My model, used for deception
Well, not my model exactly. I developed and host a web interface to the modtran model of atmospheric infrared radiation, an early example of a line-by-line code which I downloaded and use to teach and as part of a textbook. Now David C. Archibald from Summa Development Limited, Perth, WA, Australia claims that my "University of Chicago modtran facility" proves that global warming won't happen.
Archibald begins by discovering that the IR light flux at the top of the atmosphere is more sensitive to changes in atmosphere CO2 when the concentration of CO2 is lower. This will come as no surprise to regular readers of realclimate who will know that the energy flux scales with the logarithm of CO2. The log dependence is why the climate sensitivity parameter is often posed as a temperature change for doubled CO2 concentration; to first order, a change from 10 ppm to 20 would have about as much climate impact as a change from 1000 to 2000 ppm. So Archibald is right on this score, clearly climate is more sensitive to CO2 when levels are lower. However, I think most climate models are aware that atmospheric CO2 is 380 ppm rather than 10 ppm, and they predict global warming anyway. If we were starting out from 10 ppm, the warming would be even worse.
Archibald then takes an atmospheric increase of 40 ppm which he thinks will happen by the year 2030. I'd have guessed 60 ppm by then at least, the way things are going, but whatever, we'll see. He uses my setup of modtran to calculate that the IR flux to space would drop by 0.4 Watts / m2 as a result of this 40 ppm. Try it yourself. Run the model once with 375 ppm CO2 and another time with 415 ppm, and compare the Iout values in Watts / m2. The exact number you get depends on humidity, setting, clouds, etc. Formulas given in IPCC would say 0.5 Watts / m2; zeroing out water vapor in modtran gets the IR response up to 0.6 Watts / m2 for the default tropical atmosphere case. At any rate Archibald isn't wildly off here either.
But then Archibald multiplies the radiative forcing by an absurdly low value of the climate sensitivity parameter. In this case he is using the parameter in units of degrees C per Watt / m2. The two forms of the climate sensitivity parameter that we have discussed here are related by a factor of about 4 Watts / m2 for a doubling of CO2. The value Archibald uses is 0.1 degree C per Watt / m2 which was "demonstrated" in a paper entitled "CO2-induced global warming: a skeptic’s view of potential climate change" by Idso, 1998. Translated, Idso's climate sensitivity winds up to be 0.4 degrees for doubling CO2. IPCC finds it essentially impossible (yeah, I know, highly unlikely or whatever) that the climate sensitivity could be less than 1.5 degrees C for doubling CO2, and 3 degrees C is a best-guess value.
In the end, Archibald concludes that the warming from the next 40 ppm of CO2 rise (never mind the rest of it) will only be 0.04 degrees C. Archibald's low-ball estimate of climate change comes not from the modtran model my server ran for him, but from his own low-ball value of the climate sensitivity.
4 October 2007 at 8:31 AM
“It wont happen” Hello?
Ok- can someone please tell the eskimos and polar bears to stop hallucinating?
everything is really ok
That’s snow —not strawberry fields —”nothing to get hung about”
4 October 2007 at 9:32 AM
And now if Archibald could just change the laws of physics, we could make the problem go away! Sounds like an exercise in “faith-based” science. I wonder if he’d have much luck convincing some of the farmers in Oz who are losing everything they had due to drought?
4 October 2007 at 10:28 AM
Did anyone publish Archibald’s paper in a journal somewhere? The link goes to “climatepolice.com” — don’t science journals usually refuse to consider publishing papers that go out as PR first, preferring that peer review and journal publication precede public distribution?
This doesn’t even have something like “to be published in, well, submitted to, er, rejected by Energy and Environment” credentials. Yet.
4 October 2007 at 11:06 AM
A quick search on Google Scholar yeilds only one other paper by David Archibald which appeared in that bastion of critical peer review “Energy & Environment”:
http://www.lavoisier.com.au/papers/articles/Archibald.pdf
“Solar Cycles 24 and 25 and Predicted Climate Response” appearing in Energy and Environment, Volume 17 No. 1 2006, pages 29–35
ABSTRACT
“Projections of weak solar maxima for solar cycles 24 and 25 are correlated with the terrestrial climate response to solar cycles over the last three hundred years, derived from a review of the literature. Based on solar maxima of approximately 50 for solar cycles 24 and 25, a global temperature decline of 1.5°C is predicted to 2020, equating to the experience of the Dalton Minimum. To provide a baseline for projecting temperature to the projected maximum of solar cycle 25, data from five rural, continental US stations with data from 1905 to 2003 was averaged and
smoothed. The profile indicates that temperatures remain below the average over the first half of the twentieth century.”
Archibald seems to think the sun will save us from ourselves and with his most recent effort that even if the sun doesn’t step in the carbon isn’t much of a problem anyway.
Paul Middents
4 October 2007 at 12:23 PM
I think it is interesting that Archibald had to go back a decade to find a sensitivity estimate low enough to support his assertion. Even Schwartz’s musings wouldn’t do it for him. I suppose it’s an indication of the progress we’ve made if nothing else–now to be a denialist, you have to be not only delusional, but also woefully outdated.
4 October 2007 at 1:19 PM
Archibald’s garbage is not meant to fool science minded people. His article is meant for the lay public to create a sense of doubt and hesitation. This is one of the key principles of propaganda. It does not need to be true, it just needs to sound true, and then repeat it again and again and again.
I am sure someone is rewarding Archibald for his efforts. Watch for the shrill citations and repititions from the henchmen. I can only hope the organizations behind this get exposed sooner rather than later.
4 October 2007 at 1:48 PM
My understanding of the climate sensitivity parameter is that the pdf of its estimated value is heavily skewed, with a short, truncated tail to the lower (below mean) side, and a long (very long?) tail to the upper (above mean) side. Furthermore, I thought this was generally accepted amongst climate and other scientists viz. that the parameter occupied a range of possible values, hence a rigorous analysis, with whatever model, should be open enough to show an ensemble of results, generated using different values, with some indication of their relative likelihood. It’s not perfect, I know, but it’s better than saying, in effect, ‘I will assume the parameter has this value, over all other possible candidate values, and not concern myself with other possible model outcomes, however likely they might be …’. Therefore, I wouldn’t attach much credence, if any, to a modelling study that didn’t explore the range of possibilities arising from such uncertainty in parameter values, and particularly in the value of something as crucial as the climate sensitivity parameter, as in this example.
4 October 2007 at 3:29 PM
The Stephan-Boltzmann (blackbody) climate sensitivity is about 0.3 deg.C/(W/m^2). Idso claims to have “demonstrated” that it’s 0.1. How is it *possible* for climate sensitivity to be less than the S-B value? Does this require some exotic condition? Idso’s demon? Or is this actually possible for a physically plausible planetary condition?
[Response: It would require the negative feedbacks to be much stronger than they are. i.e. water vapour would have to go down as temperature rises, low clouds would have to be incredibly sensitive, high clouds not sensitive at all - and forget the ice-albedo feedback! - gavin]
4 October 2007 at 4:01 PM
A review of one of Archibald’s E&E paper is at http://n3xus6.blogspot.com/2007/02/dd.html titled “The worst climate science paper ever of all time anywhere”
Notably Archibald even has a 4 part video series on Youtube of his recent presentation to the Lavoisier Society.
http://www.youtube.com/watch?v=VDX2ExKYyqw (Part 1)
A remarkable effort.
4 October 2007 at 5:54 PM
Re: #5
Ray,
With no disrespect intended as I suspect you know as well as I that old science does not mean bad science. When wishing insights into how CO2 manages to be an effective greenhouse gas I refer to Einstein.
Best Wishes
Alexander Harvey
4 October 2007 at 6:27 PM
Archibald was doing fine until he introduced his unrealistic value of climate sensitivity parameter. George Bush Sr. once referred to a primary opponent’s ( Reagan’s) economic policy as voodoo economics. Now it seems we have voodoo climatology.
In comment #2, Ray refers (facetiously) to changing the laws of physics. Something like this has been tried before. In 1997, the Indiana House of Representatives unanimously passed a bill that attempted to legislate a value of pi. The title of the bill was “A bill introducing a new Mathematical truth”(source,”A History of Pi by Petr Beckmann-St. Martin’s Press, 1971, pp 174=177). It never did get through the state Senate and the value was grossly in error.You can’t fool Mother Nature.
4 October 2007 at 7:22 PM
Err, lawrence, when did the Indiana House of Reps try the Pi trick ? Your 1971 reference presumably doesn’t describe an event that happened in 1997.
4 October 2007 at 7:48 PM
Lawrence and David, It was 1897, and the culprit was a doctor who calculated 9 separate values for pi. The text of the law was:
“Be it enacted by the General Assembly of the State of Indiana: It has been found that a circular area is to the square on a line equal to the quadrant of the circumference, as the area of an equilateral rectangle is to the square of one side.
(Section I, House Bill No. 246, 1897) ”
http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Pi_through_the_ages.html
I sense a trend here–a learned “man of science” venturing into areas where he is untrained, just as today, most climate skeptics are not climate scientists.
4 October 2007 at 7:58 PM
Re# 11: Indiana Pi law
Lawrence, you have a typo. The law was introduced into the House in 1*8*97, not 1997. Wikipedia has a good article on the issue.
4 October 2007 at 8:40 PM
Thank you, David, Ray and Rafael. I can’t get away with anything around here!(And it’s a good thing too).
