Verbal Remarks DANIEL L. ALBRITTON, DIRECTOR OCEANIC AND ATMOSPHERIC RESEARCH NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION BEFORE THE COMMITTEE ON SCIENCE UNITED STATES HOUSE OF REPRESENTATIVES March 14, 2001 "Climate Change: An Update of the Scientific Understanding" Background points ... • There is long-standing knowledge that is known with extremely high confidence. > There is a natural greenhouse effect. It keeps the Earth warmer than it would be otherwise. > Greenhouse gases are increasing in the atmosphere because of human activities, and they are increasingly trapping more heat within the climate system. Question: What are the consequences? • Today: An updated answer based on the IPCC report "Climate Change: 2001 The Scientific Basis". > Three major findings ... 1 There is a growing collective picture of a Points ... Relative "Confidence Index" Global temperatures: Up 0.4-0.8°C over the past 100 years. • Other observed changes are consistent with this warming. > Glaciers are retreating. > The amount of snow cover is decreasing. > Average sea level has risen 0.1-0.2 meter. Question: What is the cause(s) of the observing warming? 2) There is new and stronger evidence that most of the observed warming over the past 50 years is attributable to human activities. • Key factors since the 1995 IPCC report: > Five additional years of data. > The new 1000-year record: A context for the changes of the past century Question: What could all of this mean for the future? 2000 Global-average temperature rise (°C) 3 A continued growth in greenhouse gases is Points ... Simulated climate responses for a range of emission scenarios. • Climate changes in specific regions/years cannot yet be predicted reliably. • Likely: Weather would be more variable. A Key Feature: A greenhouse warming could IPCC: 1990 1995 2001 |