Summer haze has a cooling effect in southeastern United States

May 18, 2009

(PhysOrg.com) -- Global warming may include some periods of local cooling, according to a new study by researchers at the University of California, Berkeley. Results from satellite and ground-based sensor data show that sweltering summers can, paradoxically, lead to the temporary formation of a cooling haze in the southeastern United States.

The study, to be published the week of May 18 in the journal , found that when manmade pollutants mix with the natural compounds emitted from forests and vegetation during the hot summer months, they form secondary that reflect light from the sun. Such aerosols may also contribute to the formation of clouds, which also reflect sunlight.

The results of this study suggest that climate models need to better account for the effects of organic aerosols, the authors said.

The researchers conducted observations of aerosols throughout the earth's atmosphere using space-based satellites in combination with ground-based sunphotometers between March 2000 and February 2007.

"This is the first time a study has shown that the aerosols formed from the combination of manmade and natural emissions observed from space are relevant for understanding earth's climate," said study lead author Allen Goldstein, UC Berkeley professor and chair of the Department of Environmental Science, Policy and Management.

The study began when former UC Berkeley Ph.D. student and study co-author Charles Koven showed Goldstein satellite data that indicated a summertime spike in aerosol haze in the southeastern United States. Goldstein noticed that the increased haziness, which could not be explained by human activities alone, coincided with the known regional pattern of biogenic volatile organic compounds. The emission of these compounds - natural hydrocarbons from and - increases exponentially when the temperature rises, said Goldstein.

"These natural emissions are highly volatile, and when they react with human sources of pollution in the atmosphere, aerosols are created," said Goldstein, who also holds a joint faculty appointment in the Department of Civil and Environmental Engineering. "Nobody realized until now that enough of these aerosols were forming to influence cooling over an entire region."

The researchers estimated that the cooling effect from the aerosol haze over this region in summer is outpacing the warming effect from carbon dioxide emissions by 2-to-1 in a negative feedback system.

The results do not mean, however, that aerosols negate the effects of carbon dioxide emissions, emphasized atmospheric scientist Inez Fung, co-director of the Berkeley Institute of the Environment and a co-author of the study.

"The cooling effect of the organic aerosols we are reporting here are regional and temporal; they are dwarfed by the changes in the climate we are witnessing globally," said Fung, a UC Berkeley professor with joint appointments in the Department of Earth and Planetary Science and the Department of Environmental Science, Policy and Management. "Aerosols only remain in the atmosphere for five to 10 days, whereas lingers for decades. To counter all the warming effects from greenhouse gases with aerosols, levels would have to be so high that we'd have trouble breathing, and the sky would no longer appear blue."

Source: University of California - Berkeley (news : web)

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

add to favorites email to friend print save as pdf

Related Stories

Aerosols -- their part in our rainfall

Feb 12, 2009

Aerosols may have a greater impact on patterns of Australian rainfall and future climate change than previously thought, according to leading atmospheric scientist, CSIRO's Dr. Leon Rotstayn.

Faster Climate Change Predicted as Air Quality Improves

Jun 29, 2005

Global warming may proceed faster and be more severe than previously predicted according to research about to be published in the scientific journal Nature. Reductions in airborne particle pollution, or aerosols, as air qu ...

'Asian haze' impacts on Australian rainfall

Dec 12, 2006

Elevated particle emissions resulting from increased economic activity in Asia may have increased Australia’s tropical rainfall, according to new research on the way pollution influences our climate.

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

jonnyboy
1 / 5 (2) May 18, 2009
UC-Berkeley

Need I say more?
NotParker
3 / 5 (2) May 18, 2009
"The results do not mean, however, that aerosols negate the effects of carbon dioxide emissions"

What effect is that?

UAH satellite records has April .091C above average. 30 years on the temperature change is minimal and well within the margin of error.

http://wattsupwit...pped-50/
GrayMouser
not rated yet May 25, 2009
Please ignore this article. The science is settled. No additional information is needed or desired.

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...