‘The Discovery of Global Warming’ update
If you haven't already seen the American Institute of Physics website by Spencer Weart on the 'The Discovery of Global Warming', we heartily recommend it. It provides both a summary of science, and more importantly, a history of how an obscure speculation from over one hundred years ago has become the scientific consensus of today. It has recently been updated with many more references from 1873 to the present, and so is even more worth reading. Spencer is very keen on getting feedback on the project, so don't hesitate to let him know what you think.
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Climate
14 July 2006 at 12:53 PM
Great link, which is sort of deep in the AIP website. Would not have found it otherwise, thanks for that!
14 July 2006 at 1:11 PM
I know it’s off-topic, but what are RC’s views on the newly-published Wegman, Scott and Said report (highlighted on Climate Audit, not surprisingly)?
[Response: This is probably an unavoidable off-topic, so I’ll paste in the text of Mann’s released comment on the issue, but I’m actually pretty bored of this subject by now, and I think most everyone else is too. - gavin]
14 July 2006 at 2:09 PM
Best advice is: when you’re in hole, stop digging.
14 July 2006 at 3:21 PM
Are we giving up on orbital variations then? Is CO2 the main culprit as this appears to say? Then what has caused these many cyclical and periodic rizes and declines in CO2 gas then? Are there any answers put forward? Not just the current one but the past dozens of cycles.
Among these feedbacks, the most obvious and momentous was the close connection between global temperature and greenhouse gas levels through the ice age cycles. Relatively straightforward analysis of the data showed that a doubled level of CO2 had always gone along with a rise of a few degrees in global temperature. It was a striking verification, with entirely independent methods and data, of what computer models had been predicting for the planetâ??s greenhouse future
http://www.aip.org/history/climate/cycles.htm
14 July 2006 at 4:21 PM
Lars, did you fully read that section of the book? Nobody’s giving up on orbital changes which may have led to increases in CO2 in the past.
Why do you assume that the causes of the present warming and previous warmings are identical when humans have only been burning massive amounts of fossil fuels for the last century and a bit?
14 July 2006 at 5:05 PM
With reference to Dr Mann’s dismissive reply to a careful report composed of real statisticians (of which he is not one, having said so to the NAS Panel), I’ll bring up just one misrepresentation out of the many: What Wegman et al actually said was
So far from complaining about too much reliance on peer review, Wegman was pointing out that the peer review was done between a small coterie of the author’s friends who had also staked their scientific reputations on similar results in studies that had lots of the same non-independent proxies.
[Response: Hmmm… So Wegman had access to all the peer reviews and who did them for all of the relevant studies then did he? I don’t think so. He just looked at co-authorship - which is not the same thing at all. Statements about who the peer reviewers were are just speculative with no actual facts to back them up. - gavin]
14 July 2006 at 5:46 PM
Lars, did you happen to read these pages?
Try the button on Weart’s main page labeled “Search”
I used that Search for words from your question; try searching, you ought to be led among others to these:
http://www.aip.org/history/climate/solar.htm#M_58_
http://www.aip.org/history/climate/solar.htm#L_0304
http://www.aip.org/history/climate/xsolar.htm
14 July 2006 at 6:15 PM
So Gavin, are you confirming that neither you, nor the 41 others mentioned in the “mutual admiration society” mentioned by Wegman performed peer review on each others key studies that backed AGW?
[Response: What is your point? First, how can I (or Wegman) possibly know who any paper’s anonymous reviewers are if I didn’t review it? Second, what part of ‘anonymous’ don’t you understand? and finally, where can I join this ‘mutual admiration society’? Wegman doesn’t mention it all, and certainly doesn’t give a contact number…- gavin]
14 July 2006 at 7:13 PM
Why are people not just naive, but badly mistaken about how science is done?
Because much about global warming is being written by PR firms. This PR expert got sick of it:
http://www.desmogblog.com/slamming-the-climate-skeptic-scam
“… it is infuriating - as a public relations professional - to watch my colleagues use their skills, their training and their considerable intellect to poison the international debate on climate change.
“… On one hand, you have the report of the Intergovernmental Panel on Climate Change, the largest and most rigorously peer-reviewed scientific consensus in history….
“On the other hand, you have an ongoing public debate - not about how to respond, but about whether we should bother, about whether climate change is even a scientific certainty.
“Few PR offences have been so obvious, so successful and so despicable as the attack on the scientific certainty of climate change.
“This is a triumph of disinformation.”
14 July 2006 at 7:25 PM
What will your response be? The statement by Mann doesn’t address any of the issues raised in the Wegman Report. Unfortunately the battle has now moved to the statisticians’ turf and you guys are going to have to fight on their terms. Are your methods valid? If they aren’t, we have big problems.
[Response: I don’t see how the ‘battle’ has moved at all. There is nothing original in the Wegman report except the neat, but basically meangingless, social network stuff (I’m in a clique!), and so the scientific discussion hasn’t moved on one iota. In particular, Wegman completely fails to address the issue of whether any of these critiques ‘matter’ - which was the point of the earliest responses on this topic, here or in Rutherford et al, 2005, Wahl and Ammann (2006), or the NAS report etc. The answer was, and remains, no they don’t. They could have, but they didn’t. Them’s the breaks….- gavin]
14 July 2006 at 8:04 PM
As if top climate scientists aren’t trained in statistics as much as a couple of “social scientists.” What a foolish assertion on its face.
14 July 2006 at 8:16 PM
Re: response to #10
Gavin, you say “There is nothing original in the Wegman report except the neat, but basically meangingless, social network stuff… ”
Isn’t the important issue whether the report is *correct*, not whether or not it is “original”?
[Response: If there is nothing new, how can it take the debate forward? If Wegman, ‘with [McIntyre’s] assistance’, can get McIntyre’s code to work, but doesn’t then bother to see what difference it makes to the final reconstruction (which we know is tiny - Wahl and Ammann (2006)), what has been added? - gavin]
14 July 2006 at 8:32 PM
Gavin,
I’ve read the Wegman report. The social network stuff is padding.
I’m printing out the “Dummies Guide” now to see if it addresses the issues that Wegman raised.
It will be vacation reading along with the Wegman report.
I’ll get back to you in about ten days.
Thank you for your patience.
Rhett
14 July 2006 at 9:28 PM
They’re trying to attack that work the way the creationists attack “Darwinism” — the fundie notion that if you can dethrone the Founding Father you devalue all that follows.
They’re treating early scientific work as though it were a foundation document on which everything that follows has to be based.
Reading Spencer Weart’s history should disabuse the ’skeptics’ of the notion — would y’all please read the first link, and come talk about the origins of the study of global warming?
In science early work gets attention into an area — but what people do when they study science in the area depends scarcely at all on the original work having been precise or even properly interpreted. It’s the next work and the work after that that matter.
Each new study looks at the underlying natural world and corrects what came earlier.
There’s no founding father here to overthrow.