The culprit was indeed a doctor, Dr. Edwin J. Goodman and he hoped to profit from his brainchild as follows,from the preamble to the bill” A bill for an act introducing a new mathematical truth and offered as a contribution to education to be used only by the State of Indiana free of cost by paying any royalties whatever on the same, provided it is accepted and adopted by the official action of the legislature in 1897.” An ex teacher told the legislature “The case is perfectly simple.If we pass this bill which establishesa new and correct(sic) value of pi,the author offers our state without cost the use of this discovery and its free publication in our school textbooks,while everyone else must pay him a royalty.”
Perhaps those who would repeal the Stefan Boltzmann constant in the formula for the energy radiated by a black body,might try to profit from their findings, as well.
4 October 2007 at 8:42 PM
I had thought the pi=3.0 law was passed and was law for part of a year in Indiana. Maybe not, I guess. (and obviously you meant to type 1897.) I also heard it originated from collusion with the legislature/government and industry — textbooks in this case.
4 October 2007 at 9:23 PM
Gavin,
I tried e-mailing you this but your inbox was full. Apparently the Hudson Institute thinks you, Michael E. Mann, Thibeault De Garidel-Thoron and Stefan Rahmstorf are skeptics.
LogicalScience Linky
5 October 2007 at 12:04 AM
hi everyone
I’m an observer here at realclimate, with no axe to grind on any ‘debate’. Can someone please post me to any journal articles that calculate a climate sensitivity of 2xCO2 of 3-4 Watts/m2. Please no reference to IPCC documentation, blog entries, etc. but rather to scientific articles.
I’m a computational neuroscientist and am involved in plenty of dynamic, nonlinear modeling and I would like to follow through the empirically derived steps, even if my knowledge of the physical basis is very limited.
if anyone could help out, it would be much appreciated
thanks, Steve
[Response: Of course: you want the IPCC ar4 report, box 10.2, which summarises things and points you to all the papers you could wish to read http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch10.pdf -William]
5 October 2007 at 1:09 AM
Your web interface to modtran is very great. I’ve spent some time messing around with HITRAN data, trying to convince some skeptics that the climate warms with increasing CO2 levels is based on well-established and very boring spectroscopy. As a spectroscopist, I think I get to say that. Anyway, the modtran tool makes it easier. Not that it’s likely to convince my skeptic friends, because I suspect they are in a place where evidence is not likely to make a difference. Nice job pointing out where Archibald went off, too.
[Response: Thank you. In your playing around with modtran and hitran, keep an eye out for any systematic differences between the two. The modtran model and database were old even when I installed them maybe a decade ago. If you find anything, I’d be very interested to hear. Thanks again, David]
5 October 2007 at 2:12 AM
Nothing Archibald, or the Lavoisier group says should be taken with any seriousness at all.
Archibald’s previous “scientific” “climate” paper has been described as the “The worst climate science paper, ever of all time, anywhere.”
http://n3xus6.blogspot.com/2007/02/dd.html
Here’s some of the absolute gold buried within his previous effort:
- To undertake his computations, which are supposed to indicate a strong correlation of surface temperature to the solar cycle, rather then use world wide temperature estimates (GISS, HadCRU ect…), he uses 5.
That’s right, 5 stations, all from the South East continental US, all within several hundred kilometers of each other.
- Strangely enough, each station shows a cooling trend. Hmmmmm…
- In order to make his “predictions”, of global temperature response from Archibald uses not 5 stations, but 1 station’s data (De Bilt in Holland). 1 data point. Of the thousands available.
- Archibald uses one data point per solar cycle. Why he does no use annual data for this station is a mystery, but it seems to torture the dat into giving a more impressive looking trend. No formal correlations / R^2 values are reported.
- He then uses really low estimates of Solar Cycle 24 and 25 to “predict” future world temperatures. Why he chooses these estimates is beyond me. He then confuses solar cycle length and solar cycle strength, but somehow concludes that global temperature will decrease over the next 2 cycles.
This paper is a load of garbage, and his new work seems to be no different.
The Lavoisier is an arch, Australian AGW septic group, who even our own (formerly) AGW septic government has tried to distance themselves from in recent years.
5 October 2007 at 4:36 AM
The 1.5 degree C IPCC lower end of the range for CO2 doubling climate sensitivity is suspect. Where it is based on models, nearly all the models are biased against solar activity and may be compensating for the missing solar energy with increased sensitivity or feed back to CO2. Furthermore, the models couple CO2 forcing to the whole mixing layer of the ocean while in reality the CO2 wavelengths barely penetrate more than a millimeter and so qualitatively are a complex surface effect.
Most of the non-model estimates of climate sensitivity are based on the analyses using other forcings such as solar and aerosols, and the assumption that sensitivity to CO2 will be the same, despite the differences in way these forcings couple to the climate system.
5 October 2007 at 6:06 AM
7 - It’s also worth pointing out that the “climate sensitivity” is a local linearisation of the climate system’s non-linear response to warming.
So it currently includes a [positive] contribution from the ice-albedo feedback, because our current climate possesses sea-ice that will be melted by a modest increase in temperatures. However, once the sea-ice has melted the contribution from the sea-ice albedo feedback will go, changing the climate sensitivity to further forcing.
In the other direction, at higher temperatures there is expected to be carbon-cycle feedbacks, that will amplify the warming, so then the climate sensitivty would be higher.
So climate sensitivity is not quite the be-all and end-all of climate science. In many respects it is an “old” concept, from a time of simpler models, and not one to be too hung up with.
5 October 2007 at 6:40 AM
Re: #17
Sagan was a proud skeptic and wrote an excellent book on the subject, the 2500 scientists who contributed to the IPCC were skeptics, and I like to think I am also skeptical about my own ideas. Unfortunaltely the Hudson Institue (and many others) have perverted the meaning of the word skeptic, the use of the word in their “study” is a (feeble and desperate) attempt to sow doubt by painting things in terms of scientists vs skeptics.
Sorry, just a pet peeve from an old school “hacker”.
5 October 2007 at 7:09 AM
Gavin - (My second attempt at a post). I’ve been reading your blog and Steve McIntyre’s as well, for some time now. I’ve recently posted at Climate Audit a complaint about their frequent accusations of fraud on the part of climate scientists. This generated a heated discussion. I’d like to be even-handed here and point out that the comment in #6 does not help any discussion of climate science. I would hope that such posts do not appear in the blog in the future.
5 October 2007 at 8:37 AM
wrt# 24, #6 is quite correct, this is exactly what the skeptical community appear to be doing. To deliberatly misrepresent the data in such a fashion requires either a high level of ignorance or some ulterior motive. I have noticed too many instances of the later and I find it somewhat distastful. The layperson should not be expected to be able to differentate between good science and properganda.
5 October 2007 at 8:57 AM
Martin Lewitt, Now hold on just a bleedin’ minute. The penetration of LWIR into water is immaterial, as by warming the surface, one also warms whatever water the surface layer then mixes with. Mixing occurs on very short timescales. I also see rather strong assertions of bias in your post, but zero evidence to back them up.
5 October 2007 at 9:29 AM
Off topic, but I was wondering if someone more learned than I, with access to research materials could do a post on past instances of ships “crossing the northwest passage.” The skeptical blogosphere is all abuzz with examples of ships making (or attempting to make) the journey, but there is always something fishy about them. Either they used reinforced boats/icebreakers, or it was a treacherous one way journey, or “if only the boats were faster,” or the routes were commercially inviable, or the trip took years to complete, or all fo the above.
Just a tip.
5 October 2007 at 9:45 AM
Erik - in this instance Archbald is not a climate scientist. Frankly the level of condemnation here compared to the blatant misrepresentation of science is mild.
Lavoisier Society’s own programme says “David Archibald is a Perth-based scientist operating in the fields of cancer research, climate science and oil exploration. In the cancer field, trials on a formulation he invented with professors from Purdue University are currently underway at Queensland University. In oil exploration, his company, Backreef Resources, is proceeding to a seven well programme in the Canning Basin, Western Australia. Mr Archibald has been an expert witness in the Supreme Court of NSW in the fields of petroleum geology and rolling mills in steelworks.”
http://www.lavoisier.com.au/papers/Conf2007/Workshop2007prog.html
5 October 2007 at 10:16 AM
> Martin Lewitt
Martin, where are you getting the information you post here? What source are you relying on? A cite or pointer would always be appreciated, or if you’re reporting your own work, please show it.
Other sources I find don’t match what you believe, for example
“IR radiation can represent 40%–60% (Mobley 1994) of the total downwelling surface ocean irradiance, it is almost completely (99.9%) absorbed in the upper 2 m of the water column. The
second process is the heating due to ultraviolet and visible wavelengths (VIS). VIS can penetrate much deeper than IR, and so its role in setting mixed layer depths (MLD) is far more important.”
http://www.gfdl.noaa.gov/reference/bibliography/2005/cos0501.pdf
See also http://www.agu.org/pubs/crossref/2005/2004JC002780.shtml
What are you reading that tells you the different information you posted, please?
5 October 2007 at 11:04 AM
For David Archibald/Purdue’s cancer pills (”… made from well know vegetables mainly broccoli and chilli …”), he was soliciting people to try them here: http://www.communitywebs.org/SAProstateCancer/pages/psaadelaide/documents/2005/septnlwv.pdf
5 October 2007 at 11:12 AM
I hve a question from for anyone that understands the greenhouse effect and warming simulations. We are obviously warming now. Is there a top end to the warming trend where we have so much CO2 in the air, more does not increase the greenhouse effect any more? If so what CO2 concentration would that be and what temperature would that take us to?
