Ten percent decrease water vapor in the stratosphere slows Earth’s warming trends, researchers say

A decrease in water vapor concentrations in parts of the middle atmosphere has contributed to a slowing of Earth’s warming, researchers are reporting. The finding, they said, offers part of the explanation for a string of years with relatively stable global surface temperatures.

Despite the decrease in water vapor, the study’s authors said, the overall trend is still toward a warming climate, primarily caused by a buildup in emissions of carbon dioxide and other heat-trapping gases from human sources.

“This doesn’t alter the fundamental conclusion that the world has warmed and that most of that warming has to do with greenhouse gas emissions caused by man," said Susan Solomon, a climate scientist at the National Oceanic and Atmospheric Administration and the lead author of the report, which appears in the January 29, 2010, issue of the journal Science.

Water vapor, a potent heat-trapping gas, absorbs sunlight and re-emits heat into Earth’s atmosphere. Its concentrations in the stratosphere, the second of three layers in the atmosphere, appear to have decreased in the last 10 years, according to the study.

This has slowed the rate of Earth’s warming by about 25 percent, Dr. Solomon said.

“We use the 10-10-10 to describe it,” she said. “That is, a 10 percent change in water vapor, 10 miles above our head, over the past 10 years.”

The study also found that from 1980 to 2000, an increase in water vapor sped the rate of warming — the result of an increase in emissions of methane, another greenhouse gas, during the industrial period. Methane, when oxidized, produces water vapor. Why a decrease in water vapor has occurred in the last 10 years is still unknown.

Dr. Solomon emphasized that the study focused on the atmosphere’s middle layer, not to be confused with the troposphere, Earth’s first layer. It has been known for years that water vapor in the troposphere amplifies the effect of greenhouse gas emissions.

Some climate skeptics have claimed that a spate of years with relatively stable temperatures indicates that the threat of global warming has been overblown.

Last week, the National Aeronautics and Space Administration released figures indicating that the decade ending in 2009 was the warmest on record.

Link:  http://www.nytimes.com/2010/01/29/science/earth/29vapor.html

Surprise in Earth's upper atmosphere: Mode of energy transfer from the solar wind

ScienceDaily, September 11, 2009 — UCLA atmospheric scientists have discovered a previously unknown basic mode of energy transfer from the solar wind to the Earth's magnetosphere. The research, federally funded by the National Science Foundation, could improve the safety and reliability of spacecraft that operate in the upper atmosphere.

"It's like something else is heating the atmosphere besides the sun. This discovery is like finding it got hotter when the sun went down," said Larry Lyons, UCLA professor of atmospheric and oceanic sciences and a co-author of the research, which is in press in two companion papers in the Journal of Geophysical Research.

The sun, in addition to emitting radiation, emits a stream of ionized particles called the solar wind that affects the Earth and other planets in the solar system. The solar wind, which carries the particles from the sun's magnetic field, known as the interplanetary magnetic field, takes about three or four days to reach the Earth. When the charged electrical particles approach the Earth, they carve out a highly magnetized region — the magnetosphere — which surrounds and protects the Earth.

Charged particles carry currents, which cause significant modifications in the Earth's magnetosphere. This region is where communications spacecraft operate and where the energy releases in space known as substorms wreak havoc on satellites, power grids and communications systems.

The rate at which the solar wind transfers energy to the magnetosphere can vary widely, but what determines the rate of energy transfer is unclear.

"We thought it was known, but we came up with a major surprise," said Lyons, who conducted the research with Heejeong Kim, an assistant researcher in the UCLA Department of Atmospheric and Oceanic Sciences, and other colleagues.

"This is where everything gets started," Lyons said. "Any important variations in the magnetosphere occur because there is a transfer of energy from the solar wind to the particles in the magnetosphere. The first critical step is to understand how the energy gets transferred from the solar wind to the magnetosphere."

The interplanetary magnetic field fluctuates greatly in magnitude and direction.

"We all have thought for our entire careers — I learned it as a graduate student — that this energy transfer rate is primarily controlled by the direction of the interplanetary magnetic field," Lyons said. "The closer to southward-pointing the magnetic field is, the stronger the energy transfer rate is, and the stronger the magnetic field is in that direction. If it is both southward and big, the energy transfer rate is even bigger."

