. - gavin]
[Response: I hope people don't come away with the impression that we think most science writing is junk. Up until recently, there did indeed seem to be one nearly ubiquitous problem with writing on global warming, which was the "false objectivity of balance" issue. This has largely subsided in recent times, but even that should not have been taken as a blanket indictment of science writing. In the last few years, there has been a marked change in the forcefulness of journalism related to global warming, and I'd like to think that this is part of the change in public perception on the urgency of the issue. However, like most academics, I live in a bubble and my ideas of where people get their opinions are probably not worth much. I'm a real newspaper addict myself, but given what a small fraction of the population reads the major newspapers, it's not clear how much leverage even the best science writing there has. Maybe it has a disproportionate influence because it reaches a high proportion of "opinion makers." Perhaps most people are getting their ideas from television. I'd really like to know the source of information on which people are basing opinions such as those in the poll numbers you mention above.
By looking at the gap between the magnitude of action and the magnitude of the problem, though, I have a suspicion that the poll numbers represent concern, but not deep enough concern for people to demand the kind of major actions that would be needed even to keep CO2 from going beyond doubling. Even among people who express concern, I only see the things happening that don't require any hard decisions. Some people are giving up SUV's for more efficient cars, but it's far from common. People still aren't clamoring for carbon taxes on coal, which are probably the only way to make IGCC and sequestration the coal technology of choice, and put renewables on a level playing field. Maybe the actions planned in California are the beginning of a groundswell of action, but I don't see yet that people have put the War on Global Warming in the same category as the effort that mobilized the nation to win WWII. It's really that big, maybe bigger. -raypierre]
Can you please do a post on this global warming causing H2S mass extinctions theory in terms of its validity? It is also in the Journals of Science, Nature, Geology, and Geotimes to name a few, so you can’t be accused of being “alarmist”.
Re: #44 Raypierre, you say: “CO2 and a few other GHG’s are the only game in town” and “so, there I’ve ponied up my physics. Now you have to pony up yours or fold and quit”.
The entire class of aerosols and aerosol indirect effects are another good game in town we might want to buy a ticket to see. How about changes in albedo due to things like dark-colored soot or volcanic ash covering the poles? How much do we really know about dust? The latter variables might be the minor leagues, but also interesting. How about evolution of landforms and vegetation affecting earth’s albedo across deep time? How about changes in landuse and associated teleconnections across not so deep time?
There is plenty of good physics to go around. I do not think I will fold just yet.
[Response: You haven't even made a start. You've got to tell me how these sorts of things are supposed to have accounted for the various changes across the Phanerozoic. I can tell you how CO2 causes warming and how much, and what factors tend to cause it to change. You're going to have trouble getting soot from forest fires before land plants had evolved. It's one thing to parrot a laundry list of vague possibilities. It's another to get serious about how to assess them. Note, too, that even if we knew nothing about earlier Phanerozoic climate there's plenty of cause in basic verifiable physics and the recent climate observations vs. theory to tell us that CO2 is almost certain to cause substantial future warming. The additional sources of worry I find in the Phanerozoic puzzles are just icing on the cake, as it were. If I may paraphrase your stance, it's "Let's just burn all the coal and pray for a miracle." --raypierre]
The problem with almost all alarmist speculations or non-alarmist speculations is we really have no basis to analyze the problem. We can point to various parallels in the past – mass extinctions, Medieval Warm Period, Little Ice Age – but, as they say in the investment prospectus, “past performance does not guarantee future results”.
The non-alarmists always have the odds on their side. Big shifts and changes in climate are rare. So the alarmists should have to meet a much higher standard to prove their point.
[Response: Balderdash. We have over 150 years of basic physics, going back to Fourier 1827, to go on. And as for direct proofs that climate is sensitive to CO2, the southern hemisphere cooling during the Last Glacial Maximum is about as direct as they come. No ice age in the SH without sensitivity to CO2. --raypierre]
#49 “Big shifts and changes in climate are rare. So the alarmists should have to meet a much higher standard to prove their point.”
Really? Looks to me like big shifts are pretty common, albeit in the opposite direction. And that’s not just common on geological timescales. When I engineer a large dam – one that might kill thousands if it fails – I’m obliged by internation design guidelines to consider events with annual probabilities in the order of 1 in 10^5 to 1 in 10^6. Because the consequences of failure are large. How big are the consequences of here?
Here’s an extract from Shaviv & Veizer. Note the difference in tone between this speculative description of a possible new mechanism and the Broad article. Note also the dearth of quantification:
Growing evidence, such as the correlations between paleoclimate records and solar and cosmic ray activity indicators (e.g., 10Be, 14C), suggests that extraterrestrial phenomena are responsible for at least some climatic variability on time scales ranging from days to millennia (Friis-Christensen and Lassen, 1991; Tinsley and Deen, 1991; Soon et al., 1996; Svensmark, 1998; Beer et al., 2000; Egorova et al., 2000; Soon et al., 2000; BjÃ¶rck et al., 2001; Bond et al., 2001; Hodell et al., 2001; Kromer et al., 2001; Labitzke and Weber, 2001; Neff et al., 2001; Todd and Kniveton, 2001; Pang and Yau, 2002; Solanki, 2002). These correlations mostly surpass those, if any, for the coeval climate and CO2. Empirical observations indicate that the climate link could be via solar wind modulation of the galactic cosmic ray flux (CRF) (Tinsley and Deen, 1991; Svensmark, 1998; Marsh and Svensmark, 2000; Todd and Kniveton, 2001; Shaviv, 2002a, 2002b) because an increase in solar activity results not only in enhanced thermal energy flux, but also in more intense solar wind that attenuates the CRF reaching Earth. The CRF, in turn, correlates convincingly with the low-altitude cloud cover on time scales from days (Forbush phenomenon) to decades (sun spot cycle). The postulated causation sequence is therefore: brighter sun -> enhanced thermal flux + solar wind ->muted CRF .> less low-level clouds -> less albedo -> warmer climate. Diminished solar activity results in an opposite effect. The apparent departure from this pattern in the 1990s (Solanki, 2002) may prove to be a satellite calibration problem (Marsh and Svensmark, 2003). The CRF “cloud-cover” climate link is also physically feasible because the CRF governs the atmospheric ionization rate (Ney, 1959; Svensmark, 1998), and because recent theoretical and experimental studies (Dickenson, 1975; Harrison and Aplin, 2001; Eichkorn et al., 2002; Yu, 2002; Tinsley and Yu, 2003) relate the CRF to the formation of charged aerosols, which could serve as cloud condensation nuclei (CCN), as demonstrated independently by ground-based and airborne experiments (Harrison and Aplin, 2001; Eichkorn et al., 2002).
Finally, despite the copious referencing for other links in his argument, he gives no evidence that global cloudiness is in fact decreased during sunspot maxima and Forbrush events.
#40 Raypierre comment :
so far there isn’t any viable competing theory. The GCR idea isn’t even close to being quantified well enough to be tested. In that sense, as a theory “it’s not even wrong.”
Of course, I was not thinking to GCR when I posted my comment. More simply, I refer to millenial-scale and geological-scale solar forcing (radiative and orbital) – whose GCR-cloud effect could be a retroaction (but no proof of that for the moment, I agree). I don’t know if and how we can exclude this forcing for Pleistocene T variations you described as mainly CO2-induced.
