Featured Research

from universities, journals, and other organizations

Polluted Clouds Might Bring Patchy Cooling In A Warming World

Date:
June 18, 2001
Source:
University Of Washington
Summary:
As the Earth's average temperature has risen in the last half-century with the buildup of greenhouse gases in the atmosphere, many scientists have come to see clouds, because they reflect so much of the sun's heat into space, as the biggest puzzle in interpreting the planet's changing climate picture.

As the Earth's average temperature has risen in the last half-century with the buildup of greenhouse gases in the atmosphere, many scientists have come to see clouds, because they reflect so much of the sun's heat into space, as the biggest puzzle in interpreting the planet's changing climate picture.

But new evidence suggests that the current stew of airborne chemicals and particles might be giving clouds stronger cooling properties than previously thought, said Robert Charlson, a University of Washington atmospheric chemist.

"Clouds are a devilishly difficult but extremely important aspect of the Earth's climate system," said Charlson, lead author of a paper in the June 15 edition of the journal Science that details the new evidence.

Clouds are formed as water droplets condense around particles in the atmosphere. Previous studies have shown that when the number of particles increases – because of emissions from human activities, for example – there still remains the same amount of water to spread among them. The result is more and smaller droplets, which creates more total surface area within the cloud to reflect sunlight.

The new evidence implies that droplet formation also is influenced by several other factors, including the presence of soluble gases and organic pollutants (for instance, stearic acid from a variety of sources, from forest fires to backyard grills) that are only slightly water-soluble. That means even more droplets, giving the resulting clouds even more cooling capacity.

The Earth's surface in regions where this happens will be cooled even more than would happen with normal cloud cover, a finding that could carry broad ramifications, Charlson said. The phenomenon can affect regions as large as the eastern third of the United States, the European continent or the Szechwan Basin of China.

"Roughly half the Earth is covered with clouds at any one time," he said. "Of that, some percentage is influenced by products of human activity, particularly in the Northern Hemisphere, where most people live."

Charlson was joined in the work by John Seinfeld and Athanasios Nenes of the California Institute of Technology; Markku Kulmala at the University of Helsinki; Ari Laaksonen at the University of Kuopio, Finland; and Maria Cristina Facchini at Italy's CNR-Instituto di Scienze dell’ Atmosfera e dell’Oceano.

"This work modifies the original 1920s and '30s theory to include soluble gases, such as nitric acid gas, and surface active organic materials, like smoke from forest fires and garbage incinerators," Charlson said.

The findings come from a computer model developed at Caltech that shows how the reflectivity, or albedo, of clouds is changed when various factors are introduced. The evidence raises questions about how clouds affect global climate change, but it doesn't answer them, Charlson said.

In their formation, "clean" clouds reach a point at which droplets pass a certain size threshold and begin to gather more water and grow spontaneously to ever-larger sizes. But the new study shows the chemical effects of pollution can trigger the formation of clouds or fog with tinier droplets, as small as a micron (one-thousandth of a millimeter) that are limited in their growth because of the substances going into them.

"When you get so much pollution in the air, it influences the formation of clouds," Charlson said.


Story Source:

The above story is based on materials provided by University Of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University Of Washington. "Polluted Clouds Might Bring Patchy Cooling In A Warming World." ScienceDaily. ScienceDaily, 18 June 2001. <www.sciencedaily.com/releases/2001/06/010615071805.htm>.
University Of Washington. (2001, June 18). Polluted Clouds Might Bring Patchy Cooling In A Warming World. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2001/06/010615071805.htm
University Of Washington. "Polluted Clouds Might Bring Patchy Cooling In A Warming World." ScienceDaily. www.sciencedaily.com/releases/2001/06/010615071805.htm (accessed September 22, 2014).

Share This



More Earth & Climate News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Will Climate Rallies Spur Change?

Will Climate Rallies Spur Change?

Newsy (Sep. 21, 2014) Organizers of the People's Climate March and other rallies taking place in 166 countries hope to move U.N. officials to action ahead of their summit. Video provided by Newsy
Powered by NewsLook.com
Thousands March in NYC Over Climate Change

Thousands March in NYC Over Climate Change

AP (Sep. 21, 2014) Accompanied by drumbeats, wearing costumes and carrying signs, thousands of demonstrators filled the streets of Manhattan and other cities around the world on Sunday to urge policy makers to take action on climate change. (Sept. 21) Video provided by AP
Powered by NewsLook.com
Climate Change Rally Held in India Ahead of UN Summit

Climate Change Rally Held in India Ahead of UN Summit

AFP (Sep. 20, 2014) Some 125 world leaders are expected to commit to action on climate change at a UN summit Tuesday called to inject momentum in struggling efforts to tackle global warming. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
New Music With Recycled Instruments at Colombia Fest

New Music With Recycled Instruments at Colombia Fest

AFP (Sep. 19, 2014) Jars, bottles, caps and even a pizza box, recovered from the trash, were the elements used by four musical groups at the "RSFEST2014 Sonorities Recycling Festival", in Colombian city of Cali. Duration: 00:49 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins