Subscription Center
May 18, 2009 05:00 PM | 14
Why is the southeastern U.S. getting cooler while the rest of the globe is warming? Thank the trees, say some researchers.
On sweltering summer days, trees and other plants emit volatile organic compounds, such as isoprene, which combine with manmade soot and other aerosols in the atmosphere to produce a cooling haze, says environmental scientist Allen Goldstein of the University of California, Berkeley.
Goldstein and his colleagues used satellite and ground sensor data to track air pollution. Over time, the cooling induced by the atmospheric haze has outpaced the warming due to rising carbon dioxide levels in the atmosphere, according to findings published in Proceedings of the National Academy of Sciences. "Nobody realized until now that enough of these aerosols were forming to influence cooling over an entire region," Goldstein says.
Of course, it would require a constant spew of aerosols to mimic the effect elsewhere (or on a global scale), enough to turn the sky gray instead of blue and make it difficult to breathe. So plant-produced haze isn’t likely to become a geoengineering solution anytime soon.
But the results go a long way to explain why high temperatures in the southeastern U.S. are dipping even as global CO2 levels rise. It isn't that there are more trees per se, it's that scientists now have better ways of measuring pollutants and their effect on local temperatures.
Image: © iStockphoto.com / Sebastien Windel
Tags:
climate change,
haze,
air pollution,
smog,
global warming,
trees
More News Blog:
Next: Spacewalkers complete Hubble's final tune-up
Previous: Wolfram|Alpha has arrived. Now what's it good for?
See what we're tweeting about
Deadline: Jul 15 2013
Reward: $5,000 USD
SciBX: Science-Business eXchange, a joint publication from the makers
Deadline: Jul 30 2013
Reward: $100,000 USD
The Seeker desires a method for producing pseudoephedrine products in such a way that it will be extremely difficult for clandestine che
Powered By: 
YES! Send me a free issue of Scientific American with no obligation to continue the subscription. If I like it, I will be billed for the one-year subscription.
14 Comments
Add CommentPresident Reagan was reviled by "scientists", Democrats, and the media as stupid when he said that the Great Smokey Mountains trees produced hydrocarbons that caused the mountains to be "smokey." I suspect he won't be getting an apology.
Reply | Report Abuse | Link to thisThe Blue Mountains in NSW Australia look Blue because of a similar phenomenon.
Reply | Report Abuse | Link to thisRead the title, Trees BOOST pollution, not cause it.
Reply | Report Abuse | Link to thisReagan said "trees cause more pollution than automibiles do," google it.
Plainly wrong, plainly unscientific.
"...such as isoprene, which combine with manmade soot and other aerosols in the atmosphere to produce a cooling haze..."
So, without the manmade soot ?
The title of this article sucks.
Yes this is true. It is also true that Reagan is the one who started this crap with allowing companies to move to other countries for cheap labor and low taxes. single-handedly destroying the american economy and the republicans keep trying to distract people to other things so they won't remember what was really going on. I knew about the greenhouse gasses long ago... did a presentation on it, with information I got from the CDC. I wonder who told the CDC to keep their mouths shut? Let's put the blame where it really belongs, he individual consumer who just can't live without mall-hair and cell phones.
Reply | Report Abuse | Link to thisThis link to the National Climatic Data Centra/NESDIS/NOAA seems to show the whole USA is getting colder. Here's the link to the gif for the last 12 months.
Reply | Report Abuse | Link to thishttp://www.ncdc.noaa.gov/img/climate/research/2009/apr/05_04_2009_DvTempRank_pg.gif
heh, erbarker, I think they call it "Global" warming because it occurs across a global scale.... cooling in one region for a period of a year or so doesn't negate the overall global warming trend.
Reply | Report Abuse | Link to thistharriss.... tharriss... No need to get upset. I was just pointing out that the Southeast US does not seem to be cooling any more then the rest of the US.
Reply | Report Abuse | Link to thisAs for Global Warming http://earthobservatory.nasa.gov/IOTD/view.php?id=36699 shows that 2008 was the coolest year since 2000, but still in the top ten hotest years. I think that all in all when the sun becomes active again, if it does, we may get really hot,
Even if the scientists discover better ways of measuring pollutants, I guess the world, not only America, is affected with the basic Global Warming problem and the primary reason known world wide is the CO2 reason which constitutes more than 75% of the reason of global warming.
Reply | Report Abuse | Link to thisInstead the action should be more on resolving old problems than researching on new reasons for the problem.
Well, I live in South Florida...and it ain't getting any cooler down here!!!
Reply | Report Abuse | Link to thisWell I live in NC and I must say it has been very comfortable here for a number of years. I doubt whether this article included Florida. Not many trees left down there and it sure is hot.
Reply | Report Abuse | Link to thisIt's not only the USA, cooling while climate changes.
Reply | Report Abuse | Link to thisEarthe's amtosphere is a self regulating chaotic system. The heat energy is more an more concentrated to the oceans, because streams like the gulf stream (northern atlantic) or the adria-stream (mediterranian sea) break down an cannot further dissipate heat energy.
This leads to a cooling at some sites (Europe in the 50's latitudes, e.g.) and to warming at others (south east asia, constant ''El NInjo'' years, because upwelling of cool water at the westcoast of South America is cut of by high streaming velocity).
Taking in account the Stephan-Boltzmann-Law of the black radiator, we see energy loss of a surface going proporional to temperatures fourth potential (T exp 4).
So the rising temperature differences lead to an increased radiation of the earth to the universe, leading to a backdriving force, with maintaines the small temperature window, that allows life to persist.
This is not really new, russian scientists did develop this theory (now becoming practised), a four decennials ago. By that scenario, life on earth may be conserved only in the deep oceans, when a point of no return is overcome, that makes the Oceans to freeze completely.
It's not only the USA, cooling while climate changes.
Reply | Report Abuse | Link to thisEarthe's amtosphere is a self regulating chaotic system. The heat energy is more an more concentrated to the oceans, because streams like the gulf stream (northern atlantic) or the adria-stream (mediterranian sea) break down an cannot further dissipate heat energy.
This leads to a cooling at some sites (Europe in the 50's latitudes, e.g.) and to warming at others (south east asia, constant ''El NInjo'' years, because upwelling of cool water at the westcoast of South America is cut of by high streaming velocity).
Taking in account the Stephan-Boltzmann-Law of the black radiator, we see energy loss of a surface going proporional to temperatures fourth potential (T exp 4).
So the rising temperature differences lead to an increased radiation of the earth to the universe, leading to a backdriving force, with maintaines the small temperature window, that allows life to persist.
This is not really new, russian scientists did develop this theory (now becoming practised), a four decennials ago. By that scenario, life on earth may be conserved only in the deep oceans, when a point of no return is overcome, that makes the Oceans to freeze completely.
In reference to the first comment , I don't think 'trees' are why they call the smoky's 'smoky. Its named for the 'fog' which is not a function of trees or air pollution, its an issue of precipitation, just in case you think he wasn't a moron - or if you spell potato with an extra 'e'.
Reply | Report Abuse | Link to thisAir pollution is definitely on the increase as more cars driven by fossil fuels start to be used. The particulate in the air can cause lung cancer and heart disease and the total world is affected by the global warming.
Reply | Report Abuse | Link to this<a href="http://bingoonline4you.com">play bingo games online</a>