Look up “Darwinist” to see the foolishness that comes from thinking that attacking early work is a sane way to evaluate later work, eh?
14 July 2006 at 9:34 PM
RE 9 (Roberts):
Hank, here is a film clip of Luntz repudiating his prior stance on his AGW campaign.
Hopefully back OT, the AIP website is indeed a treasure and IMHO there should be a link on the homepage or FAQ or somewhere like that.
Best,
D
14 July 2006 at 10:25 PM
Long term time series measurements like this one deserve a place in the AIP document (if you have them, I didn’t find them searching).
http://www.fou.uib.no/fd/1997/f/406001/IMG00004.GIF
“Smoothed monthly mean temperatures for the 3 deepest standard depths (1200m, 1500m, 2000m) are shown in Figure 4 for the period 1948-1995. Notice that a recent warming has occurred, starting at 2000m in 1985, then gradually penetrating upwards through 1500m in 1987 and reaching the 1200m level in 1990. The temperature increase is about 0.07°C, and nearly constant with depth.”
The main page is: http://www.fou.uib.no/fd/1997/f/406001/
It begins:
“Having performed daily oceanographic measurements in the deep Norwegian Sea since 1 October 1948, Ocean Weather Ship Station (OWS) Mike, at 66N,02E, can present the longest existing homogeneous time series from the deep ocean. …”
Note this is not a statistical model; this is temperature.
15 July 2006 at 12:26 AM
I have already know that the reason why china is poor in the science field.
In china,there are few of science blogs,few of science magzines and few of science chairs.Our science education is not universal.
we can’t combine the science research with the common people.
your country,has done very well.
15 July 2006 at 3:02 AM
The social network analysis section of the WSS report is absolutely fascinating.
I would love to see such an analysis for a typical congressman, for example, Barton.
15 July 2006 at 4:05 AM
Re #10 response: Gavin, you forgot to mention the other sort-of original part of the Wegman recommendations, which is to employ a lot more statisticians in climate science research.
[Response:I have yet to see any evidence for the implicit assertion that statistitians bring forth the true answers whereas other scientists don’t. My guess is that there are clever statisticians as well as poor statisticians - probably as in other disciplines. There are as far as I know a number of statisticians involved in climate research already, and they bring in benefitial new aspects to the analysis, but physicists are just as important (if not more) for advancing the climate science. I sounds as if Wegman has some naive idea are some kind of magicians who can bring out the right numbers (?). -rasmus]
15 July 2006 at 6:21 AM
It’s possible I’ve missed it — in which case please ignore this comment — but I don’t see a reference to “the other CO2 problem”, ocean acidification, in Spencer Weart’s very useful study. If there is none, then I suggest you consider including one in a future revision. Further references can be found in the wikipedia entry - including to The Royal Society report last summer, and the NSF NOAA USGS workshop report by J A Kleypas et al published at the beginning of this month.
15 July 2006 at 10:07 AM
#12:
“[Response: If there is nothing new, how can it take the debate forward? If Wegman, ‘with [McIntyre’s] assistance’, can get McIntyre’s code to work, but doesn’t then bother to see what difference it makes to the final reconstruction (which we know is tiny - Wahl and Ammann (2006)), what has been added? - gavin]”
The Wegman Report (page 49) says:
“As mentioned earlier in our background section, tree ring proxies are typically calibrated to remove low frequency variations. The cycle of Medieval Warm Period and Little Ice Age that was widely recognized in 1990 has disappeared from the MBH98/99 analyses, thus making possible the hottest decade/hottest year claim. However, the methodology of MBH98/99 suppresses this low frequency information. The paucity of data in the more remote past makes the hottest-in-a-millenium claims essentially unverifiable.”
On page 14, the Report elaborates on this point:
“Wider rings are frequently produced during the early life of a tree. Thus the tree rings frequently contain a low frequency signal that is unrelated to climate or, at least, confounded with climatic effects such as temparature. In order to use tree rings as a temperature signal successfully, this low frequency component must be removed. … Because the early history of tree rings confounds climatic signal with low frequency specimen specific signal, tree rings are not usually effective for accurately determining low frequecny, longer-term effect. … Thus tree ring proxy data alone is not sufficient to determine past climate variables.”
This sounds like an important issue. Did Wahl and Ammann (2006) address this issue? Has anyone?
Thanks.
[Response: Yes. The whole point of Esper et al was to demonstrate that tree ring composites can have low frequency variability. The whole point of the MBH approach was to use multiple proxies that would bring together information from different archives and hopefully compensate for the different weakness in each separate archive. However, the first paragraph you quote is very poor in its understanding - the IPCC 1990 graphic was a schematic, not a reconstruction, and the understanding that the medieval climate anomaly was not as coherent in time or space than the 20th Century change had begun well before MBH - and was most recently demonstrated in D’Arrigo et al and Osborne and Briffa. - gavin]
15 July 2006 at 10:23 AM
Re #17,
Hank,
How do you explain the cooling trend 1955/1960 until 1985/1990(!) in the deeper North Atlantic (or worldwide in all oceans down to 700 m for 1980-1990 according to fig. 1 in Levitus e.a.) in a world with increasing GHGs and stabilising aerosols (SO2 emissions are stable since 1975, be it with a huge shift from North America and Europe to SE Asia). IMHO there is something like natural variability at work (changes in cloud cover - not directly linked to any forcing - come into mind)…
15 July 2006 at 11:08 AM
To compound the paranoia, I wonder if it would be fruitful to do a cohort analysis of the people who keep harping on Mann, et. al.
I am sure lots can be said about the details of climate reconstruction for the past millenium or two. And any statistician who is willing to learn enough about climate science to contribute should try his or her hand by the usual methods, submitting work to established scientific journals. I think it is clear that scientists sometimes get the statistics wrong, but it is also true that statisticians sometimes get the science wrong and misinterpret what they think the statistics are saying. But I find it very hard to believe that the NAS is unreliable in such matters. While not accepting everything that Mann, et. al. concluded, the NAS committee did accept their main conclusions and also pointed out that these conclusions have been confirmed by multiple other studies. They are also consistent with other independent threads of evidence.
Conservatives, in particular, who often object to sociallly constructed definitions of truth, should be wary of those who think they can and should skew the debate by choosing their authorities with a desired end in mind.
I haven’t yet read everything in Spencer Weart’s compendium, but the history makes clear how science in an area like climatology progresses. It is a long complex process with many false starts, but at a certain point, a general consensus on certain basics becomes established. Later, details of this consensus may be modified, but the basic conclusions remain the same. I think the preponderance of evidence shows that the late 20th century warming is unprecedented and human contribution through greenhouse gas emissions is a primary cause. If you set the entire American Statitistical Association to work on the subject, you wouldn’t change that.
15 July 2006 at 11:16 AM
I am quite reluctant to weigh in into the HS debate, as I am interested in the science, not the politics around it (I was heavily involved in politics, and had my fair share of beaten by police sticks, water guns and tear gas, but that is not relevant here).