[Response: Not really. There are seventy atmospheres of CO2 on Venus, and if you added more, it would warm even further, is my understanding. David
[Response:
5 October 2007 at 11:56 AM
Chris, try the button labeled “Start Here” at the top of the page.
5 October 2007 at 1:21 PM
Re. Timothy (#22) and the climate sensitivity parameter, I agree totally that we shouldn’t get fixated on it, and I also accept that it’s something of a crude measure, hence the need for modelling studies to include some representation of the parameter uncertainty in the results, rather than sticking to just one value. These semi-empirical models are all prone to model equifinality to some extent, whether the simulated state in question is an end state, or a transient one to which particular scenarios run under different parameter values can converge.
That said, and despite the crudeness of the sensitivity measure, the long, upper tail on the pdf has to be a matter of concern. On the one hand, it gives those who wish to rebut the idea that Man is changing the climate an excuse to say that our forecasts are too vague to be useful, or to be taken seriously. On the other, it represents a possibility that we are not just in trouble, but that we could actually be in very serious trouble indeed. I know that Mike Schlesinger is going to be working on further studies to see what extra data, and over what timescales, might help us constrain the upper tail, but the possibility arises that no amount of data will do this, or at least, not in time for us to act on it with enough warning to prevent serious problems. One possibility is that the inherent non-linearities in the parameter, which you very rightly highlight, prevent constraint of the upper tail; another might be that the whole climate system gets much noisier and more chaotic, because of extra energy driving the system, so in some wise we lose the signals that might constrain the upper uncertainty. What then, guys, what then?
Nick O.
5 October 2007 at 1:35 PM
Hank, I tried that, I couldn’t find much about theoretical upper limits to global warming by CO2. I did find one 1985 paper that was pedicting a maximum of 4-5K which seems way too low. Can you give me any more specific references, or possibly to an earlier discussion of this on this site? Thanks
5 October 2007 at 1:35 PM
31 Chris
no there is no top end, but the radiative forcing by CO2 incraeases not linearly proportional to CO2 concentration, but logarithmically to CO2 concentration for more info I recommend previous posts:
http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument/
http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii/
5 October 2007 at 4:57 PM
I can understand why Archibald, an Australian, would want to deny CC. Australia is perhaps CC’s first big victim among developed nations. It’s really bad there, with worse predicted.
I developed some survey Qs for a survey course around 1996, actually conducting it on residents in Chicago Collar Counties. Some Qs related to possible GW harms, like “has your house been flooded in the past 5 years”; and some related to GW beliefs. I expected that the flooded would be more likely to believe in GW, but the results were that they were much less likely to believe in GW (holding education and other variables constant). I then reasoned that people who had been harm would much prefer to believe their harm was a fluke (once in a 1000 year thing), and would find it untenable that the same or worse might be coming in the near future.
Unfortunately I didn’t reach .05 significance, more like .1 or .2 on that (can’t remember). The differences were between the harmed and not-harmed were huge, but the number of respondents was was very low. And that’s because the basment Public Opinion Lab on the NIU campus in DeKalb had been extremely flooded and the lab was only ready at the very end of the semester — flooded in a area that had never before in history experienced flooding.
Also, when the lab lady was instructing us on how to administer the Qs, I mentioned the flood may have been due to GW. She laughed in my face, but I whipped out a manual I’d just study from IL Natural Resources, a study on GW which predicted that area (among many others) might get flooded….
5 October 2007 at 6:29 PM
Another off-topic comment, but there are likely to be many who will want to obtain a copy of the .pdf file, “The Threat to the Planet: Dark and Bright Sides of Global Warming”, available from Dr. James Hansen’s web site, as the first file listed under the heading Files of Interest:
http://www.columbia.edu/%7Ejeh1/
(Hope I did this correctly. Hint: could certainly use a preview capability…)
[Response: Previews re-installed…. let me know if there is a problem - gavin]
5 October 2007 at 6:44 PM
#35 31 Chris
“no there is no top end, but the radiative forcing by CO2 incraeases not linearly proportional to CO2 concentration, but logarithmically to CO2 concentration for more info I recommend previous posts”
Thank you Andree that is what I was looking for.
5 October 2007 at 7:53 PM
Sorry to be off subject here. But I have two questions. 1) I have seen several places claims that the ENSO has been/ is being changed by AGW. Is there evidence for this? 2) The magnetic north pole is moving towards Russia (through the Arctic). Does this effect currents or climate? Thanks
5 October 2007 at 8:35 PM
Gary,
Re 1)–a pretty good, albeit brief discussion here:
http://www.realclimate.org/index.php/archives/2007/08/regional-climate-projections/
Re 2) Almost certainly not. The geomagnetic field only affects charged or magnetized particles. I suppose that when the field starts to flip, you could see some effect due to solar particle events, but that’ll be the least of our worries.
5 October 2007 at 9:10 PM
Re the topic, “My model, used for deception”…
Anyway, you know what the denialists say about models
5 October 2007 at 10:14 PM
There are other papers that state that solar cycle 24 will be the start of a Maunder like minimum. For example:
http://adsabs.harvard.edu/abs/2004ApJ…605L..81B
“We have examined the long-term trends in the solar variability that can be deduced from some indirect data and from optical records. We analyzed the radiocarbon measurements for the last 4500 years, based on dendrochronology, the Schove series for the last 1700 years, based on auroral records, and the Hoyt-Schatten series of group sunspot numbers. Focusing on periodicities near one and two centuries, which most likely have a solar origin, we conclude that the present epoch is at the onset of an upcoming local minimum in the long-term solar variability. There are some clues that the next minimum will be less deep than the Maunder minimum, but ultimately the relative depth between these two minima will be indicative of the amplitude change of the quasi-two-century solar cycle.”
There are also other papers that have presented arguments for a smaller climatic forcing function.
I have been following cycle 23 and can attested that it is very unusual. The sun is currently in a spotless state, the solar large scale magnetic field is dissipating. The solar cycle will be 132 months old (11 years) December 31, 2007. If the solar hypothesis is real the cycle will flat line, and the planet will cool.
I thought with flat lining there would be a 2C cooling and quite rapidly.
6 October 2007 at 12:16 AM
Re #35: […but the radiative forcing by CO2 incraeases not linearly proportional to CO2 concentration…]
But on the other hand, warming of the oceans should release significant amounts of CO2…
6 October 2007 at 6:24 AM
Re: #26 and #29
For a discussion of the ocean skin layer and infrared penetrance see:
http://www.realclimate.org/index.php/archives/2006/09/why-greenhouse-gases-heat-the-ocean/
It speaks of micrometers and not millimeters so I was being a little generous. Given such low penetrance, this CO2 radiation will be much more effected by mist, spray and foam, and should more directly impact evaporation than radiation which penetrates 10s of meters.
What differences in forcings is it safe to ignore in the models? Is radiation which mere micrometer penetrance at a complex ocean surface really equivilent to radiation which can support tropical kelp forests at 200ft depth? See:
http://www.sciencedaily.com/releases/2007/09/070926142907.htm
I don’t think, given what we know about the differences, that we can really accept immateriality or equivilence as the null hypothesis. Models based on that assumption have failed to reproduce solar cycle signatures found in the data:
http://www.amath.washington.edu/research/articles/Tung/journals/solar-jgr.pdf
I quote from the article:
“Our procedure for the solar-cycle signal yields an interesting pattern of warming over the globe. It may be suggestive of some common fast feedback mechanisms that amplify the initial radiative forcing. Currently no GCM has succeeded in simulating a solar-cycle response of the observed amplitude near the surface. Clearly a correct simulation of a global-scale warming on decadal time scale is needed before predictions into the future on multi-decadal scale can be accepted with confidence.”
6 October 2007 at 7:42 AM
Feeling the need to try to add a little insight, I have been taking a little look at “feedback factors” as in the equation:
dT(final) = dT(forcing) * f
or more usefully:
dT = dF * C * f
(where T = temperature, f = feedback factor and F a Flux or Forcing and C is the baseline climate sensitivity i.e. for a clear atmosphere)
and a formula for combining “feedback factors” :
f = f1*f2 / (f1 + f2 - f1*f2)
This can be rearranged to give:
f = 1/ ((1/f1)+(1/f2) - 1) and generalises to
f = 1/(SUM(1/fi) - (N-1)) where the fi are N individual “feedback factors”.
Rearranging again we have;
1/f = 1 - SUM(1-1/fi)
and substituting: ai for (1-1/fi) and a for 1 - 1/f
1-a = 1 - SUM(ai)
This gives an insight into what the “feedback factors” are.
for now dT = dF/(1-a) * C
Each ai represents the closure of a proportion of the channel through which passes heat from the surface into space. E.G. the proportion of the bandwidth that is blocked.
The ai are additive:
a = SUM(ai)
with the provision that the closure of a particular piece of bandwidth is not counted twice as where the spectra of two gasses overlap.
Now dT = dF/(1-a) * C generalises to
dT = d(F/(1-a)) * C = ( dF/(1-a) + F * d(1/(1-a)) ) * C
where d(1/(1-a)) = 1/((1-a)^2) * da
Now dF can be regarded as a true forcing but to make sense F must refer to the total outbound heat flux.
In general the ai are not constants but are dependent on T and possibly the evolved history of the planet.
So for an ai(T) that is dependent on temperature we have (in isolation)
dT = F / ((1-a)^2) * d(ai(T)) * C
It is important to note that it is the total heat flux F not just the originating forcing component dF that is acted upon. In this way very small changes in ai(T) can give rise to large changes in temperature.