It seems to show that complex life can survive several thousand ppm CO2. That should counter claims that 600ppm is likely to make humans extinct.
What is makeing humans extinct will be:
- rising sea levels
- No food
- No clean water
- Catastrophic weather events on a daily/weekly base
- war over clean water and food
And based on PETM and similar events which ongoing around 100.000 years there is enough time for humans to becoem extinct.
If not – than this survivors will not have a life we life today it will be underground – no sun and not much living on the earth.
The PETM took a few 1000 years till it ‘arrived’ – the diffrent this time is we putting more greenhouse gasses into the air (exalerating) and faster.
In an event marking the start of the Eocene, the planet heated up in one of the most rapid and extreme global warming events recorded in geologic history, currently being identified as the ‘Paleocene-Eocene Thermal Maximum’ or the ‘Initial Eocene Thermal Maximum’ (PETM or IETM). Sea surface temperatures rose between 5 and 8Â°C over a period of a few thousand years…
Also a diffrent chemistry of the air will manipulate species evolution (Oxygen levels).
This has been allready documented on small genoms (fruit flys for a fact, which got a fast birth rate).
[Response: Don't forget that the biggest change in chemistry will be the acidification of the ocean. This would be a disaster in waiting even if CO2 caused little or no warming. The chances of human extinction seem pretty low to me, though a lot of other species will likely go extinct and there is a lot of bad stuff that could happen short of extinction of the humans. --raypierre]
Identification of the causes of past climate change requires detailed knowledge of one of the most important natural factorsâ��solar forcing. Prior to the period of direct solar observations, radionuclide abundances in natural archives provide the best-known proxies for changes in solar activity. Here we present two independent reconstructions of changes in solar activity during the last 1000 yr, which are inferred from 10Be and 14C records. We analyse the tree-ring 14C data (SHCal, IntCal04 from 1000 to 1510 AD and annual data from 1511 to 1950 AD) and four 10Be records from Greenland ice cores (Camp Century, GRIP, Milcent and Dye3) together with two 10Be records from Antarctic ice cores (Dome Concordia and South Pole). In general, the 10Be and 14C records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates. Differences between 10Be records from Antarctica and Greenland indicate that climatic changes have influenced the deposition of 10Be during some periods of the last 1000 yr. The radionuclide-based reconstructions of past changes in solar activity do not always agree with the sunspot record, which indicates that the coupling between those proxies is not as close as has been sometimes assumed. The tree-ring 14C record and 10Be from Antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr.
Raypierre: You say: “I can tell you how CO2 causes warming and how much, and what factors tend to cause it to change.”
Raypierre, so can I! But I am still a little unclear on your hypothesis. Are you saying that other radiative forcings besides CO2 have not been significant contributors to climate change throughout the Phanerozoic? Are you also saying that aerosols are not significant to the present climate? I think you do not intend to answer in the affirmitive to either of these questions.
As far as ascribing significance to aerosols in the geologic past, I was simply envoking uniformitarianism. The physics operates today, so it must have operated in the past. Do you disagree with the physics or uniformitarianism? I think neither.
Raypierre, you go on to say: “Note, too, that even if we knew nothing about earlier Phanerozoic climate there’s plenty of cause in basic verifiable physics and the recent climate observations vs. theory to tell us that CO2 is (almost) certain to cause substantial future warming.”
Since we both agree that Stephan-Boltzmann is a physical law, will you not enlighten the readers by telling us more about the reasons you are not *completely* certain? Are you really that agnostic about the physics?
You also say: “You’re going to have trouble getting soot from forest fires before land plants had evolved. It’s one thing to parrot a laundry list of vague possibilities.”
And you also hung this on me: “If I may paraphrase your stance, it’s “Let’s just burn all the coal and pray for a miracle.”
But I never said either. You were being broadly misleading. Please do not try and win the argument by hooking stupid ideas to me. You seemed rather angry.
Raypierre, I think we probably agree on more than you think, but a reader from the general public might understandably be confused.
[Response: I'll repeat my challenge in another way: The work of Berner and others has shown how to explain certain major features of the Phanerozoic climate, assuming that sensitivity to radiative forcing is similar to that in standard climate models. The direction of the remaining mismatch, if anything, points toward climate being more susceptible to major changes than standard models predict. This class of theories doesn't by any means explain all features of Phanerozoic climate, but can you come even THAT close with any quantified model that has low sensitivity to CO2? Remember that if you are invoking any hypothetical stabilizing feedback mechanism (e.g. Lindzen's Iris) for consistency you have to apply that stabilization to all radiative forcings on an even footing. That comment applies to volcanic aerosol forcing, as well as hypothetical cloud forcing from GCR (if the proponents of that theory ever manage to get halfway reliable quantifications of the forcing).
As for "praying for a miracle," what else would you call it if you're going to argue for not worrying about CO2 emissions on the basis of some possible stabilizing feedback which might possibly be revealed someday by the Phanerozoic studies, but for which there is currently no evidence whatsoever (and which indeed would contradict most of the rest we know about climate physics)? And if you're sincerely worried about the possibility that the public might get "confused" you ought to look closer to home, and specifically at the AAPG's endorsement of Crichton's "journalism." --raypierre]
The number of possible forcings over geologic time is indeed bewildering. I have long been hoping for attention to be paid to this issue, just for curiosity’s sake.
I am glad to see a compilation of CO2 concentrations since the Permian. I was wondering about various CO2 regulating effects. For instance, the Hercynian mega-cycle would potentially yield a CO2 drawdown similar to that proposed for mechanical weathering related to Tertiary mountain building (how sure is the Tertiary drawdown attributed to this cause btw.?). Similarly, the later Cimmerian mega-cycle.
On exotic forcings, how much effect do 1st/2nd order eustatic sea level changes have? Presumably significant changes in the percentage of Earth’s surface covered by water must have an influence, and when these are due to variable spreading ridge production and ocean basin volumes, then presumably this effect is largely independent of CO2? concentrations.
If this is covered in any of the papers referenced, my excuses. I’ll download them tomorrow.
Re #56: Bryan, I would say it was more impatience than anger. Ray’s point, which you continue to refuse to recognize, is that the argument that anthropogenic CO2 is the predominant influence on the present warming is based on physics and quantified observations. Your assertions, on the other hand, are pure handwaving. Do you imagine that numerous climate scientists haven’t examined each of the factors to which you refer? If you disagree with their conclusions (which are based on the numerous references given on this site), it’s time for you to start putting up some *numbers* to support your case. Absent that, I suggest that it would be more constructive for you to ask questions than to continue making baseless assertions. Note that you’re trying to carry on this argument with someone who (among other things) writes textbooks on climate physics.
“In my view, as geologists, if we want to seriously enter this debate, we must do so not only on the grounds of historical geology, but also on the ground that the debate it is currently being waged, atmospheric physics (Wien’s Displacement Law, Stefan Boltzman Law, the First Law of Thermodynamics, fluid dynamics, ocean heat storage and transfer, etc. etc.). How can we as a society ethically offer up opinions on the validity of anthropogenic climate forcings (and that is mostly about the physics), without having at least some level of basic knowledge? We need to quit pretending that this thing is nothing more than a great political conspiracy, and if we can, challenge it on the basis of solid science (observational and theoretical), not just arm waving. As petroleum geologists, we superbly understand the history of climate change as recorded in the rock record. Painfully however, we really do not understand much about the physics (incredibly complex and numerous coupled interactions of multiple laws) governing these changes. Since we adhear to uniformitarianism (present is key to past), maybe we should break down and begin learning something new about the present.