I must admit that I was shocked the first time that I saw the HS, as that was against all knowledge that I had about a MWP and a LIA at that time. Of course, if there is new scientific evidence, that should be used, but there was little explanation about what that evidence might have been. So I was quite skeptic about the HS from the first moment on (not about (A)GW, be it that the (A) IMHO has less influence than said in many horror stories). Thus that makes that I have some bias against HS curves…
After the NAS report and now the Wegman report, it is clear that neither the choice of some tree series, nor the statistical methods used in MBH98/99 were appropriate. That has nothing to do with personal attacks, but with using only proxies which show a real correlation with temperature and using the right statistical methods.
Are the more recent reconstructions (using RegEM) better? I don’t know, but I like to see the comments by a statistician outside the field to give his/hers opinion. Anyway, many of the more recent reconstructions still use the tree series, in one form or another, which are rejected by the NAS panel.
Is this all relevant? Yes and no. It is not relevant for the reality of (A)GW. But it is highly relevant for knowing how large natural variability in the pre-industrial past was, as that gives a clue to what the future may bring. Past variability makes the difference between a disaster (if MBH98/99 was right) and a benign warming (if Moberg is right. Although Moberg also used the tree series in question, his method downplayed their influence).
So let the climate community admit that the HS has problems, that the recent reconstructions are not much better, and move on to look for better methods and better proxies to find out what really happened in the past thousand(s) years…
15 July 2006 at 12:23 PM
Re 18,22 etc. (social networks)
You can do your own analysis using Touchgraph Googlebrowser. I posted some static analyses here a while back.
15 July 2006 at 1:03 PM
Ha! New Hope (whois still shows their old name and owner) now also shows up in the Internet FAQ on the very short list of Internet “Weather Services” providers.
Now this exemplifies a lobbying firm at its best, eh? — the Western Coal Association’s advocacy PR firm listed in the Internet FAQ along with NOAA, umich.edu and wunderground as a reliable source for weather-related information.
Here’s the entire category - Weather Services:
http://www.faqs.org/ftp/pub/pub/faqs/internet-services/list
telnet downwind.sprl.umich.edu 3000 or 141.212.196.177
http://www.weather.net/ [Freese-Notis Weather Page] offers: InterRAD/RainRAD + Commodities trade reports with weather
http://www.awc-kc.noaa.gov/spc/ [Storm Prediciton]
http://www.mit.edu:8001/usa.html [WWW Weather Map]
http://www.geopages.com/RodeoDrive/1089/index.html
http://cirrus.sprl.umich.edu/wxnet/ [WeatherNet]
http://www.nhes.com/ [World Climate Report] < =======(!)
http://ferret.wrc.noaa.gov/ferret/main-menu.html
http://www.wunderground.com/ [Weather Underground, Inc] offers: Live access to climate data
>(Note this FAQ does include ‘WWW weather’ as weather, and misspell ‘prediction’ — so as usual with the Internet, not all’s clear.
15 July 2006 at 3:52 PM
>17, 21
You ask how I explain the results in Levitus et al. Why ask me? Their conclusions appear at the end of the paper you link to.
“In terms of the causes of the increase in ocean heat content we believe that the long-term trend as seen in these records is due to the increase of greenhouse gases in the Earthâ��s atmosphere [Levitus et al., 2001]. In fact, estimates of the net radiative forcing of the Earth system [Hansen et al., 1997] suggest the possibility that we may be underestimating ocean warming. This is possible since we do not have complete data coverage for the world ocean. However, the large decrease in ocean heat content starting around 1980 suggests that internal variability of the Earth system significantly affects Earthâ��s heat balance on decadal time-scales.”
15 July 2006 at 4:05 PM
Re #21: Broadly speaking, why would one expect ocean warming to be even? That it is uneven is no surprise since warming occurs near the surface and ocean water is moved around via currents that are themselves uneven. Regarding the North Atlantic, why wouldn’t we expect the relatively slow movement of the deeper currents to result in a significant lag between surface warming (or the relative lack thereof due to aerosols) and warming at depth? Your cloud ideas remain highly speculative.
15 July 2006 at 5:01 PM
Spencer -
I read and enjoyed your book as the first in a series of personal updates on AGw. I also visit the AIP site on occasion. Thanks for the continuing effort. The search feature is very useful, as here. I notice there is a category called ‘events since 1998′ on the menu. Is there also one summarizing major findings or papers since the book’s publication?
.
Thanks,
John Althauser
Urbana, IL
15 July 2006 at 5:17 PM
Re my #28: The reference was to what is now #22 (FE). Speaking of clouds, it appears that a major part of the prior uncertainty (is that what you mean by “natural variability”?) has now been resolved: http://www.nasa.gov/vision/earth/environment/pollution_clouds.html .
Re #24 (FE): “Past variability makes the difference between a disaster (if MBH98/99 was right) and a benign warming (if Moberg is right. Although Moberg also used the tree series in question, his method downplayed their influence).” Ferdinand, you know that this is wrong and why it’s wrong. It’s become an article of faith among denialists because without it they are left with nothing to argue from. If you want to prove it’s right, point me to where differences in paleo reconstructions have been used to adjust climate sensitivity. (As an aside, there’s nothing in MBH 98/99 that implies a “disaster,” whatever that means.)
15 July 2006 at 6:39 PM
Re #27, 28
Hank, while the overall heating of the oceans in the full period 1955-2000 is reproduced by climate models, any cyclic (internal, natural) variation in the order of 10-100 years is significantly not captured by the models. Thus the fast increase in ocean heat content 1990-2000 is likely a composite of forced warming and natural variability. Which leads to the question of what is the weigth of the different forcings and natural variability…
Steve, the Levitus figures give a cooling in the period 1980-1990 for all oceans (except the Indian) for both hemispheres, and globally for a depth until 700 m. The figures that Hank quoted are from a particular (deeper) part of the North Atlantic, but fit in the general trends. But both show huge variations around an upgoing trend.
That changes in cloud cover may have something to do with this can be read in the works of Wielicki and Chen, and further by Pinker e.a.. The change in insolation in the tropics (~ 3 W/m2, caused by a reduction of low cloud cover) over the past 15 years is an order of magnitude larger than calculated from the increase in GHGs…
15 July 2006 at 7:01 PM
The ExxonSecrets website has some mapping of organizations and individuals funded by Exxon to work on global warming.
http://www.exxonsecrets.org/
15 July 2006 at 9:29 PM
a. The whole networking thing is a strange. Said )the third author( was a PhD student of Wegman, Scott and Wegman serve on all sorts of committees together. George Mason is a hotbed of right wing think tankers. usw
b. The basis of ocean acidification can be found at http://www.aip.org/history/climate/Revelle.htm
15 July 2006 at 9:33 PM
Spencer, I’ve only taken a brief look at the site but I think you have done a great job! Keep up the good work and I hope to have a detailed read of it in the next month or so.