As it happens the effect of increased CO2 could be regarded as a pseudo forcing (as it is most commonly) or as a small closure of the available bandwidth ie as a component of da. It is perhaps more consistent to regard all changes to the atmospheric content that reduce the available bandwidth in the same way. There is no fundamental difference between the ways that H20 and C02 act as greenhouse gases to imply one should be a forcing and the other a feedback, it is purely a matter of convenience. Also it can be noted that the “feedback factors” are not feedbacks in the strictest sense as they are simply temperature dependent modifications the proportion of the bandwidth that is blocked or as the “resistance” the atmosphere presents to the escaping heat flux.
We know that the earth is warmer than it would be without greenhouse gases. And we can give some experimental value to (1-a) and the various ai (H20,C02,CH4, etc.). We also have a value for C so some sort of lower limit can be put on the current effective instantaneous Climate Sensitivity that is undeniable. I sincerely hope so.
I do not have the time to continue this at this moment but I hope this part is of some interest to the circumspect.
Best Wishes
Alexander Harvey
6 October 2007 at 11:29 AM
Re # 27 cce: Ships crossing the Northwest Passage?
I don’t who is making that claim, but a recent Reuters news article suggests it is not likely:
Despite warming, ships to shun Northwest Passage
By David Ljunggren
OTTAWA, Oct 3 (Reuters) - While there has been much talk that Arctic trade routes will open up as northern ice melts, shipping companies and experts say using the fabled Northwest Passage through Canada’s Arctic archipelago would be too difficult, too dangerous and totally impractical… Michael Gardiner, assistant commissioner of the Canadian Coast Guard for the Arctic, said there had only been 150 transits in the last 100 years, most by coast guard vessels.
“The Northwest Passage in its entirety has often been described at shipping conferences … as a rock pile. It’s very tricky navigation through most of it,” he said.
And if a ship got into trouble the rescue effort would be massively complex and costly, said Bob Gorman of Enfotec, which provides ice navigation services in the Arctic. “It’s just not a route well traveled … there are no tugboats nearby, there are no shipyards nearby, there are no repair facilities, there is no port of safe refuge. You are really out in the wilderness,” he said. …
http://www.reuters.com/article/basicindustries-SP-A/idUSN2538211120071005
6 October 2007 at 12:57 PM
As a layman reading Alexander’s paper I thought it was phrased argumentatively and could lead to ad hom’s rather than examination of his ideas.
Alexander’s Figure 12 (showing A correlation between temperature and solar cycle length - rather than amplitude) seemed the key point of the paper, on which his predictions are based. The question: is this spurious or have others noted this correlation for other locations? Seems a basic way to test the main idea in the paper without getting sidetracked on other issues.
Also, his Figure 10 shows solar cycle amplitude which, by eye, seems to correlate somewhat with known temperature trends. I thought it would be helpful to have a plot of solar cycle length superimposed on this figure - is this available somewhere? That is, does solar cycle length correlate with the following solar cycle amplitude?
6 October 2007 at 1:26 PM
Why doesn’t increased water vapor lead to decreased insolation?
Several of the absorption bands seem not to be saturated.
http://en.wikipedia.org/wiki/Image:Solar_Spectrum.png
6 October 2007 at 1:37 PM
[[Where it is based on models, nearly all the models are biased against solar activity]]
In what way? All the models I’m familiar with take solar activity into account.
6 October 2007 at 4:12 PM
This is in response to Alexander Harvey in #44.
You are clearly familiar with some of the aspects which are involved and I appreciate your efforts.
I will set aside the mathematics at this time - although someone else may be better equipped to deal with it than I.
However, I believe there are a few issues worth pointing out.
First, you state in #44:
There is a fairly big difference between water vapor and carbon dioxide: water vapor doesn’t stay in the atmosphere for very long - perhaps a few weeks. It falls out in the form of rain and snow. As such a pulse of water vapor won’t stay in the atmosphere long enough to raise the temperature significantly and the original equilibrium (prior to the pulse) will be quickly re-established. However, carbon dioxide stays in the atmosphere for a very long time. In fact, a substantial percentage of a pulse of carbon dioxide will remain in the atmosphere even a hundred thousand years. For the original equilibrium to be reestablished, you have to have mineralization - and that takes a long time.
As long as there is more carbon dioxide in the atmosphere than before, it will reduce the percentage of thermal radiation which is able to leave the atmosphere, which means that the climate system must heat up if the rate at which energy leaves the climate system is to equal the rate an which energy enters the climate system. Since it stays in the atmosphere longer, it will raise the temperature gradually over the decades. As the temperature rises, water vapor evaporates at a higher rate, raising the water vapor content of the atmosphere, further amplifying the the increased greenhouse effect of the additional carbon dioxide.
Second, carbon dioxide isn’t always considered a forcing - and I believe this is somewhat in step with one of the points in your post - although there are certainly times even in the paleoclimate record when it has been so. (A good example would be the Permian Triassic extinction which was driven largely by the eruption of a supervolcano in Siberia, raising the CO2 levels to around 3000 ppm.) Sometimes increased insulation due to a periodic shifting of the earth’s orbit towards the sun will raise the temperature first and the carbon dioxide will follow - with higher temperatures reducing the amount of carbon dioxide which the ocean will have the capacity to hold - and the amount of carbon dioxide which plants are able to absorb given droughts. Another may be the raising of the temperature of permafrost which will release methane and carbon dioxide, increased moisture in the polar altitudes resulting in more methane in growing bogs, but there are other feedbacks to the carbon cycle.
The feedbacks from the carbon cycle may become important - inasmuch as higher temperatures brought on by our own anthropogenic emissions of carbon dioxide may raise temperatures enough that it will cause the climate system to start emitting more carbon dioxide of its own. Some of those feedbacks seem to be kicking in a little already.
What constitutes a forcing? Anything which reduces or increases the rate at which energy leaving the climate system is not equal to the rate at which energy enters the climate system - and does so long enough that the equilibrium temperature has the chance to shift.
Second, you state in #44:
There are a couple of problems here, one related to the physics and one related to the nature of science itself.
First the physics. There is no such thing as an instantaneous climate sensitivity. More greenhouse gas (whether it is carbon dioxide or water vapor) will reduce the ability of thermal radiation to leave the atmosphere, but it will not instantaneously raise the temperature. That takes time - as it will take time for the surface to rise in temperature - even before one takes into account any feedbacks.
Second, nothing in science is undeniable. Leave the “undeniable” to Descartes. What science deals with is the cummulative weight of the evidence - but if some skeptic is willing to snuggle up to the belief that everything that they see and remember was put there five seconds ago, they can certainly do so. Regardless, we are pretty confident that the Charney climate sensitivity is roughly three degrees Celsius. (We have about 400,000 years of climate data to back that up.) However, this is in the short-run.
According to Hansen, long-term is more like six degrees. Then of course there is the feedback from the carbon cycle itself.
One more point…
This is actually a little earlier in your post, but it is also a little more technical, so I am putting it off to last.
You state in #44:
The problem is that even if radiation is absorbed, lets say in the lower troposphere by water vapor, an equal amount of radiation will be emitted by water vapor in the same band. Some will be upwelling, some will be downwelling. For that which is upwelling, if the bands overlap with carbon dioxide in the upper troposphere or lower stratosphere where the atmsophere is dry, it will be absorbed and an equal amount will be reemitted in the same band. Likewise some of the emission by carbon dioxide will be upwelling and some will be downwelling. Whenever the thermal radiation is downwelling, it will tend to increase the greenhouse effect.
I suspect the problem here is that you are thinking of greenhouse gases as blocking thermal radiation such that once the radiation is absorbed there isn’t any reemission. But they don’t block - they absorb and emit - in both directions. Without the greenhouse gases thermal radiation would simply be radiated into space and there would be no downwelling of thermal radiation - just the absorbtion of sunlight.
But greenhouse gases are a part of the atmosphere and render it opaque to thermal radiation - which means that some will be downwelling. It is the downwelling that reduces the rate at which energy is leaves the climate system until the temperature of the system rises enough that the rate at which energy enters the system equals the rate at which energy leaves the system - and a new equilibrium is established.
However, overlapping bands in the lower troposphere where water vapor dominates will keep carbon dioxide from absorbing any significant amount of radiation - in the lower troposphere itself. This is where a band will be saturated by a given greenhouse gas - and one needs to avoid double-counting.
Anyway, thank you for throwing some light on this. Hopefully I have managed to illuminate things a little as well.
6 October 2007 at 6:20 PM
Timothy,
My thanks go to you for taking the trouble of replying in such detail.
I shall try to respond in the same manner when I can. I have a fair amount on just now but hopefully this thread will stay alive long enough to offer me such an opportunity.
For now just my thanks must suffice.
Best Wishes
Alexander Harvey
6 October 2007 at 9:00 PM
#47, the water (and CO2) bands seen in the solar visible and near IR are called vibrational overtones. If molecular vibrations are harmonic, the nuclei moving like a perfect spring, only transitions between the closest vibrational levels are allowed. As real springs, molecular vibration is anharmonic. It is this anharmonic component that makes allowed vibrational transitions which take you from one vibrational level to much higher ones. These are VERY weak.
The water vapor bands that are most important to the greenhouse effect are those that result from rotational transitions (changes in the rotational quantum numbers) in the IR, and somewhat the bends. These are saturated in the CO2 sense.
A more detailed explanation would be, well much more detailed, so perhaps this is not the place.