“I would offer an analogy: If we are arguing with a reservoir engineer as to whether or not there are enough reserves left to justify the development well we are proposing, it helps us if we know some fundamentals of basic reservoir engieering. We become much more persuasive if we can show the engineer that we have already calculated the reserves using his beloved equations. Try this sometimes. It works!”
Reasonable advice both from and to a petroleum geologist, IMHO. You could start with re-reading the extensive replies to your comment #5 above.
Finally, regarding your accusation that Ray must be “agnostic” about the physics since he ascribes a degree of uncertainty to predictions of additional warming due to CO2, it seems very strange that someone with even a modicum of scientific training would be confused on this point.
#54 Raypierre comment :
“Don’t forget that the biggest change in chemistry will be the acidification of the ocean. This would be a disaster in waiting even if CO2 caused little or no warming. The chances of human extinction seem pretty low to me, though a lot of other species will likely go extinct and there is a lot of bad stuff that could happen short of extinction of the humans.”
Again, I disagree with such a pessimistic and one-sided view. As far as I know, biological modelisation of planktonic response to acidification (low. 0,1 to 0,4 pH from now to 2100) is still in its infancy. Forams and coccoliths have a rather high rate of reproduction – a not-so-bad adaptative profile – and these species have survived to many abrupt climate changes of the past million years. Preliminary lab. experiences cannot be accepted as realistic simulations : Riebesell et 2000, for example, upwarded ambient atmosphere of a coccoliths monuculture to 800 ppm CO2 in 9 days !! That’s not conclusive for real-word adaptive behavior of theses micro-organisms over the forthcoming nine decades.
I don’t say : there is no problem. But rather : let’s be cautious and avoid the catastrophic claims, or the credibility of science will be seriously weakened.
Re #59: Steve, you said: “Ray’s point, which you continue to refuse to recognize, is that the argument that anthropogenic CO2 is the predominant influence on the present warming is based on physics and quantified observations.”
Steve, I largely agree with Ray (defer to his expertise) on that point. What has given you the idea that I have not recognized his point? I quarrel with RC over giving the public the perception that the community has all of the important climate issues resolved. Yes, there have been many advances in recent years, but the poor model performance in replicating some important climate metrics point to possible potholes which are not being clearly communicated to the public and policy makers. Maybe these are why Ray is not *completely* sure. My argument is that the climate science community should not cease (by force of tyranny of the majority) to think critically about many of these forcings and feedbacks which still are poorly understood. Maybe they are, but I am not seeing the papers.
The ratio of species changes dramatically, that’s the issue. This isn’t about extinction of specific primary producer species, it’s about which ones predominate and which ones become more susceptible to viruses and bacteria as calcite becomes soluble in surface sea water in about 2100.
Oceanography: Sick seas
SUMMARY: The rising level of carbon dioxide in the atmosphere is making the world’s oceans more acidic. Jacqueline Ruttimann reports on the potentially catastrophic effect …
Nature 442, 978 – 980 (31 Aug 2006)
Suppose we had been observing global cooling instead of global warming. What remedies would have been proposed? “Use all the oil you can!” “Buy really fuel-inefficient cars!” “Don’t use any renewable sources of energy if you can avoid it!”
The human race has always been inclined to blame itself for whatever troubles that arise, and offerings to the gods have always been a part of the solution, may they be in form of slaughtered lambs or giant wind-powered generators. This is the main source of my personal scepticism of any theories of impending climatic doom.
And, if you live in Scandinavia, as I do, retreating glaciers are indeed an ominous sign – but advancing ones are even worse.
Comment by Anders Lundqvist — 14 Nov 2006 @ 5:35 PM
Re #49, 50
Raypierre – balderdash? – your comment about my post #49.
First, I didn’t say anything about CO2 in my post and I don’t doubt it is a major factor in global warming.
Second, you then go on to cite the Last Glacial Maximum as evidence of something, more or less helping me make my point that you can’t just cite the past to predict the future.
Third, as for the basic physics, can it tell me when I can start building my beach house on some farm land I’m thinking of buying in South Georgia?
Regarding Post #50, the link goes to a graph covering millions of years. I guess we could find another graph covering billions of years that wouldn’t even show Earth on it. That would be a real big change, right?
What if the natural “balanced” climate cycle would bring an iceage?
But due to AGW its not happening – and its just slowering the effect of AGW?
And more importend on the bottomline what helps such hypotetical statement in such a debate?
We should try avoiding any unnatural interference with systems which a) can lead to extinct of the human species – b) Can not be calculated with currrent data/know-how and computer capacity – c) Can bring our planet into a state which is considerate unbalanced in relation to present and past states(climate).
We have the know how today to sustain this “paradies like” planet – under the circumstances and what is on stacks we should act yesterday rather than later.
Re #61: Bryan, up in #7 you wrote: “What would also be misleading would be giving policy makers and the public an impression that we now understand all of the complex, non-linear interactions between all the forcings and feedbacks significantly well to forecast future climate with skill across multi-decadal time. Just because Stefan-Boltzmann and Wein are beyond dispute, the best geological evidence available (most of the last 25% of earths history) tells us that CO2 is not the only game in town. It is the very tricky interaction of CO2 with a number of the other forcings that is really the question. To give one example, the role of aerosols and their associated feedbacks is still incompletely understood, but we know to some extent there is a cooling effect. There might be high aerosols and high CO2 (both can be natural and or man-made), and maybe a cooler than expected climate. What about the feedbacks associated with both? How do they all interact?”
A “cooler than expected climate”!? I’d call that a fundamental disagreement (noting that you were referring to future climate rather than to the Phanerozoic, although it appears you were trying to refer to some sort of evidence from the Phanerozoic). There is a big distinction between saying the science is incomplete and that there is a degree of uncertainty about the timing and extent of future warming and saying, as you do, that the uncertainty is large enough to allow for the present warming trend to reverse into cooling. It isn’t.
With respect to your reference to climate models being unable to forecast climate with skill on a multi-decadal basis, I suppose one can define terms to make that a true statement (and rumor has it that there’s even a whole blog devoted to that purpose), but having done so it is dishonest to try to backtrack such a conclusion into questioning what can be known from the physics and observations. Recall that a century ago Arrhenius got an answer (for warming due to climate sensitivity to increased CO2) in the right ballpark without any model as such. It might be useful for you to have a look at this RC post
Yes. I quote the abstract of a more recent paper of Riebesell (2004) :
Abstract Rising atmospheric CO2 and deliberate CO2 sequestration in the ocean change seawater carbonate chemistry in a similar way, lowering seawater pH, carbonate ion concentration and carbonate saturation state and increasing dissolved CO2 concentration. These changes affect marine plankton in various ways. On the organismal level, a moderate increase in CO2 facilitates photosynthetic carbon fixation of some phytoplankton groups. It also enhances the release of dissolved carbohydrates, most notably during the decline of nutrient-limited phytoplankton blooms. A decrease in the carbonate saturation state represses biogenic calcification of the predominant marine calcifying organisms, foraminifera and coccolithophorids. On the ecosystem level these responses influence phytoplankton species composition and succession, favouring algal species which predominantly rely on CO2 utilization. Increased phytoplankton exudation promotes particle aggregation and marine snow formation, enhancing the vertical flux of biogenic material. A decrease in calcification may affect the competitive advantage of calcifying organisms, with possible impacts on their distribution and abundance. On the biogeochemical level, biological responses to CO2 enrichment and the related changes in carbonate chemistry can strongly alter the cycling of carbon and other bio-active elements in the ocean. Both decreasing calcification and enhanced carbon overproduction due to release of extracellular carbohydrates have the potential to increase the CO2 storage capacity of the ocean. Although the significance of such biological responses to CO2 enrichment becomes increasingly evident, our ability to make reliable predictions of their future developments and to quantify their potential ecological and biogeochemical impacts is still in its infancy.