15 July 2006 at 11:26 PM
I’ve looked at the Wegman report. I have not gone over it in detail. These are my impressions from a brief reading.
I am a statistician who has mostly worked on environmental problems. I also have a biological background. I have mostly worked on ecological, physiological, hydrological, chemical and sedimentological data.
Briefly I agree with most of their criticism of the paleoclimate reconstructions. I have not looked at their social network analysis in sufficient detail to make an informed comment. They seem to have misunderstood the attribution of recent warming to greenhouse gas forcing.
Wegman et al. claim that the principal component analysis was incorrectly centered and that this could create a hockey stick even if there wasn’t one there. On the data that they have presented I would have to agree with them. I think they are also right when they suggest that different types of time series models be tried.
They seem to be under the impression that Mann et al. are claiming that because both temperature and CO2 are increasing that there is a causal relationship. This looks like a misunderstanding to me. As I understand it the attribution of recent temperature increases to greenhouse gas forcing depends on three main arguments.
The first is the claim that the warming over the past century is far faster than any warming period on record thus implying that a different mechanism is involved.
The second is is the claim that the pattern of temperature changes over the past century can be replicated by models including greenhouse gas forcing but not otherwise.
The third is the claim that the pattern of changes is what would have been expected from greenhouse gas forcing not that which would have been expected from other causes.
The hockey stick supported the first argument. However this was always the least important argument. As has been pointed out before on this blog it doesn’t matter what the cause of previous warmings was. It just matters what the cause of the current one is.
The hockey stick is irrelevant to the second and third arguments. The third one about the pattern of changes always seemed to me to be the strongest one.
What follows are some of my observations on why people are talking past each other. As I understand it the general circulation models are deterministic. People in climate modeling develop a lot of expertise in creating deterministic models but not necessarily enough in creating stochastic models. There seems to be a shortage of people who have both a good feel for climatic processes and a good feel for random processes. The way into climate modeling may discourage people from developing both. And both are needed in paleoclimate reconstructions.
There is a quotation by George Box that is well known among statisticians. “All models are wrong. Some models are useful.” Most phenomena can be modeled in many ways. There is a danger of a statistician unfamiliar with the subject matter of a study choosing a model for it mathematical tractability or familiarity rather than because it aids understanding. A statistician working on paleoclimate data needs to have an understanding of climate processes in order to create truly useful models. I’m not sure Wegman et al. realize this.
15 July 2006 at 11:32 PM
Re: â��The Discovery of Global Warmingâ�� update — Excellent treatment of both science and history - many thanks to Spencer Weart. I wonder about the cutoff at May 2001 however - are there any plans to continue the timeline?
16 July 2006 at 9:45 AM
Does this report from the BBC on a possible new history of molecular oxygen (O2) levels have reprocussions in the GW debate?
16 July 2006 at 10:51 AM
Re Gavin’s response in 21:
“the understanding that the medieval climate anomaly was not as coherent in time or space than the 20th Century change had begun well before MBH”
Even I knews that. I long ago learned that, no matter how expert you might be in your own field, it takes at least two years of study of a new subject—about the time of pre-thesis graduate work—to get to the point where you can start saying sensible things, and even then many of them are wrong. It takes longer to be able to comment usefully. The only way a statistician is going to be able to advance the subject is by taking the time to familiarize himself with it at a professional level, not by jumping in to debate one narrow point.
16 July 2006 at 11:22 AM
Lloyd, thanks for your perspective. The danger in a purely statistical analysis comes when you use the word “cause” since statistics won’t tell you anything about cause and effect. Another danger with a purely statistical analysis is not understanding the physical processes behind the measurements. How, for example, does a particular temperature proxy like a tree ring reflect the climate conditions for that year? Or for a CO2 measurement in an ice core, how does a layer of ice get physically created, compacted and sampled? It seems that that requires a broad understanding of biology and physics.
16 July 2006 at 12:07 PM
>37 Jhm
The new model confirms the older models, according to the story about the charcoal study. See the chart there of two
“… models describing oxygen (O2) level changes in the atmosphere - a new model (A) and a popular, older one (B) …” — the new information about timing and type of plant involved in the fires fits the atmosphere models.
16 July 2006 at 3:55 PM
I am currently reading a book by Richard Hamblyn: The invention of Clouds (http://paperfrigate.blogspot.com/2004/12/hamblyn-invention-of-clouds.html) which also provides a fascinating account an important part of the history of meteorology/science, for those who find science history or meteorology history interesting.
Rasmus
16 July 2006 at 4:23 PM
I know this is a bit off topic, but I could not help my self to share:
http://articles.moneycentral.msn.com/SavingandDebt/SaveonaCar/WhyNowsTheTimeToBuyAnSUV.aspx?GT1=8386
I hope no one runs and buys one…
16 July 2006 at 6:17 PM
Models gone wild! Re: Lloyd no. 35, the second pillar of attribution is model based. Model based evidence is dependent on the quality of the models (not profound). Climate modelers also have a practice of assuming that ensembles of models “tackle model uncertainty”. Keep in mind also, that the third pillar of attribution, the pattern of changes, is also at least partially informed by insight from models.
Pillar number one is the weakest pillar. Pillars three is partially dependent on pillar two. Recent evidence now shows, that all the AR4 models, yes “all”, show a systematic bias against solar forcing, the leading competing theory to anthro GHG warming. They all have a positive albedo bias. For references, see the Roesch (2006) and Bender (2006) in my comments here: http://scienceblogs.com/stoat/2006/07/climate_change_in_hadgem1.php#comment-170704
[Response: First off, the ‘positive’ bias in the albedo is on the order of 1%, leading to a potential bias against solar irradiance forcing of ~1.4% which compared to the uncertainty in the solar forcing itself is negligible. Secondly, the actual mean albedo is still not that well known - true, recent estimates are lower than the earlier numbers which most GCMs were tuned against, but I would be hesitiant in assuming that a 1% change in global albedo will suddenly make a big difference in response. That is not our experience at all. - gavin]
16 July 2006 at 6:38 PM
Re: #42,
There must be something wrong with that article. Given the crisis in the Middle East, economists are predicting $4 per gallon prices in the coming months, even weeks ahead. If this occurs, this is certainly no time to buy an SUV. (Is there ever a good time to buy one?)
16 July 2006 at 6:55 PM
Re: response to #19
Rasmus, the implicit assertion is actually somewhat different from what you wrote. Rather than being “that statistitians bring forth the true answers whereas other scientists don’t,” the assertion is that statisticians are much less likely to make errors in statistical analyses. This seems like common sense to me. In my field of biology, we commonly consult and/or collaborate with statisticians in order to help ensure the analysis is done correctly; I can’t imagine that such a practice would harm climate research.
16 July 2006 at 8:30 PM
Lloyd, your #35 made things clearer.
Can you say or point to more elsewhere about deterministic and stochastic modeling?
It sounds like it’d be an educational conversation for people like me to watch, if it’s going on elsewhere.
