Water calculations throw light on greenhouse effect

Scientists have calculated exactly how water behaves - how the water molecule moves and what its precise geometry is - on a microscopic scale and more accurately than ever before.

Because water vapour - rather than the much-maligned carbon dioxide - produces most of the greenhouse effect on Earth (the absorption and retention of sunlight in Earth's atmosphere) this discovery offers the hope, for the first time, of calculating data vital in understanding the greenhouse effect.

Dr Oleg Polyansky, of University College London (UCL), working with an international team, has developed a high resolution predictive model for the spectrum of water using 10 years' worth of time on the fastest super-computer in the United Kingdom.

In making its calculations, the team took account of the effects of quantum electrodynamics (one of the most arcane theories in modern physics) as well as a mixture of Einstein's relativity and the quantum theory of atomic particles. This allowed the team to make first-principle calculations which approach experimental accuracy for the first time.

Dr Polyansky said, "Water vapour produces 60% of the greenhouse effect, thus knowing just how water works is vital to understanding issues like global warming and to help us do something about them. Only by using theories such as quantum mechanics, electrodynamics and relativity can we hope to understand even simple molecules under conditions where we just can't do laboratory experiments."