6 October 2007 at 9:04 PM
#44, Alexander Harvey says: “There is no fundamental difference between the ways that H20 and C02 act as greenhouse gases to imply one should be a forcing and the other a feedback, it is purely a matter of convenience.”
My understanding of how feedback and forcing are used, is that forcing is external to the climate system, as for example solar insolation. If, for example, CO2 is added to the system from burning fossil carbon, it is being introduced from a source isolated from the climate system in any meaningful sense and is a forcing. If it is added by warming of the oceans, then it is being added from inside the system in response to temperature increase and is a feedback. To paraphrase, a feedback in one situation is a forcing in another, but it is either or, not both at the same time.
6 October 2007 at 9:07 PM
lgl–most incoming solar radiation is in the visible. Water would absorb what is in its absorption band, but once excited, it would tend to relax collisionally, so that energy would mostly go into heating the atmosphere anyway. Still, the outgoing flux of LWIR is much higher than that of incoming LWIR.
6 October 2007 at 9:50 PM
Re 44: I believe you can rearrange the final equation into a simpler form:
N = On(e.Se/Ns^E)
7 October 2007 at 6:20 AM
Australia is about to have a Federal Election and John Howards Liberal Party has a bunch of so called intellectuals - Archibald - who will say anything , regardless of the consequences, to get their party back in power. Politics has a lot to answer for in Australia in regards to climate change, especially if you would like to live in a world of 1000ppm CO2, as some buisiness men think would be pretty cool.
7 October 2007 at 11:10 AM
Timothy (50), a clarification please.
Does upwelling “re-emission” from water vapor really get absorbed by high altitude CO2? Why would H2O radiate, not in its natural spectra, but in CO2s spectra (other than the minor overlapped bands)? [I’m not sure if this would alter your basic premise, however.]
Isn’t there some point, eventual equilibrium of sorts, when greenhouse gases do “block” (absorb without re-emission) terrestrial radiation? Otherwise we would not see any vacant spectra in the, say, satellite imaging of terrestrial radiation, would we?
A helpful post. Thanks. You, too, A. Harvey.
7 October 2007 at 1:53 PM
Re 54#
“most incoming solar radiation is in the visible”, well - more 50/50 I would say. But yes, the energy would heat the atmosphere and a lot of that energy would radiate back to space and not reach the surface. This should give less heating of the surface and less outgoing LWIR.
In addition the H2O absorption bands in the LWIR seem to be much more saturated that those in the solar IR spectrum.
If more of the insolation is absorbed in high troposphere the increase in GHG should also make it more difficult for that energy to reach the surface.
Thirdly, increased evaporation brings more heat to “high up” (how high?). The GHG would not influence the upwelling but would reduce the downwelling IR, right?
I see from the radiation budget that the absorbed solar, evapotranspiration and outgoing thermals add up to about 170 W/m2. I don’t know how much of this is radiated back to ground but I would assume that this incoming radiation also face an increased greenhouse effect, which should then have a cooling effect.
To get to the point. I am looking for a paper (free on the web of course) where these effects are described/estimated and how they are treated in the models.
7 October 2007 at 2:19 PM
In answer to the question, “who are the organizations that continue to fund baseless attacks on climate science?” here are some of the main players:
The American Petroleum Institute: http://www.api.org/
The Edison Electric Institute: http://www.eei.org/
In the past, the now-disbanded Global Climate Coalition was the front organization for fossil fuel interests who want to prevent any reductions in fossil fuel use. Essentially, these interests know that renewables are simply less profitable and will be expensive to produce, requiring massive amounts of investment in production facilities and electrical grid infrastructure. It’s cheaper to spend hundreds of millions on slick PR campaigns designed to create doubt in the public’s mind over climate science than it is to replace fossil fuels with renewables.
Essentially, that’s the problem. An 80-90% reduction in CO2 emissions really requires an 80-90% reduction in fossil fuel sales. That energy demand must be met with real renewable sources, primarily wind and sunlight, and energy efficient technology. That requires replacing the existing trillions of dollars of fossil fuel infrastructure with trillions of dollars of renewable infrastructure, and nobody seems to want to spend the money. Vast sums will have to be spent to create a renewable-energy based infrastructure - which means a lot of economic activity, but which also means turning the global economic order upside down. No oil-selling country or corporation on the planet wants to see U.S. energy demand drop, regardless of their political viewpoint.
Across the U.S. right now we have a wave of ‘feel-good’ proposals, with local and national politicians pledging their green values left and right - but when it comes to funding real changes, it’s just not happening. Fossil fuel companies and government economists are still working on the assumption that U.S. fossil fuel demand and consumption will continue to increase over the next twenty years.
Taking action on global warming is now seen as politically popular, so we’re seeing a lot of rhetoric - but no real large-scale changes in the energy picture have been proposed by politicians to date.
7 October 2007 at 2:55 PM
lgl, OK, think about this. First, the amount of energy at wavelengths shorter than the absorption bands of the GHGs is well over 50%. Second, warming the atmosphere does heat the surface, since it means that the net outgoing radiation is less. Yes, the ghgs do absorb in their lines, but they don’t care whether radiation is outgoing or incoming–and there’s a whole lot more outgoing LWIR than incoming (look at a spectrum of Earth’s thermal radiation). And yes, water vapor does transport energy into the lower troposphere. However, it drops it there. The only way for it to escape is via outgoing IR radiation. I would strongly recommend that you get the science of the greenhouse effect under your belt before tackling the scientific literature. Check out the text by Ray Pierrehumbert http://geosci.uchicago.edu/~rtp1/ClimateBook/ClimateBook.html
7 October 2007 at 5:19 PM
Thanks Ray, at first it looked quite promissing.
CONTENT
5.10 Effects of atmospheric solar absorption . . . 198
but where is it?
Ah.. “Chapter 5, is about 3/4 complete now”
Please hurry Pierrehumbert! I’m waiting for this.
Meanwhile, just to make sure, are you really saying that none of the heat brought to the atmosphere by thermals and solar absorption is radiated back to the surface? And if it is, why do not GHGs have any impact on this radiation?
7 October 2007 at 5:25 PM
Further to #56: Guy Pearse, a former advisor to Howard, has written a book about Australian politics and climate change:
“…He reveals that the government has no plans whatsoever to reduce Australia’s emissions, and explains why this is bad for Australia’s economy. He exposes a prime minister wilfully blind to Australia’s real Interests - a man who has allowed climate change policy to be dictated by a small group of Australia’s biggest polluters and the lobbyists they fund…”
http://www.highanddry.com.au/
And a couple of articles about the book and the politics:
http://www.newmatilda.com/home/articledetail.asp?ArticleID=2363
http://newmatilda.com/home/articledetailmagazine.asp?ArticleID=2421&HomepageID=216
I think Howard, Bush and Harper all sing from the same songbook.
7 October 2007 at 6:59 PM
Ray> First, the amount of energy at wavelengths shorter than the absorption bands of the GHGs is well over 50%.
Still, looking at the solar spectrum:
http://en.wikipedia.org/wiki/Image:Solar_Spectrum.png
it appears that a lot of incoming solar energy between 900 and 2000nm is absorbed by water vapor. Does anyone know if this negative feedback from water vapor increasing with temperature is included in the climate models?
[Response: It actually isn’t much of a feedback (since it mostly intercepts energy in the troposphere that would have been absorbed by the surface), and yes, this is included in most GCMs with reasonable radiation models. - gavin]
8 October 2007 at 1:24 AM
Ups, I made a mistake in 61#
I should of course have said “to the atmosphere by thermals and evaporation” not “to the atmosphere by thermals and solar absorption” You were quite clear about the solar.
I have this notion that heat released high up in the atmosphere will not warm the planet as much as if it was released very low in the atmosphere, maybe this is where I’m taking the wrong path?
8 October 2007 at 2:44 AM
Very enlightening discussion. Many thanks. I really question Archibald’s methods and so should you all.
8 October 2007 at 5:32 AM
[[Isn’t there some point, eventual equilibrium of sorts, when greenhouse gases do “block” (absorb without re-emission) terrestrial radiation? ]]
They can’t absorb without emitting.
8 October 2007 at 5:41 AM
Re: #59 Ike, “Fossil fuel companies and government economists are still working on the assumption that U.S. fossil fuel demand and consumption will continue to increase over the next twenty years.”.
Sounds plausible, however doesn’t the reality of Peak Oil, begin to pull the rug out from under this premise? Or does oil start to become a non issue in the context of the bigger picture when taken together with natural gas and coal?
My personal hunch is that as technology progresses it becomes increasingly feasible for larger swaths of the general population, to become completely energy independent, thereby breaking the the energy companies monopoly.
I think this is the scenario that they dread the most and will surely fight to the death to maintain their lucrative status quo regardless of the consequences.
8 October 2007 at 8:19 AM
“Peak Oil” just means “invest in oil companies”. What they sell will just keep getting more valuable.
Demand hasn’t slacked much with the increases in price so I don’t have much faith in alternate energies saving our bacon.
8 October 2007 at 10:31 AM
Demand has continued to soar despite the higher prices. The demand for energy has never been higher than it is right now. The higher prices support the more costly refining that once precluded bringing certain types of fossil fuel reserves into production.
8 October 2007 at 10:45 AM
Barton (66), I understand the logic of that, but the puzzle is: a bunch of radiative power in a certain band leaves the earth’s surface, but is not much seen at the top of the atmosphere. Where did it go??
8 October 2007 at 12:27 PM
Rod, the ‘band’ refers to counting a lot of photons in arange of energies. It’s not a unique entity that persists, it’s a measurement.
