The Biggest Control Knob: CO2 in Earth's Climate History
It's been a busy past two months of weather and climate change news, and I haven't found time to blog about the research presented at December's American Geophysical (AGU) meeting in San Francisco. That is the world's largest scientific conference on climate change, and the place to be if you want to get the pulse of the planet. The keynote speech at the AGU meeting was given by Dr. Richard Alley of Penn State University. Dr. Alley is the Evan Pugh Professor of Geosciences at the Pennsylvania State University, and one of the most respected and widely published world experts on climate change. Dr. Alley has testified before Congress on climate change issues, served as lead author of "Chapter 4: Observations: Changes in Snow, Ice and Frozen Ground" for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), and is author of more than 170 peer-reviewed scientific articles on Earth's climate. He is also the author of a book I highly recommend--The Two Mile Time Machine, a superb account of Earth's climate history as deduced from the 2-mile long Greenland ice cores. A standing-room only audience of over 2,000 scientists packed the lecture hall Dr. Alley spoke at, and it was easy to see why--Alley is an excellent and engaging speaker. I highly recommend listening to his 45-minute talk via a very watchable recording showing his slides as he speaks in one corner of the video. If you want to understand why scientists are so certain of the link between CO2 and Earth's climate, this is a must-see lecture.
Figure 1. Dr. Richard Alley of Penn State University, delivering the keynote speech at the 2009 AGU conference on climate change.
The Biggest Control Knob: CO2 in Earth's Climate History
Earth's past climate has been shaped by a number of key "control knobs"--solar energy, greenhouse gas levels, and dust from volcanic eruptions, to name the three main ones. The main thrust of Dr. Alley's speech is that we have solid evidence now--some of it very new--that CO2 has dominated Earth's climate over the past 400 million years, making it the climate's "biggest control knob". Dr. Alley opens his talk by humorously discussing a letter from an irate Penn State alumnus. The alumnus complains that data of temperatures and CO2 levels from ice cores in Antarctica don't match:
"CO2 lags Earth's temperature...This one scientific fact which proves that CO2 is not the cause of recent warming, yet...Dr. Alley continues to mislead the scientific community and the general public about 'global warming'. His crimes against the scientific community, PSU, the citizens of this great country, and the citizens of the world are significant and must be dealt with severely to stop such shameful activities in the future".
Dr. Alley explains that the irate alumnus is talking about the Antarctic ice core record, which shows that as we emerged from each ice age, the temperature began increasing before the CO2 did, so increased CO2 was not responsible for the warmings that brought us out of these ice ages. Climate change scientists and skeptics alike agree that Earth's ice ages are caused by periodic variations in Earth's orbit called Milankovich Cycles. "There's no doubt that the ice ages are paced by the orbits", says Dr. Alley. "No way that the orbit knows to dial up CO2, and say 'change'. So it shouldn't be terribly surprising if the CO2 lags the temperature change. The temperature never goes very far without the CO2. The CO2 adds to the warming. How do we know that the CO2 adds to the warming? It's physics!"
Dr. Alley then discusses that the physics that govern how CO2 absorbs and re-emits heat energy, when plugged into state-of-the-art climate models, show that about half of the observed 5 - 6°C natural warming that occurred since the last ice age ended was due to extra CO2 added to the atmosphere. At the peak of the Ice Age, CO2 was about 190 ppm. By the end, it was about 280 ppm (Figure 1). Earth's orbital variations "forced" a warming, which caused more CO2 to escape from swamps and oceans, with a time lag of several centuries. The increased CO2 reinforced the warming, to double what it would have been otherwise--a positive feedback loop. "Higher CO2 may be forcing or feedback--a CO2 molecule is radiatively active regardless of how it got there", says Dr. Alley. "A CO2 molecule does not remember why it is there--it only remembers that it is there". In other words, the fact that higher CO2 levels did not trigger an end to the Ice Age does not mean that the CO2 had no warming effect. Half of the the observed 5 - 6°C natural warming that occurred since the last ice age ended was due to the extra CO2 added to the atmosphere. So, the irate PSU alumnus was half right. The CO2 does lag temperature. However, we can only explain approximately half of the warming since the last ice age ended if we leave out the increase in CO2 that has occurred. "If higher CO2 warms, Earth's climate history makes sense, with CO2 having caused or amplified the main changes. If CO2 doesn't warm, we have to explain why the physicists are so stupid, and we also have no way to explain how a lot of really inexplicable climate events happened over Earth's history. It's really that simple. We don't have any plausible alternative to that at this point".