However, Lyons, Kim and their colleagues analyzed radar data that measure the strength of the interaction by measuring flows in the ionosphere, the part of Earth's upper atmosphere ionized by solar radiation. The results surprised them.

"Any space physicist, including me, would have said a year ago there could not be substorms when the interplanetary magnetic field was staying northward, but that's wrong," Lyons said. "Generally, it's correct, but when you have a fluctuating interplanetary magnetic field, you can have substorms going off once per hour.

"Heejeong used detailed statistical analysis to prove this phenomenon is real. Convection in the magnetosphere and ionosphere can be strongly driven by these fluctuations, independent of the direction of the interplanetary magnetic field."

Convection describes the transfer of heat, or thermal energy, from one location to another through the movement of fluids such as liquids, gases or slow-flowing solids.

"The energy of the particles and the fields in the magnetosphere can vary by large amounts. It can be 10 times higher or 10 times lower from day to day, even from half-hour to half-hour. These are huge variations in particle intensities, magnetic field strength and electric field strength," Lyons said.

The magnetosphere was discovered in 1957. By the late 1960s, it had become accepted among scientists that the energy transfer rate was controlled predominantly by the interplanetary magnetic field.

Lyons and Kim were planning to study something unrelated when they made the discovery.

"We were looking to do something else, when we saw life is not the way we expected it to be," Lyons said. "The most exciting discoveries in science sometimes just drop in your lap. In our field, this finding is pretty earth-shaking. It's an entire new mode of energy transfer, which is step one. The next step is to understand how it works. It must be a completely different process."

The National Science Foundation has funded ground-based radars which send off radio waves that reflect off the ionosphere, allowing scientists to measure the speed at which the ions in the ionosphere are moving.

The radar stations are based in Greenland and Alaska. The NSF recently built the Poker Flat Research Range north of Fairbanks.

"The National Science Foundation's radars have enabled us to make this discovery," Lyons said. "We could not have done this without them."

The direction of the interplanetary magnetic field is important, Lyons said. Is it going in the same direction as the magnetic field going through the Earth? Does the interplanetary magnetic field connect with the Earth's magnetic field?

"We thought there could not be strong convection and that the energy necessary for a substorm could not develop unless the interplanetary magnetic field is southward," Lyons said. "I've said it and taught it. Now I have to say, 'But when you have these fluctuations, which is not a rare occurrence, you can have substorms going off once an hour.'"

Lyons and Kim used the radar measurements to study the strength of the interaction between the solar wind and the Earth's magnetosphere.

One of their papers addresses convection and its affect on substorms to show it is a global phenomenon.

"When the interplanetary magnetic field is pointing northward, there is not much happening, but when the interplanetary magnetic field is southward, the flow speeds in the polar regions of the ionosphere are strong. You see much stronger convection. That is what we expect," Lyons said. "We looked carefully at the data, and said, 'Wait a minute! There are times when the field is northward and there are strong flows in the dayside polar ionosphere.'"

The dayside has the most direct contact with the solar wind.

"It's not supposed to happen that way," Lyons said. "We want to understand why that is."

"Heejeong separated the data into when the solar wind was fluctuating a lot and when it was fluctuating a little," he added. "When the interplanetary magnetic field fluctuations are low, she saw the pattern everyone knows, but when she analyzed the pattern when the interplanetary magnetic field was fluctuating strongly, that pattern completely disappeared. Instead, the strength of the flows depended on the strength of the fluctuations.

"So rather than the picture of the connection between the magnetic field of the sun and the Earth controlling the transfer of energy by the solar wind to the Earth's magnetosphere, something else is happening that is equally interesting. The next question is discovering what that is. We have some ideas of what that may be, which we will test."

Co-authors on the papers include colleagues at Chungbuk National University in South Korea and SRI International in Menlo Park, Calif.

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Mysterious, glowing clouds appear across America’s night skies

Geophysical Research Letters, 36, L08502; doi:10.1029/2009GL037524.

Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent

John Turner (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.), Josefino C. Comiso (NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.), Gareth J. Marshall, Tom A. Lachlan‐Cope, Tom Bracegirdle, Ted Maksym, Michael P. Meredith, Zhaomin Wang, and Andrew Orr (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.)

