Science news - might be of interest to gardeners

stitches216(8/9 Hou-Galv)July 13, 2006

Saw this article today. Long, but fascinating, if you can get through it all...

Trying to think of a memory trick to keep the point in, "Dark dust, rain's a bust."



NASA scientists have determined the formation of clouds is affected by the lightness or darkness of air pollution particles. This also impacts Earth's climate.

In a breakthrough study published Thursday in the online edition of Science, scientists explain why aerosols -- tiny particles suspended in air pollution and smoke -- sometimes stop clouds from forming and in other cases increase cloud cover. Clouds deliver water around the globe, and they also help regulate how much of the sun's warmth the planet holds. The capacity of air pollution to absorb energy from the sun is the key.

"When the overall mixture of aerosol particles in pollution absorbs more sunlight, it is more effective at preventing clouds from forming. When pollutant aerosols are lighter in color and absorb less energy, they have the opposite effect and actually help clouds to form," said Lorraine Remer of NASA's Goddard Space Flight Center, Greenbelt, Md. Remer worked closely with the study's lead author, the late Yoram Kaufman of Goddard, on previous research into this perplexing "aerosol effect."

With this new understanding, scientists working to predict how the Earth's climate is changing will be able to take a big step forward. The effect of the planet's constantly changing cloud cover has long been a problem for climate scientists. How clouds change in response to greenhouse-gas warming and air pollution will have a major impact

on future climate.

Using this new understanding of how aerosol pollution influences cloud cover, Kaufman and co-author Ilan Koren of the Weizmann Institute in Rehovot, Israel, estimate the impact world-wide could be as much as a 5 percent net increase in cloud cover. In polluted areas, these cloud changes can change the availability of fresh water and regional temperatures.

In previous research by the authors and their colleagues, both effects that aerosols have on clouds were seen with data from NASA satellites. Over the northern Atlantic Ocean, clouds that often produce heavy rain storms grew taller and were more frequent when plumes of pollution from North America or dust from Africa's Sahara Desert were present. However, when smoke from large fires billowed into the sky over South America's Amazon River basin, clouds were consistently fewer than when the air was relatively clear.

With these observations alone, the scientists could not be absolutely sure the aerosols themselves were causing the clouds to change. Other local weather factors such as shifting winds and the amount of moisture in the air could have been responsible, meaning the pollution was just along for the ride.

"Separating the real effects of the aerosols from the coincidental effect of the meteorology was a hard problem to solve," Koren said. In addition, the impact of aerosols is difficult to observe, compared to greenhouse gases like carbon dioxide, because aerosols only stay airborne for about one week, while greenhouse gases can linger for


To tackle this problem, Kaufman and Koren assembled a massive database of global observations that strongly suggests it is the darkness (absorbs sunlight) or brightness (reflects sunlight) of aerosol pollution and not weather factors that cause pollution to act as a cloud killer or a cloud maker. These measurements were culled from the NASA-sponsored Aerosol Robotic Network of ground-based instruments at nearly 200 sites worldwide.

The scientists conducted an extensive survey of sky conditions at 17 locations (including Washington, Rome, Beijing, and Mexico City) that represented different types of air pollution and weather patterns. Automated instruments that act like a camera's light meter to record how much sunlight was coming from the sky took readings several times an hour at different times of the year.

No matter where in the world the measurements were taken or in what season, Kaufman and Koren saw the same pattern. There were lots of clouds when light-reflecting pollution filled the air, but many fewer clouds were recorded in the presence of light-absorbing aerosols. "The probability that such a consistent relationship between aerosols and their effects on clouds is due to some other factor is very unlikely," Koren said.

NASA's satellites, computer models, and technology will continue to advance our understanding of how aerosol pollution affects the Earth's climate. NASA's formation of flying satellites, with the cloud-piercing instruments onboard the Cloudsat and CALIPSO spacecraft, are helping answer challenging questions such as the role of clouds in global warming and the influence of aerosols on rainfall and hurricanes.

