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
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If Galileo said the star would be at a point in 5 hours and it was not, would that have worked?
Granted, he had the advantage of a 24hr time frame to demonstrate his theory, but it matched... every time.
Huh? No, the red line is the actual carbon concentrations measured in the atmosphere, and the green line is the projection of actual concentrations that should have occurred based on accumulation and CO2 residence time, preached by the IPCC and CDIAC. There is a clear discrepancy, and they proceed to bring up the AGW people's common way of explaining that discrepancy, and then they attack that theory as well.
And, dismissing a paper written by two distinguished scientists just because of the URL on which it was published is shallow thinking. I don't know much about that particular site, but I know about the people who wrote the article. Talk to me about the content of the paper, not where it was published.
Wow what a portrait! Which one are you Oz? Lol.
Oh I bet chasing hurricanes is hair-raising. I just hope you're safe this year in your little adventures. Glad you get some fun in too :)
See ya soon!
the levels are rising, the molecules are stagnating, and CO2 is a greenhouse gas. the mechanisms that digest CO2 have always been in place, and they don't seem to be having any increase in impact or effectiveness; not in comparison to the rate of growth shown in 2nd graph of man's global CO2 output. why not chew on that alongside what you are presenting.
The first graph is demonstrating how human contribution can only explain the total increase if CO2 all stagnates up to 200 years, as the CDIAC says it does. That's not an absurd illustration to put in a paper like that.
And no, that green line in the 4th graph is exactly what should have happened based on what the CDIAC says is true about CO2. There is obviously something wrong with their statement that "Atmospheric CO2concentrations had not changed appreciably over the preceding 850 years, so it may be safely assumed that they would not have changed appreciably in the 150 years from 1850 to 2000 in the absence of human intervention", or else the red line wouldn't have such a more gradual curve than what it should have.
The paper goes on to talk about how AGW scientists continue to try to explain this away by human effects on carbon sinks through environmental damage. They then adjust the curve of human yearly emissions to perfectly fit the actual measured concentrations curve. When they did that, they found that we would have had to been contributing negative carbon-related human activity during two periods in history, which is impossible.
What about this doesn't make sense?
Now, I'm not saying humans aren't contributing anything, because they are, but based on this there is something wrong with saying we are contributing ALL of it. There is likely something else going on which is greatly contributing to the rise.
Along with Levi's, here's mine in case you haven't seen it. Will be updated after 2010 comes in. Levi says 30 years, but 10 will be plenty statistically, imo. No way the temps rise fast enough. Just not plausible. Of course, that might change in the next 10 years, but I highly doubt it. That trend line should jump less and less over time.
Really no need to get into the minutia, other than for academic purposes. The predictions validate or they don't.
Harper's Humiliating Muzzle on Scientists
Canada is becoming a global joke as our world-class experts are prohibited from speaking.
These experts might back up their arguments by citing relevant scientific work, not pdfs of "Musings on CO2", which themselves contain only passing references to missing .ppt files on random Norwegian servers.
The saddles in the CO2 could easily be explained if the uncertainty of the values in CO2 mixing ratio in 1940 were shown. Those are ice cores, not atmospheric measurements. The errors are larger. If the authors had any idea of the uncertainty of the values, they'd have plotted them, unless they had a forgone conclusion in mind. Maybe if they'd contacted the provider of the data, they'd get that.
They then blow up the discussion of the apparent increase in uptake rate of the planet with an argument of the damage factor that goes basically nowhere. The increase of CO2 in the atmosphere is 1-2 ppm per year. They just plot that tiny number on a scale that has the total CO2 on the wrong axis (once on purpose, once for no clear reason), and say "see".
In the end, they take potshots at Hansen et al., calling him personally myopic, proclaiming he has *perversely convinced himself* his results are valid, and "unable to notice the absurdity" of his own arguments.