The conclusion is important, and it was the sense of my reply to Raypierre’s excessive alarmism. An other recent work show that pluridecadal variability of 0,1 to 0,3 pH is common in Pacific coral reefs (Pelejero 2005). So life is life, its evolution and adaptation to local conditions is a very complex matter – for this issue, what do we know exactly about functional genomics of calcification in plankton and coral species?
I agree with you that modifications in relative populations dynamics (rather than global extinction) is a most probable consequence of rapid environmental changes predicted for the 21st century.
published in Nature on September 29, 2005 reports that ocean acidification could result in corrosive chemical conditions that would be reached much sooner than previously thought.
Within 50 to 100 years, there could be severe consequences for marine calcifying organisms, which build their external skeletal material out of calcium carbonate, the basic building block of limestone.
Most threatened are cold-water calcifying organisms, including sea urchins, cold-water corals, coralline algae, and plankton known as pteropods–winged snails that swim through surface waters.
Chemical Saturation State:
Projections for the “chemical state” of the surface ocean for years 2000 (top) and 2099 (bottom) given as the median of 10 ocean models. The magenta colored line (seen only in 2099) separates saturated waters (orange colors) from undersaturated waters (blue colors).
- rising sea levels
- No food
- No clean water
- Catastrophic weather events on a daily/weekly base
- war over clean water and food
It is difficult to understand how sea level rising at mm or even cm rates per year will drown many people.
Drought (presumably resulting in no food) – I believe most peer reviewed studies actually predict total greater food growing capacity in a warmer world.
Heatwaves, no clean water, plaques, war – Those problems are most likely to be solved by a prosperous economy with access to energy, and would likely be made worse by devoting excessive resources to reducing GHG emissions.
Catastrophic weather events on a daily/weekly base – Is there any credible study indicating a sufficient increase in catastrophic weather events to threaten the lives of a significant portion of the world’s population?
Notwithstanding the respectable qualifications of the contributors to RealClimate, I think the credibility of the site is at serious odds with its objectives: I quote, â??RealClimate is a commentary site on climate science by working climate scientists for the interested public and journalists. We aim to provide a quick response to developing stories and provide the context sometimes missing in mainstream commentary..â??. However, everywhere on this site I do not observe a balanced view. The aim of this web site looks more like â??â?¦We aim to provide a quick response to stories challenging the greenhouse global warming theory because we believe it is a scientific fact and we will counter with anything we can find that supports our view and our confidence that our climate models are infallible.â?? Why donâ??t you present an objective view of this important issue?
As you dismiss yet another article, again resorting to unnecessarily insulting and arrogant language, perhaps you can explain why the climate of earth 125,000 years ago was warm enough to enable the growth of coral in a temperate latitude off the coast of south west Australia? The evidence for this is a fossilised coral reef sitting 3 to 4 metres above the present sea level. It is estimated to be 125,000 years old. The location (around 33 degrees latitude) is well south of present coral waters.
Re #72: Robert, the period you refer to is the Eemian, which was known to be about 2C warmer (in places) and to have sea level about 6m higher than present. Since the current southern extent of tropical coral is no more than 400km north of the latitude you mention, the presence of that reef doen’t seem remarkable. As to why the Eemian was warmer than the present, at least in some regions, see here.
Regarding the site, please bear in mind that anthropogenic global warming is a scientific fact and that there is no obligation to make room for contrary views if those views are incorrect.
It is difficult to understand how sea level rising at mm or even cm rates per year will drowning many people.
U missed something – who talks about drowning?
This happens from many factors forced by rising sea levels. Such as water becomes salted from sea water – the complete economic gets unbalanced and species extinct( Yes new comes to – but into an unbalanced cycle). People are forced to move – leaving all they got – if this happens to millions – maybe u can try to imagine.
Drought (presumably resulting in no food) – I believe most peer reviewed studies actually predict total greater food growing capacity in a warmer world.
And what means “most peer reviews studies”? Do you can provide a link – i doubt it.
Drought brought us many results eg. less food yes – also forces people to move – also killing economics – destroying jobs – Just checkout http://de.wikipedia.org/wiki/Aralsee the image is kinda self explaining.
Also plaques come up from this – also geological events (Sahara winds).
Heatwaves, no clean water, plaques, war – Those problems are most likely to be solved by a prosperous economy with access to energy, and would likely be made worse by devoting excessive resources to reducing GHG emissions.
You total messing here around with diffrent events.
You also give ur personal individual few of things which is total wrong.
Your conclusion shows how much u not into renewable energy efforts – see next point.
I think this site gets spamed by paid trolls latly.
To clear ur messy statement do the following.
Point ur browser to google – than click on news – than enter “heatwave”. This brings up news from this year heatwaves which u obvisiously missed out – maybe u are 1 of the few who have no access to american television?
Again, basic chemistry is one thing, real life (or developmental and evolutionary biology) another. My purpose is not to say that acidification of oceanic water have no predictable effect, but that predictions are far less simplistic than global extinction spectra. I remind conclusion of Royal Societies rapport (2005), section 3.8 :
On the effects on calcification: It is expected that calcifying organisms will find it more difficult to produce and maintain their shells and hard structures. However, the lack of a clear understanding of the mechanisms of calcification and its metabolic or structural function means that it is difficult, at present, to reliably predict the full consequences of CO2-induced ocean acidification on the physiological and ecological fitness of calcifying organisms.
If we go back to the subject of Raypierre paper here, the problem deals with popularization of climate topics. The more alarmist you are on objectively indecise matters, the less credible you are (for these matters and also for others), because your readers suspect you are animated by a strong prejudice. As we say in French : tout ce qui est excessif est insignifiant.
The paper you cite (Pelejero 2005) does not go as far as you think it does. It discusses the response of one species of coral in one reef. It does not discount the seriousness of the acidification problem.
Comment by Joseph O'Sullivan — 15 Nov 2006 @ 12:12 PM
Re #79: Bear in mind that Pat Michaels, the author of this paper, is rather notorious for being in the pay of the U.S. coal industry. It’s rapidly becoming a better idea to simply ignore such things rather than grant them the credibility associated with a refutation.
