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New Study: Water Vapour a Major Cause of Warming and Cooling
American researchers have discovered that the amount of water high in the atmosphere is far more influential on world temperatures than previously thought.
The study, published in the journal Science, says a 10 per cent drop in humidity 10 miles above the Earth’s surface explains why global temperatures have been stable since the start of the century, despite the rise in carbon dioxide in the atmosphere.
And a rise in water vapour in the 1980s and 90s may also explain why temperatures shot up so quickly in the previous two decades, they say.
Water vapour has long been recognised as an important greenhouse gas. Like methane and carbon dioxide, it absorbs heat from the sun that would otherwise be reflected back into space, keeping the planet warm.
However, most computer models that predict climate concentrate on the levels of water lower down in the atmosphere.
Dr Susan Solomon, of the US National Oceanic and Atmospheric Administration, said: ‘Current climate models do a remarkable job on water vapour near the surface.
‘But this is different — it’s a thin wedge of the upper atmosphere that packs a wallop from one decade to the next in a way we didn’t expect.’
Observations from weather balloons and satellites show that ‘stratospheric water vapour’ increased in the 1980s and 1990s and dropped after 2000.
The changes took place in a narrow altitude region of the atmosphere where they would have the biggest impact on climate.
The reasons why water vapour rises and falls remain a mystery, the scientists say. However, the study estimates that the drop in water vapour since 2000 caused surface temperatures to rise 25 per cent more slowly than they would have done otherwise.
And the increase in stratospheric water vapour in the 1990s is likely to have accelerated the rate of global warming by around 30 per cent, the scientists say.
The stratosphere is a region of the atmosphere from about eight to 30 miles above the Earth’s surface. Water vapour enters the stratosphere mainly as air rises in the tropics.
Daily Mail: Water vapour a ‘major cause of global warming and cooling’
Published Online January 28, 2010
Science DOI: 10.1126/science.1182488
Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming
Susan Solomon,1 Karen Rosenlof,1 Robert Portmann,1 John Daniel,1 Sean Davis,1,2 Todd Sanford,1,2 Gian-Kasper Plattner3
Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here, we show that this acted to slow the rate of increase in global surface temperature over 2000 to 2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% compared to estimates neglecting this change. These findings show that stratospheric water vapor represents an important driver of decadal global surface climate change.
1 NOAA Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO, USA.
2 Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA.
3 Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.
Comment from Junkscience.com:
Pardon us for being less than impressed.
For years the air transport industry has been under assault because aircraft contrails allegedly do damage “wetting the Stratosphere”. Likewise the fossil fuel industry and agriculture because methane was supposed to loft to the Stratosphere where it decomposed to water vapor and carbon dioxide. Again, Stratospheric wetting was supposed to be a major concern and now: “Oops! It’s getting dry up here.”
Well guess what? Here’s another hypothetical means of adjustment in Stratospheric moisture levels: Svensmark Effect.
Undeniably Sol’s magnetic exuberance has been rather subdued of late, allowing more galactic cosmic rays (GCRs) to penetrate the Solar System, increasingly ionizing the atmosphere. Is this causing greater flocculation and droplet formation, causing water vapor to condense and fall out of the Stratosphere? We have no idea… and neither do modelers.
Granted, the addition of yet another item to the enormous list of things poorly understood about the climate and not represented (or wildly misrepresented) in models will make no real difference (unlike things well understood since any addition to such a miniscule list inflates it dramatically). Adding yet another excuse to the list of reasons “expected” warming failed to materialize is hardly cause for celebration though, is it.