Importance of clouds

Present models of climate change are inadequate because they do not sufficiently account for clouds, researchers told a climate science conference in Vienna this week.

"Clouds are important - they represent one of the largest sources of uncertainty in climate modelling," said Keith Browning of the University of Reading. "Until we can tie that down, we cannot say how accurate these models are."

As leader of a consortium of European universities, Professor Browning has developed a computer model that simulates how clouds develop over areas about 100 kilometres across and ten kilometres high. He feeds in information on the temperatures, the wind speed and the humidity of the air. The computer model then generates the types of clouds that are likely to form. To test the model, Professor Browning watches how these clouds evolve with time and compares that with real clouds.

"Clouds move water vapour around the planet and water vapour is a more important greenhouse gas than carbon dioxide," said Professor Browning.

At a different conference session, scientists heard how the River Pang, a tributary of the Thames, could provide a model for water management following a climate change in Europe.

As part of a European research project, Alan Gustard, of the Institute of Hydrology in Wallingford, modelled the water flow in the River Pang, which had been reduced to a trickle after too much water was pumped from the ground to supply the town of Didcot. The river recovered only after this pumping was scaled back.

The National Rivers Authority had measured the flow rates of the river daily for 30 years, and Dr Gustard used this information along with rainfall measurements and pumping rates to recreate the situation on a computer. With his collaborators in Spain and Greece, he is now working on what would happen if the climate changed while the rate of pumping ground water remained the same.