NASA Leads Study of Unprecedented Arctic Ozone Loss

October 02, 2011

PASADENA, Calif. - A NASA-led study has documented an unprecedented depletion of Earth's protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.

The study, published online Sunday, Oct. 2, in the journal Nature, finds the amount of ozone destroyed in the Arctic in 2011 was comparable to that seen in some years in the Antarctic, where an ozone "hole" has formed each spring since the mid-1980s. The stratospheric ozone layer, extending from about 10 to 20 miles (15 to 35 kilometers) above the surface, protects life on Earth from the sun's harmful ultraviolet rays.

The Antarctic ozone hole forms when extremely cold conditions, common in the winter Antarctic stratosphere, trigger reactions that convert atmospheric chlorine from human-produced chemicals into forms that destroy ozone. The same ozone-loss processes occur each winter in the Arctic. However, the generally warmer stratospheric conditions there limit the area affected and the time frame during which the chemical reactions occur, resulting in far less ozone loss in most years in the Arctic than in the Antarctic.

To investigate the 2011 Arctic ozone loss, scientists from 19 institutions in nine countries (United States, Germany, The Netherlands, Canada, Russia, Finland, Denmark, Japan and Spain) analyzed a comprehensive set of measurements. These included daily global observations of trace gases and clouds from NASA's Aura and CALIPSO spacecraft; ozone measured by instrumented balloons; meteorological data and atmospheric models. The scientists found that at some altitudes, the cold period in the Arctic lasted more than 30 days longer in 2011 than in any previously studied Arctic winter, leading to the unprecedented ozone loss. Further studies are needed to determine what factors caused the cold period to last so long.

"Day-to-day temperatures in the 2010-11 Arctic winter did not reach lower values than in previous cold Arctic winters," said lead author Gloria Manney of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the New Mexico Institute of Mining and Technology in Socorro. "The difference from previous winters is that temperatures were low enough to produce ozone-destroying forms of chlorine for a much longer time. This implies that if winter Arctic stratospheric temperatures drop just slightly in the future, for example as a result of climate change, then severe Arctic ozone loss may occur more frequently."

The 2011 Arctic ozone loss occurred over an area considerably smaller than that of the Antarctic ozone holes. This is because the Arctic polar vortex, a persistent large-scale cyclone within which the ozone loss takes place, was about 40 percent smaller than a typical Antarctic vortex. While smaller and shorter-lived than its Antarctic counterpart, the Arctic polar vortex is more mobile, often moving over densely populated northern regions. Decreases in overhead ozone lead to increases in surface ultraviolet radiation, which are known to have adverse effects on humans and other life forms.

Although the total amount of Arctic ozone measured was much more than twice that typically seen in an Antarctic spring, the amount destroyed was comparable to that in some previous Antarctic ozone holes. This is because ozone levels at the beginning of Arctic winter are typically much greater than those at the beginning of Antarctic winter.

Manney said that without the 1989 Montreal Protocol, an international treaty limiting production of ozone-depleting substances, chlorine levels already would be so high that an Arctic ozone hole would form every spring. The long atmospheric lifetimes of ozone-depleting chemicals already in the atmosphere mean that Antarctic ozone holes, and the possibility of future severe Arctic ozone loss, will continue for decades.

"Our ability to quantify polar ozone loss and associated processes will be reduced in the future when NASA's Aura and CALIPSO spacecraft, whose trace gas and cloud measurements were central to this study, reach the end of their operational lifetimes," Manney said. "It is imperative that this capability be maintained if we are to reliably predict future ozone loss in a changing climate."