Jet streams are shifting and may alter paths of storms and hurricanes

Storm paths in North America are likely to shift northward as a result of the jet stream changes. Hurricanes, whose development tends to be inhibited by jet streams, may become more powerful and more frequent as the jet streams move away from the sub-tropical zones where hurricanes are born.

ScienceDaily (April 17, 2008) — The Earth's jet streams, the high-altitude bands of fast winds that strongly influence the paths of storms and other weather systems, are shifting--possibly in response to global warming. Scientists at the Carnegie Institution determined that over a 23-year span from 1979 to 2001 the jet streams in both hemispheres have risen in altitude and shifted toward the poles. The jet stream in the northern hemisphere has also weakened. These changes fit the predictions of global warming models and have implications for the frequency and intensity of future storms, including hurricanes.

Cristina Archer and Ken Caldeira of the Carnegie Institution's Department of Global Ecology tracked changes in the average position and strength of jet streams using records compiled by the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Protection, and the National Center for Atmospheric Research. The data included outputs from weather prediction models, conventional observations from weather balloons and surface instruments, and remote observations from satellites.

Jet streams twist and turn in a wide swath that changes from day to day. The poleward shift in their average location discovered by the researchers is small, about 19 kilometers (12 miles) per decade in the northern hemisphere, but if the trend continues the impact could be significant. "The jet streams are the driving factor for weather in half of the globe," says Archer. "So, as you can imagine, changes in the jets have the potential to affect large populations and major climate systems."

Storm paths in North America are likely to shift northward as a result of the jet stream changes. Hurricanes, whose development tends to be inhibited by jet streams, may become more powerful and more frequent as the jet streams move away from the sub-tropical zones where hurricanes are born.

The observed changes are consistent with numerous other signals of global warming found in previous studies, such as the widening of the tropical belt, the cooling of the stratosphere, and the poleward shift of storm tracks. This is the first study to use observation-based datasets to examine trends in all the jet stream parameters, however.

"At this point we can't say for sure that this is the result of global warming, but I think it is," says Caldeira. "I would bet that the trend in the jet streams' positions will continue. It is something I'd put my money on."

The results are published in the April 18, 2008, Geophysical Research Letters.

Link to article: http://www.sciencedaily.com/releases/2008/04/080416153558.htm

Cyclones spurt water into stratosphere, feeding global warming

ScienceDaily (April 21, 2009) — Scientists at Harvard University have found that tropical cyclones readily inject ice far into the stratosphere, possibly feeding global warming.

The finding, published in Geophysical Research Letters, provides more evidence of the intertwining of severe weather and global warming by demonstrating a mechanism by which storms could drive climate change. Many scientists now believe that global warming, in turn, is likely to increase the severity of tropical cyclones.

"Since water vapor is an important greenhouse gas, an increase of water vapor in the stratosphere would warm the Earth's surface," says David M. Romps, a research associate in Harvard's Department of Earth and Planetary Science. "Our finding that tropical cyclones are responsible for many of the clouds in the stratosphere opens up the possibility that these storms could affect global climate, in addition to the oft-mentioned possibility of climate change affecting the frequency and intensity of tropical cyclones."

Romps and co-author Zhiming Kuang, assistant professor of climate science in Harvard's Faculty of Arts and Sciences, were intrigued by earlier data suggesting that the amount of water vapor in the stratosphere has grown by roughly 50 percent over the past 50 years. Scientists are currently unsure why this increase has occurred; the Harvard researchers sought to examine the possibility that tropical cyclones might have contributed by sending a large fraction of their clouds into the stratosphere.

Using infrared satellite data gathered from 1983 to 2006, Romps and Kuang analyzed towering cloud tops associated with thousands of tropical cyclones, many of them near the Philippines, Mexico, and Central America. Their analysis demonstrated that in a cyclone, narrow plumes of miles-tall storm clouds can rise so explosively through the atmosphere that they often push into the stratosphere.

Romps and Kuang found that tropical cyclones are twice as likely as other storms to punch into the normally cloud-free stratosphere, and four times as likely to inject ice deep into the stratosphere.