Unsurprisingly, a quick scan of the linked document shows that he’s up to his old tricks. To list one very obvious example, at the bottom of page five he writes:
“Recently, Overpeck et al. projected a massive melting of Greenland and Antarctica’s ice sheets, resulting in a sea-level rise of 12-18 feet. This is the same sea level that occurred in the last interglacial, about 130,000 years ago. Overpeck et al. made this projection because their model for 2100 gives higher arctic temperatures than in the last interglacial; sea levels rose that much during the interglacial. Nowhere do Overpeck et al. mention that all the available models require thousands of years of warming to melt most of Greenland’s ice and that it must take even longer in Antarctica. A run of three emissions scenarios used for the next 100 years with 18 climate models yields a mean sea-level rise from Greenland of .06 inch per year around 2100. As noted above, all models project that Antarctica gains ice in a warming world.”
So what’s wrong with this statement? See this previous RC post for the details, but the upshot is that at the time Michaels wrote that passage he was well aware that leading modelers (most prominently Jim Hansen and Richard Alley) have determined that the simple melting slab view of melting that’s included in the models Michaels referenced does not reflect reality, and that the dynamic melting that has been observed in the real world will cause a far more rapid collapse of the ice.
Joseph, I agree with you, and never said acidification is not a (potentially) serious problem. Pelejero et al. did find decadal 0,1 to 0,3 pH variations in Flinders reef over the past three centuries, without noticeable modifications of growth for the concerned porites. That was just an example of a local adaptation to local variations (and a reminder of the amplitude of such variations for a south Pacific coral reef). But sure, a lowering of 0,2 to 0,4 oceanic pH over the next century will exert a strong selective pressure on calicfication species.
Re “Again, I disagree with such a pessimistic and one-sided view. As far as I know, biological modelisation of planktonic response to acidification (low. 0,1 to 0,4 pH from now to 2100) is still in its infancy. Forams and coccoliths have a rather high rate of reproduction – a not-so-bad adaptative profile – and these species have survived to many abrupt climate changes of the past million years. Preliminary lab. experiences cannot be accepted as realistic simulations : Riebesell et 2000, for example, upwarded ambient atmosphere of a coccoliths monuculture to 800 ppm CO2 in 9 days !! That’s not conclusive for real-word adaptive behavior of theses micro-organisms over the forthcoming nine decades.”
On the other hand, coral reefs are dying from acidification all over the world, and they were centers of ocean biological activity. The ocean is in danger from acidification even if natural selection will help some survivors adapt to it. Don’t forget how natural selection works — time and death.
Re “Suppose we had been observing global cooling instead of global warming. What remedies would have been proposed? “Use all the oil you can!” “Buy really fuel-inefficient cars!” “Don’t use any renewable sources of energy if you can avoid it!”
The human race has always been inclined to blame itself for whatever troubles that arise, and offerings to the gods have always been a part of the solution, may they be in form of slaughtered lambs or giant wind-powered generators. This is the main source of my personal scepticism of any theories of impending climatic doom.
And, if you live in Scandinavia, as I do, retreating glaciers are indeed an ominous sign – but advancing ones are even worse.”
Along those lines, what if we had been threatened by a Martian invasion?
There is a difference between magical thinking and drawing conclusions from empirical evidence and experiment. You are wrong to ascribe scientists’ conclusions on global warming to the former.
#84 : “On the other hand, coral reefs are dying from acidification all over the world, and they were centers of ocean biological activity.”
I disagree. Again, we should be precise in our assertion. Have a look on Royal Societey 2005 report : Acidification is NOT a past and present stress for coral reefs “all over the word” – even for cold-water corals which will be the more concerned by the phenomenon on short term (Lophelia sp. notably). Main actual threats on coral reefs are warming-induced bleaching (catastrophic El Nino 98), human pollutions in lagoons and coastal areas, parasitic invaders (algae, etc.). But acidification per se is not still a problem for reefs and the recent trend is rather clearly positive for some large-studied genus like Porites (for example Buddemeier 2004 : “Calcification rates of large heads of the massive coral Porites increased rather than decreased over the latter half of the 20th century”. On Porites : Bessat 2001, Lough 2000, etc.).It’s difficult to draw global conclusions because of the numerous factors involved in each local conditions. All the more so that even the most extensive surveys do not cover all the coral area and biodiversity. But for that I know, coral reefs do not presently die of the 0,1 pH acidification since pre-industrial times. It does not mean that a 0,4 pH centennal drop is not a serious concern for all calcifying organisms: it is ! In my sense, avoiding premature and catastrophic claims, amplifying research efforts is a the better way to deal with it – except if you have a political agenda and want to impress imaginations for rapid collective decisions. But it’s no more science.
Re #87: I think Charles is correct that the damage to coral reefs that has been seen in the last decade or so is from warming (possibly with an additional effect from acidification, but likely that would be hard to tease out of the data at this relatively early stage) , noting that the tropical seas have warmed more than the global average. It seems entirely plausible that some coral species will do a little better in water that is a bit warmer or a bit more acid, but even more plausible that it will be a different story if they are put into a temperature and acidity range that is well outside of the one in which they evolved.
In the just past issue of the New Yorker (probably still available today), Elizabeth Kolbert has a long article on ocean acidification. I wasn’t able to read the whole thing, but it appears to have a lot of up-to-date material from interviews of many of the leading researchers.
Re #87: Charles, I recall several years ago a popular hypothesis which linked some of the decline of Carribean corals to dust being transported from Africa due to drought and landuse changes there. Can you update me on whether the dust hypothesis ever caught hold?
Perhaps I missed something, but Bill Broad may have been blind-sided by gun-for-hire “scientists” (paid by the black-gold naysayers) who deride anthropogenic climate change because it interferes with business. Thus, his take may have been flavored with doubt, although that does not justify the tone of the story. Tuesdays forray into even more questionable impact “science” without sufficient skepticism or caveats (this was based on an abstract to AGU) does not bode well for readers of Science Times or policy makers who read it.
Agreed, George. That’s why I was hoping he’d come here or otherwise tell us what his sources and references were for what he wrote. The man’s been fooled before, for example he coauthored the primary “nerve gas factory” story used to rush an attack into Iraq. Oops.
[Response: I'm rather disappointed in Broad. I sent him an email pointing out this article and discussion and all I got from him was the response "Thanks for writing. Saw it." I hope he's at least reading this discussion, even if he doesn't seem to care enough to explain how he went so wrong, or even acknowledge the shortcomings of his article. --raypierre]
The farmer plants by the kind of weather he had the year before. Energy in the atmosphere increases variability. So, whether a farmer’s area is colder or warmer, wetter or drier, the extra energy in the atmosphere is going to increase the variability in weather that the farmer can expect.
Re: In reply to comment 52: “Finally despite copious referencing for other links in his [Their. The paper quoted was by Shaviv & Veizer], he gives no evidence that global cloudiness is in fact decreased during sunspot maximum and Forbrush events.”
The following paper “Empirical evidence for a nonlinear effect of galactic cosmic rays on clouds” by, R. Harrison and D. Stephenson, provides evidence that global cloudiness is in fact decreased during sunspot maximum and Forbrush events.
“During sudden transient reduction in cosmic rays (e.g. Forbush events), simultaneous decreases occur in the diffuse fraction. The diffuse radiation changes, are therefore, unambiguously due to cosmic rays. Although the statistically significant non-linear cosmic ray effect is small, it will have a considerably larger effect on longer timescale climate variation when day-to-day variability averages out.” [See note end of this comment.]