Other institutions participating in the study included Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany; NASA Langley Research Center, Hampton, Va.; Royal Netherlands Meteorological Institute, De Bilt, The Netherlands; Delft University of Technology, 2600 GA Delft, The Netherlands; Science Systems and Applications, Inc., Greenbelt, Md., and Hampton, Va.; Science and Technology Corporation, Lanham, Md.; Environment Canada, Toronto, Ontario, Canada; Central Aerological Observatory, Russia; NOAA Earth System Research Laboratory, Boulder, Colo.; Arctic Research Center, Finnish Meteorological Institute, Finland; Danish Climate Center, Danish Meteorological Institute, Denmark; Eindhoven University of Technology, Eindhoven, The Netherlands; Arctic and Antarctic Research Institute, St. Petersburg, Russia; National Institute for Environmental Studies, Japan; National Institute for Aerospace Technology, Spain; and University of Toronto, Ontario, Canada.

For more information on NASA's Aura mission, visit: http://www.nasa.gov/aura . For more information on NASA's CALIPSO mission, visit: http://www.nasa.gov/calipso .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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First complete map of Antarctica ice flow

[ First complete map of the speed and direction of ice flow in Antarctica, derived from radar interferometric data. Image credit: NASA/JPL-Caltech/UCI ]

08.18.11

By Alan Buis
NASA Jet Propulsion Laboratory


PASADENA, Calif. - NASA-funded researchers have created the first complete map of the speed and direction of ice flow in Antarctica. The map, which shows glaciers flowing thousands of miles from the continent's deep interior to its coast, will be critical for tracking future sea-level increases from climate change. The team created the map using integrated radar observations from a consortium of international satellites.

"This is like seeing a map of all the oceans' currents for the first time. It's a game changer for glaciology," said Eric Rignot of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California (UC), Irvine. Rignot is lead author of a paper about the ice flow published online Thursday in Science Express. "We are seeing amazing flows from the heart of the continent that had never been described before."

Rignot and UC Irvine scientists Jeremie Mouginot and Bernd Scheuchl used billions of data points captured by European, Japanese and Canadian satellites to weed out cloud cover, solar glare and land features masking the glaciers. With the aid of NASA technology, the team painstakingly pieced together the shape and velocity of glacial formations, including the previously uncharted East Antarctica, which comprises 77 percent of the continent.

Like viewers of a completed jigsaw puzzle, the scientists were surprised when they stood back and took in the full picture. They discovered a new ridge splitting the 5.4 million-square-mile (14 million-square-kilometer) landmass from east to west.

The team also found unnamed formations moving up to 800 feet (244 meters) annually across immense plains sloping toward the Antarctic Ocean and in a different manner than past models of ice migration.

"The map points out something fundamentally new: that ice moves by slipping along the ground it rests on," said Thomas Wagner, NASA's cryospheric program scientist in Washington. "That's critical knowledge for predicting future sea level rise. It means that if we lose ice at the coasts from the warming ocean, we open the tap to massive amounts of ice in the interior."

The work was conducted in conjunction with the International Polar Year (IPY) (2007-2008). Collaborators worked under the IPY Space Task Group, which included NASA; the European Space Agency (ESA); Canadian Space Agency (CSA); Japan Aerospace Exploration Agency; the Alaska Satellite Facility in Fairbanks; and MacDonald, Dettwiler and Associates of Richmond, British Columbia, Canada. The map builds on partial charts of Antarctic ice flow created by NASA, CSA and ESA using different techniques.

"To our knowledge, this is the first time that a tightly knit collaboration of civilian space agencies has worked together to create such a huge dataset of this type," said Yves Crevier of CSA. "It is a dataset of lasting scientific value in assessing the extent and rate of change in polar regions."

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Tohoku tsunami created icebergs in Antarctica

Before (left) and after (right) photos of the Sulzberger Ice Shelf illustrate the calving event associated with the Japan earthquake and resulting tsunami that occurred on March 11, 2011. The icebergs have just begun to separate in the left image. Credit: European Space Agency/Envisat
08.15.11

By Patrick Lynch, NASA Goddard Space Flight Center
Steve Koppes, University of Chicago


A NASA scientist and her colleagues were able to observe for the first time the power of an earthquake and tsunami to break off large icebergs a hemisphere away.