17 July 2006 at 8:36 AM
The suggestion by Wegman et al. that long memory time series should be tried in modeling paleoclimate seems reasonable to me. This is going to need someone who is familiar with both climate processes and with new methods in time series. This is going to be needed in order to come up with models that are both physically plausible and interpretable and mathematically tractable. If you can’t find someone with the necessary experience working on climate data then I would suggest someone with experience working on climate related data. Perhaps hydrological data.
What we need to know is not so much whether current temperatures are unprecedented in the last thousand years but whether the current rate of temperature change is unprecedented in that period. A re analysis with better methods might answer that question. At the least it would give us a better idea of the limits of our knowledge.
It’s time to admit that mistakes were made in the paleoclimate reconstructions and that improvements can and should be made.
#39 Eric we can’t prove the mechanism of global warming from observational data alone. We can’t do controlled experiments and have only one planet to work with. We can just say that the observations are consistent with certain mechanisms.
#45 Hank deterministic models always give the same results given the same inputs. Stochastic models usually don’t give quite the same result when repeated with the same inputs. The first are taught in applied mathematics departments. The second are taught in statistics departments.
Which is the more useful type of model depends on the questions asked, the processes involved and the resources available. Not many people have a lot of skill with both. It is not easy to derive the random behavior of a process from its deterministic aspects if one cannot perform experiments. I suspect that the creation of deterministic general circulation models does not necessarily help their creators as much as might be expected in predicting the random aspects of weather and climate. One necessarily ignores or tries to average out random elements when creating these models. This could leave one without guidance when one is confronted by randomness such as that in paleoclimate estimation.
These are my observations and impressions and I haven’t seen things put this way elsewhere.
[Response: Improvements can always be made, but the choices made in the MBH report were reasonable judgment calls. It’s obviously important to know what impacts they have, but for the centered PCA change, the impact is very small (see http://www.realclimate.org/index.php/archives/2005/02/dummies-guide-to-the-latest-hockey-stick-controversy/ or the Wahl and Amman (2006) paper (their scenario 5d) (the fourth panel in this figure.). - gavin]
17 July 2006 at 10:18 AM
Statement from a “denialist”(who shall remain unnamed):
“Earth has warmed from about 287 K to about 287.6 K during the Twentieth Century. At most, increased radiative forcing from added atmospheric carbon dioxide can account for ~0.17 K (an increase in Earth’s estimated mean surface temperature of <0.06%). The IR absorbency bandwidths where atmospheric carbon dioxide is active are either saturated or approaching that state. This means the trivial warming attributable to increased atmospheric carbon dioxide is almost complete.”
Comments?
[Response: Steve Milloy again. Complete cr*p again. Neither CO2 nor water vapour nor CH4 nor O3 nor N2O spectra are saturated. - gavin]
17 July 2006 at 11:05 AM
Re: #46
This statement is false. Did the unnamed denialist provide any context (reference, calculation, logical argument) to support this? It’s a very common tactic of denialists simply to make a false claim, confident that their listeners/readers don’t know enough about the subject either to see through it, or to check references. You, however, came to the right place.
Even *if* this were true, it’s irrelevant. If I’m standing in 5 feet of water, unable to swim, I’m still safe. If sea level rises two feet (a mere 0.005% compared to the depth of the Marianas trench), I drown. It’s another very common (and totally misleading) tactic of denialists to make modern warming *seem* insignificant by comparing it to the largest number they can plausibly suggest.
The center of the absorption band is saturated, but not the wings. Also, even when saturated, increasing CO2 can warm the surface. Doing so decreases the “optical depth” of the atmosphere, raising the altitude at which the atmosphere glows at the pure-blackbody temperature. Raising the “skin height” warms the surface due to the increase of temperature with greater depth in the atmosphere.
17 July 2006 at 11:09 AM
Google: I found that in only one place, at the junkscience site — unsigned — as of today.
Don’t rely much on people who don’t footnote or even sign their work.
17 July 2006 at 6:54 PM
1) Thanks for this “Discovery of Global Warming” update. I had seen the book before and glanced at the website. This gave me the impetus to read some major pieces, all informative, and bearing amazingly well on many issues at hand here. The cycles of questioning, observation, speculation, measurement, debate, and even forgetting, are all part of the process.
2) Gavin and Michael - I saw the transcript of your discussion with Lou Dobbs 7/13/6 courtesy of www.desmogblog.com! All to the good, though I can only imagine that it’s tough to switch gears when he cuts you off by agreeing with you! Asking you to offer solutions was quite a challenge - taking you out of your comfort zone. How will you bone up on solutions for the next discussion? I recommend efficiency, renewables, and conservation (as always). Nuclear? That’s the big government solution, with big bureaucracy, regulation, and subsidies. The free-market, high-tech approach of Amory Lovins (at www.rmi.org ) would be to his liking. Dobbs’ key phrase: “this is a can-do country”. You bet.
3) About that OT Wegman report - there are some good responses to it floating about. Please choose wisely. (More free advice later.)
17 July 2006 at 10:36 PM
#43 Martin,
The best indicator that the mechanism of temperature change in the past 150 years is different from what occurred earlier would be sustained rates of temperature increase that were unprecedented. I think high temperatures are less of an indicator than high rates of temperature increase. And yes we do need better reconstructions of past temperatures.
But by themselves temperature changes will only be indicative. To draw conclusions about causes one needs to have an idea of the processes involved and what they can and can’t do. What the paleoclimate record potentially can do is to provide a reality check on models.
In climate science one cannot get the conclusive proof that one can from say a mathematical theorem or from a designed experiment. It has been pointed out on this blog that we have only one world and cannot do the required experiments on it. What we can do is come up with physically possible explanations and test them. If a hypothesis is consistent with the available data and no one has been able to come up with an alternative hypothesis that fits then we provisionally accept the hypothesis. It is always possible that someone will come up with an alternative hypothesis in the future but we don’t hold our breath waiting.
Some people claim that climate is too complicated and detailed modeling is a hopeless task. This would leave us without a way of telling whether temperature rises are being driven by greenhouse gases or not. It is a position that fails if anyone comes up with a model that adequately explains what is happening.
The general circulation models appear to to be a reasonable but not perfect fit to what has been happening in the past century. No one has been able to create a model that fits the data that is not sensitive to greenhouse gases. In particular there does not appear to have been a solar forcing that would explain the temperature increases of the past quarter century.
I think the argument that the fingerprint of changes is what would be expected of greenhouse gas rather than solar forcing depends on the most robust aspects of the models. Gavin, Rasmus could you do a post comparing what you would expect from greenhouse gas forcing with what you would expect from solar forcing? And then could you compare both with what is happening?
