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Itsdb |
04/10/06 |
Air trends 'amplifying' warming
By Richard Black
Environment Correspondent, BBC News website, in Vienna
Reduced air pollution and increased water evaporation appear to be adding to man-made global warming.
Research presented at a major European science meeting adds to other evidence that cleaner air is letting more solar energy through to the Earth's surface.
Other studies show that increased water vapour in the atmosphere is reinforcing the impact of man-made greenhouse gas emissions.
Scientists suggest both trends may push temperatures higher than believed.
But they say there is an urgent need for further research, particularly at sea.
Dimming no more
Between the 1950s and 1980s, the amount of solar energy penetrating through the atmosphere to the Earth's surface appeared to be declining, by about 2% per decade.
This trend received some publicity under the term "global dimming".
But in the 1980s, it appears to have reversed, according to two papers published last year in the journal Science.
The decline in Soviet industry and clean air laws in western countries apparently reduced concentrations of aerosols, tiny particles, in the atmosphere.
These aerosols may block solar radiation directly, or help clouds to form which in turn constitute a barrier; or both effects may occur.
The lead researcher on one of those Science papers was Martin Wild from the Institute for Atmospheric and Climate Science (IACETH) in Zurich, and this week he has been discussing the implications of those findings at the European Geosciences Union (EGU) annual meeting in Vienna.
Correlations and causality
The reversal of "global dimming" has been proposed in some circles as an alternative explanation for climatic change, removing the need to invoke human emissions of greenhouse gases.
Dr Wild dismissed this picture. His analysis suggests that "global dimming" and the man-made greenhouse effect may have cancelled each other out until the early 1980s, but now "global brightening" is adding to the impact of human greenhouse emissions.
"There is always this argument that maybe the whole temperature rise wasn't due to greenhouse warming but due to solar variations," he told the BBC News website.
"During the solar dimming we had really no temperature rise. And only when the solar dimming disappeared could we really see what is going on in terms of the greenhouse effect, and that is only starting in the 1980s."
Analyses of global temperature indicate that a sharp upward trend commenced in the early 1980s.
But, said Dr Wild, there are strong regional variations in the "solar brightening" trend.
"In Eastern Europe, we see a very strong recovery [in solar radiation] - almost back to what it was before dimming began," he said.
"But India continues with the dimming - that's very much thought to be due to increasing air pollution.
"The general position is that air pollution is still increasing in the tropics, but decreasing outside the tropics; so probably that will amplify warming a little bit outside the tropics but not inside."
Data deficit
There are, Dr Wild admitted, holes in the picture of change.
"The term 'global dimming' is a bit dangerous," he said. "I usually call it 'solar dimming' not 'global dimming' because we really only know about this where we have measurements; and we don't have measurements at many places, for example over the oceans, or land in the tropics."
More research facilities are needed, he said, in tropical regions, particularly sub-Saharan Africa, and especially the oceans.
As well as extending measurements of solar energy reaching the Earth's surface, he urged more research on aerosol concentrations in the atmosphere and on trends in cloud cover.
Rolf Philipona from the World Radiation Center in Davos, Switzerland, is attempting to improve aerosol measurements in northern Europe.
"We're trying to put a paper together which shows the aerosol depth and the amount of aerosol in the air column from about six to eight stations in Europe," he told the BBC News website.
"In Germany and Switzerland we would have stations very high up, extending all the way to the North Sea."
Last year Dr Philipona released research indicating that European warming is largely driven by increases in humidity.
The mechanism is that rising levels of what are conventionally called "greenhouse gases", such as carbon dioxide and methane, cause more evaporation of water, which in the atmosphere is itself a greenhouse gas.
He believes this is having more impact than changes to the transmission of solar energy through the atmosphere.
"From my results I believe it's the greenhouse warming and in particular the water vapour feedback," he said.
"Studies and papers are also coming now which are looking more closely at what water vapour is doing in other regions; and there are several pieces of work showing water vapour is increasing over land areas like the United States."
Satellites and ships
A further implication of "global brightening" is that the temperature difference between night and day may reduce.
The "blanket" of greenhouse gases in the atmosphere has a net heating effect during day and night, whereas changes in solar energy reaching the surface are felt only in daytime.
Disproportionately higher night-time temperatures have already been noted in many parts of the world, and research in the Philippines has linked this trend to a reduction in rice yield.
The conclusions presented here present two major challenges to the research community.
One is to find ways of extending experimental investigations into the oceans and the developing world.
The second is to integrate them into computer models of climate, something which is only just beginning to happen.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
So what now? Less industry, cleaner air, reduction of nasty aerosols, the world's getting brighter - and it's only contributing to global warming - we must be doomed.
Should Bush run right out and sign Kyoto...or would that only make the problem worse?
Steve |
Clarification/Follow-up by tomder55 on 04/11/06 5:23 pm:
forgot to source my response .
Space .com Clarification/Follow-up by Itsdb on 04/11/06 7:14 pm:
Ronnie:
Americans are getting wise to Bush and his inept policies. When will he answer the hard questions?
Argumentative and irrelevent.
As for answering the hard questions, apparently you haven't been listening. It's almost impossible to hear him over the shrill voices on the left and slanted news coverage. Of course that doesn't explain why you dismiss those answers when provided directly to you on these boards.
Clarification/Follow-up by Erewhon on 04/11/06 8:29 pm:
Steve,
YOU say it's irrelevant, but what is your opinion against the majority of Americans? How will you convince fleeing masses of Republicans to come back to the Leader's side?
You might gain lasting fame by being the last American to believe anything Bush says. I suppose it's better than being ignored.
Same old mantras, Steve. I listen very carefully to everything Bush says, whether it has substance (rarely), or none at all (usually).
From the anti-Bush (it's called 'opposition' and is legal in democracies, alhtough Fascists don't like it!) left-wing biased pinko commie media:
On Sunday, "The Washington Post" reported the Bush administration is studying options for strikes against Iran.
An account by "New Yorker" magazine's Seymour Hersh said one Pentagon plan included using tactical nuclear weapons against Iran's underground nuclear sites. Hersh wrote that U.S. planning was spurred by Iranian President Mahmoud Ahmadinejad's recent threats against Israel and the U.S.
One of Hersh's sources was quoted as saying that President Bush thinks he must do "what no Democrat or Republican, if elected in the future, would have the courage to do."
Do you think he will use the Nuke to effect regime change? Is that OK in your book?
LOL
I dismiss your answers usually on the grounds that I do not believe them. Please don't let opposition upset you. It is okay to disagree!
Clarification/Follow-up by Itsdb on 04/11/06 8:37 pm:
It was irrelevent to my post.
Now focus here Ronnie, I didn't ask about Bush policies, Letterman or the 'hard questions.' I didn't ask about the opinion of the majority of Americans, the 'fleeing masses of Republicans,' the 'same old mantras,' whether or not opposition is legal or if I mind it, the 'left-wing biased pinko commie media' or 'options for strikes against Iran.'
I asked if Bush should sign Kyoto (a pet liberal cause) or if signing Kyoto would make the problem (global warming, the subject of the post) worse.
It's good to know you admit you dismiss my answers just because you "do not believe them," I've known that for a long time. The shame is you claim to be a proponent of truth but dismiss it just because you "do not believe" it coming from me.
I realize truth is malleable to you, but it isn't to me, so it isn't opposition I mind - it's opposition that has a pertinacious disregard for the facts.
Steve
Clarification/Follow-up by Erewhon on 04/11/06 11:46 pm:
I believe that you believe what you say is true. I just happen to disagree with you. So sue me!
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