So the Sidons and D'Aleo 2007 pdf is an utterly clueless, useless contribution to any discussion of the effect of CO2 on climate. We can have this talk about a useful paper, not some mistake ridden, insulting manifesto these guys did in their spare time. You want to try again?
then there is the old CDIAC.. did these guys just release a hit and call themselves bigger than Jesus? so what. look at the red line. it goes up. the CDIAC estimate is based on data sets and subject to the limits of knowledge about CO2 sequestration, and climatology for that matter.
is it the work of distinguished science to "(go) on to talk about how AGW scientists continue to try to explain this away by human effects on carbon sinks through environmental damage. They then adjust the curve of human yearly emissions to perfectly fit the actual measured concentrations curve. When they did that, they found that we would have had to been contributing negative carbon-related human activity during two periods in history, which is impossible." as you summed up for me?
for this, my skepticism is warranted.
I grew up in the Okanagan Valley B.C.
We walked on frozen snow from November to March - that was what I thought winter was.
Just got back from there yesterday and there is NO SNOW in the valley. NO SNOW on the mountains
S.F.A. snow this winter
That is Climate Change
They did that! What are you talking about? They did the accumulation of each successive year in the next graph down:
Hello? The quote from Hansen clearly says: "peaked near 1980", followed by: "has since declined". That, in plain English quite clearly means: "dates AFTER 1980", when, indeed there WAS some international effort to reign in CO2 emmissions.
How the hex does WW2 figure into that? Answer: It doesn't. That kind of inflammatory language is added ONLY to get a rise out of the reader. It's called an Ad Hominem attack, and it is one of the classic hallmarks of pseudoscience!
NO reputable scientist would write that and claim that it was a scientific argument. I don't care how many "credentials" they have, and I don't care what you say to try to defend it... That article Is NOT science, and those author(s) are NOT scientists! At least not as those of us who are (or were) in the scientific community use those terms.
do you understand i have been talking about this as the absurd one? ok, now apply that knowledge to what i've stated.
then for the one you keep posting, i said stuff like: "then there is the old CDIAC.. did these guys just release a hit and call themselves bigger than Jesus? so what. look at the red line. it goes up. the CDIAC estimate is based on data sets and subject to the limits of knowledge about CO2 sequestration, and climatology for that matter." and "the one you reference makes no compelling argument. that is what it looks like when you map modeled data over actual data. the red line actually looks like a good 'best fit' for the green line." the CDIAC is modeled data. it is their precise model. it is off. and..?
And that's happened before. During Jurassic, it was much warmer there.
Goodnight.
You guys write it off because of the authors, you write it off because of the site it was on, you twist what they were trying to prove, and don't even give it a chance. I can't compete with that kind of stone-faced resolve.
It's late anyway and time for me to get off. Night all.
facts are hard to come by these days, it seems everything is a projection.
No, you're wrong about that, Levi. I'll take what you say seriously IF (and only IF) it follows the rules of scientific argumentation and civil discourse. That "paper" you posted does neither. It is JUNK, pure and simple! In fact, more that I think on it, it reads like some of the postings on this blog. It certainly would never have been accepted for publication in ANY reputable scientific journal. I had come to expect better from you than that.
If you have any dreams of entering into a scientific career, then you had better get used to criticism. And VERY CAREFULLY evaluating what you read, write and publish.
Anyway... Goodnight. Hope for a better day tomorrow...
you might understand someday. this them vs. us attitude is usually symbolic of a skewed perspective. for instance, i try to be open to all the evidence with equal scrutiny, and in doing so i see over-shooting doomsday scenarios comfortably passed on as an impending reality. from the far AGW side there is some real crap. so i think it's important to learn the skills of recognizing slant from both the AGW side, but also the other side; apparently your side. but why Take a side? i like that you often come across with your own take on things, using your increasingly expertise knowledge on tropics to self support opinions. i wish for you to do the same with the GW/AGW debate. temper the matter with the full discourse on the subject, and steer clear of wishcasters, doomcasters, and listcasters :)
Tornado Warning
SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
109 AM CDT THU MAR 25 2010
TXC187-250630-
/O.CON.KEWX.TO.W.0001.000000T0000Z-100325T0630Z/
GUADALUPE TX-
109 AM CDT THU MAR 25 2010
...A TORNADO WARNING REMAINS IN EFFECT UNTIL 130 AM CDT FOR EAST
CENTRAL GUADALUPE COUNTY...
AT 105 AM CDT...NWS METEOROLOGISTS CONTINUED TO DETECT A TORNADO.