Sunlight warms the Earth. The solids heat up. The molecules in the solid Earth aren’t free to bounce around, they’re pulling and tugging at each other but (short of boiling to vapor, for example) don’t break apart and float freely. All the pieces are moving, the motion of the atoms produces photons. The range of motion isn’t in discrete steps because everything’s tugging on everything else in a solid, so any range of motion possible can produce a photon of that amount of energy. From Earth in sunlight, it’s the ‘infrared band’ that’s produced.
That “band” is like a battle plan, it does not survive first contact with the enemy — the next molecule that any of those photons hits absorbs its energy. Photon’s _gone_.
On average.
Some photons from the ground, and from low clouds, and from water vapor in the atmosphere, do make it all the way out into space — you can look at the satellite photographs in the infrared bands. Compare those wavelengths to the wavelengths in which our atmosphere is less opaque to infrared.
But on average, in the dense lower atmosphere, a photon hits a molecule; the molecule’s energy increases, in some vibrational mode, while also transferring energy among those modes internally and banging into other molecules. The original photon no longer exists, it’s a bookkeeping entry for transfer of energy.
Higher in the atmosphere the gas molecules are more widely separated. While they’re not banging into one another, each one can emit photons at the specific wavelength defined by the ways its atoms can vibrate.
We talk about an average altitude (6 km and rising) where — on average — photons interact less often and more of them escape into space, removing energy from the planet.
So — there’s where your “band” goes.
Imagine a pool game in which, half the time, your white cue ball would change to another ball on impact, and if a couple or three of the other balls displaced from the rack happened to hit the right way, one of them would turn into another white cue ball.
8 October 2007 at 2:10 PM
lgl,
Once energy is absorbed by either the atmosphere the ocean or solid Earth, it is part of the system that determines climate. The only way it can escape is as radiation–and because of the temperature of Earth, mainly IR radiation. Rod, you asked where the energy goes. It goes mainly into thermal excitation of molecules in the atmosphere and also on Earth’s surface–at least until the temperature rises enough to restore equilibrium where incoming energy equals outgoing energy.
8 October 2007 at 4:13 PM
Igl (#64) wrote:
Actually this much is right.
In terms of optical thickness, longwave’s which are at a greater altitude have considerably less “distance” to travel to reach space. And the path will be one of multiple absorptions and emissions is a random walk. Therefore that which is closer to the surface is much more likely to return to the surface, and that which is closer to space (in terms of optical thickness) is more likely to make it to space.
But there are two qualifications to keep in mind. First, optical thickness is roughly distance, but with lower atmospheric density - which decreases exponentially with altitude, etc along the longwave’s path taken into account. In fact, optical thickness is actually dimensionless. Second, one can’t actually treate the energy as a single photon since the energy gets lost to collisions, spread out between different molecules in still other collisions, etc. But an early, first conceptual approximation may be thought of as a single photon or parcel of energy.
*
Anyway, if you haven’t already, I would check your question in 61 against Ray’s comment in 60. There is still a great deal of longwave being radiated by greenhouse gases going to surface. However, when he states that that which is absorbed coming up from the surface tends to be lost in collisions (see 54), this is only because the time between collisions for any given molecule tends to be much shorter than the half-life of an excited state. About a millionth of the timespan. As such, when a molecule radiates a photon, this is due to the molecule having received energy through collisions in the same way that molecules lose energy due to collisions.
Now why don’t the molecules lose this energy before they emit - given the timespans?
Most actually do lose energy that way.
But why do any radiate.?
Because we are dealing in half-lifes. The molecules have no “knowledge” of how long they have been in an excited state. They spontaneously decay. As long as a certain number are in an excited state at any given time, a certain number will undergo spontaneous decay over a given period. The coins get passed around, but whereever they are, they keep getting tossed - and some come up heads.
Hope this helps…
8 October 2007 at 4:48 PM
Dear bobn,
Re: #55
I always welcome constructive criticism.
When you have some, do please post it.
FWIW the origin of the equations is not my work and has been around in the literature for at least 20 years.
Best Wishes
Alexander Harvey
8 October 2007 at 7:30 PM
Re 64. lgl, Your intuition is mainly correct, but you need to define what you mean by “high up in the atmosphere”. Essentially that means that the optical path of the photons is longer than the residual distance to the top of the atmosphere. That depends on the density of molecules that can absorb the photon on its upward path. As we raise the ghg content of the atmosphere, we effectively raise the altitude at which IR photons are able to escape, meaning that less energy is able to rise up that high. Thus the part of the atmosphere from which radiation can escape is colder and so radiates less, meaning more energy stays in the climate system. That’s one way to look at it–essentially the same as that in “A Saturated Gassy Argument”.
8 October 2007 at 9:12 PM
Barton, Ray, Hank, Timothy, et al: I may be getting it. I’ll try a simple example, and see if it works. The 15um band radiates a bunch from the surface. Spectral analysis shows about (eyeballing it — assume for discussion) 5% transiting and leaving the atmosphere. I assume this 5% either made it out directly, or with the absorption - many collisions - secondary emission chain of events (and maybe going through that chain many times). The other 95% will get absorbed and, following roughly the same general process above, 1) re-radiate directly back to the ground (a very tiny portion of the 95%), 2) pass energy to other molecules through multiple collisions and finally end up adding to the “steady state” kinetic energy of atmospheric molecules and heat the atmosphere (bigger than #1, but still small), 3) go through the process chain above and finally break the chain(s) by emitting back to the surface (my guess, the vast preponderance of the 95% that didn’t make it out). Though I’m not sure why the downward re-emission doesn’t get absorbed by other greenhouse gases before it reaches the ground. Or… maybe it does and just keeps going through the cycle chain numerous times with the overwhelming probability that it will finally go down to the surface rather than up and out…???
Is this, while oversimplified, generally close?
8 October 2007 at 10:35 PM
I know it is off the topic, but apparently IPCC have underestimated the level of CO2e in the atmosphere…
http://www.abc.net.au/lateline/content/2007/s2054168.htm
Any comment on this from RC?
[Response: This is very confused and misleading. The AR4 WG1 report showed that the positive forcings from WM-GHGs were around 2.7 W/m2, which is 455 CO2_equivalent, but the climate basically only cares about the total forcing - which includes cooling from aerosols and the effects of soot and ozone and solar and the like. The more relevant net forcing is estimated to be around 1.6 W/m2 (which is about 380 CO2_e). Statements like Flannery’s implying that the IPCC doesn’t know what’s in it’s own reports or that suddenly there are more GHGs than we thought are just silly. He should know better. The situation is bad enough without the exaggeration. - gavin]
8 October 2007 at 10:56 PM
This question is climate related, but not related to this article:
Some skeptics point out that man-made emissions account for only a small percentage of total CO2 emissions into the atmosphere; the rest being from natural sources. I’m finding this hard to reconcile with the large CO2 jump following 1975. Are they saying that only 3-7% of the 380ppm C02 concentration in 2007 is man-made? Which would mean that a large natural CO2 increase occurred following 1975. Am I missing something here? Someone explain this to me. What is meant in these statements?
9 October 2007 at 12:21 AM
thanks Gavin, I thought is sounded strange… I’ve found he gets quite a bit wrong on energy issues so the alarm bells usually go off when he comes out with this sort of stuff. I guess it shows the poor state of the debate in our country when he is considered one of the ‘front men’.
To the rest of the world… please don’t judge us because we are Australian, most of us are ashamed enough already!
9 October 2007 at 1:02 AM
Rod, maybe David Archer can comment — someone who actually understands MODTRAN and the math, I hope, will. I think words are just approximations at best, and I don’t pretend to be able to handle the math.
9 October 2007 at 1:07 AM
Re: #78 (John Galt)
You’ve been fed a classic piece of denialist propaganda. What they omit to mention is that natural CO2 emissions to the atmosphere (from oceans, biosphere, etc.) is balanced by natural absorption (by oceans, biosphere, etc.). That’s why, for over 10,000 years, CO2 concentration was reasonably stable at about 270 ppmv.
You may even hear the false claim that more CO2 is emitted by a large volcanic eruption like Mt. Pinatubo or el Chicon, than all human activity since the beginning of time. This is just plain false. CO2 emission from large volcanos is measured in megatons, but the CO2 emissions from the U.S. alone, in one year alone, count in the gigatons. And of course, 1 giga = 1000 mega.
The truth is that all the rise in CO2 concentration since pre-industrial times is due to human activity. This is beyond doubt; the carbon in fossil-fuel CO2 has a different “isotopic signature” from that due to natural emissions, and the changing isotopic composition of atmospheric CO2 is a “smoking gun” proving that the increase is from fossil fuels.
Not only is this claim junk — it’s not even very good junk.
9 October 2007 at 1:07 AM
Oh, further for Rod, this is another diagram from the same source Timothy Chase pointed to in the parallel conversation (this thread seems more the right place for it). Your description above fits this, I think?
http://www.aer.com/images/rc/heattrap_thumbb.gif
9 October 2007 at 1:17 AM
John Galt, look up “biogeochemical cycling” to answer the point about humans adding only “a small percentage of total CO2 emissions” — what is happening that changes climate is that CO2 from fossil fuels that doesn’t all get cycled by natural processes (about half the total produced by burning fossil fuels so far is still in the atmosphere, the other half did get taken care of by nature). The “natural carbon sinks” only accept so much — the rest accumulates fast in the atmosphere and won’t get taken care of by natural cycling for some centuries. And if the natural processes get overloaded and quit working, then the excess will accumulate faster.
