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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Radar Image of Tropical Low 1
TROPICAL CYCLONE ADVICE NUMBER 9
Issued by the BUREAU OF METEOROLOGY, DARWIN
at 5:00 am CST Sunday 28 March 2010
A Cyclone WARNING continues for coastal and island communities from Milingimbi
to Numbulwar, including Nhulunbuy and Groote Eylandt.
A Cyclone WATCH continues for coastal and island communities from Maningrida to
Milingimbi and Numbulwar to Port McArthur.
At 3:30 am CST a Tropical Low was estimated to be 75 kilometres south southwest
of Nhulunbuy and 125 kilometres north of Alyangula and moving southwest at 12
kilometres per hour.
The low is currently located near the coast and is expected to develop into a
tropical cyclone in the next 6 to 12 hours.
GALES with gusts to 110 kilometres per hour are expected to develop between and
MILINGIMBI AND NUMBULWAR, including GROOTE EYLANDT, today.
Tides will be HIGHER THAN NORMAL between ELCHO ISLAND and NUMBULWAR, including
GROOTE EYLANDT, today. Large waves may produce MINOR FLOODING of low-lying
coastal areas.
HEAVY RAIN may lead to localised flooding and significant stream rises in the
Arnhem and Roper-McArthur Districts during Sunday.
Details of Tropical Low at 3:30 am CST:
.Centre located near...... 12.8 degrees South 136.5 degrees East
.Location accuracy........ within 55 kilometres
.Recent movement.......... towards the southwest at 12 kilometres per hour
.Wind gusts near centre... 85 kilometres per hour
.Severity category........ below cyclone intensity
.Central pressure......... 999 hectoPascals
The next advice will be issued by 8:00 am CST Sunday 28 March.
Others agree. ”Aircraft are likely to be a significant factor in future climate, but probably not via their contrails,” NASA’s James Hansen told NOVA . “I think our main concern about aircraft will be their CO2 emissions, not contrails, which are a pretty small climate force.”
Growing food here..I've had a near month here & there where suddenly it's near daily dimmed sun from so many contrails turned to clouds. That plus SAL & it can be a weird blown haze, not a regular dust event. It delays harvet, even without the SAL. Not that I have any clue what's exactly going on but I'm observant, it's certainly a change from what would have been.
Other countries boast about their climate control attempts for like Olympics & stuff. Our country has an agency for it, there is some info out there that admits frequent cloudseeding & companies that advertise their services. I don't really see enough evidence to think we are being sprayed like rats with birth control or some other harmful substance..
Link
There just ain't no point in debating.
where are the SSTs "colding" in the Atlantic?
perfect day in ECFl today.
WTH do you mean? I am sure *alomst* every has at least read it and at least carefully considered what was posted.
I do not see where you are talking about. I see some areas are warmer like in the Atlantic and near the Islands and a few areas maybe that are cooler, but not to the emphasis that you are showing
You make no sense. You are only serving to diminish your side's argument and I'll tell you what I tell the over zealous skeptics as well: .... Do yourself a favor and post a valid point rather than "lalalala you're no expert can't hear you lalala." Get over yourself.
Might want to research what happened and give an informed answer.
Do a lot of fishing in the Atlantic from Dallas? I think we all know why you are cheering for higher SSTs.
wrong and wrong. There is no fact that determines what CO2 will do to our atmosphere. There is evidence on both sides and it's your argument and others who say "Well let's treat it like it's real so that just in case it is, we'll be okay and if it's not then we will have done good!" That line of thinking has happened in history. It didn't end well.
Yep. Nice day. It's a great day in fact. Now back to whining ...
So why don't you go to a football blog and discuss it all with some intelligent folks, then?
Hey everyone, we are morons because we visit a weather blog. (If only it were really just about weather...)
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
Read it and weep.
have a great Saturday everyone.
am off to make strawberry shortcake.
are we going to get one more cold front in florida?
Developed and proven through the joint efforts of NASA and CNES, high-precision ocean altimetry measures the distance between a satellite and the ocean surface to within a few centimeters. Accurate observations of variations in sea surface height—also known as ocean topography—provide scientists with information about the speed and direction of ocean currents and heat stored in the ocean. This information, in turn, reveals global climate variations.
With OSTM/Jason-2, ocean altimetry has come of age. The mission will serve as a bridge to transition collection of these measurements to the world's weather and climate forecasting agencies, which will use them for short- and seasonal-to-long-range weather and climate forecasting.
Sea level rise is one of the most important consequences and indicators of global climate change. From Topex/Poseidon and Jason-1 we know mean sea level has risen by about three millimeters a year since 1993. This is about twice the estimates from tide gauges for the previous century, indicating a possible recent acceleration. OSTM/Jason-2 will further monitor this trend and allow us to better understand year-to-year variations.
The speedup of ice melting in Greenland and Antarctica is a wild card in predicting future sea level rise. Measurements from Jason-1 and OSTM/Jason-2, coupled with information from NASA's Gravity Recovery and Climate Experiment (Grace) mission, will provide crucial information on the relative contributions of glacier melting and ocean heating to sea level change.
