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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And fringe? Data is data.
Not debunking anything. Just showing the prediction vs. actual.
I do, however, think in 10 years there will be way too much temp to make up.
But that's my opinion. Everyone is free to have their own interpretation of that graph.
I agree that we have a lot to learn about GW. Just take away the A, for now. ;)
I fully agree it is worthwhile and will take time to understand it all.
Maybe it is MM CO2 emissions. Maybe it isn't.
If the temperature trend in 10 years is still showing less than 1C increase by 2100, does that matter?
How about 20 years? 30 years?
I agree there can be junk posted on both sides.
I believe the science to be valid, for the most part. I just don't think enough is known. It is extremely complex.
All the details don't matter if 2-4C is predicted and it ends up being 1C or less. The prediction is then false, which means the hypothesis must be false... or it would have validated. Something was miscalculated.
As mentioned, not saying the science isn't valid. Just a science in its infancy, relatively speaking. Takes time to discover and understand it all and I fully support the science.
We'll see how it progresses.
Here is an interesting data set for review :)
Written on March 26, 2010 at 4:08 pm by John Ohab
How does Geoscience Support Marine Corps Operations? [Interview]
Bob Freeman works for the Office of the Oceanographer of the Navy.
When Marines land on a beach and push inland to secure a strategic objective, the physical environment can either be a tactical asset or a dangerous impediment.
Marine Corps weather specialists ensure that the “boots on the ground” get a tactical advantage through detailed knowledge of the operational environment.
“We’re responsible for everything from the bottom of the ocean to the sun,” explained Marine Corps Master Sgt. Kari Hubler in a March 24 interview on Pentagon Web Radio’s webcast “Armed with Science: Research and Applications for the Modern Military.” Listen to the full interview.
Hubler, a 17-year veteran of the Marine Corps’ meteorology and oceanography community, serves as an instructor and curriculum developer at the Naval Meteorology and Oceanography Professional Development Center in Gulfport, Miss., a joint Navy and Marine Corps training center.
“Environmental parameters ultimately affect any given mission or capability,” she explained. “We provide climatological information to help in the mission planning process, and we provide environmental information to the on-scene combatant commanders to help make tactical decisions during operations.”
Hubler explained that the Marine Corps fights on land, in the air and on the sea, and their environmental specialists must be able to provide support for the full range of military operations.
The first is the air.
“We do aviation forecasting, … forecasting upper-air parameters such as winds, temperature, moisture – all things that have a direct effect on the safety of aviation operations,” she said.
I work in prediction (or rather hopefully prevention) of anthropogenic earthquakes. So I am even in more of the "quack" realm than the weatherman :). At least I have noted one other geomechanical blogger on this list. Seriously. There are such things. The Dallas area earthquakes last summer were caused by wastewater injection of near a fault (an accident waiting to happen IMHO). NPR and other media outlets blamed it on fractures but there is tons of microseismic data out there which shows seismic events associated with fractures are less than 0 magnitude.
While I support the science behind AGW, this snowball fight is keeping us away from 4 main points
1) We use far too much foriegn energy and now we have the Chinese to compete with;
2) The Chinese are taking concrete steps to ensure a sustainable energy future, unlike ourselves, by reducing their energy intensity (and hence carbon intensity);
3) There is no reason that the US cannot within 10 years eliminate 50% of our energy use through elimination of waste (AND SAVE MONEY IN THE LONG TERM!!!)
4) R&D projects are just that, R&D.
An example of R&D versus current claims.
One thing that is talked about a lot is carbon storage. I've worked on projects. Guess what. We have tons of folks thinking that you can stick what becomes carbonic acid into the ground without consequences. Depleted oil and gas fields make excellent places to put CO2 BUT they are limited. Anywhere else you run the risk of setting off.... earthquakes.
One project that is often touted as successful for storing carbon is the Sliepner project off of Norway. Well, in the Utsira formation there have been two incidents lately... Veslefrikk (googel Veslefrikk cuttings) and Tordis (googel Tordis crater).
The point is that any injection underground is risky and although there are SAFE places to do it they are limited. Hence it is not a silver bullet.
REDUCE ENERGY INTENSITY NOW (and likewise cut our carbon by 50%). I don't know why the anti-AGW forces are so intent on letting China kick our rear end in energy related matters and are against SAVING MONEY. And I don't know why the pro-AGW folks don't keep pointing to this VERY LOW HANGING FRUIT.
Except for the solar water, the money I spent will pay out in 11 years :) At the current price of electricity, natural gas, and oil.
Link
RAIN WILL OVERTAKE MOST OF THE OUTLOOK AREA TONIGHT...WITH ISOLATED THUNDERSTORMS POSSIBLE MAINLY SOUTH OF HIGHWAY 6 AFTER 10 PM. ALTHOUGH NO SEVERE WEATHER IS EXPECTED... LOCALLY HEAVY RAINFALL WILL BE POSSIBLE ACROSS THE OUTLOOK AREA.
west and north
24 Jul
24 Aug
24 Sep
BBL
May I recommend James Hansen's book Storms of My Grandchildren? If I read him correctly, he says the science of climate change is, while complex, well established, highly verifiable -- and far from being in its "infancy." Much data has been collected and analyzed. (One lack is a recent record of atmospheric aerosols.) And it says we are rapidly approaching tipping points -- a rate of ice-sheet melting that becomes unstoppable, for example -- beyond which nothing we do or slow or cease doing can alter the onset of a very different world from the one we are struggling to know.