"It is ... widely believed that global warming will lead to changes in the frequency and intensity of tropical cyclones," Romps and Kuang write in Geophysical Research Letters. "Therefore, the results presented here establish the possibility for a feedback between tropical cyclones and global climate."

Typically, very little water is allowed passage through the stratosphere's lower boundary, known as the tropopause. Located some 6 to 11 miles above the Earth's surface, the tropopause is the coldest part of the Earth's atmosphere, making it a barrier to the lifting of water vapor into the stratosphere: As air passes slowly through the tropopause, it gets so cold that most of its water vapor freezes out and falls away.

But if very deep clouds, such as those in a tropical cyclone that can rise through the atmosphere at speeds of up to 40 miles per hour, can punch through the tropopause too quickly for this to happen, they can deposit their ice in the warmer overlying stratosphere, where it then evaporates.

"This suggests that tropical cyclones could play an important role in setting the humidity of the stratosphere," Romps and Kuang write.

Romps and Kuang's research was funded by the Eppley Foundation and NASA.

Geophysical Research Letters, 36, L03803; doi:10.1029/2008GL036076.

Cause of the widening of the tropical belt since 1958

Jian Lu (Advanced Study Program, National Center for Atmospheric Research, Boulder, CO, USA; and Center for Ocean-Land-Atmosphere Studies, Calverton, MD, USA), Clara Deser (National Center for Atmospheric Research, Boulder, CO, USA), and Thomas Reichler (Department of Meteorology, University of Utah, Salt Lake City, UT, USA)

The Great Frost of 1709, the Winter of 2009, and the Polar Vortex

February 11, 2009

Dear Readers,

Some of the most popular articles posted recently on this blog have been about the 1709 Great Frost in Europe. That article came from New Scientist (click here and hit the page-down key twice). If you read it closely, you will notice that it mentions that the normal cause of cold weather in western European winters are the winds coming from Siberia and blowing toward the west, but in the winter of 1709, the winds were coming from the west and the south.

"The most immediate cause of cold winters in Europe is usually an icy wind from Siberia. 'What you would expect would be long runs of easterly winds with a well-developed anticyclone over Scandinavia sucking in cold air from Siberia,' says Wheeler. Instead, his data show a predominance of southerly and westerly winds -- which would normally bring warm air to Europe. 'There were only occasional and easterlies and those were never for more than a few days,' says Wheeler. Another odd finding was that January was unusually stormy. Winter storms tend to bring milder, if wilder, weather to Europe. 'This combination of cold, storms and westerlies suggests some other mechanism was responsible for that winter.' "

Right now, western Europe is again experiencing very cold and stormy weather (although, I dare say that once in a while this is to be expected in the winter, is it not?). Are there any similarities between now and 300 years ago?

Well, maybe.

NASA's Earth Observatory has posted an interesting report (click here and hit the page-down key twice) on the stratospheric conditions over the Arctic from January 10 through February 4. During that time, the polar vortex split into two vortices (click here to see the still graphic representations), and these vortices were consequently at slightly lower latitudes, spinning in counter-clockwise directions, thus pulling winds across northern Europe from the west.

[The animation of the splitting of the polar vortex is really fascinating. NASA's Earth Observatory has posted an animation that shows the changes in temperature in the stratosphere, going up to about 20 kilometers. What it shows is perhaps disturbing. But who really knows? The satellites have not been up there all that long observing. But to my simple eyes, it looks like our planet coughed out a bunch of really hot air straight up over the Arctic. Notice that temperatures start out in the -88 °C range, and by the time they finish, they have gone up to 12 °C -- and we are talking about the stratosphere here! not the surface. OK, so here is the link to the QuickTime animation -- it is well worth waiting for it to download. Note, also, that on occasion, the servers at NASA appear to be overloaded, so you may not always be able to get into the link, but keep trying.]

The New Scientist article points out that although there were three very large volcanic eruptions during the end of the Little Ice Age (a regional phenomenon, not a real ice age), the summer of 1707 was extremely hot, despite a solar minimum.

