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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Because the main boundary currents of the Atlantic Ocean always flow in a clockwise motion, following the Atlantic Gyre. Due to Ekman Transport and the normal trade wind pattern of the Atlantic, net water motion is all towards the center of the Atlantic ocean, forming a hill of slightly higher water. The surface water then tries to flow down the sides of the hill due to gravity, moving the water towards the area of less density. But this is when the Coriolis Force kicks in, much like with air motion, and curves the surface water to the right as it flows down the hill, forming the clockwise motion of the gyre.
Because of this grand ocean current pattern, the Loop Current can't just go deviating off of the course and slam into the western gulf. Also, the Gulf Stream likely helps keep the Loop in check by drawing a large volume of water constantly escaping through the Florida Straights to the east. This, much like a bath tub drain, will tend to pull surrounding water towards it. This keeps the Loop Current "attracted" towards the east, as this is where the main water flow in the gulf is headed.
That's correct in large scale oceans, this really has to do with water flowing somewhere has to go somewhere.
Right, but from what I know of ocean currents, they all have to eventually align with the gyre, and the Loop does have somewhere to go, through the Florida Straights. If the Florida Straights weren't there, then maybe it would go into the western gulf instead, but actually there wouldn't even be a Loop Current, at least as we know it today, if the Florida Straights were closed off. The Loop and the Gulf Stream are connected. Water is constantly going somewhere in that area, and the Loop can't just decide that it wants the water to go somewhere else. The Gulf Stream is constantly pulling at it.
That was about 10 hours ago
MAP 6.0 2010/03/25 05:29:25 13.823 120.070 18.0 MINDORO, PHILIPPINES
Spin Cycles
Winding path of warm water creates gulf's eddies
1. Warm water from the Caribbean Sea enters the gulf.
2. A "Loop Current" gradually forms in the eastern gulf. Eventually, the loop breaks off and forms an eddy.
3. The eddy has a core of warm water, and rotates clockwise as it moves west across the gulf. Clockwise-rotating eddies in the northern hemisphere are called anticyclones.
4. Smaller eddies spin off the warm anticyclones. These rotate in the opposite direction, and are called cyclones.
A. In an anticyclone, warm water converges in the eddy center and is pushed toward the seaþoor. Anticyclones contain few nutrients to support plant and animal life. They can be thought of as "ocean deserts."
B. Cyclones draw cold, nutrient-rich water from the deep gulf up toward the surface. Near the surface the combination of sunlight and plenty of nutrients creates an "ocean oasis," with abundant plankton for marine animals to eat.
From TRMM TMI TA data, weekly 0.25 degree grid SST binary files were processed using a Remote Sensing Systems SST algorithm. Specific regions of these weekly maps are displayed in the following examples to highlight the temporal changes which occur in major global currents. We can see the variation of the sea surface temperature throughout the regions and locate thermal boundaries or fronts.
The Gulf of Mexico Loop Current and Gulf Stream
The African Agulhas Current
The Kuroshio Current off Japan
spacetop
The Gulf of Mexico Loop Current and Gulf Stream
The figure below shows the Loop Current in the Gulf of Mexico and the Gulf Stream along the east coast of the United States. Warm water in this region flows northward through the Yucatan Strait into the Gulf of Mexico, where it turns westward and exits through the Straits of Florida to join the Gulf Stream flow. The distance which the Loop Current pushes north into the Gulf of Mexico is seasonally related (extending farther in summer months, less so in winter months). The eastern and western edges of the Loop Current are bound by the geography of the Gulf of Mexico basin.
Approximately once each year, the current pinches off to create a warm anticyclonic eddy that drifts slowly westward. The feature to the west of the Loop Current is such an eddy. Later, in March, 1998 the Loop Current completed the separation begun in these images and another anticyclonic eddy was created.
The way we're warming the planet, we can probably expect sea levels to rise at least a meter, on average, by the end of the century. That's what most scientific projections suggest, anyway. One kink, though, is that that's just an average—the seas won't go up uniformly by one meter all across the globe. Some places will see much higher rises than that, some places much lower. Michael Lemonick has a great Environment360 piece delving into some of the factors that make sea-level rise so odd and unpredictable. Wind patterns, for instance:
The trade winds that blow west across the tropical Pacific, for example, move water in the same direction, boosting average sea levels by as much as 24 inches on the western side of the ocean—in places such as the Philippines—compared with those in northern South America. If those winds shift with climate change, so would local sea levels.
Meanwhile, if the Gulf Stream in the Atlantic starts slowing down at all due to a combination of warmer temperatures and Greenland's melting ice sheet, that could force ocean water to pile up and raise sea levels along the eastern United States as much as 8 inches higher than the global average. Even more bizarrely, as the polar ice sheets shrink, that could affect the Earth's gravitational field in unexpected ways, sloshing the water around the planet unevenly:
About a year ago, Jerry Mitrovica, a geophysicist who teaches an entire course on sea level at Harvard, co-authored a paper in Science that laid out what would likely happen if the West Antarctic ice sheet, the smaller of the two sheets that cover the Antarctic continent, were to melt. (Like a complete shutdown of the Gulf Stream, this is not considered likely anytime soon. But recent satellite measurements have shown that glaciers that drain the ice sheet have begun moving faster toward the sea).