“This study has found a small yet statistically significant effect of cosmic rays on daily cloudiness that supports the global results from satellite data (Marsh & Svensmark 2000). The method used is independent of the satellite results, and uses date from different sites extending over a longer period.”
Notes & Comments:
1) Harrison and Stephensonâ??s paper discusses GCR modulation effects which are minor as the earth’s magnetic field is currently at a 100kyr maximum. In the next comment, a paper is quoted that provides evidence that the earth’s magnetic field suddenly increases on a 100kyr cycle and that this change and other observed changes in the geomagnetic field (not insolation cycles), is a trigger for glacial terminations and other major changes in the geoclimatic record. The next paper provides an explanation for the 100 kyr eccentricity paradox.
2)Note GCR modulation effects are less when the earth’s magnetic field is high and/or when the sun is at a maximum in its magnetic cycle.
The comment ” the tired old beast of Galactic Cosmic Rays (GCR) raises its hoary head…” [and] “There has been no recent trend in cosmic rays that could conceivably account for the recent warming…” discounts or perhaps completely ignores recent data and analysis that provides support for the hypothesis that GCR modulation is a first order climate forcing function.
What is the evidence that GCR modulation effects on cloud cover have had a major affect on the earth’s climate in the past? How will GCR modulation affect climate in the future?
The paper “The Glacial Cycles and Cosmic Rays” by J.Kirkby, A. Mangini, and R. Muller (2004) examines changes in the geomagnetic field, that are concurrent with major planetary temperature changes. Due to GCR modulation effects on clouds, it is hypothesized that a stronger geomagnetic field results in warmer temperatures and a weaker field, colder temperatures. The authors examine deep sea sediments and find as have others that the geomagnetic field peaks at 100 kyr intervals. Further the authors find at termination II (Warming that led to the Eimen interglacial) that the records show that the warming started when insolation was at a minimum. They also find that the termination II warming and other warming events coincide with periodic geomagnetic field maximums.
“In this paper we propose the glacial cycles, rather than being driven by insolation cycles as in the present standard model, are initially driven by cosmic ray changes, probably through their effects on clouds.”
“Recent measurements suggest that long-term records of variation of Earth’s magnetic field – in both strength and magnetic inclination – show orbital frequencies -… The 800 kyr record known as Sint-800 is reported to show no such cycles; however we will present a new analysis here that shows such cycles are in fact present in this record.”
“We present a new spectral analysis of cosmic ray flux recorded in the BE10 content of deep ocean sediments, which shows the present of orbital cycles. Further we present additional results based on the BE10 record and on precisely-dated speleothems that reinforce the causality problem with the Milankovitch model and support our conclusion that cosmic rays appear to be driving the glacial cycles.”
“The worst fault of the article, though, is that it leaves the reader with the impression that there is something in the deep time Phanerozoic climate record that fundamentally challenges the physics linking planetary temperature to CO2. This is utterly false, and deeply misleading.”
Well statistically CO2 is linked to planetary temperature more as an effect not substantially as a cause. So this is a very strange thing to say.
[Response: This is garbage. Where are you getting your information? So tell me your brilliant theory explaining how the high CO2 in the atmosphere of Venus today is a consequence of some other factor which is maintaining the high Venus temperature. Publish it and you'll be an instant scientific superstar. Your comments seem to be just trolling rather than any earnest attempt at contributing to the discussion, and there are limits to how long you'll be allowed to just post noise. --raypierre]
Hi, raypierre. Instead of commenting on a single throw-away statement, I would rather get an opinion on the two papers referenced by William Astley. Reading them, I get the impression of a far greater correlation of cosmic radiation and climate than I had been led to believe. The suggestion that glacial cycles are driven by the inclination of the Earth’s orbit around the sun rather than eccentricity is interesting. Is it a coincidence they both have the same period? And all three glacial cycles show up in the ice age record, and eccentricity amplifies some of these cycles, so I have a hard time dispensing with eccentricity.
However, I do not see how much relevance this has to the present climate. The shortest cycle they identify is 100 Ky. And I would like to know just how large this “small but statistically significant” effect is in meaningful units such as watts per square meter.
#87 Bryan, I suppose you refer to Shinn and Griffin hypothesis (transport of pathogens from African dust to Carribean corals). Sorry, I’ve no particular information about these reefs, which are threatened by a lot of factors (including diseases, but also hurricanes, overfishing and pollution). The most recent publication I find around the African dust hypothesis is
Weir-Brush, J.R., V.H. Garrison, G.W. Smith and E.A. Shinn. 2004. The relationship between Gorgonian coral (Cnidaria: Gorgonacea) diseases and African dust storms. Aerobiologia 20: 119-126
Comment by Charles Muller — 19 Nov 2006 @ 10:07 PM
Let me second the call for Raypierre to do something more than pounce on the #96 post that carelessly used the word planetary when probably Earth was intended.
I’ve never seen a convincing explanation of how temperatures can begin decreasing when CO2 levels are high as they are at the end of each interglacial. Or, is it that for some reason CO2 levels begin decreasing on their own and that is what brings down temperatures â�� some unknown, mysterious regulator of CO2?
About the inclination theory, the inclination of the Earth’s orbit around the Sun has changed over a 100k year cycle for the last million years or so. When there is less inclination, the Earth is cooler. When there is more inclination, the Earth is warmer. Is this just an odd coincidence or is there some link between Earth’s temperature and the inclination. Muller originally proposed that there might be space dust in the orbital plane that came into the atmosphere to cool the planet during times of low inclination. That theory so far hasn’t panned out. So this GCR connection is a second attempt to find a link.
The relevance to the present is that our orbital inclination has been declining since around the start of the Holocene.
Re #97, Blair Dowden, and #99, Jim Cross — I believe these topics have been rather thoroughly gone over on at least two previous threads. I recommend finding and reading those.
Comment by David B. Benson — 20 Nov 2006 @ 7:13 PM
I’ve seen a lot about how astronomical influences cause warming which triggers CO2 release from the oceans and increasing green space, but little or nothing about how cooling occurs in the presense of high CO2. The warming side is plausible but what about the cooling side? Yes, the oceans can start to absorb CO2 when they cool but doesn’t that only happen after the cooling starts? So, let me repeat, how does the cooling start?
Bryan Sralla (#89) here is a good site on the dust hypothesis http://coastal.er.usgs.gov/african_dust/index.html
The corals reefs in the Caribbean are deteriorating. The researchers see correlation between high dust deposits and coral death and are looking for causation.
Re “When there is less inclination, the Earth is cooler. When there is more inclination, the Earth is warmer. Is this just an odd coincidence or is there some link between Earth’s temperature and the inclination.”
Inclination by itself does nothing at all to the average temperature of the Earth, because the insolation remains exactly the same on average — Earth is still a sphere and the Solar constant doesn’t change. Changes in inclination can cool or warm the Earth when continents and oceans are differently angled to the Sun, however, something which depends purely on the arrangement of things on Earth’s surface. There is an inclination signal in Earth’s climate history, but it appears to be an extremely minor one. What would amplify that tiny forcing? (Not necessarily a rhetorical question.)