Figure 2. Ice core record from Vostok, Antarctica, showing the near-simultaneous rise and fall of Antarctic temperature and CO2 levels through the last 350,00 years, spanning three ice age cycles. However, there is a lag of several centuries between the time the temperature increases and when the CO2 starts to increase. Image credit: Marian Koshland Science Museum of the National Academy of Sciences: Global Warming Facts and Our Futures, originally provided to that site by Kurt Cuffey, University of California, Berkely.
CO2 and temperatures rise and fall in synch
Dr. Alley continues with a discussion of how CO2 and temperature levels have risen and fallen in synch over most of geologic time. But for many years there was still a mystery: occasionally there were eras when temperature changes did not match CO2 changes. But new paleoclimate research, much of it just in the past two years, has shown that nearly all of these mis-matches were probably due to suspect data. For example, the mismatch in the Miocene Era has significantly improved, thanks to a new study published this year by Tripati et al. Another example occurs during the Ordovician Era 444 million years ago, as discussed in a recent post at the excellent skepticalscience.com blog.
Figure 3. Atmospheric CO2 and continental glaciation, 400 million years ago to the present. The vertical blue bars mark where ice ages have occurred. The length of the blue bars corresponds to how close to the Equator the ice sheets got (palaeolatitude, scale on the right side of the plot). The left scale shows atmospheric CO2 over the past 400 million years, as inferred from a model (green area) and from four different "proxy" fossil sources of CO2 information. This is Figure 6.1 of the Palaeoclimate chapter of the 2007 IPCC report.
Is there anything else we should be worried about?
Dr. Alley continues with a discussion of other influences that may be able to explain global warming, such as volcanos, changes in solar output, and cosmic rays. A whole bunch of the competing hypotheses don't work", says Dr. Alley. "When there's a bunch of big volcanos, they make it cool. If volcanos could get organized, they'd rule the world. There might be a tiny bit of organization due to flexing of the crust, but they're not controlling the world".
Regarding solar changes: "When the sun changes, it does seem to show up in the temperature record. As far back as we can see well, the sun is friendly, it doesn't change much. If the sun changed a lot, it would control things hugely. But it only changes really slowly--as far as we can tell. The record doesn't go back as far as we'd like, and there's work to be done here--but it just doesn't seem to be doing much".
Figure 4. Greenland ice core proxy measurements of temperature (top curve) and cosmic ray flux (bottom curve) for the past 60,000 years. The Earth's magnetic field weakened by 90% 40,000 years ago, for a period of about 1,000 years, but there was no change seen in the temperatures in Greenland.
Regarding cosmic rays: "The sun doesn't change much, but the sun modulates the cosmic rays, the cosmic rays modulate the clouds, the clouds modulate the temperature, and so the sun is amplified hugely. It's really interesting hypothesis, there's really good science to be done on this, but there's reason to think its a fine-tuning knob". He goes on to show an ice core example from a period 40,000 years ago (Figure 4) where the Earth magnetic field had near-zero strength for hundreds of years. This allowed a massive flux of cosmic rays to penetrate to the Earth's surface, creating a huge spike in ice core Beryllium-10, a radionuclide made by cosmic rays. If cosmic rays were important to climate, we would expect to see a corresponding major swing in temperature, but the ice core shows no change during the period of enhanced cosmic ray bombardment 40,000 years ago. "We had a big cosmic ray signal, and the climate ignores it", Dr. Alley comments.