If you simply spread the resulting increase in sea level evenly around the world, it would amount to about 5 meters’ worth. But the ice sheet’s gravity is currently keeping sea level artificially low in the Northern Hemisphere, so if it disappeared, the actual increase along the U.S. mid-Atlantic coast would be more like 6.3 meters. In other words, as the West Antarctic Ice Sheet melts and loses mass, its pull on the surrounding ocean will lessen. Seas will drop around Antarctica and parts of the Southern Hemisphere, and that water will be displaced to more northerly areas, such as the east coast of the U.S.
Now that the gorilla has made its presence known, Stouffer is working with Mitrovica to understand its effects in greater detail. A joint paper, due out in a few months, will look into the gravitationally driven sea-level changes a melting Greenland could trigger. “The signal is so large,” says Stouffer, “that if you own beachfront property in Iceland, and all of the ice on Greenland melts and adds seven meters to average sea level, you end up with more beach. But in Hawaii, you get your seven meters of sea-level rise plus an extra two or three on top of that. It’s phenomenal to me that it matters that much.”
http://www.tnr.com/blog/the-vine/the-oddities-sea-level-rise
A Well formed Cyclone has the best available Energy to tap as these Eddy's or Loop current are the Energizers of the Big ones,esp the CV Vortexes.
So when we get deep into August and into September,those SST's become critical as to how Strong the Storm can become,and sustain.
And it dosent has to Sustain at Peak Cat numbers once they move out toward a Coastlines as we saw with the past Big Hurricanes.
Once the Energy is transferred to the Surge ,its going somewhere,even if the Storm Winds down by a Cat Size or 2.
Its the water that does the deed,But the Winds drives the Surge Values up to the catastrophic heights.
Thats why Cat Size at Landfall isnt really the Number to watch,..its the Surge Height at Landfall.
Eddy's usually go to the west, but on the continental shelf you find places that are warm pockets from shallow waters and hot temperatures and strong sun angle.
The place where Charley intensified was shallow water with not much current flow, making the water heat up easily. North of Key west that pocket has very high SST's values during the summer months.
You can see where it got it strength from in this image...
The National Hurricane Center is in the middle of a large expanse of middle-class suburbs. Apartments, condominiums, townhouses and homes are all available, although the quality of the neighborhoods may vary
Tropical Cyclone Bulletin #4
TROPICAL STORM AGATON (OMAIS)
========================================
Subject: Tropical Storm "AGATON" has maintained its strength as it moves away from the country.
At 11:00 PM PhST, Tropical Storm Agaton (Omais) located at 16.1ºN 132.6ºE or 820 km east northeast of Virac, Catanduanes has 10 minute sustained winds of 35 knots with gusts of 45 knots.
Additional Information
=======================
The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 11 AM tomorrow.
Ya it was very impressive to have gone through that storm. The pressure difference at my house was so great it sucked the attic door open with the house closed up.
It would have been a story that no one could have even imagined. Charley passing to the south still sucked tons of water out of Tampa bay and it was almost 100 miles to the south.
Growing up in Orlando and now living in St. Petersburg, FL I never realized how low line these areas really were until you see it every day. A strong tropical storm will make major flooding problems here.
Charley was a Fast Mover coming in at a Oblique angle to the Coastline,so the Surge wouldnt have had time to build up as in a Large Hurricane coming in from Tampa's West,or Sw,as Elena almost did in 85.
Charley did show many,that it very Important to watch the actual Storm as the Nickname Right turn Charley fooled many a Good forecaster who was focused on the NHC track,and not the Storms Movement that suddenly put Punta Gorda in Harms Way.
If in the Warned area,..take all the steps you need to be ready.
Felt like a different city after it passed, I never thought I'd ever see all of Orlando darkened with no lights. Very strange and there wasnt any sounds either
This video documents approximately 2 hours of Hurricane Charley as it moved across southwest Florida on August 13, 2004. Towns include Punta Gorda, Port Charlotte, North Port, Fort Ogden and Arcadia. The lower left portion of the map represents the Punta Gorda, Port Charlotte, and North Port areas. Note that only extreme eastern North Port received hurricane conditions.
Next, the small community of Fort Ogden would take the full brunt of the storm. Hurricane Charley then struck the town of Arcadia, located just to the right of dead center on the map.
Ruskin Radar Loop
I know with the eye-wall you have alot of evaporation cooling and water condensing from the strong updrafts cooling the air(might have used the wrong words). You know how a strong thunderstorm approaches you and the air is getting sucked into the storm, the air always feels really warm and humid, when the storm passes the air is cooler.
Well same concept but happening very fast and in a large scale.
The attic door being sucked up is from the advancing eye-wall pressure gradient. The forward speed also had to do with the issue. But its basically the pressure is changing so rapidly the house with all the doors closed has a hard time changing its pressure with the storm. The wind pressure from high winds also aids in this situation.
StormChaser is right that there is a lot of evaporational cooling going on and by the time you get to the center of the storm the air has been getting rained on for quite some time, and the heaviest rains are at the eyewall. But, if you end up inside the eye, and the eye is at least partially clear, you should see a rise in temperature due to sinking air in the eye that warms by compression.
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Back later.
The sound of them is going through our building and im on the back side.
St. Pete Indy Cars
Track Map
South Florida StormWatch
(main site)
Eyjafjallajokull
This is my Favorite LOOP
Ya, convection is really starting to fire up.
At least it looks like straight line winds with not much shear. but I might be wrong. But there will be strong gust associated with the line coming ashore later tonight into early morning for Tampa Area.
You can barely see it on the long range radar, so its more than 300 miles away, I think it might be a bit longer than 3 hours to get to that area. But is seems to be picking up forward speed.
Long Range Radar
Viewing: 351 - 401
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