I’m not sure I completely followed everything in the paper, but it seems to be a variation of the standard Milankovitch explanation that uses a convenient, periodic skipping of one of two or two of three of the 40k cycles to arrive at the 100k cycle of deglaciation in the late Pleistocene.
As an observer becoming deeply interested in climate change, I have just begun reading some of the excellent material in RealClimate.
I recently entered into e-mail correspondence with David Smith (a well-regarded business journalist for Sunday Times, UK) chiding him gently for taking up a rather sceptical position on climate change without having any real grasp of the fundamentals. I think I made him realise how much industry lobbying and ‘cuckoo science’ is muddying the waters. Smith quoted a recent lecture by Lord Lawson, to which I replied ‘same old canards’! It is most important to have reliable sources and also people who can publicly counter the dross.
On a specific point relating to comment 101, I recently came across William Ruddiman’s paper ‘Ice-Driven CO2 Feedback on Ice Volume’- Feb 2006, which I thought highly pertinent to this discussion. Would any expert care to comment? http://www.climate-of-the-past.net/cpd/2/43/
In the News & Views article “Global change: Plankton cooled a greenhouse” by Birger Schmitz (Nature 407,
143-144; 2000), the period of “superwarm” conditions at the Palaeocene/Eocene boundary should have been cited
as lasting about 60,000 (not 150,000) years. Proof corrections made to the paper concerned (by S. Bains et al. 407,
171-174; 2000) were not passed on to the News & Views author.
Google Scholar will find more on how the planet has responded after previous rapid increases in CO2, although “rapid” in prehistory is extremely slow compared to the current rate of CO2 increase. So just because nature handled the natural CO2 extremes doesn’t serve as assurance that nature can respond 10x or 100x faster to handle human activity.
Abrupt climate change: evidence, mechanisms and implications
File Format: PDF
Glacial integrative modelling. 12.00 Discussion. 12.15 Dr Hugh Jenkyns. University of Oxford. Evidence for rapid climate change. during the Jurassic and … http://www.rmets.org/pdf/Programme.pdf
“… ocean has absorbed about one-third of the CO2 released from all human activities (emissions from fossil fuels, cement manufacturing, and land-use changes) from 1800 to 1994 (Sabine et al., 2004).
“Over the next few millennia, the ocean is predicted to absorb approximately 90 percent of the CO2 emitted to the atmosphere, after atmospheric CO2 concentrations are stabilized. In the geologic past, the ocean has experienced periods of large fluctuations in ocean chemistry and circulation that undoubtedly led to alterations in ocean ecosystems, but the concern today is that the current rate of warming and acidification is probably much faster than experienced in the past, perhaps too fast for ecosystems to adapt to the changes.
“Changes in the ocean’s pH are already affecting the calcium carbonate system in the ocean (Feely et al., 2004), which is shown by expansion of areas of undersaturation of calcite and aragonite in the global ocean. Such undersaturation will potentially have a serious impact on marine organisms…..”
Re #105: It is very much convenient in the sense that explaining the shift in glacial cycle length (the mid-Pleistocene transition) has been the fundamental problem in attributing the glacial cycles to orbital variations. Huybers appears to have nailed it (although I’m not sure this is universally accepted as yet). The remaining problem is to figure out the exact feedback mechanism by which the relatively subtle orbital forcings (too weak to drive the glacial transitions directly) result in the observed climate shifts.
Thanks, Hank. It seems most of those papers, except the last, seem to be dealing with extreme anoxic events on the Palaeocene-Eocene boundary. Admittedly, that may be where we are headed, but I would still put the odds of it to be rather slim.
I’m looking for something more relevant to the Pleistocene era and the rather routine, albeit slow, dropping of CO2 levels at the end of the interglacials. Maybe I’m making too big a deal of this. My understanding is that as the ocean cools it can absorb more CO2 and that is one of the main reasons that CO2 levels drop at the end of the interglacials. My problem, however, is understanding how the cooling starts when the CO2 levels are high. Wouldn’t the high CO2 level, by itself, prevent cooling unless there was a rather large reduction in solar radiation?
“Inclination by itself does nothing at all to the average temperature of the Earth, because the insolation remains exactly the same on average — Earth is still a sphere and the Solar constant doesn’t change.”
So the theory goes. Nevertheless, the Pleistocene ice age cycles do seem to parallel the inclination of the Earth’s orbit. My point was: “Is this a coincidence?” I doubt if it is a coincidence but I’m not sold on the GCR theory yet.
RE: #110 – There is a theory, railed against  by many who frequent RC, that the closure of the Isthmus of Panama set into motion new oceanic modes of oscillation (we’re talking very long period ones, way longer than anything like the PDO or the more controversial / debated AMO). Who’s to say that the glacial – interglacial back and forth is not a very long wave oscillation at its heart, which does not in any way depend on the Sun, inclination, wobble, volcanoes / aerosols, etc?
[Response: Anybody who has a clue I would imagine. You need a part of the system to have a memory that is long enough to encompass your putative internal oscillations. Certainly the ocean circulation is not sufficient (a couple of thousand years maybe), neither is the carbon cycle (a few thousand years), ice sheets might approach it, but why those oscillations would be precisely timed to the orbtial forcing would appear to be fatal problem with your theory. - gavin]
Re #111: Since all three influence climate, it’s necessary to take into account the combined effect. In any case, current thinking seems to be that we are now in for a very long inter-glacial due to the CO2 we have already added to the climate system.
Re #110: Jim, I think the straightforward explanation for how the cooling begins is simply that the orbital cycles combine to reduce insolation, and feedbacks take over from there. If you look at some of those other Huybers papers you should also find a discussion of the uneven response to insolation of the northern and southern hemispheres, which is why the role of obliquity is so important.
Also, I think there may be some confusion about obliquity vs. inclination. The former is the tilt of the axis relative to the orbital plane while the latter refers to changes in the Earth’s orbital plane relative to the ecliptic. If I understand it correctly inclination is considered unimportant compared to the other three Milankovitch orbital cycles (I assume because it has little variance or because the variance doesn’t have much effect) and so is hardly ever mentioned.
BTW, while apparently there are yet two other orbital parameters (for a total of six), the other two are not deemd to be Milankovitch cycles since they have no effect on climate. Since I understand that even mentioning these two parameters always results in an argument, that’s enough said about them.
Re #113: Just to add to Gavin’s point, I have never seen anyone proposing such a theory, and for sure I’ve never noticed anyone “railing” against it on RC or anywhere. I have seen a perfectly reasonable statement of the hypothesis that the isthmus closure changed ocean currents in a manner that played a significant role in the transition from the Eocene to the present colder climate regime (noting the absence of a long-term oscillation component along the lines you describe), but why in the world would anyone rail against such an idea?
Actually, Steve, the more I thought about my own question the more I began to think about it as you suggest. So maybe I was making too big a deal of it anyway.
It seems that it is almost certain that astronomical events/cycles are driving long term climate change, even though we humans temporarily (I mean in a geological sense) may be overriding and/or augmenting the longer term astronomical cycles. So to answer my own cooling question, at some point, even the high CO2 levels that are in the atmosphere at the end of each interglacial cannot compensate for the insolation changes and other feedback.