18 July 2006 at 4:27 AM
Re: response to #43,
Gavin, the 1% globally averaged surface albedo errors would correspond to 1.7W/m^2, the average albedo errors of the AR4 models Roesch’s IPCC diagnostic project reported were 0.016-0.019, which corresponds to 2.6-3.1 W/m^2. Now in Hansen (2005), I believe you used GISS-EH. Its global albedo came in over 1 SD below the model average, almost spot-on the higher of the satellite observations. In that paper you were reporting that the earth was now absorbing 0.85+/-0.15W/m^2 more than it was radiating into space, and that of the 1.8W/m^2 of forcing increase since 1880, 0.85 W/m2 remains, i.e., remains in the pipeline corresponding to 0.6 degrees C of committed future increase. The actual albedo errors to that contribute to the global average that Roesch reports, are quite large and concentrated in regions of snow cover, times of snow melt and in the tropical deserts. The coupling between the errors and the annualized net energy balance will be nonlinear, but the global average of the errors suggest their magnitude is too large to dismiss as unlikely to make a big difference.
The whole AR4 suite of models is biased against solar forcing by on average over 1.5 times the forcing increase we are trying to simulate, and more than an order of magnitude larger than the accuracy we need balance the energy budget for attribution and climate commitment studies. With models being so central to attribution studies and even “independent observational” studies, we should not be “hesitant”, to point out that it is premature to make important policy decisions based on model projections.
Any models managing to balance their energy budgets to under 1W/m^2, with these surface albedo errors, must have other compensating errors in forcings, sensitivities or internal feedbacks. We know of many more problems with models than just this albedo bias. Of particular importance, this diagnostic study, showed that all the models have this systematic positive bias to a greater or lesser degree, so the practice of combining them into ensembles to somehow reduce their errors and increase their credibility is called into question.
There is no doubt that models are much improved since the TAR, and that these diagnostic studies will contribute to further progress. Unfortunately, premature “confidence” in the models has damaged the reputation of this science which has already made important qualitative contributions and has promise for useful quantitative results in the future.
Despite the problems we will always have judging how to spin up the oceans and climate to uncertain past conditions, I look forward to studies with corrected models, accurate enough to carry climate commitment properly forward into attribution studies of the recent warming, ideally all the way from the Maunder minimum, to the historically high levels of solar forcing of the last 60 years.
James Hansen, Reto Ruedy, Larissa Nazarenko, Makiko Sato, Josh Willis, Anthony DelGenio, Dorothy Koch, Andrew Lacis, Ken Lo, Surabi Menon, Tica Novakov, Judith Perlwitz, Gary Russell, Gavin A. Schmidt, Nicholas Tausnev (2005). “Earth’s Energy Imbalance: Confirmation and Implications”. Science. DOI:10.1126/science.1110252
Roesch (2006) “Evaluation of surface albedo and snow cover in AR4 coupled climate models” http://www-pcmdi.llnl.gov/ipcc/abstract.php?ipcc_publication_id=36
[Response: You are making a fundamental error. Just because two quantities are in the same unit, it doesn’t mean they can be usefully compared. There is a huge difference in the net imbalance and an error in two compensating fluxes. Think of this as trying to model a lake - the ‘control’ lake level is a function of the water coming in and going out which we know must be balanced. Now we add some extra water (or slow the rate of outflow), and we calculate the rate of lake level rise. The lake level rise can be estimated very clearly, despite not being absolutely sure of what the actual level in the lake is. Thus the rise estimated is largely independent of the absolute level. This is exactly what happens in the AR4 models. They are tuned to a particular ‘level’ (i.e. global albedo) and are in balance, and the imbalances that occur when GHGs are added are largely independent of that level. I will point out also that the AR4 models are mainly tuned to ERBE data, not CERES - which was not available during the model development process.
Your statements regarding solar forcing biases make no sense. An increase in solar irradiance (say from solar min to solar max, which is about 1.3 W/m2) need to be converted to a TOA forcing to see it’s effect and the albedo comes into that calculation F_solar = 1.3 * (1-a)/4, so the difference in F_solar as a function of a 1% error in ‘a’ is tiny - around 0.003 W/m2. How this can be described as a major bias is beyond me. -gavin]
18 July 2006 at 5:36 AM
Re #47, Response from Gavin
[Response: Steve Milloy again. Complete cr*p again. Neither CO2 nor water vapour nor CH4 nor O3 nor N2O spectra are saturated. - gavin]
As a matter of interest, do you happen to know how saturated they are - 20%, 80%, whatever ? Particularly for CO2, of course.
[Response: I’m not sure a simple percentage is a useful diagnostic. The net forcings increase at different rates (logarithmically for CO2 at least up to 1000ppm, like sqrt(conc) for methane and N2O), and the saturating bands are included in those estimates. -gavin]
18 July 2006 at 7:45 AM
Re #48 and “increasing CO2 can warm the surface. Doing so decreases the “optical depth” of the atmosphere”
Don’t you mean increasing CO2 INCREASES the optical depth of the atmosphere?
18 July 2006 at 8:00 AM
#51 Lloyd,
There is a lag in climate response to an increase in forcing. Solar forcing has been at a plateau of high activity for over 60 years. This current level of activity has been characterized as the highest in 8000 years, with only an 8% probability (based on the paleo record) of continuing another 50 years. (Solanki, 2004, 2005, correspondence w/Muscheler 2005)
Climate commitment studies by Wigley (2005) and Meehl (2005) showed that due to the thermal inertia of the oceans that most of the temperature response to an increase in forcing took place in the first 100 years, and that sea levels may continue to rise for 1000 years before equilibrium is achieved.
Hansen (2005 above) reported that the lag was a function of the climate sensitivity, “The lag could be as short as a decade, if climate sensitivity is as small as 0.25-C per W/m2 of forcing, but it is a century or longer if climate sensitivity is 1-C perW/m2 or larger.”
Obviously we need models that can balance the energy budget and represent the heat flux into the oceans to accurately reproduce the climate commitment from all the increase in solar forcing from up to 100 years or more previous to the recent warming. One also must consider that equilibration to this solar forcing would have been delayed by the aerosol cooling. How does one properly attribute this? Is the recent rapid warming a rebound from the ending of negative aerosol forcing, or a delayed equilibration to the still persisting plateau of solar forcing?
While the GHGs probably also made a significant contribution, keep in mind that past attribution studies were probably made with models with the systematic surface positive albedo biases I discussed above. This reduction in the solar contribution to the energy budget would have to be made up with increased forcings or sensitivities elsewhere in the models (compensating errors), in order to match the 20th century climate. This perturbs the whole climate model, including probably attribution of the warming earlier in the century. Since the albedo bias reduced the sensitivity of the models to solar forcing, it would also reduce the equilibration lag time, so that less climate commitment from increases in solar forcing would be carried through to later years. I don’t think we can know whether most of the recent warming is attributable to GHGs or to solar (including prior commitment) until better studies are done with corrected models. I look forward to that.
Meehl G. A., et al. Sciencexpress, 10.1126/science.1106663 (2005).