Kelly Brunt, a cryosphere specialist at Goddard Space Flight Center, Greenbelt, Md., and colleagues were able to link the calving of icebergs from the Sulzberger Ice Shelf in Antarctica following the Tohoku Tsunami, which originated with an earthquake off the coast of Japan in March 2011. The finding, detailed in a paper published online today in the Journal of Glaciology, marks the first direct observation of such a connection between tsunamis and icebergs.

The birth of an iceberg can come about in any number of ways. Often, scientists will see the towering, frozen monoliths break into the polar seas and work backwards to figure out the cause.

So when the Tohoku Tsunami was triggered in the Pacific Ocean on March 11 this spring, Brunt and colleagues immediately looked south. All the way south. Using multiple satellite images, Brunt, Emile Okal at Northwestern University and Douglas MacAyeal at University of Chicago were able to observe new icebergs floating off to sea shortly after the sea swell of the tsunami reached Antarctica.

To put the dynamics of this event in perspective: An earthquake off the coast of Japan caused massive waves to explode out from its epicenter. Swells of water swarmed toward an ice shelf in Antarctica, 8,000 miles (13,600 km) away, and about 18 hours after the earthquake occurred, those waves broke off several chunks of ice that together equaled about two times the surface area of Manhattan. According to historical records, this particular piece of ice hadn't budged in at least 46 years before the tsunami came along.

And as all that was happening, scientists were able to watch the Antarctic ice shelves in as close to real-time as satellite imagery allows, and catch a glimpse of a new iceberg floating off into the Ross Sea.

"In the past we've had calving events where we've looked for the source. It's a reverse scenario – we see a calving and we go looking for a source," Brunt said. "We knew right away this was one of the biggest events in recent history – we knew there would be enough swell. And this time we had a source."

Scientists first speculated in the 1970s that repeated flexing of an ice shelf – a floating extension of a glacier or ice sheet that sits on land – by waves could cause icebergs to break off. Scientific papers in more recent years have used models and tide gauge measurements in an attempt to quantify the impact of sea swell on ice shelf fronts.

The swell was likely only about a foot high (30 cm) when it reached the Sulzberger shelf. But the consistency of the waves created enough stress to cause the calving. This particular stretch of floating ice shelf is about 260 feet (80 meters) thick, from its exposed surface to its submerged base.

When the earthquake happened, Okal immediately honed in on the vulnerable faces of the Antarctic continent. Using knowledge of iceberg calving and what a NOAA model showed of the tsunami's projected path across the unobstructed Pacific and Southern oceans, Okal, Brunt and MacAyeal began looking at what is called the Sulzberger Ice Shelf. The Sulzberger shelf faces Sulzberger Bay and New Zealand.

Through a fortuitous break in heavy cloud cover, Brunt spotted what appeared to be a new iceberg in MODerate Imaging Spectroradiometer (MODIS) data.






[Nearly 50 square miles of ice broke off the Sulzberger Ice Shelf on the coast of Antarctica, resulting from waves generated by the Tohoku earthquake and tsunami that struck Japan in March 2011]

"I didn't have strong expectations either way whether we'd be able to see something," Brunt said. "The fastest imagery I could get to was from MODIS Rapid Response, but it was pretty cloudy. So I was more pessimistic that it would be too cloudy and we couldn't see anything. Then, there was literally one image where the clouds cleared, and you could see a calving event."

A closer look with synthetic aperture radar data from the European Space Agency satellite, Envisat, which can penetrate clouds, found images of two moderate-sized icebergs – with more, smaller bergs in their wake. The largest iceberg was about four by six miles in surface area – itself about equal to the surface area of one Manhattan. All the ice surface together about equaled two Manhattans. After looking at historical satellite imagery, the group determined the small outcropping of ice had been there since at least 1965, when it was captured by USGS aerial photography.

