Water vapour is a major cause of global warming and cooling find scientists

Telegraph.co.uk 29 January 2010

By Louise Gray

Water vapour is a major cause of global warming and cooling, according to a new study that will spark further debate over the science of climate change.

The research by scientists at the American weather service found water vapour high in the atmosphere is far more influential on world temperatures than previously thought.

During the 1990s one third of the increase in global temperatures was due to an increase in water vapour. In the same way a drop in water vapour after 2000 could explain the recent slowdown in global warming.

The researchers insist their findings do not mean that global warming is not caused by man made greenhouse gases. But the effect of natural water vapour high up in the air may also be having an effect.

The research comes amid fears global warming has been exaggerated. The United Nations’ climate science panel the Intergovernmental Panel on Climate Change (IPCC) admitted last week that it made a mistake by claiming that the Himalayan glaciers could melt by 2035.

It followed another row surrounding the science behind climate change, dubbed “Climategate”, when it was alleged leaked emails showed scientists at the University of East Anglia were willing to manipulate climate change data.

The new research by US National Oceanic and Atmospheric Administration is published in the journal Science, one of the most respected in the world.

Susan Solomon, who led the research and worked on the IPCC, said climate scientists need to take into account the effect of water vapour high in the atmosphere when studying global warming.

“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,”

Vicky Pope, Head of Climate Change Advice at the Met Office, said the research does not change the long term trend of warming caused by man made greenhouse gases. But it does show how water vapour in the stratosphere is also affecting temperature.