Raimund Muscheler, Fortunat Joos, Simon A. Müller and Ian Snowball (2005). “Climate: How unusual is today’s solar activity?”. Nature 436: E3-E4. http://dx.doi.org/10.1038/nature04045
S.K. Solanki, I.G. Usoskin, B. Kromer, M. Schussler, J. Beer (2004). “Unusual activity of the Sun during recent decades compared to the previous 11,000 years.”. Nature 431: 1084-1087. DOI http://dx.doi.org/10.1038/nature02995
S. K. Solanki, I. G. Usoskin, B. Kromer, M. Schüssler and J. Beer(2005). “Climate: How unusual is today’s solar activity? (Reply)”. Nature 436: E4-E5. DOI http://dx.doi.org/10.1038/nature04046
Wigley T. M. L., et al. Sciencexpress, 110.1126/science.1103934 (2005).
18 July 2006 at 8:10 AM
Re #53, Response from Gavin
Couldn’t you say that, for the relevant wavelengths, there is a certain amount of energy that leaves the surface of the earth, and a certain amount that escapes to space ? Why wouldn’t the ratio of the two give a reasonable figure for saturation ?
(Of course this would only be saturation by wavelength. If I understand it correctly, there is a fair amount of overlap between different GHGs in terms of the wavelengths they grab. So “saturation by individual GHG” would take a bit of thought to define meaningfully.)
18 July 2006 at 8:19 AM
R:: 52 response from Gavin,
I am not talking about a change in solar irradiance from the solar cycle when discussing the model bias. The change is between the climate and the model. A 0.01 positive surface albedo error, would be applied to the solar flux at the surface of 169W/m^2, which gives 1.69W/m^2. This is the average flux that is in the climate, but not in the model. To avoid any TOA confusion, remember that at the bottom of the atmosphere, per Hansen again “The observed annual mean rate of ocean heat gain between 1993 and mid-2003 was 0.86 +/- 0.12 W/m^2 per year for the 93.4% of the ocean that was analyzed.” These figures are comparable. I admit land based albedo errors are not as tightly coupled to the oceans as an ocean albedo error, but we can’t be comfortable dismissing the large land errors, in the non-linear climate system. It is possible for instance, that the increased local warming pins or shifts climate features to certain regions for longer periods of time, in a way that increases the coupling.
[Response: You stated there was a bias against solar forcing, which I took to mean the change of climate due to solar forcing. I apologise if that wasn’t what you meant. But my first point still stands - the imbalance can be seen to high accuracy despite uncertainties in the individual fluxes - and we do not know them to better than a few W/m2 in any case. We do know that they must have been close to balance, and now they are not. I can measure the lake level rising with an accuracy of millimeters even I don’t know the depth of the lake to better than a few meters. - gavin]
18 July 2006 at 9:14 AM
Re: #54
Doh! I stand (sit, lie down, and run in place) corrected.
18 July 2006 at 11:00 AM
Re: Response to #52, the lake part
Gavin, I have tried to be fair to your lake analogy and see if it can apply somehow. I knew it would be a copout to say it was an oversimplification, because all analogies are. But I couldn’t get my mind around balancing models around the albedos, because I could see how it would be done, since albedos are also a function of climate due to snow cover and vegetation changes. So, I translated your lake analogy to balancing heat flows and the energy budget instead. If all we care about is the rate at which the lake is rising, that is equivilent to just caring about the net energy flux, and you are right, it the absolute level of the water and the total amounts of energy don’t matter. If the systems behavior is l linear and the inputs and outputs are not changing, we can even make predictions. However, the absolute levels of the inflows and outflows and the mechanisms become important once we start trying to attribute relative importance to each, or need to estimate what the rise will be in response to changes in inputs, etc. For instance, if a 1 acre lake is rising 1 ft per year, because of an inflow of 1 acre ft per year, and the outflow is dammed. That is a different situation than a lake rising 1 ft per year, because of a 2 acre ft per year inflow balanced by a 1 acre ft per year outflow. In the case of the dam, a doubling of the inflow, doubles the rate of rise, until the dam is topped. In the case without the dam, a doubling of the inflow, triples the rate of rise, assuming the rate of outflow doesn’t change, however, we don’t know the response function of the outflow.
In the case of the climate, attribution studies were attempted back when models were not fitted to much more than temperature. With the advent of coupled models, with studies attempting to simulate climate commitment and future sea level rise from heat flows, models actually do have to balance the energy budget. But I don’t think we can assume there will be a simple counter balancing of flux errors about this balancing of the energy budget, because models today are expected fit far more than just the energy balance. Trying to fit temperatures, cloud cover, ocean currents, snow cover, etc. all at the same time, brings in a lot of other constraints, which will force some elements of the models closer to the absolute physical values. Both the heat flow into the oceans, and the albedo error we have been discussing, are net heat fluxes at the surface, averaged both globally and annually. So they are directly comparable in terms of the energy budget, although there is quite a contrast in temporal and geographical distribution of the details of the two quantities. With this size of errors, one has to question how the model balances the energy budget, and yet still matches so many other diagnostic statistics. Has it recovered the solar heat it lost through surface albedo error, through increased sensitivity to GHGs? Given the range of model sensitivities the particulars of the distribution of compensating errors must vary.
[Response: The models are usually tuned in two specific ways - firstly to have a reasonable global albedo (target range around 30% to 32% given the uncertainties in the data), and secondly to have a net long term surface heat budget close to zero. Both of these things are usually accomplished by adjusting minor cloud parameters. If the albedo was clearly shown to be exactly 30.5%, we would have no problem adjusting the models to match - these kinds of adjustments are made all the time as a function of changes in the cloud routines, boundardy layer or surface code. Generally, the sensitivity to increasing CO2 is not affected by these changes, however, there are obviously compensating adjustments to the other fluxes - generally within their uncertainties except in some key problematic locations. You need to appreicate that these changes in the fluxes are really small compared to the absolute flux, on the order of a few percent at most - thus they don’t generally change the big picture climate in the models and I have seen no evidence that there is a systematic relationship to the sensitivity. It certainly doesn’t show up in the AR4 models - try plotting sensitivity or feedabck strengths against the albedo offset (Soden and Held, J. Climate, 2006 for instance). - gavin]
18 July 2006 at 11:11 AM
#51 Lloyd,
Maybe you’d find this useful:
http://en.wikipedia.org/wiki/Image:Climate_Change_Attribution.png
18 July 2006 at 11:54 AM
Gavin, if the artwork linked in #60 is sound, you all might consider recommending the artist’s site– that one ends in 1990 and is based on a DOE model. I wish more scientific illustrators did such clear charts.