[Thick cloud cover briefly fell away to reveal this first image of icebergs breaking away from the Sulzberger Ice Shelf due to sea swell from the Tohoku Tsunami, which had originated 8,000 miles away about 18 hours earlier. The icebergs can be seen behind a thin layer of clouds just off the ice shelf near the center of the image. Source: MODIS Rapid Response/NASA.]



The proof that seismic activity can cause Antarctic iceberg calving might shed some light on our knowledge of past events, Okal said.

"In September 1868, Chilean naval officers reported an unseasonal presence of large icebergs in the southernmost Pacific Ocean, and it was later speculated that they may have calved during the great Arica earthquake and tsunami a month earlier," Okal said. "We know now that this is a most probable scenario."

MacAyeal said the event is more proof of the interconnectedness of Earth systems.

"This is an example not only of the way in which events are connected across great ranges of oceanic distance, but also how events in one kind of Earth system, i.e., the plate tectonic system, can connect with another kind of seemingly unrelated event: the calving of icebergs from Antarctica's ice sheet," MacAyeal said.

In what could be one of the more lasting observations from this whole event, the bay in front of the Sulzberger shelf was largely lacking sea ice at the time of the tsunami. Sea ice is thought to help dampen swells that might cause this kind of calving. At the time of the Sumatra tsunami in 2004, the potentially vulnerable Antarctic fronts were buffered by a lot of sea ice, Brunt said, and scientists observed no calving events that they could tie to that tsunami.

"There are theories that sea ice can protect from calving. There was no sea ice in this case," Brunt said. "It’s a big chunk of ice that calved because of an earthquake 13,000 kilometers away. I think it's pretty cool."

And as all that was happening, scientists were able to watch the Antarctic ice shelves in as close to real-time as satellite imagery allows, and catch a glimpse of a new iceberg floating off into the Ross Sea.

More . . .    http://climate.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=565 

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Researchers document ice loss after Antarctic shelf collapse

[The Larsen B ice shelf began disintegrating around Jan. 31, 2002. Its eventual collapse into the Weddell Sea remains the largest in a series of Larsen ice shelf losses in recent decades, and a team of international scientists has now documented the continued glacier ice loss in the years following the dramatic event. NASA’s MODerate Imaging Spectroradiometer (MODIS) captured this image on Feb. 17, 2002. (Credit: MODIS, NASA's Earth Observatory)]

08.02.11

An international team of researchers has combined data from multiple sources to provide the clearest account yet of how much glacial ice surges into the sea following the collapse of Antarctic ice shelves.

The work by researchers at the University of Maryland, Baltimore County (UMBC), the Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, Centre National de la Recherche Scientifique at the University of Toulouse, France, and the University of Colorado's National Snow and Ice Data Center, Boulder, Colo., details recent ice losses while promising to sharpen future predictions of further ice loss and sea level rise likely to result from ongoing changes along the Antarctic Peninsula.

"Not only do you get an initial loss of glacial ice when adjacent ice shelves collapse, but you get continued ice losses for many years – even decades – to come," says Christopher Shuman, a researcher at UMBC's Joint Center for Earth Systems Technology (JCET) at NASA's Goddard Space Flight Center, Greenbelt, Md. Shuman is lead author of the study published online July 25 in the Journal of Glaciology. "This further demonstrates how important ice shelves are to Antarctic glaciers."

An ice shelf is a thick floating tongue of ice, fed by a tributary glacier, extending into the sea off a land mass. Previous research showed that the recent collapse of several ice shelves in Antarctica led to acceleration of the glaciers that feed into them. Combining satellite data from NASA and the French space agency CNES, along with measurements collected during aircraft missions similar to ongoing NASA IceBridge flights, Shuman, Etienne Berthier, of the University of Toulouse, and Ted Scambos, of the University of Colorado, produced detailed ice loss maps from 2001 to 2009 for the main tributary glaciers of the Larsen A and B ice shelves, which collapsed in 1995 and 2002, respectively.