How sensitive is climate to a doubling of CO2?
The IPCC report talks extensively about computer climate models' calculations of "climate sensitivity"--how much Earth's climate would warm if CO2 doubled from pre-industrial levels of 280 ppm, to 560 ppm (we're currently at 390 ppm). A mid-range number from the 2007 IPCC report often used by climatologists is that the climate sensitivity is 3°C for a doubling of CO2. Dr. Alley takes a look at what paleoclimate has to say about the climate sensitivity to CO2. "The models actually do pretty well when you compare them to the past. The best fit is 2.8°C.
Dr. Alley concludes, "Where we really stand now, is, we're not quite at the pound on the table, this story is very clearly not done. But an increasing body of science indicates that CO2 has been the most important controller of global average climate of the Earth."
I'll have a new post Sunday or Monday.
Jeff Masters
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 — Blog Index
By: STORMTRACKER 13 Chief Meteorologist Matt Meister
A strong spring storm produced snow at a rate of three inches per hour, whiteouts, hazardous travel conditions and even quite a few lightning strikes as it blasted southward late Tuesday and early Wednesday. Road closures along Interstate 70 in several places west of Denver, along Interstate 25 between Greenland and Lincoln Avenue and on Colorado 86 from Franktown to Limon had travelers scrambling to find a way home as roads quickly deteriorated from Denver to Colorado Springs and vicinity with the storm's arrival.
Reports of power outages in Pueblo West came in to NEWSCHANNEL 13 at the beginning of the 10pm newscast as the band shifted southward out of the Pikes Peak Region to the highway 50 corridor as blinding snow enveloped communities along highway 50. Snow will continue to be heavy over the Wet and Sangre de Cristo's and parts of the plains early on Wednesday and travel will remain difficult across the region.
Snowfall reports as of early Wednesday morning include:
19" Pincliffe
15.5" Evergreen
15" 12 NW of Golden
10" Greenwood Village
8.5" 5 NE of US Air Force Academy
8.2" 6 E of Monument
8" NW Colorado Springs
8" Salida
8" 5 SE of Franktown
8" Boulder
7.5" 6 ENE of Black Forest
7.2" Castle Rock
7" 6 SE of Falcon
6.5" 2 NE of Security
5.2" Broadmoor
Reports are still coming in and we'll update frequently...
http://www.krdo.com/Global/story.asp?S=12193668
More moisture does not necessarily mean more clouds. There are several areas on earth that have high heat, high humidity and no clouds. Atmospheric conditions have to be right for cloud formation to occur. Higher global temperatures also mean a thicker troposphere.
Well, yes and no. As our planet is now a cloud covered world would be colder. But if you have enough GHGs in atmosphere, cloud cover would just be an additional blanket. See Venus.
However, without GHGs Earth would be little more than an ice ball.
You're saying one thing, but your graph is saying another. The graph is showing specific humidity up to 900mb which apparently dropped and seems to have remained flat.
The only articles I'm finding on the subject relate to stratosphere(which has experienced a drop in moisture), but that's a bit higher than 850mb.
If you have sources for the tropospheric "drying" I'd be interested in reading them.
~X~
LOL!
GOES SST/SSH images for 3/24/2010
Click any image for a full-screen plot
There's no control knobs on anything anymore... kind of an anachronism, like "potting" the audio up in a broadcast control room.
Kinda' makes me nostalgic.
Hi all, have a good night, think I'll stick to the SVU re-run -- less violence.
More water vapor does mean more overall cloud-cover, don't confuse the issue by being all specific. OVERALL it means more clouds, based on the IPCC models. Now if the moisture doesn't rise as fast with the temperature then we have lower relative humidities and the story gets more complicated.
The number on the graph which you think is 900 is 300, Atmo mis-read it too the first time. The font is small on the resized image. Also, I should have labeled it more clearly, that particular image is from the 500mb level. Every level above 850mb up to 300mb (where humidity measurements stop on the reanalysis) is flat or decreasing, which you can view here.