"...the 1690s saw a string of cold summers and failed harvests, while the summer of 1707 was so hot people died from heat exhaustion. Overall, the climate was colder, with the sun's output at its lowest for millennia. There were some spectacular volcanic eruptions in 1707 and 1708, including Mount Fuji in Japan and Santorini and Vesuvius in Europe. These would have sent dust high into the atmosphere, forming a veil over Europe. Such dust veils normally lead to cooler summers and sometimes warmer winters, but climatologists think that during this persistent cold phase, dust may have depressed both summer and winter temperatures."

I think we all remember that 2007 was an extremely hot year, and consequently the sea ice at the North Pole melted in a dramatic fashion.

But it would be a real stretch to try to say that that makes current conditions similar to those of 300 years ago.

And, these past few years, we have been having something of a solar minimum, too, but I doubt we can make any hay out of that, either.

No, the main thing to note, in my opinion, are not the similarities, but the fact that this year the planet appeared to belch out the excess heat that had accumulated at latitudes further south, when it moved north and appeared to blast through the vortex and split it.

OK, this is the first time that I have tried to embed a video, so let's see if this works: QuickTime video of stratospheric temperatures and the polar vortex splitting in two.

And, all I can say about that is that I hope that this manuever really got rid of some of the excess heat, thereby improving the Earth's energy imbalance. Does anyone have any thoughts on this? Would love to hear from you.

p.s. Oh, yeah, and before I forget, wasn't it in January that while temperatures in Europe and the U.S. were so low, the temperatures in the Arctic were so high that Arctic sea ice growth just about ground to a complete halt?

NSIDC (Click here and hit page-down key twice):

"...January 15 to 26, ice extent saw essentially no increase; an unusual wind pattern appears to have been the cause."

And, have a look at the truly sad state of the ice on January 23, 2009 (click here for the image). In fact, I just looked at today's Envisat image, and the sea ice to the north of Ellesmere Island and Greenland actually looks worse than it did on the 23rd.

NASA's Earth Observatory: Stratosphere Influences Winter Weather, January 10 – February 6, 2009

Stratospheric temperatures over the Arctic, January 10 (left) – February 6 (right), 2009.

Polar vortex. Left: January 10, 2009. Right: February 6, 2009.

BLOGGER'S NOTE: It is well worth downloading this file to watch the incredibly high temperatures that occurred at an altitude of 30 km over the Artic in late January and early February (they went from –88 °C to +12 °C). Quicktime animation of polar stratospheric temperatures and vortex (THE LINK HAS BEEN REPAIRED): http://earthobservatory.nasa.gov/images/imagerecords/36000/36972/npole_gmao_200901-02.mov

NASA, February 7, 2009 – Winter turned fierce in the opening weeks of 2009. A bitter cold snap set in over much of the United States, and temperatures plummeted beyond –30 °C (–22 °F) in parts of the Upper Midwest. On February 2, portions of Western Europe were doused with heavy snow. England received the brunt of the storm with up to 20 centimeters (8 inches) of snow falling in London. It was the heaviest snowfall southeastern England had seen in nearly 20 years, reported BBC News. So why all the nasty weather? Part of the answer lies in the stratosphere, some 20 kilometers (12 miles) above the Earth’s surface.

Starting in January and extending into early February 2009, wind and temperature patterns in the stratosphere changed dramatically. In just a few weeks, temperatures climbed by about 50 °C (90 °F) on average, with larger spikes in places, and winds flipped direction, changing by nearly 100 meters per second (200 m.p.h.). That change influenced weather patterns lower in the atmosphere. These images and the associated animation show how the stratosphere changed and help illustrate why the United States and Europe were in the grip of such odd weather. The still figures show temperatures (top) and vorticity (bottom) on January 10 (left) and February 2 (right). The images are based on assimilated weather observations of the atmosphere from the Goddard Modeling and Assimilation Office at NASA Goddard Space Flight Center.

In the winter, little to no sunlight reaches Earth’s northern extremes. Deprived of energy, the stratosphere over the Arctic grows cold. These were the conditions present on January 10, 2009, as shown in the top left image. The cold air mass creates a low-pressure system that sits over the Arctic throughout the winter. Farther south, where the Sun is shining, the air is warmer and air pressure is higher. Air flows away from the high-pressure system towards the low-pressure system. Because the Earth is turning, the air is deflected to the right as it moves north, creating a strong counterclockwise (west to east) current of wind which scientists call the polar night jet.