I am aware of the difference between obliquity and inclination. I understand that inclination changes would not affect the amount or pattern of solar radiation reaching Earth, whereas obliquity and eccentricity would. Nevertheless, I find some of Muller’s papers intriguing. Here’s a link that has links to a lot of his articles:
There is also a link to a movie of the four inner planets motions over the last 3 million years.
So I still suspect that inclination is somehow involved in longer term climate changes simply because it lines up so well with the glacial cycles. There is not just not a clear causal connection that is apparent between the two.
Have you looked at citebase or Google Scholar to see if his ideas have had legs? It’s been a while. Note the timestamp on his “what Greenland looks like today” illustration; I wonder if that view is any different now? http://muller.lbl.gov/photos/greenland.gif 06-Oct-1997 14:18 381k
Re #s 116/7: A quick look at Muller’s main page seems to support Hank’s supposition. I also found this more recent paper co-authored by Muller that supports obliquity as the dominant factor and doesn’t even mention inclination. As there has been a very large amount of published activity in this field over the last ten years, the apparent absence of follow-on research relating to inclination and the concomitant presence of papers focused on obliquity (and not just by Huybers and his co-authors) as the dominant cycle would seem to tell the tale. Some time with Google Scholar might turn up a review paper from circa five years ago that makes mention of the abandonment of the inclination hypothesis, but in my limited experience with these things very often the only indication of abandonment is a halt to the papers and citations thereof.
I should add that whenever I spot an interesting older paper I make a practice of checking through Google Scholar first before posting about it. It saves everyone’s time and minimizes confusion.
Re #115: Steve, the papers referenced by William Astley in #94 and #95 (eg. this) make the case that orbital inclination affects cosmic ray flux, which affects climate. Further, contrary to what has been said here on RealClimate, they claim there is a “small but statistically significant” correlation between cosmic rays and climate. They do not say cosmic rays explain most of the warming in the past few decades, in fact they do not tell us the magnitude of the effect.
If there is a problem with what these papers are saying, I would like to know what it is.
The 100kyr change in the earth’s orbital inclination is hypothesized to result in a 100kyr periodic significant increase in the earth’s magnetic field. A significantly stronger geomagnetic field would reduce the Galactic Cosmic Ray (GCR) flux.
The following is a link to Yamazaki and Oda’s Paper “Orbital Influence on Earth’s Magnetic Field: 100,000 – Year Periodicity in Inclination” (Comment Yamazaki and Oda estimated field strength by measuring magnetic field inclination.)
“A continuous record of inclination and intensity of the Earth’s magnetic field during the past 2.25 million years, … reveals the presence of the 100,000 year periodicity in inclination and intensity. … we propose a model in which the strength of the geocentric axial dipole field varies with 100,000 year periodicity, …”
Yamazaki and Oda do not provide a physical explanation for the observed periodic changes in the geomagnetic field, however, using the following hint from their paper and information from another paper (see below) a straw man hypothesis can be created.
Also from their paper “secular variations with periodicities longer than the electric diffusion time of the core, which is considered to be about 10,000 years may indicate the presence of external energy sources”. The external energy source could possible be Coronal Mass Ejections or particle acceleration due to magnetic field reconnection (connection of the sun’s magnetic field to the earth’s which accellerates particles.) The sun is more active at higher latitudes. The earth would be exposed to higher latitude areas of the sun when its orbit is inclined.
A 100kyr cyclic change in the earth’s magnetic field due to orbital inclination and the subsequent reduction in GCR due to a stronger geomagnetic field is a possible explanation for the 100 kyr eccentricity paradox which is discussed in the next paper.
In Muller and MacDonald’s paper “Spectrum of 100-kyr glacial cycle: Orbital Inclination, not eccentricity” they note the interglacial breaks appear at 100-kyr intervals while the orbital eccentricity has a 95kyr and 125 kyr cycle which is a paradox. Also they note insolation changes associated with orbital eccentricity is not sufficient to explain the dramatic warming that ends the glacial period. That is particularly true with the current interglacial as the orbital eccentricity was at at a minimum as compared to other cycles.
Muller and MacDonald, in their paper, hypothesize that galactic dust might cause the climatic change. That hypothesis appears to not be correct. The 100kyr cyclic geomagnetic field which in turn modulates GCR is a possible physical explanation of the paradox.
The second orbital paradox is discussed in the following paper by Maureen Raymo
“The 41 kyr world: Milankovich’s other unsolved mystery”
In this paper Raymo notes that the glacial cycles should be affected by precission in addition to obliquity. In addition, Raymo notes the macroclimate is warmest when the obliquity is the greatest, which is contrary to standard insolation explanation of the glacial cycles. Raymo does not have a solution for the noted paradoxes.
A possible hypothesis to explain this observation would be that the sun periodically interacts with the earth (an interaction with a periodicity of less than 10,000 years) which creates or maintains the geomagnetic dipole field. A higher obliquity it is hypothesized would result in a stronger geomagnetic field and visa versa. This 41kyr cycle in the geomagnetic field strength is also observed, however, there is currently no physical explanation of why the field is varying periodically.
Comment by William Astley — 25 Nov 2006 @ 11:11 PM
From the criticism of Broadly’s Article:
“Current climate models do not reproduce the weak pole to equator gradient believed to characterize these climates” (paleo- warm climates)
The current climatic models also cannot reproduce the climate from 3 million years ago to 780,000 years ago when the climate followed a 41 kyr cycle as opposed to the current cycle – 100 kyr saw tooth.
From Maureen Raymo and Kerim Nisanioglu’s 2003 paper “The 41 kyr world: Milankovitch’s other unsolved mystery”
“While many investigates have attempted to model the 100 kyr world few have … A notable exception is Andre Berger … who used a two-dimensional model to try to simulate the growth and decay of ice sheets over the last 3 million years. (Berger et al. 1999), While the obiquity period is present in the model output, precissional variance in ice sheet mass is also stongly present. In other words, although they successful model the lack of the 100 kyr eccentricity cycle, they were not able to model an sheet that varies only at the obliquity frequency.” (i.e. 41kyr)
Does that indicate that the current climate models are not correct? What would be the consequent if the current models missed a key macroclimate forcing function?
See comment #120 for details concerning the 41kyr and 100 kyr Paradox.
See comment #95 that references the paper “The Glacial Cycles and Cosmic Rays” by Kirby, Mangani and Muller, that proposes that the cosmic ray fux modulated by changes in the earth’s magnetic field and solar changes initiates the main phases of the glacial cycle, in addition to the multitude of semi-periodic rapid change events, rather than insolation changes.
Another good paper on GCR is “On climate response to changes in the cosmic ray flux and radiative budget” Published 2005 by the Israel physicist Nir Shaviv.
“We examine the results linking cosmic ray flux (CRF) variations to global climate change. …then proceed to study various periods over which there are estimates for radiative forcing, temperature change and CRF variations relative to today. These include the Phanerozoic as a whole, the Cretaceous, the Eocene, the Last Glacial Maximum, the 20th century, as well as the 11 year cycle…
Subject to the above caveats and those described in the text, the CRF/climate link therefore implies that the increased solar luminosity and reduced CRF over the previous century should have contributed a warming of 0.47 +/-0.19C, while the rest should be mainly attributed to anthropogenic causes. Without any effect of cosmic rays, the increase in solar luminosity would correspond to an increased temperature 0.16C +/-C.”