The ’start here’ link at top of page will help with the basic questions like this.
9 October 2007 at 3:29 AM
thanks Gavin, I’ve written to the ABC and asked them to clarify with Mr Flannery and if appropriate, issue a pulic retractment.
9 October 2007 at 4:36 AM
Re #78 The pre-industrial level of CO2 was measured around 1900 at 280 ppm, and that value has been confirmed by the analysis of ice cores. Today the level of CO2 is at 380 ppm, an increase of almost a third.
If you go to the NASA site you can see the latest measurements of atmospheric CO2 taken on top of Manua Loa, in the centre of the Pacific. See http://www.esrl.noaa.gov/gmd/ccgg/trends/
What the skeptics are arguing is the the change during one year, as shown by the red curve,is much greater than the net change each year shown in the black curve. The seasonal change in CO2 is caused by the blooming and decay of vegetation on the continents, which are mainly in the northern hemisphere. That has a net effect of zero on the annually averaged CO2 level.
Or it would have, but with the burning of the rain forests in fact there is more CO2 released into the atmosphere than the pasture lands that replace them can absorb. So the rise in CO2 and the resulting global warming is not just a result of burning fossil fuels. Land use change is also having a not insignificant effect.
9 October 2007 at 4:41 AM
Re #78
I should have written a NOAA website not NASA, but it is no less authoritative.
9 October 2007 at 5:49 AM
Re 78:
Each year vegetation takes up ~110 gigatons (1 billion metric tons) of carbon from the atmosphere through photosynthesis. And each year, plants, animals, and microbes respire about ~110 gigatons of carbon back in to the atmosphere. Over the last several hundred millions, some amount of carbon on the order of ~5000 gigatons wasn’t respired back to the atmosphere but trapped in the lithosphere becoming what we know as fossil fuels. Our civilization is now burning fossil fuels, emitting some of that carbon back in the atmosphere on the order of several gigatons per year.
So to answer your question, yes, annually the amount of carbon released by burning fossil fuels is only 3-7% of that respired (”natural emissions”) by the biosphere. The important distinction to be made is that the carbon cycle without fossil fuel emissions would be much closer to a steady-state. That is the amount taken up by photosynthesis is very close to the amount respired.
So, each year we are adding a few gigatons of carbon to the atmosphere, even though the anthropogenic carbon emissions are small compared the natural fluxes. This can all be solidly demonstrated by measuring the changes in the isotopic composition of atmospheric carbon dioxide. I refer you to the some of the great climate science links provided by Real Climate in the panel above on the right, if you want to learn more.
9 October 2007 at 6:04 AM
“John Galt” posts:
[[Some skeptics point out that man-made emissions account for only a small percentage of total CO2 emissions into the atmosphere; the rest being from natural sources. I’m finding this hard to reconcile with the large CO2 jump following 1975. Are they saying that only 3-7% of the 380ppm C02 concentration in 2007 is man-made? Which would mean that a large natural CO2 increase occurred following 1975. Am I missing something here? Someone explain this to me. What is meant in these statements?]]
The amount emitted by human technology in one year is small compared to the total out there. But it has been emitted for many years now. About 28% of the CO2 currently in the air is manmade.
The human amount is small compared to the natural emissions as well, but the natural emissions are largely matched by natural absorptions. For example, the oceans emit about 90 gigatons of carbon every year, but absorb 92 gigatons. It’s the human emissions that are driving the net increase every year, just like a small trickle into a bathtub that is full to the top will cause an overflow. The comparison of human emissions to natural emissions is disingenuous, because natural emissions are largely balanced by sinks and human emissions are not.
9 October 2007 at 7:30 AM
Timothy,
Re: #50
I think have found a copy of “Charney J 1979 Carbon Dioxide and Climate: A Scientific Assessment” and I shall read it before making any comment.
I am aware of some of the mechanisms involved in the absorption and emission of radiation in the atmosphere. I will if I may suggest a modification to that which you wrote.
In that absorption does not necessary equal emission. It depends on the temperature. For instance in the H20 bands there is a net flux in the direction of decreasing temperature. Eventually this turns into a net outboud flux at the TOA.
You can get a feel for this from MODTRAN if you select low altitudes and select “looking up”.
In the “looking up” mode it gives you the “Path Length Radiance” e.g the component that comes from the atmosphere not directly from the surface.
At low altitudes e.g. .01km the band (wavenumber 100-400) “shines” with a temperature of ~288K i.e. surface air temperature.
At 1 km it shines with a temperature of ~280K.
At 4 km at around ~260K.
The actual temperatures that MODTRAN assigns to 1km and 4km are higher 281.7K and 262.2K.
If you do the same “looking up” you get very similar radiation temperatures. The band is close to thermal equilibrium which is I think what you were describing. But as there is a temperature gradient so there is a net flow upwards.
In these bands the “direct” radiation from the Earth’s surface is blocked. The downflow and upflow are all but identical at low altitudes. From the point of view of the ground surface that band is effectively closed.
This could lead to a paradox as at TOA this band radiates with strengths between the yellow and light blue lines ie an equivalent temperature of between 220K and 240K. This is more or less a net outbound flux.
From MODTRAN we have a net upward flux at the surface that is less than half the TOA outbound flux. I think that this is the sort of difficulty that you are aware of.
It would be much more accurate to not use the word blocked but to say that the “blocked” bands were “thermal bands” and the clear bands were “radiative bands”. As an approximation the “thermal bands” radiate at around 220K and the clear bands at around 288K. The fourth power of (288/220) is ~1/3 so a significant reduction in outbound radiation results from “blocking” a band.
A word of caution MODTRAN seems to have a rule that the temperature at the 12km altitude is fixed as is the lapse rate.
Now as more greenhouse gases enter the atmosphere due to outputs of CO2, CH4 and the effect of rising temperature on H2O vapour. The “thermal” output will become increasingly important and the direct radiative component less so. This will mean that the upper troposphere temperature will become increasingly important as a means of removing heat from the system.
I for one should like to know if the assumption of constant lapse rate and a constant 12km temperature that “seem” to be built into MODTRAN are realistic.
I do not know the sensitivity of outbound radiation to temperatures in the upper troposphere but based on MODTRAN my best guess is that a temperature rise of 1C might contribute 0.75 W/m2.
On the other hand increasing greenhouse gases will I think mean that more energy would need to be supplied to the upper atmosphere to power the thermal radiation output there. These are areas that I know little about but would be interested to know more.
I will write again regarding your other points when I can.
Best Wishes
Alexander Harvey
9 October 2007 at 7:39 AM
Re Myself #79
I have always used this http://geosci.uchicago.edu/~archer/cgimodels/radiation.html interface to MODTRAN.
If you want the “lookig up” and some other features you may need to do the same.
9 October 2007 at 8:24 AM
re #75. Ray Ladbury states that “as we raise the ghg content of the atmosphere, we effectively raise the altitude at which IR photons can escape.”
As I understand it, this altitude or level is referred to as the effective radiating level and is measured by examining brightness temperatures of various parts of the IR spectrum from space. Thus, IR travelling through the atmospheric window has a brightness temperature of 288K, that in the water vapour absorbing bands of 275K and that passing through the CO2 band of 215K.
My question is this. As we continue to pump more CO2 into the atmosphere, the climate remains in disequilibrium with more incoming than outgoing energy. It seems to me that, in theory, this could be demonstrated by plotting a falling brightness temperature for IR in the CO2 absorbing band against increasing atmospheric CO2 concentration. Have these measures been made? If not, why not? Is it becauswe we haven’t had access to the appropriate equipment for long enough to show a trend?
I would appreciate help with the above but, while you are at it, perhaps someone could also explain the logical difficulties I have with my understanding of brightness temperatures and their relationship with altitude. My (possibly dodgy) logic tells me that a lower brightness temperature would indicate less effluent energy per se rather than emission height. (I accept that there will be less radiation at the colder temperatures of the higher atmosphere so I may be quibbling over terminology).
Finally, I am uncertain why climatologists are so confident that water vapour is a positive feedback. (If it is, I assume that the brightness temperature of IR in the water vapour absorbing bands should also be dropping). I accept that extra surface warmth will increase atmospheric water vapour but will also increase convection which will carry more energy high into the atmosphere above the water vapour level. Water vapour will also presumably translate into more cloud. This, in turn, could increase albedo and absorb some solar energy before it got to the surface. As clouds act as black body radiators in the IR range, clouds could make it more likely that IR would escape to space than to reach the surface. It seems to me (in my ignorance), therefore, that it is quite complicated to decide whether water vapour will be a positive or negative feedback.
9 October 2007 at 8:56 AM
Re #91
Douglas,
I am not sure how they measure radiation temperatures in practice but in principle if the gas has two or more emission bands you compare their relativ intensities. As gases get hotter they tend to emit more in all bands but the increase is greater at shorter wavelengths. Comparing two or more wavelengths, and after a fair amount of calibrating and you can give a value to the effective radiation temperature of the gas.
If you are inside the gas and the radiation is in thermal equilibrium with the gas then this is the gas temperature. If you are outside the gas it can be more an indicative than an absolute value.
Perhaps someone who knows how it is done in practice will come along and correct me.
The absolute brightness is not the important part it is the ratios between different wavelengths. Much like a furnace changes colour when you look through a spy hole. It is the colour not the intensity that indicates the temperature. I have done this and it works.