And please, don't compare Earth to Venus....that's one of their worst arguments that they've ever attempted.
Roughnecks and Roustabouts Jobs
The true entry-level jobs on an oil rig are Roughneck or Roustabout. Some consider the terms interchangeable. You might also see the titles of Leasehand or Floorhand used instead of Roughneck and Roustabout.
Its a good Job in the Oil Industry for someone interested. I did for 8 years in the GOM.
Hiya ms,,good to see ya,grab a Hard Hat,some safety goggles out da shack and hop in.
LOL
Hey Jeff will the itcz rise during the hurricane season, and help provide a return of moisture to the islands and the NE tip of SA.?
..some folks will believe anything seems.
Why CO2 is suddenly a poison instead of a life-giving gas is beyond me. The AGW's own research into the far past shows the earth has had much greater concentrations of CO2 in the atmosphere before now, and before humans started creating it.
Go go man..!
Hows the Chase scenario Team shaping up?
LOL
Yawn,..
But we sure reaching the masses with a good message.
FEMA: Hurricane Preparation 2010
I hope or we all have to be performing our rain dances. Me and the fam. are planning to take a trip down there this summer, last time we went in dec. of '02 we got drenched, the whole blasted place flooded out!
Only certain plants and only if they have enough nutrient and water, otherwise it will become a negative feedback loop.
http://adsabs.harvard.edu/abs/2005AGUFMGC13B1229D
http://www.asi.org/adb/04/03/05/co2-plant-growth.html
Presslord was one and the other a good friend as well..
But I borrowed a quote from Superman himself,who overcame many and more real obstacles in his later life to contribute..
He once said,
"Either you decide to stay in the shallow end of the pool or you go out in the ocean."
No matter what they say or do,one can waste all their time on worrying bout me,saying dis or dat or whatever.
Ill be in da deeper water always,caring not about things like that.
LOL! Too funny.
Buff it up every 12 hours
U betcha..nice tie in for sure.EL,
Merci beaucoup..
We all need to be more self aware as to others,myself included.
Im a work in a progress as well.
How long will it take till the temp catches up with the Co2?
Well I went to bed last night with rocks being thrown at me and awoke up to um again this am,but hey.
Dis too will pass cher.
Some need to lay off others disputes that were none of their buisness,even after it was resolved in a man to man peaceful manner.
Some like to mimic the atmospheres trend and tendency to seek chaos.
Jazz Fest is da next up here so wees gonna throw down big time sum,cher..
LOL
Im gonna go eat some Blackberry Pie,with ice cream.
"Lol you really gonna go there? The good doctor's purpose for posting this entry was to highlight the main points of Dr. Alley's talk. How many posters here do you think actually spent an hour watching that thing before posting? Look at all the opinions flying around right after they visited the blog. I read the whole entry as I always do. The petty arguments you come up with continually amaze me."
I just wonder whether you are who you say you are. If you really were of high-school age and keen on science, then you should have jumped on the chance to watch an interesting talk like that. It would have been like the finest mental elixir possible. Irresistible. Instead what do you do? You post an article that is directly refuted in the Good Doctor's post and by Dr. Alley in his talk. That actually seems like a bone-headed move.
You post like someone who is actively working to spread doubt and uncertainty, like someone who is paid to do that kind of thing. I do not know if that is happening or if it indeed is exactly how your posts originate, but that is the appearance. It is a regrettable impression to give other people.
By the way, EstherD really handed your head to you on a platter last night.
One more comment and then I'm off to bed...
Most of the anti-global warming arguments seem to start off saying something to the effect: "How can we trust climate models based on inadequate data and theory? Climate is just too complicated!" Then, when it comes time for the counter-argument, suddenly all these mechanisms and interactions that were "too difficult to model" have become so simple and transparent that they can be explained in 25 words or less, so that even someone like me with a good science background but little knowledge of climate theory can understand completely and accept the conclusions without reservations. Sorry, folks, but you CANNOT have it both ways. If the science is HARD for one side, then it's gotta be hard for BOTH sides! Which is why I'm not in the least bit persuaded by hand-waving arguments... from EITHER side. I am actually inclined to trust the mathematical models more than I trust the "just so" stories, possibly because that was (once) how I made my living.