[The Landsat Image Mosaic of Antarctica (LIMA) provides this “flyover” view of the Larsen Ice Shelf’s long reach out into the Weddell Sea. (Credit: LIMA)]

"The approach we took drew on the strengths of each data source to produce the most complete picture yet of how these glaciers are changing," Berthier said, noting that the study relied on easy access to remote sensing information provided by NASA and CNES. The team used data from NASA sources including the MODerate Imaging Spectroradiometer (MODIS) instruments and the Ice, Cloud and land Elevation Satellite (ICESat).

The analysis reveals rapid elevation decreases of more than 500 feet for some glaciers, and it puts the total ice loss from 2001 to 2006 squarely between the widely varying and less certain estimates produced using an approach that relies on assumptions about a glacier's mass budget.

The authors' analysis shows ice loss in the study area of at least 11.2 gigatons (11.2 billion tons) per year from 2001 to 2006. Their ongoing work shows ice loss from 2006 to 2010 was almost as large, averaging 10.2 gigatons (10.2 billion tons) per year.

More . . .   http://climate.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=558

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Cold front, warm front

[acquired November 26, 2011]

Weather fronts are as familiar as rain. For those who live outside of Earth’s tropics, the movement of warm and cold masses of air creates the weather, and when the two clash, it often rains. Understanding what happens when cold and warm air meet (cold and warm fronts) has given meteorologists the ability to predict the weather.

But for all of their familiarity with fronts, scientists have only recently gotten a detailed view of them. These four images contrast computer models of weather fronts (lower images) with the view from NASA’s Cloudsat (top), a space-based radar. The radar instrument on the satellite provides a detailed view of the cloud structure and precipitation in the clouds, helping scientists refine their understanding of common weather patterns and improve their ability to predict the weather.

The left image pair shows a cold front moving from left to right into a warm mass of air. The cold, dense air lifts the warm air like a wedge. The rising, warm air forms distinctive anvil-shaped clouds, visible in both the satellite and model image. Along the leading edge of the front, the rising air can develop into intense thunderstorms with heavy bursts of rain if there is enough moisture in the air.

Rain droplets send a stronger radar signal back to the satellite. This means that areas of heavy rain are dark blue, while lighter rain is lighter in color. The Cloudsat image shows a single area of concentrated rain surrounded by a line of lighter rain. The less detailed model shows a broad swath of rain. Cloudsat also reveals a line of low, rain-producing clouds behind the front that the model missed.

The right image pair shows a warm front moving from left to right over a cold mass of air. In this case, the lighter, warmer air lifts gradually over the cold air. The rising air cools and condenses into a wide area of clouds and steady rain. While both the satellite and the model detect the rain (shown in dark blue), Cloudsat shows more rain over a wider area.

Cloudsat launched on April 28, 2006, and began to take measurements a little over a month later. The moment the satellite turned on, its first image showed the structure of both a cold front and a warm front in detail scientists had never seen before. In the five years since, the instrument has provided numerous observations of cloud structures, from the unusual—hurricanes—to the mundane, common fronts.


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Two NASA Sites Win Webby Awards

WASHINGTON -- Two NASA websites have been recognized in the 15th Annual Webby Awards -- the leading international honor for the world's best Internet sites.

NASA's main website, www.NASA.gov, received its third consecutive People's Voice Award for best government site. NASA's Global Climate Change site at http://climate.nasa.gov/, which won last year's People's Voice Award for science, won the 2011 judges' award for best science site.

"NASA is committed to sharing its compelling story with people everywhere and with every communication tool," said David Weaver, NASA's associate administrator for communications. "We are very grateful to the online community for its continued support of what we are doing, and are excited about our future."

NASA recently posted new interactive pieces on the 30th anniversary of the Space Shuttle Program and the 50th anniversary of the first U.S. spaceflight. And in the last year, the agency has streamlined its online video presentation into a single player and deployed a version of the site optimized for mobile devices.