THIS TORNADO WAS LOCATED OVER EAST CENTRAL GUADALUPE COUNTY...OR 8
MILES EAST OF SEGUIN...MOVING SOUTHEAST AT 30 MPH.
THE TORNADO WILL CONTINUE TO MOVE OVER RURAL AREAS EAST OF SEGUIN
AND WILL LIKELY WEAKEN TO BELOW SEVERE LEVELS BY 130 AM.
LAT...LON 2964 9768 2950 9777 2957 9795 2965 9788
TIME...MOT...LOC 0608Z 305DEG 25KT 2956 9782
Let's look at this another way...
Science, like most human activities is basically a game. And like all games, it has rules. If someone refuses to abide by the rules of a game, then I am justified in refusing to play with them, because no one should be obligated to play a game with someone who is known to cheat. In this case, I refuse to "play" by refusing to take seriously (or even to read) the offending paper. Why? Because if I cannot trust someone to abide by even the most basic rules of civil discourse, then I certainly cannot trust them to abide by the rules of scientific argumentation. Which means EVERYTHING in that paper is suspect, to the point that I cannot be certain that ANYTHING in it is accurate, truthful, or correctly and fairly presented. Anyone who would stoop to Ad Hominem attacks has NO ethics whatsoever, or at least none that I can count on. Anyone who is capable of such a gross violation of the rules is certainly capable of many lesser indiscretions. So with all the other good papers in the literature, it's just not worth my time... I simply trash that one and move on. You should, too.
There is no "other side" in science, there is just data, and interpretation. I and probably many others enjoy the links and discussions you post, so don't take it too personally if people call you out on posting non-scientific papers with ebullient language and very few actual conclusions.
Levi --
Let me be the first to second these two comments. Please DO continue to post. I always enjoy reading your tropical weather-related postings, and I often learn new stuff from them. Most of the time I have enjoyed reading your GW postings, too, even when I don't agree with your conclusions. Just not this last one.
Besides, taking risks and making mistakes is how we humans learn, although at times that can be a pretty painful way to get educated. In fact, in the early days of the 'net, when it was still mostly ARPAnet, I had an email sig that said something like: "I know we're supposed to learn from our mistakes. But WHY does a good education require so MANY?!" ;)
I agree and hope that things will stay as quiet as possible in April this year as we start heading into the Summer before H Season....We will probably have a few strong fronts or lows move through the SE in April but based on the water temp scenario, I would rather have them sooner than later in April.
Water temps still around 60 in Apalachicola on Wednesday morning when I had no luck fishing for the first Spring wave of trout and redfish.........Gotta wait a few more weeks for the fishes to come out of their winter slumber up here.......... :)
Ummm, is the last frame supposed to say 2005?
Buoy 42022 isn't reporting Data for last 45 days: No data available., but neighboring buoys are in the 60's....
Station 42040 was disestablished effective 10/7/2009.
I was pretty sure we had a CO2 problem up through my final semester of college at A&M. We covered it well in atmo chem, physical climatology, atmo physics (covering radiative transfer), atmo thermo. Then, in my very last semester, I started asking too many questions in air pollution meteorology and a course styled global climate change, and of my adviser, the physical climatology prof. Started scrutinizing the data and the assumptions used in the conclusions. I got familiar with what little we actually know about the climate system.
They tried to get me onboard and it almost worked. I don't think there was any ill will or conspiracy or anything like that. I just think that most of my profs believe it would be positive if CO2 were to be controlled along with the byproducts of doing so. Some, however, do harbor misgivings about the same things I do.
A few spotty areas of 300 K in the loop current (80 F).
Figure 1: Aqua/MODIS SST composite produced by the SPoRT group at NASA's Marshall pace Flight Center.
Age of pixels in above plot in days:
Figure 2: Latency of pixels in Figure 1 in days.
Source: http://weather.msfc.nasa.gov/sport/modis/sst_comparison.html
Could be a hair warmer in the loop current than shown in Figure 1.
And you said 5 - 7 degree warmup in a week? That sounds tough to do. And 80 degree weather? Someone has a mean 24 hour temp of 80 degrees? Where? (I think you are 2 months early with that)
You weren't giving buoy readings in the loop current.
I'll post the link before you go crazy! Drink coffe and relax!
Go crazy? As far as relaxing...I'm relaxed.
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