Posted on 05/05/2007 9:21:22 AM PDT by Maelstorm
Science Daily — There seems to be something new under the sun -- in the sky, specifically -- that could complicate scientists' efforts to get a fix on how much the world will warm in the future. Greenhouse gases are not the only things in the air that influence the temperature of our atmosphere. Clouds and small airborne particles called aerosols also play an important and complicated role. And now a new ingredient has been discovered: an extensive and previously unseen "twilight zone" of particles that represents a gradual transition from cloud droplets to dry particles.
In a recent study published, scientists from the Weizmann Institute, Rehovot, Israel, and NASA's Goddard Space Flight Center, Greenbelt, Md., document for the first time that air around clouds that was previously considered clear is actually filled with particles that are neither cloud droplets nor typical dry aerosols such as dust and air pollution. Worldwide, up to 60 percent of the atmosphere labeled as cloud-free in satellite observations is actually filled with this twilight zone of in-between particles, according to the study.
"With the highly sensitive Earth-observing instruments NASA has used since 2000, we can distinguish aerosols and clouds in greater detail than ever before," said Goddard's Lorraine Remer, a co-author on the study. "But the area around clouds has given us trouble. The instruments detected something there, but it didn't match our understanding of what a cloud or an aerosol looked like. What we think we're seeing is a transitional zone where clouds are beginning to form or are dying away, and where humidity causes dry particles to absorb water and get bigger."
Precisely accounting for everything in the atmosphere that can influence changes in global temperatures is critical to scientists' quest to accurately predict what Earth's climate will be in the future. The latest report from the Intergovernmental Panel on Climate Change, which assessed the potential risks of human-induced climate change, notes that the overall effect of clouds and aerosols on the amount of heat held in the atmosphere is still uncertain. Finding a previously unknown ingredient in the mix further complicates an already complex picture, but it also holds out the promise of resolving some nagging problems in climate change science.
"The effects of this zone are not included in most computer models that estimate the impact of aerosols on climate," said lead author Ilan Koren of the Weizmann Institute "This could be one of the reasons why current measurements of this effect don't match our model estimates." The study was published April 18 in the American Geophysical Union's Geophysical Research Letters.
Atmospheric scientists have been aware of an indistinct "halo" of particles immediately surrounding individual clouds, which are sometimes visible to the naked eye. These are thought to be aerosols accumulating moisture and growing in size, or a cloud droplet shrinking as it evaporates. But the newly detected twilight zone extends far beyond single clouds to fill an entire cloud field.
The research team first came across evidence for this transitional zone in satellite measurements of aerosols that looked "suspicious," according to Remer. "After working with several years of data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua spacecraft, we consistently saw what appeared to be elevated levels of aerosols near clouds. But we couldn't be sure that the instrument wasn't actually detecting stray light bouncing off of the clouds."
The region around clouds is difficult to accurately observe with instruments like MODIS because they operate like our eyes, collecting light reflected by objects below. Scientists interpret the different characteristics of the light received, matching them to known light patterns from different objects such as clouds. But clouds are notorious light scatterers, and the "glare" from the edge of clouds makes it hard to clearly detect what is around them. To be on the safe side, scientists mapping worldwide aerosols with MODIS avoid a 1-kilometer border around clouds.
To find out whether the apparent aerosol detection around clouds in the satellite data was real, Koren and his colleagues, including the late Yoram Kaufman of NASA Goddard, turned to an independent observing system on the ground: the NASA-sponsored Aerosol Robotic Network. The automated instruments in this global network minimize scattered light effects as they track the sun and take readings of the amount and size of aerosols in a narrow column of atmosphere between the instrument and the sun. When the sun is blocked by a cloud, the instrument doesn't make one of its regularly scheduled readings, which provides an indirect measure of the presence of a cloud.
Combining thousands of observations from 15 sites around the world, the researchers found that the amount of aerosol systematically increased as clouds got closer, as did the size of the particles. This held true regardless of whether the site was in a relatively clean setting or one where aerosols from air pollution or biomass burning were common.