Earth's oceans are a thermostat for our planet, keeping it from heating up quickly. More than 80 percent of the heat from global warming over the past 50 years has been absorbed by the oceans. Scientists want to know how much more heat the oceans can absorb, and how the warmer water affects Earth's atmosphere. OSTM/Jason-2 will help them better calculate the oceans' ability to store heat.
The mission will also allow us to better understand large-scale climate phenomena like El Niño and La Niña, which can have wide-reaching effects.
OSTM/Jason-2 data will be used in applications as diverse as, for example, routing ships, improving the safety and efficiency of offshore industry operations, managing fisheries, forecast-ing hurricanes and monitoring river and lake levels.
OSTM/Jason-2's primary payload includes five instruments similar to those aboard Jason-1, along with three experimental instruments. Its main instrument is an altimeter that precisely measures the distance from the satellite to the ocean surface. Its radiometer measures the amount of water vapor in the atmosphere, which can distort the altimeter measurements. Three location systems combine to measure the satellite's precise position in orbit. Instrument advances since Jason-1 will allow scientists to monitor the ocean in coastal regions with increased accuracy, almost 50 percent closer to coastlines that are home to nearly half of Earth's population than before. OSTM/Jason-2 is designed to last at least three years.
After its launch from California's Vandenberg Air Force Base aboard a United Launch Alliance Delta II rocket, OSTM/Jason-2 will be placed in the same orbit (1,336 kilometers) as Jason-1 at an inclination of 66 degrees to the equator. It will repeat its ground track every 10 days, covering 95 percent of the world's ice-free oceans. A tandem mission with Jason-1 will further improve tide models in coastal and shallow seas and help scientists better understand the dynamics of ocean currents and eddies.
Do you think it's going to happen, or not? Gloating over the fact that SOME people predicted that it would happen earlier than later ignores the consequences of when it does happen. Also, you ignore the fact that prior to the 2007 Arctic summer melt MOST scientists didn't think it was going to happen for another 50 to 100 years. Nobody was saying it was going to happen in a couple of decades (or less).
There's an obvious reason why there was a seismic shift in how a lot critics, including the likes of Pat Robertson and the Bush Administration, changed their views of global warming in the fall 2007.
Here we are almost 3 years later with a still warming climate and diminishing Arctic ice and people still have their heads buried in the sand.
it makes you laugh and nothing is really ever accomplished.
guess no one wants to track the cyclone threatening Australia.
I think that quote of Alley is about what happened at various times in the earth's past, like hundreds of millions of years ago. When I look at that graph, I don't see room for doubt about the present. CO2 makes the earth warmer and cooler depending on whether there is more or less. All the naysayers deny just that simple statement if you really read their posts. They have nothing to say about how much warming to expect. There is no expertise on the blog on that subject. They do not know how to even begin to talk about that question.
yea I noticed that, they have it named as TC 22, BOM does not as of yet, but that could just be that they are behind as well. Looks to me like this will be officially named soon
Not what I meant, I was referring to the bickering and name-calling that has been going on the last few days while debating GW; which seems to happen more often on here than not.
Not everyone is ever going to agree, come to a compromise or even acknowledge opposing views. When the debate resorts to name-calling and gets personal it makes it painful to watch at times.
Exactly right. It is exactly like the three stooges.
If I said that the warming was all Co2 related,..Id be wrong 100%.
But we have to at some point be realists and go with what the Best available minds,data and peer reviewed science says.
To do less is to deny the truth.
And when the truth is denied,well things can spiral into Chaos,as the do here when the data is presented,..
The Data has no dog in the fight,..I remind my self daily.
And when we went to the Moon in 68,,we did it on the data,not the skeptical side.
Skeptics dont travel well in Truth.
And thats why I keep a slide rule on my desk too.
Yes, it is dreadfully painful.
Skeptic =/= Naysayer, I think Co2 raises temps. I don't know by how much. I rather think it will be rather negligible. I also wonder if perhaps a warmer climate would benefit mankind as a whole. There's no reason arguing and shoving your opinion in my face though. Maybe you're right, but from an economic perspective it doesn't matter. Mankind won't react until the effects are too catastrophic to circumvent regardless. That being said I've said it and will say it again. Noah didn't build a dam, he built an ark. We should do the same.
FEMA: Hurricane Preparation 2010
I usually polish up my Soul on Sunday.
Lotsa Churches here...and America's First and Oldest Cathedral as well
And Palm Sunday in NOLA is nectar for us.
But thanx for the concern.
I do get your drift on the Ark..though.
I try never to be post 666 here too.
That's part of the signal yes. When the water temperature profile has warm water east of Japan, cold south of Alaska/west of North America, and cold water at the equator, then you've got a cold(negative) PDO.
Well it looks pretty nice. It has an upper anticyclone centered right over it which is providing a beautiful outflow setup with the subtropical jetstream to the south. The SSTs are warm and everything else. The land is handicapping it obviously, but I bet it would be exploding if it were mostly over the water. It looks like just a rain event with gusty winds, but the rains could be quite heavy with this one, especially since it's a slow mover. Flooding will probably be a major problem in the Northern Territory and northwest Queensland. At first glance the JTWC track looks good. The storm should eventually turn inland after hugging the coastline for a while.
Yeah, and it looks like there are more where that came from. The sun is rising now. The convection in bands over the Gulf of Carpentaria is quite impressive.
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