The lower pair of images represent the air mass or polar vortex that controls the wind pattern. Essentially, the winds are strongest at the edge of the polar vortex (where the pressure difference between the air masses is greatest). The area of red in the lower left image represents polar air that typically sits over the Arctic during January. In general, strong winds circle the red regions, or areas of high vorticity, in a counterclockwise direction. These winds, moving at speeds well above 100 miles per hour, influence winds and weather patterns closer to Earth’s surface. Their influence means that weather in England and Western Europe typically comes from the west. Over England, western winds blow in ocean air warmed by the Atlantic Gulf Stream.

The big change in the Arctic came when the polar vortex ripped apart. A developing weather system in the lower atmosphere traveled upward into the stratosphere. The disturbance nudged into the center of the Arctic air mass, elongating it and eventually splitting it like a cell in mitosis. By February 2, two air masses existed, each with a jet of wind circling it counterclockwise as depicted in the lower right image.

Warm air filled the gap between the two colder air masses, and temperatures high over the North Pole climbed, as shown in the upper right. Now the colder air had shifted farther south over Canada and Siberia. Over North America, this piece of the stratospheric polar vortex had a deep reach into the lower atmosphere (troposphere), which created strong winds from the north that carried cold Arctic air far south into the United States.

In Europe, the split in the air mass actually changed the direction of winds in the lower atmosphere. The second piece of the polar vortex was centered east of Western Europe, as shown in the lower left image, and it too was surrounded by a jet of strong wind moving counterclockwise. Like the segment of the polar vortex over North America, this piece of the polar vortex also had a deep reach into the lower atmosphere. It caused cold continental air to blow in from the east, replacing the warmer air that typically blows in from the west. As the frigid air moved over the North Sea, it picked up moisture, which fell over the United Kingdom and parts of France as heavy snow.

Data provided by the Goddard Modeling and Assimilation Office, courtesy of Paul Newman. Caption by Holli Riebeek with information provided by Paul Newman.

BLOGGER'S NOTE: Link (sometimes, especially on the weekends, the server at NASA just can't handle the volume, but keep trying, you will get there from here!): http://earthobservatory.nasa.gov/IOTD/view.php?id=36972

Geophys. Res. Lett., 36, L03805; doi:10.1029/2008GL036223.

Impacts of climate change on stratospheric ozone recovery

D. W. Waugh, L. Oman (Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA), S. R. Kawa, R. S. Stolarski, S. Pawson, A. R. Douglass, P. A. Newman (Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, MD, USA), and J. E. Nielsen (Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA)

Abstract

Global Warming May Delay Recovery Of Stratospheric Ozone

ScienceDaily (Feb. 4, 2009) — Increasing greenhouse gases could delay, or even postpone indefinitely the recovery of stratospheric ozone in some regions of the Earth, a new study suggests. This change might take a toll on public health.

Ozone hole around South Pole in 2003. View of the South Pole from NASA's TOMS (Total Ozone Mapping Spectrometer) satellite. Blue and green indicate relatively large amounts of ozone. Red and yellow mark the "ozone hole," an area of decreased ozone. (Credit: NASA)

Darryn W. Waugh, an atmospheric scientist at Johns Hopkins University in Baltimore, and his colleagues report that climate change could provoke variations in the circulation of air in the lower stratosphere in tropical and southern mid-latitudes — a band of the Earth including Australia and Brazil. The circulation changes would cause ozone levels in these areas never to return to levels that were present before decline began, even after ozone-depleting substances have been wiped out from the atmosphere.

"Global warming causes changes in the speed that the air is transported into and through the lower stratosphere [in tropical and southern mid-latitudes]," says Waugh. "You're moving the air through it quicker, so less ozone gets formed." He and his team present their findings in the journal Geophysical Research Letters.

Dan Lubin, an atmospheric scientist who has studied the relationship between ozone depletion and variations in the ultraviolet radiation that reaches the Earth, says Waugh's findings could bode ill for people living in the tropics and southern mid-latitudes.