Did you mention the environment? I think that's another key issue improved by alternative fuel.
Hurricane season in about 2 months. I feel like the first person in the stands watching the Coast Cities scatter away from the opening gate.
Sources: NOAA ESLR CO2 and Vostok Temps
the sky
Not in its infancy? I disagree.
Name another established (not much more to discover and learn) science that is not, off the top of my head, 500 years old.
As an example, let's take physics that has 2400 years of study under its belt. Yet, the theory of relativity, only 90 or so years from acceptance as the unifying theory, has fallen apart at the sub atomic level.
Just an example.
And, again, I applaud that and want it to continue.
With all due respect I sure will be glad when Dr Masters changes the "subject"
I am a "No Beleiver" of this....
Taco :0)
729. I reiterate, with all due respect...then you haven't been paying attention. Perhaps Atmo gets the respect since he's a degree meteorologist...I can respect that. Keep in mind that those of sound scientific and methodological background aren't necessarily wrong because they don't have the correct degree. I'd like to know where I've posted incorrect information....
pearlandaggie--I've paid close attention for a long time--and atmosaggie is the only global warming skeptic I've seen post meaningful rebuttals to anthropogenic global warming. All the other deniers have only posted junk.
I like you guys a lot, but you're being disingenuous if you allow this comment to stand.
EDIT: Oh, wait...it was apparently the same bullsheet as when I left several months back! LMAO
Data isn't meaningful?
Speaks volumes.
looks like another cyclone developing in the north region of Australia
TROPICAL CYCLONE ADVICE NUMBER 4
Issued by the BUREAU OF METEOROLOGY, DARWIN
at 11:00 am CST Saturday 27 March 2010
A Cyclone WATCH continues for a developing tropical low for coastal areas and
island communities from Cape Don to Nhulunbuy.
At 9:30 am CST a Tropical Low was estimated to be 165 kilometres north northeast
of Milingimbi and 235 kilometres northwest of Nhulunbuy and moving east
southeast at 10 kilometres per hour.
There is the possibility of a Tropical Cyclone developing but GALES are not
expected in coastal areas within the next 24 hours, however gales may develop
later.
Details of Tropical Low at 9:30 am CST:
.Centre located near...... 10.7 degrees South 135.3 degrees East
.Location accuracy........ within 120 kilometres
.Recent movement.......... towards the east southeast at 10 kilometres per hour
.Wind gusts near centre... 85 kilometres per hour
.Severity category........ below cyclone intensity
.Central pressure......... 1003 hectoPascals
The next advice will be issued by 5:00 pm CST Saturday 27 March.
What don't you believe? Do you believe we can do as we please with no reaction? For every action there is a reaction. If you don't believe the science then merely open your eyes to the world around you. It's not that hard to see.
Look up, those are chemtrails not clouds. What is their purpose? Why aren't people such as you more inquisitive about things like this? You spend alot of time on a blog dedicated to weather and yet don't believe it's changing after all we're seeing. What do you believe in?
What is inaccurate about this:
And/or this:
I'm listening.
I also like the geological perspective in terms of weighting.
Don't confuse localized ecosystems with global.
Two completely different topics.
What was local about my post? The chemtrails ARE global. What is their purpose and how are they affecting the global environment? Are they reflecting sunlight, or trapping it?
"What is inaccurate about this?"
The claim that the gif and png images are relevant?
Fair enough
Don't know enough about it to comment, but the topic is CO2 and temps.
Welcome to the blog.
You should watch the video. Maybe read up on carbon sequestration in seafloor sediments, plate tectonics, subduction zones, volcanos, CO2, some chemistry, weathering of rocks, Milankovitch cycles, foramanifera, isotopes used as proxy measurements for temperature and air CO2 concentrations (easily the most difficult piece), snowball earth, the great die off when 95% of all species went extinct, a bit of geomorphology, etc.
Irrelevant to what?
Thanks for the welcome.
Question. If the chemtrails were either reflecting or trapping sunlight wouldn't this affect temps? Could it also affect CO2 levels somehow given this interaction of reflecting or trapping sunlight, the temps, and the aerosols that are being spewed into our atmosphere? For the longest I was hoping many of you here would be delving into this stuff but the subject seems taboo everywhere.
No need. It either validates or it doesn't.
Again, the minutia behind the predictions is irrelevant, other than for better understanding.
If it doesn't validate, it is wrong. It's not rocket science.
Knock yourself out with that.
If you predict 2C-4C and I predict <1C by 2100, all that matters is what the temperature is at 2100.
Only need another 10 years of data, but at that point I'll bet anyone a $10K donation to the charity of their choosing that +2C in 2100 from 2000 will not happen.
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