"NASA has a very broad-based Web team that can take content, literally the best raw material in the universe, and create compelling imagery, video and multimedia pieces to tell the agency's story," said Internet Services Manager Brian Dunbar in the Office of Communications at NASA Headquarters in Washington.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Global Climate Change site for the agency's Science Mission Directorate.

"NASA satellites take key measurements of our climate, and the Global Climate Change site gives the public access to that data as a visual, immersive experience," said Randal Jackson, JPL's Internet communications manager for the Global Climate Change site. "We're grateful for the high degree of interest the public has shown in Earth's vital signs."

NASA has had a Web presence almost since HTML was invented in the early 1990's, but the site's popularity skyrocketed after a 2003 redesign and relaunch focused on making it more usable and understandable for the general public. Since then, there have been more than 1.5 billion visits to the site, and its customer-satisfaction ratings are among the highest in government and comparable to popular commercial sites.

Reaching beyond the agency's website, NASA's online communications include a Facebook page with more than 368,000 "likes"; a Twitter feed with more than a million followers; and more than 160 accounts across a variety of social media platforms. Last fall, NASA placed first by a wide margin in the L2 Digital IQ Index for the Public Sector study that ranks 100 public sector organizations in the effectiveness of their websites, digital outreach, social media use and mobile sites.

The Office of Communications and the Office of the Chief Information Officer, both at NASA Headquarters, manage the agency's website.

Presented by the International Academy of Digital Arts and Sciences, the Webby Award recognizes excellence in technology and creativity. The academy created the awards in 1996 to help drive the creative, technical, and professional progress of the Internet and evolving forms of interactive media. While members of the International Academy of Digital Arts and Sciences select the Webby award winners, the online community determines the winners of the People's Voice Awards.

To find all the ways you can connect and collaborate with NASA, visit: http://www.nasa.gov/connect.

The California Institute of Technology in Pasadena manages JPL for NASA.

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Benefits of cleaner vehicles

04.05.11

By Adam Voiland
NASA's Earth Science News Team

A new analysis, published this week and conducted by a team of scientists led by Drew Shindell of NASA's Goddard Institute for Space Studies (GISS) in New York City, shows stricter vehicle emission standards would yield major health, agricultural, and climate benefits.

Shindell and colleagues used a comprehensive computer model and climate simulator — one of the first capable of accounting for the role of short-lived particles expelled in vehicle fumes called aerosols — that shows vehicle fumes exact an enormous toll in all countries and especially in the developing world.
The scientists used modeling techniques developed at GISS to compare a baseline scenario that assumes existing emission standards remain unchanged in coming decades with a second scenario that has most countries adopting stringent standards similar to those in place in Europe and North America. Vehicles in those two regions produce less particulate matter and less polluting gases, such as nitrous oxides and carbon monoxide, due to the use of particle filters and cleaner-burning fuels.

The aggressive scenario assumes, for example, that China, India, and Brazil adopt "Euro 6" standards by 2015, a regime that would reduce emissions of particulate matter by about 85 percent, nitrogen oxides by about 65 percent, and carbon monoxide by about 70 percent for passenger vehicles. The aggressive scenario assumes major emissions reductions in Latin America, Africa, and the Middle East, the regions with the laxest emissions standards. Emissions rules in North America are slightly more stringent than European standards already, so in North America the baseline and aggressive scenarios were identical.

The team's findings were published this week in the inaugural edition of Nature Climate Change.

Human toll, plant toll

Particulate matter from vehicle fumes can slip past the body's defenses — hair-like structures in the respiratory tract and hairs in our noses — and penetrate deep into the lungs. There, it can spark a range of diseases such as asthma, cardiovascular disease, and bronchitis.