"We found that the region affected by this cloud field 'twilight zone' extends to tens of kilometers beyond the identified cloud edge," said Koren. "This suggests that 30 to 60 percent of the atmosphere previously labeled as 'cloud-free' is actually affected by cloud-aerosol processes that reflect solar energy back into space."
Introducing this new factor could lead climate scientists to recalculate their best estimates of how Earth's atmosphere holds and reflects solar energy -- the key to accurately predicting the future of global warming. "Current estimates of the effect of aerosols on global temperatures, which is primarily cooling, may be too small because the large contribution from this transition zone has been overlooked," Remer said. "If aerosols are offsetting warming more than we thought, it's possible that warming could increase more than expected in the future if aerosols continue to decline, as has been reported recently."
This summer the scientists hope to get a closer look at the "twilight zone" and the hard-to-detect particles inside it with new measurements by the Aerosol Robotic Network and NASA aircraft.
Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center.
We really don’t know clouds at all.
THey should take away John Edwards hairspray and reduce aerosols in the air by 99.9999%.
they hadn’t figured this out before? And they claim to have been doing careful science?
referance PING
Not many people know the difference between clouds and chemtrails.
There are two types who observe nature closely. Scientists and poets. The problem is that there is a lot more nature to observe than there are observers who bother to report what they have observed.
We really don’t know clouds at all.
-—<>-—<>-—<>-—<>-—<>-—
ROTFLMPO...
Gee... that’s a catchy phrase... rather rhythmic... perhaps it would be the start of some really good poetry... or maybe even a song?
LOL
Thanks a ton. Now I’ve got to go out on a beautiful Saturday afternoon to do yard work with that song stuck in my head.
Or, PERHAPS, ol’scientists...
... the warming might just be less than the vaunted models are predicting!
What maroons!
The first the thing they can use with this data is predict the weather for next weekend more accurately so we can plan our day off, and not have to wonder, if we need to bring our coats because the globally warm weather forcasted will turn out instead to be a cold day with a chance of evening showers. Good grief they cant even get the short term forecast correct!
LOL! You owe me a new keyboard, monitor, and another cup of coffee
I should probably attribute quotes, but if it is well-known I usually don’t.
Send in the clouds.
—the more they find out, the less they really know—
From the article “typical dry aerosols such as dust and air pollution”, so if the aerosols are helping to offset warming, then all the work being done to cut down pollution and clean up the atmosphere is actually causing the earth to warm. This must really mess with the minds of environmentalists. They can either cut pollution and increase global warming, or pollute more and cut global warming.
Looks like they don’t know the full story. Regardless, the left has been acting as if GW is 100% caused by man, because they like the idea of shutting down all development, all business, and having us live in tents in the woods.
Sheesh... I really am driven nuts by these people who claim we know so much more than we actually DO know about climate, and the factors controlling it.
This CAN’T be news to most of the people who have spent any time at all studying satellite maps. Think about the difference between “IR”,”Water Vapor” and “Visible (clouds)” satellite maps you’ve looked at during hurricane or other weather events! There are ALWAYS stark differences between these... and not all of that can be explained easily.
Of course what really gets my goat worse is how they continue to be determined to shrug off the fact that the SUN has changed output over the last century and is now as hot as it’s been in the last 10,000 years... foolishness... but of course, nothing except CO2 produced by man could possibly be the most important effect. Tell that to Mars, that has warmed just as much, and gets only half the radiation from the Sun that we get...
Growl!
That was the basic idea when Global Cooling was the rage. lol
I think this demonstrates how very complex and also how dangerous to have an political ideology drive scientific conclusions. It illustrates that they clearly don’t know what they’d be fixing let alone all the risks if they are wrong.
Well, like a couple of the other posters here, I had such a good, immediate ‘guffaw’ that if I had a full mouth of coffee, you would have owed ME a keyboard, too! Great use of a “quote”!
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