18 July 2006 at 12:42 PM
Hank - here’s some other images from the same source:
http://www.globalwarmingart.com/wiki/Image:CLIMAP.jpg
http://www.globalwarmingart.com/wiki/Image:Holocene_Temperature_Variations_Rev.png
http://www.globalwarmingart.com/wiki/Image:Post-Glacial_Sea_Level.png
http://www.globalwarmingart.com/wiki/Image:IPCC_Radiative_Forcings.gif
http://www.globalwarmingart.com/wiki/Image:65_Myr_Climate_Change_Rev.png
http://www.globalwarmingart.com/wiki/Image:Carbon_Emission_by_Region.png
http://www.globalwarmingart.com/wiki/Image:Greenhouse_Gas_by_Sector.png
http://www.globalwarmingart.com/wiki/Image:Major_greenhouse_gas_trends.png
http://www.globalwarmingart.com/wiki/List_of_all_images
18 July 2006 at 12:53 PM
Re: response to 59,
Gavin, correcting a positive surface albedo bias with a negative cloud albedo bias of unrelated geographical distribution just doubles the error in the model. You don’t know whether you are correcting the solar sensitivity, or just unrealistically altering cloud feedbacks to who knows what forcings. If we did know this a apriori, then we wouldn’t need the models.
18 July 2006 at 6:54 PM
Re: my 63 comment
I reported earlier that the GISS-EH model probably used in Hansen (2005), had a globally averaged albedo over 1 SD below the mean and close to the more positive of the satellite observations. Perhaps attempting to compensate for one error with another, explains another reason Roesch (2006) found this model notable. It was one of only 4 models to show a positive Snow Cover Area trend at at time when the climate was showing a negative Snow Cover Area trend.
[Response:It was GISS-ER in Hansen et al 2005 - gavin]
18 July 2006 at 7:07 PM
I did not see the reference to the ‘Wegman’ article and I have reviewed all of your comments. Someone please provide a web address for this article. Thanks.
18 July 2006 at 7:39 PM
Gavin, Martin,
In addition to this discussion, one may not forget that there is an observed inverse correlation between TOA solar irradiance and (low) cloud cover, see the caption in Fig. 1 of Kristjansson e.a.. During a solar cycle, this causes a +/- 1-2% change in global low cloud cover. SST temperature differences can go to up to 0.3 C within a sun cycle. Thus anyway, the -relative- small changes in TOA solar irradiance seems to be strengthened by changes in cloud cover.
What that means for long-term changes in solar irradiance is quite uncertain, but strengthens the possibility that these are underestimated in current climate models.
18 July 2006 at 11:46 PM
65, Leon: There’s a link on this page that’ll download a copy of Wegman:
http://scienceblogs.com/stoat/
19 July 2006 at 4:09 AM
Ferdinand (Re: 66)
Thanx for the reference. The Roesch paper also emphasized the importance of SSTs: “The time slice simulation using ECHAM5 with prescribed SST and sea-ice suggests that accurate SSTs and ice coverage are fundamental for a correct prediction of SCA trends.” I presume, that whereas the subtropics were important in your cite, that it is the higher latitude SSTs are what is more influential snow cover. Although, it is undoubtedly all coupled at some time scale. Modelers have a difficult task of validating their models against so many qualitatively different observations, all the while their models are expected to also display the internal variability of the natural climate.
19 July 2006 at 1:41 PM
Here’s an image I haven’t seen before that seems rather good.
I’d like climatologists’ opinions on — accurate? convincing?
http://users.aber.ac.uk/sfg4/ipcc%20projections.jpg
19 July 2006 at 5:48 PM
I first learned about global warming when I was in elementary school. There were many other students who were interested in science and so we then had the chance to really hear about this. I then also read about global warming in a nice book about our planet that I read in 1993 titled, Save The Earth. When I learned about global warming I was learning about how it was a difficulty in our planet’s atmosphere where a big round entrance had formed above the Antarctica region, being the south pole area. If I remember right, apparently this gap in outer space and in the atmosphere somehow created the continual warming of our planet.
19 July 2006 at 10:00 PM
Ok, if we have CO2 fluctuations over the years and 5 in the last 400,000 years http://www.androidworld.com/Vostok_Ice_Core.jpg What caused them to be periodic? Periodic volcanic activity? http://www.androidworld.com/Mauna_Loa.jpg Or something else or combinations of something else?
[Response:Orbital forcing - see Hays, Imbrie and Shackleton (1974) and all subsequent references…. - gavin]
19 July 2006 at 11:15 PM
Lars, look among the links in the footnotes here:
http://www.nature.com/nature/journal/v324/n6093/abs/324137a0.html
20 July 2006 at 7:55 AM
Re #71 and ” When I learned about global warming I was learning about how it was a difficulty in our planet’s atmosphere where a big round entrance had formed above the Antarctica region, being the south pole area. If I remember right, apparently this gap in outer space and in the atmosphere somehow created the continual warming of our planet.”
No, you’ve conflated two issues there — ozone depletion and global warming. The widespread use of chlorofluorocarbons in the 20th century depleted stratospheric ozone and created the ominous “hole in the ozone” over Antarctica. The problem, while still serious, is under control because the 1987 Montreal Protocol (revised a couple of times since then) has pretty much banned the use of CFCs.
Global warming is due primarily to the release of carbon dioxide (CO2) when fossil fuels are burned. The amount of CO2 in the air has risen by over a third since the industrial revolution started (from about 280 parts per million by volume to about 380 ppmv). As a result, the world has warmed by about 1 degree Kelvin. Fossil fuel use is increasing so quickly that warming of 1.5-6.0 degrees is likely in the next century. This is enough to have a major, probably negative, effect on human agriculture.
21 July 2006 at 8:28 AM
Re #70,
Hank, if that picture is true, we are heading for temperatures higher than during the Cretaceous, a period with CO2 levels 4-10x higher than pre-industrial and a different (warmer) continents location… Seems a little overblown…
24 July 2006 at 3:26 PM
This should change something — now we have rapid changes far faster than the human fossil fuel release, in geologic history. Any temperature records that would go with this or similar?
Found here, a press release:
http://www.sciam.com/print_version.cfm?articleID=0006E0BF-BB43-146C-BB4383414B7F0000
“… the Bishop tuff, a volcanic layer tens to hundreds of meters thick that is exposed at the earth’s surface as the Volcanic Tablelands in eastern California. This massive deposit represents what is left of the estimated 750 cubic kilometers of magma ejected during the formation of the Long Valley supervolcano caldera some 760,000 years ago.
….
…. Alfred Anderson of the University of Chicago and his colleagues studied the size of the bubbles under a microscope to estimate how long it took the magma to leak out. Based on these and other experiments and field observations from the 1990s, geologists now think that the Bishop tuff–and probably most other supererupted debris–was expelled in a single event lasting a mere 10 to 100 hours. “
31 July 2006 at 4:17 PM
Re #76 “This should change something — now we have rapid changes far faster than the human fossil fuel release, in geologic history. Any temperature records that would go with this or similar?”
Hank, Have you read “The two mile time machine” by Richard Alley? That tells of rapid warming much faster than now with no greenhouse gas forcing! At least not methane or carbon dioxide. It happened only 10,000 years ago.
6 June 2008 at 8:16 AM
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