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stitches216(8/9 Hou-Galv)

Wow Stitches! Your post has been at the top of the list for a whole two weeks! It must be fascinating! You sure know how to start popular threads! What a genius! Guess that light colored dust has been mighty plentiful in the skies over your neck of the swamp lately, huh? What's it like to talk to yourself in a forum?

(Don't reply to that, old fella!)

Rap, just give this thread a decent burial, and stick to posting war-between-the-sexes humor.

    Bookmark   July 28, 2006 at 4:19PM
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carrie751(z7/8 TX)

Stitches, this is a very interesting article, and I thank you for posting it. I think everyone has been too busy looking for those clouds to post a response.

    Bookmark   August 2, 2006 at 6:28PM
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Sorry, it got me thinking of all kinds of stressful things such as ... how much bad stuff is going up due to coal fired power plants, will the mercury make our Bass dangerous to eat, how can we cut back our energy usage, do we have any aerosol sprays around here (Lysol, under the sink), is allowing foreign investors to buy our power plants such a great idea - does it matter, will consumption voluntarily be reduced, why do so many people run sprinklers in the early afternoon, where do they think water comes from, is there anything that will make people think beyond themselves?

In short, I got a headache from gritting my teeth!
The article is interesting and the timing was perfect since it ties in with National Geographic's articles on coal, nuclear power and global warming.

    Bookmark   August 3, 2006 at 9:54AM
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pjtexgirl(7b DFW)

Honest to goodness I really have trouble believeing the same people who can't predict the weather (rain or not in Texas my case of interest) can go on and on about how they can track global warming etc....The Earth's climate is ever changing. It's been that way all along. Our global climate changes during out orbit around the sun. That's why the Earth has ice ages and hot periods(dinosaurs) throughout our Earth's history. The dinosaurs went extinct and there was an ice age way before we came along according to scientists. Texas used to be a sea(there are sea animal fossils in my top soil). Things change all the time. Weather changes all the time. I just think these people are guessing just like the rest of us. PJ

    Bookmark   August 3, 2006 at 2:54PM
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stitches216(8/9 Hou-Galv)

PJ and Jacquelyn, many of the thoughts you have expressed occur to me too. I really posted the article only because it had fresh science findings in it, at least, findings I had not read anywhere else before.

I have become a little burned out about the seemingly incessant and obsessive weaving of every scientific finding about meteorology into the getting to be suffocating fabric of global warming thoughts. I think we're all gonna die from the energy wasted on re-discovering over and over what we cannot control, before we die from the uncontrollable itself.

The clincher for me was a few months back, when I read (or saw on TV) a report about some current in the Atlantic Ocean. Supposedly, if that current changes in some way, the planet could be in for another Ice Age. Fear of that change in that current is driven by observations that are interpreted to conclusions that - guess what? - global warming is what's changing the current.

Get it? No matter what happens to the planet's climate - even an Ice Age - it's because of global warming. It's like, if you want to be Chicken Little about global warming, the deck is stacked; you can't go wrong.

Then the blame game and the my science is more solid than your science food fights get going.

Then the policy wonks, with all their science-backed, correct prescriptions for all the drastic behavioral changes that humans - especially Americans - "should" be making, that lead to all the unintended consequences that no scientists can foresee (because they could not possibly gather enough data), out-shout everyone in every discussion until you pray that some heat wave or Ice Age could just shut them up (or make them keep to themselves) and make them just leave the rest of us be, baked or frozen.

I need to go out and run our noisy gasoline-powered mower, before the neighborhood lawn inspectors park their 4-ton SUV out front and idle it for 5 minutes while making notes about how our grass is too tall, for a "nastygram" to be produced using all the kilowatt hours it'll take to get one of those written and mailed to us.

I'm not hyperventilating or raving mad, just venting like I need to now and then about life's absurdities. It's probably global warming that's making me short tempered and causing a snowball effect of additional CO2 dumping into the air. I just saw an article today about the unusual snowfall in South Africa...of course we know why that happened! Forget the lawn, it's Margarita Time!

    Bookmark   August 3, 2006 at 8:23PM
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