If ozone levels never return to pre-1960 levels in those regions, "the risk of skin cancer for fair-skinned populations living in countries like Australia and New Zealand, and probably in Chile and Argentina too, will be greater in the 21st century than it was during the 20th century," says Lubin, who is at Scripps Institution of Oceanography in La Jolla, Calif., and did not participate in the research.

Ozone is a gas which is naturally present in the atmosphere and absorbs ultraviolet radiation from the Sun that can harm living beings—for instance, by causing human skin cancer. This protective molecule has been in decline in the stratosphere since the 1970s due to an increase in atmospheric concentrations of human-made substances (mostly chlorofluorocarbon and bromofluorocarbon compounds) that destroy ozone. Since the late 1980s, most countries have adhered to the Montreal Protocol, an international treaty to phase out production of ozone-depleting substances.

Researchers at NASA Goddard Space Flight Center in Greenbelt, Md., collaborated with Waugh in the new study. The team forecast effects on ozone recovery by means of simulations using a computer model known as the Goddard Earth Observing System Chemistry-Climate Model.

Not all regions face worse prospects for ozone recovery as a result of climate change, the scientists find.

In polar regions and northern mid-latitudes, restoration of ozone in the lower stratosphere will suffer little impact from increasing greenhouse gases, their projections indicate.

Indeed, in the upper stratosphere, climate change causes a drop in temperatures that slows down some of the chemical reactions that destroy ozone. So, recovery might be reached in those parts of the atmosphere earlier than forecast, even decades before the removal of ozone-depleting gases.

While scientists have long suspected that climate change might be altering the dynamics of stratospheric ozone recovery, Waugh's team is the first to estimate the effects of increasing greenhouse gases on the recovery of ozone by region.

Waugh says his study will help scientists attribute ozone variations to the right agent.

"Ozone is going to change in response to both ozone-depleting substances and greenhouse gases," he says, "If you don't consider climate change when studying the ozone recovery data, you may get pretty confused."

Waugh, D. W., L. Oman, S. R., Kawa, R. S. Stolarski, S. Pawson, A. R. Douglass, P. A. Newman, & J. E. Nielsen. Impacts of climate change on stratospheric ozone recovery. Geophys. Res. Lett, 36, L03805 DOI: 10.1029/2008GL036223

Geophysical Research Letters, 36, L01801; doi: 10.1029/2008GL035863

Editors' Highlight

Atmosphere driven by cascades, an aid to numerical weather prediction

Numerical weather forecasting typically involves complex and nonlinear calculations, although many have theorized that there must be a simpler way to model terrestrial weather. To help search for this way, Lovejoy et al. (2009) hypothesized whether simplicity can be reached through seeing weather dynamics as cascade processes in which large structures modulate smaller ones and the process repeats to smaller and smaller scales, generating extremely variable fractal structures. The authors analyzed data from 1000 orbits of the Tropical Rainfall Measuring Mission satellite and found that shortwave and longwave radiance and reflective properties planet-wide follow predictions of cascade models with good agreement from planet scales down to 10 km. Because radiances and atmospheric dynamics are strongly coupled, the authors concluded that weather can be accurately modeled as a cascade process.

Atmospheric complexity or scale by scale simplicity?

S. Lovejoy (Physics, McGill University, Montreal, Quebec, Canada), D. Schertzer (CEREVE, Université Paris Est, Marne-la Vallée France), V. Allaire (Physics, McGill University, Montreal, Quebec, Canada), T. Bourgeois (CEREVE, Université Paris Est, Marne-la Vallée France), S. King, J. Pinel, and J. Stolle (Physics, McGill University, Montreal, Quebec, Canada)

Letter abstract

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Nature Geoscience 2, 28-31 (2009)
Published online: 14 December 2008 | doi:10.1038/ngeo388

Age of stratospheric air unchanged within uncertainties over the past 30 years

A. Engel¹, T. Möbius¹, H. Bönisch¹, U. Schmidt¹, R. Heinz², I. Levin², E. Atlas³, S. Aoki⁴, T. Nakazawa⁴, S. Sugawara⁵, F. Moore⁶, D. Hurst⁶, J. Elkins⁶, S. Schauffler⁷, A. Andrews⁶ and K. Boering⁸

Link to abstract: http://www.nature.com/ngeo/journal/v2/n1/abs/ngeo388.html