Ozone, the product of reactions between nitrogen oxides, carbon monoxide or hydrocarbons, and sunlight, can harm both people and plants. In humans, it inflames the lining of air passages making breathing more difficult and can scar lungs after long periods of exposure. In crops, it damages cell membranes, slowing photosynthesis and reducing yields.

"The adoption of aggressive standards by 2015 would set the world on a course to prevent the deaths of 200,000 people, save 13 million tons of cereal grains from ozone damage, and save $1.5 trillion in health damages each year after 2030," Shindell said.

After five years, that would amount to saving a million lives, more than 50 million tons of food, and $7.5 trillion in human health damages. Health damages are based on an accounting technique economists use to weigh the benefits of life-saving regulations called the “value of a statistical life.”

For comparison, the United Nations estimated that the earthquake and tsunami that struck the northeast coast of Honshu had caused about 27,600 deaths and produced between $185 and $308 billion in damages at the end of March. Hurricane Katrina killed 1,836 people and produced about $81 billion in damages.

The analysis also breaks down potential health benefits by region and finds benefits varied widely. Overall, the modeling found that stricter standards would prevent the most deaths in China, India, and North Africa, regions where unfiltered soot-producing diesel engines remain ubiquitous.

While reductions in particulate matter tend to produce local health benefits, the scientists found health and agricultural benefits from reduced ozone disperse more widely. That means for some countries — India, for example — changes in emissions from neighboring countries could have as much impact as local emission changes.

"There is no one-size-fits-all approach to emissions standards. Different countries are going to need different approaches," Shindell said.

A climate connection

The new study shows that the same measures that benefit human health and agriculture would also make a significant dent in climate change in the near term.

While it is well-established that carbon dioxide released by vehicles contributes to global warming, it has been much less clear how the combination of shorter-lived aerosol particles vented by vehicles — such as black carbon, sulfate, and organic carbon — affect climate.

While some of these aerosols reflect sunlight and produce a cooling effect, others absorb light and warm the atmosphere. Aerosols from vehicles can also impact the development of clouds in ways that have poorly-understood consequences for climate.

Shindell's modeling shows that stringent emissions standards would reduce .20 °C (.36 °F) of warming in the Northern Hemisphere from 2040 to 2070. That's largely because more stringent standards would reduce emissions of black carbon, a constituent of soot, and carbon monoxide, a precursor of ozone. In comparison, the Northern Hemisphere has warmed by about .3 °C (.54 °F) per decade in the last three decades.

"Though the stringent standards would provide a clear climate benefit in the near term, the impact of accumulating carbon dioxide from vehicles is so large that there would still be an overall warming impact from vehicle emissions, albeit a lesser one than if they were not enacted," Shindell said.

Soot readily absorbs sunlight causing the atmosphere to warm. It also accelerates warming by coating the surfaces of snow and ice and reducing their reflectivity. Likewise, ozone, a greenhouse gas, warms the Earth.

As with the health benefits, the model projects the climate impacts of more stringent standards would vary significantly depending on the region. Cooling effects of sulfates, which highly are reflective, are minimized over parts of the Earth such as ice sheets and deserts that are also highly reflective, while the same areas exaggerate the warming from soot.

Emissions from India, for example, produced a particularly strong regional warming response because of the close proximity of large swaths of snow and ice in the Himalayas. The same was true of the Middle East and North Africa because of deserts in the region.

[Ozone, produced by chemical reactions between vehicle exhaust and sunlight, damages crops and reduces yields.

Credit: NASA Goddard's Scientific Visualization Studio]


To date, most studies have looked at the health, agricultural, or climate impacts of emissions in isolation. Shindell's analysis is one of the first to analyze the closely-intertwined impacts together — an approach that is more realistic.

"This is exactly the kind of study that is needed for policy-makers. Take a real policy scenario, and examine the impacts on a whole range of issues — air pollution, climate, crops, etc. and then use those results to find win-win solutions across very varied regions," noted Gavin Schmidt, another climatologist based at GISS.

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