The Outlook Is for Warming, with Measurable Local Effects

摘要

Our planet's climate is warming up. The effects are, for the first time, visible on a regional scale. Global warming. Few phrases elicit so much controversy today. But is our climate truly changing? And if it is, do we know why it is changing? At the United Nations, the Intergovernmental Panel on Climate Change (IPCC) certainly thinks the world is getting wanner and puts much of the blame on human activity. In its 2001 Third Assessment Report, the IPCC projects that average global temperature will increase by 1.6° to 6℃ by 2100. The report indicates that, globally, the 1990s were the warmest decade on record, with 1998 the single warmest year. Accompanying this global-scale temperature increase were changes in other climate variables, such as precipitation, snow cover, glacier extent, and sea level. The changes in these variables are broadly consistent with the IPCC's estimate that Earth's surface warmed by roughly 0.6℃ over the 20th century. The 2001 IPCC report concluded that "there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activity."