Temperature and other climatic indicators such as tree rings show that the 1990s have been the hottest decade of the last 1,000 years in the Northern Hemisphere. The longest temperature record is from Central England, where 1999 is on course to be the warmest year since records began in 1659. For the United States, 1999 will likely be the second warmest year on record since 1880. Global land temperatures for 1999 appear to be the second highest in history, while combined land and sea temperatures rank fifth.
The rapid rate of warming since 1976, approximately 0.2 degrees C per decade, is consistent with the projected rate of warming based on human- induced effects. In fact, scientists now say that they cannot explain this unusual warmth without including the effects of human-generated greenhouse gases and aerosols.
Articles in the US press imply that the global warming threat is being oversold, by citing particular examples of short-term natural changes. But the overall pattern of recent short-term changes is in fact consistent with scientists' projections of the impacts of global climate change. The critical point is that we continue to see confirmation of the long- term warming trend. Scientists on both sides of the Atlantic are carefully looking at all of the evidence and using it to refine our understanding of global climate.
The basic science of global warming has not changed since the topic was raised earlier in this century. Furthermore, the consensus of opinion has been growing, within both the scientific and the business communities. Our new data and understanding now point to the critical situation we face: to slow future change, we must start taking action soon. At the same time, because of our past and ongoing activities, we must start to learn to live with the likely consequences - more extreme weather, rising sea levels, changing precipitation patterns, ecological and agricultural dislocations, and the increased spread of human disease.
Our agencies are doing their part to provide the best possible data, understanding and forecasts for policy-makers as they deal with these difficult issues. Ignoring climate change will surely be the most costly of all possible choices, for us and our children.
PETER D EWINS
Chief Executive Officer, UK Meteorological Office
D JAMES BAKER
Under Secretary, US National Oceanic and Atmospheric Administration