So thanks, Levi, but I don't need any more pretty pictures. And your position is quite clear -- I am just not convinced.
So let me repeat... The datsets are much too short and far too noisy to give anything other than a weak level of confidence. Especially when using eyeballs rather than mathematical tools, given that the human visual system is well-known for detecting non-existent "features" in a random bunch of points, and "correlations" where none exist in actual fact.
You responded as if that didn't hurt at all.
Alright, I can respect your skepticism based on lack of data. I can't prove my position any more than I believe the other side can prove their's based on available data. The next 30 years of observation should help a ton, but I have an opinion that is supported by evidence just as the other side's opinion is. We shall see who is right, or maybe neither is.
Ooo! Ouch! Tough guy.
"Global warming: so simple a high school kid has it figured out."
Lol...I just don't remember Pat writing like that before. I may be wrong. But with his stature in the WU community, I guess I expected more. And I guess I watch too many reruns of the Beverly Hillbillies!
Publication of deliberately false climate change data literally ought — i.e., MUST — be treated, not as a peccadillo, but as a Crime Against Humanity.
My remark here is not an expression of an emotion, but of an intellectual and humanitarian reaction of a scientist to falsification of data that could be as bad in its effect as long-term global warming itself, by permitting the latter to thrive, and acquire an egregious and panhumanly disastrous momentum.
If this were World War III such people would be shot, and with far, far greater warrant than even those human catastrophes.
A scientist is a kind of Protective Angel for Humanity. Why? Simply because he lives and breathes for Truth.
——— * ———
As for the falsifiers of data, or criminal social parasites, let me switch from the second to the first of my scientific careers, long ago at M.I.T., where I was — a then VERY rare! — theorist in neuroscience, trying to make sense of the human brain as a whole and all the astonishing behavior and abilities it gives rise to.
A SIDE interest of mine, then and later, was the queer and baffling, and decidedly chilling, phenomenon of the psychopath, a.k.a. sociopath. The essential trait of such people is that have little or no conscience, and yet they can be at the same time profoundly convincing to the layman — i.e., virtually all of us.
The incidence of these curious and horrific people in the body of the whole of humanity is estimated to be of the order of 1/200. This is misleading, however, because the pathology is a matter of degree, or properly illustrated by an intensity-frequency curve.
To put it simply, a psychopath can and does lie without a blink, either external or internal. And often does so for profit or simply out of total indifference to the harm he works upon the innocent and the virtuous.
I have little doubt that the purveyors of purposefully, and dangerously, falsified Global Warming data ARE in many instances psychopaths, whose falsifications tend to put ALL of us at risk.
Even heads of great corporations can be, in various ways and degrees, psychopathic. (Psychopathy probably had some partly useful — personal OR social — function in the long-ago past of Homo sapiens. It is certainly common enough in our politicians nowadays!)
— Patrick Michael Gunkel (Princeton, NJ)
POSTSCRIPT: Two decades ago I was neutral, but skeptical, about global warming. Later I realized that we simply could not tolerate the risks it potentially posed. One does not play games, or take chances, when essentially the whole of civilization and humanity MAY be in peril.
None of us can escape from the need for such caution, and where even the very survival of our species over Eternity may just be confronted with the possibility of extinction through carelessness or ignorance, or a shallow and selfish morality, or ideology or skepticism, or a universal involvement in petty and personal disputes between men fighting in diapers. (Phenomena we have seen often enough in World Wars and in Wars Ancient, but no less pathetic and mindless.)
In short, All of the Future hangs by a single tenuous thread from each and ever Present.
Viewing: 101 - 151
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 — Blog Index