Climate Report Acknowledges Human Impact

A new report to Congress from the U.S. Climate Change Science Program says the North American temperature changes from 1950 to 1999 are unlikely due to natural climate variation. Instead, they were most likely caused by anthropogenic emissions of greenhouse gases, such as carbon dioxide, the report says. This conclusion is a marked departure from the Bush Administration's previous views on climate change, which emphasized uncertainties about the human influence on climate. The report also notes several new findings. One is that satellite measurements show that parts of the West Antarctic ice sheet have experienced thinning that appears to be contributing to the rise in sea level. Others are that the portion of the Arctic Ocean covered by perennial sea ice has declined by about 9% per decade since 1978 and that the rate of heat storage in the world's oceans has increased by more than a factor of three since 1951. Another finding is that the rise in sea level per decade must result from added water mass from melting ice sheets and glaciers as well as from thermal expansion.