31 March 2007
In February 2007 the Intergovernmental Panel on Climate Change (IPCC) released the first of a series of reports which will make up the Fourth Assessment Report (AR4). “Climate Change 2007: The Physical Science Basis”, assesses the current scientific knowledge of the natural and human drivers of climate change, observed changes in climate, the ability of science to attribute changes to different causes, and projections for future climate change.
This report expresses much greater confidence than past assessments that most of the observed warming over the past half-century is caused by human activities (greater than 90% certainty) and concludes, from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level, that warming of the climate system is unequivocal.
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