Best Wishes
Alexander Harvey
9 October 2007 at 9:24 AM
Rod B., You are indeed close. Basically, all the IR from the surface in the H2O and CO2 bands gets absorbed. Most of the energy goes into collisions with other atmospheric molecules (mostly not ghgs). Some small fraction is emitted from excited ghgs (excited either by collision or by IR). Some goes up, some down. Repeat ad infinitum or ad nauseum, whichever comes first. Eventually, you reach a level where the amount of a particular ghg is small enough that the chances a photon is absorbed are small. Water vapor peters out. Then much higher, CO2 peters out. The ghgs at this level radiate at their effective temperature in the relevant IR line, and that ~5% is what you see from space. I’m sure Gavin, Ray, et al. are wincing at my oversimplification, but in the limit of the spherical horse, that’s how I understand it.
9 October 2007 at 10:01 AM
John Galt (#78) wrote:
John,
Skeptics point out a lot of things.
They’ve pointed out that CO2 actually has no effect upon the climate system, that what is actually changing the climate system is some sort of delayed reaction to the rise in solar temperatures from the earlier part of this century, that can’t be explained except by mysterious heat retention in the ocean but which we’ve picked up somehow in the rise of rivers. They’ve pointed out that greenhouse gases don’t work because the hot air rises up before it gets a chance to radiate, that there is no such thing as average temperature, that the average temperature hasn’t been rising, that its really magnetic fields thats causing the temperature to rise and even that carbon dioxide can’t be in the upper troposphere or the stratosphere because its heavier than air and when it comes as exhaust, it goes sideways then falls immediately to the ground.
As I have said, they point out a lot of things, and its usually horse-hockey. And by the way: I didn’t make any of the above up. Its all stuff that’s been published - although the last was in a letter to the editor - by someone who claimed to be a high school science teacher. And all of this is something I’ve run into this year.
But it might help to know their source.
However, from what I have seen of the accounting, we pretty-well know its us thats put it up there. Pretty much all of it, down to within a few percent. Although nature has been kind so far in sweeping the majority of it under the rug - or to be more precise - into the oceans and even trees. But the oceans might not be such a good idea. And it has a higher content of a lighter isotope of carbon in just the right percentage to show that it came from fossil fuels.
PS
Just out of curiosity: who are you?
9 October 2007 at 10:21 AM
Ray (David Archer, Gavin …) — one question I keep coming back to.
We see weather satellite photographs in many different infrared wavelengths. Some show land/water/low clouds; some show water vapor. Other similar imagery shows concentrations of CO2 at different locations and heights in the atmosphere.
Those images are made with the photons that do move directly from source to satellite — right?
And photographs in the infrared of the limb of the Earth, like photographs in visible light, are showing the scattered light and infrared from the gases of the atmosphere. Right?
9 October 2007 at 10:28 AM
John Galt,
By all means, natural sources of CO2 emission dwarf those of humans. They always have and will continue to do so. However, until somebody figures out a way to tell those pesky plants, animals, etc. to quit decaying, the only source we can control is anthropogenic. What is more, the ~5% emitted by humans is actually a huge amount, and the fact that human emissions have increased exponentially (compared to stasis in natural sources) is very worrying. I actually find it hard to believe that the folks who propagate such statements are unaware of how misleading they are, but I would be willing to allow them to cop to whatever they think is the lesser charge: mendacity or willful ignorance.
9 October 2007 at 10:55 AM
Alexander Harvey (#89) wrote:
I am aware of the fact that it becomes easier for the radiation to escape as the peaks become narrower due to diminished temperature, and likewise, diminished air density makes the paths longer with upwelling radiation. But I don’t see this as a violation of Kirchoff’s Law: that absorptivity and emissivity are equal under Local Thermodynamic Equilibrium - as Kirchoff’s Law describes the local behavior.
Alexander Harvey (#89) wrote:
As I understand it, brightness temperature deals with how much radiation is being emitted at a particular wavelength. It says nothing about how much is being absorbed, and therefore would not necessitate a violation of Kirchoff’s law under and circumstances, high pressure or low pressure, warm or cold - for any greenhouse gas.
Alexander Harvey (#89) wrote:
Top of the Atmosphere. If this is CO2, by 30 km it is already in non-LTE, although the temperatures don’t really begin to diverge significantly until about 50 km.
Anyway, thank you for the response. At the very least, we seem to pretty much understand things the same way - except with respect to Kirchoff’s Law. But perhaps there is something I am just not seeing and I have misunderstood Kirchoff’s Law. Something which Eli said would seem to suggest so.
Take care.
9 October 2007 at 1:19 PM
Hank,
This is a SWAG, but I think that in order to provide images, they have to be direct from the source to the detector. Now, I’m trying to think how I’d image at different levels. One way would be to take advantage of line broadening and image in the tails of the line. You could do this either using a band-gap engineered detector, or more likely by subtracting two filtered images. I’d be really interested to know whether my guess is close.
9 October 2007 at 3:11 PM
In reference to comment #89 Alexander states:
“I do not know the sensitivity of outbound radiation to temperatures in the upper troposphere but based on MODTRAN my best guess is that a temperature rise of 1C might contribute 0.75 W/m2.
On the other hand increasing greenhouse gases will I think mean that more energy would need to be supplied to the upper atmosphere to power the thermal radiation output there. These are areas that I know little about but would be interested to know more.”
If I understand correctly what process Alexander is interested in The following is from “Global Warming The Complete Briefing ” third edition by John Houghton - U of Cambridge Press, 2004
He describes the process in the upper atmosphere as follows:”Let us imagine, for instance, that the amount of carbon dioxide in the atmosphere suddenly doubled everything else remaining the same(figure 2.8).What would happen to the numbers in the radiation budget presented earlier? The solar radiation would not be affected.The greater amount of carbon dioxide in the atmosphere means that the thermal radiation emitted from it will originate on average from a higher and colder level than before. The thermal radiation budget will therefore be reduced,the amount of reduction being about 4 watts per square metre( a more precise value is 3.7).
” This causes a net imbalance in the overall budget of 4 watts per square metre.More is coming in than going out. To restore the balance the surface will warm up.If nothing changes apart from the temperature -in other words, the clouds, the water vapour, the ice and snow cover and so on are the same as before - the temperature turns out to be about 1.2 C.”
The figure referred to shows 240 W/M^2 incoming (net solar radiation) and 240 leaving. When the carbon dioxide is suddenly doubled the amount leaving is reduced by 4 watts per square meter to 236. Balance is restored to 240 and if nothing else changes apart from the temperature of the surface and lower atmosphere, the surface rises by 1.2 C. If feedbacks are accounted for the average temperature of the surface rises by about 2.5C.
Hopefully, this will add to further clarification of the energy balance process.
9 October 2007 at 5:56 PM
The responses to “John Galt” have been many and excellent, but perhaps I can add a tiny bit of value. There is a low-level and a high-level answer to the “CO2 is mostly of natural origin” objection. Here’s the low-level answer:
If we add up the human and natural components of the carbon cycle, we find that sources add up to 217.1 gigatons of carbon (GtC) annually, and that sinks add up to 213.8 GtC. The annual difference of 3.3 GtC is what causes the steady increase in atmospheric CO2. Now, human emissions contribute 5.5 GtC annually, and other human activities (cutting trees, etc.) another 1.6 GtC. Of the gross 7.1 GtC caused by humans, 3.2 GtC stays in the atmosphere, and 2 GtC are absorbed by the oceans. That leaves 1.9 GtC unaccounted for. The mechanisms taking up the missing carbon are under study — leading candidates include more rapid absorption than expected into vegetation and soils. Bottom line: it’s not surprising that humans are causing increases in atmospheric CO2, it’s surprising that we are not adding more.
The fact that the added carbon is overwhelmingly of human origin has been well established by isotopic analysis, among other methods.
And here’s the high-level answer:
If you really think that climatologists, upon hearing this, will clap their foreheads and cry out “Of course! We forgot all about natural CO2! How could we have been so foolish?”, then you and I are inhabiting different realities.
9 October 2007 at 8:43 PM
Ray and others, Eli pointed to a new online textbook that goes into detail about how satellite instruments are used to detect sea surface temperatures in the infrared, it’s good info generally about how it’s done. Directly to that section: http://www.ccpo.odu.edu/SEES/ocean/ocean_lectures/sst_lecture/Part_2/index.htm
9 October 2007 at 8:50 PM
Ryan P. (87) re J. Galt
It would be helpful to include all natural sources and sinks of CO2 for comparison. Barton (88) added some. I thought Timothy would too in (94) but he just couldn’t make it past his diatribe [;-). I wonder (and have asked) the effect of carbonaceous rock as a sink. It also seems that because of the magnitudes involved, a slight anomaly in the natural source/sink process could have an impact. This is a pure speculative question, however. I agree that the argument from my fellow skeptics that ‘man adds just some tiny percent of the total added CO2′ is looking at just a piece of the puzzle, is a blind alley, and misleading.
9 October 2007 at 9:59 PM
> asked … carbonaceous rock as a sink …
Answered — explained by experts in the field
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html
http://www.geo.arizona.edu/geo4xx/geos478/
From the discussion at http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/001004less_than_a_quarter_.html
10 October 2007 at 2:49 AM
Greenhouse gases are warming the planet and will continue to do so. Argue about the rate as much as you wish. This is a recent event only and was not significantly present beyond a century ago. Key point.
Some other influence(s)directly caused significant changes to global climate over the last 3000 years and longer - without greenhouse gases. Indisputable! Argue about this for as long as you like. It did happen.
Solar cycles appea