Under discussion during Wednesday's Envisat Symposium is how researchers use this ability to peer further through time, addressing the leading scientific question of our time the likely extent of climate change. Human activities have been changing the chemical composition of the atmosphere, leading to an increased retaining of heat popularly termed the 'Greenhouse Effect'.

Successfully predicting the long-term effects of this change requires enhanced characterisation and understanding of the complex processes making up the Earth System. The multi-sensor Envisat is well matched for such an aim, the Symposium heard, and has demonstrated its ability to directly measure greenhouse gases.

Teams from the University of Heidelberg, Bremen and the National Institute for Space Research (SRON) in the Netherlands showed how they are using data from Envisat's Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument to track trace gases in the atmosphere and produce daily global maps of atmospheric methane. Carbon dioxide is the best known greenhouse gas, but methane is able to trap more than 21 times more heat per molecule.

"Accurately characterising methane sources and distribution is very important to increase the accuracy of climate models," said Michael Buchwitz of the University of Bremen. "Methane comes from natural sources such as wetlands, but human activities produce a lot as well. For example, the image shows methane given off from rice fields in the Ganges Valley in India, and also from extensive cattle ranching in South America."

Methane is eventually broken down by chemical reactions in the atmosphere, but carbon dioxide is a longer-lived greenhouse gas. Surface vegetation stores a vast amount of carbon, only released into the atmosphere when land is cleared or burnt.

So mapping land cover and land cover change is a crucial part of climate studies, and also for implementing the 1997
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Contact: Mariangela D'Acunto
mariangela.d'acunto@esa.int
39-069-418-0856
European Space Agency
9-Sep-2004

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