Arctic is Warming Rapidly

The Arctic is warming nearly twice as rapidly as the rest of the globe、according to the final report of the Arctic Climate Impact Assessment、a four-year study conducted by an international team of 300 scientists. In Alaska、Western Canada、and Eastern Russia、average winter temperatures have increased as much as 3-4°C (4 to 7°F) in the past 50 years. Snow cover extent has declined by about 10 percent during the past 30 years、and permafrost has warmed by up to 2°C (3.6°F) in recent decades. The average extent of sea-ice has declined by 15-20 percent over the past 30 years.

Based on a mid-range estimate of future emissions of greenhouse gases and projections from models used by the Intergovernmental Panel on Climate Change、the assessment projects that at least half the summer sea ice in the Arctic will melt by the end of this century、along with a significant portion of the Greenland Ice Sheet. The region overall is projected to warm an additional 4-7°C (7 to 13°F) by 2100.

These changes would contribute to global sea-level rise and would intensify global warming through a variety of feedback mechanisms. They also are expected to threaten the survival of some arctic animal species、such as polar bears and some seals、and would present many challenges to the health and food security of indigenous cultures.

資料來源：U.S. EPA、2004

Study Finds Human Contribution to European Heatwave in 2003

A team of British scientists has developed a way to estimate the extent to which human-induced climate change affects the probability that aheatwave might occur in today's climate. Their conclusion: climate change has at least doubled the risk of a major heatwave in continental Europe.

Peter Stott of the UK Met Office's Hadley Center for Climate Prediction and Research and colleagues compared two sets of simulated European summer temperatures from a climate model、one set that incorporated the effect of human contributors to climate change (greenhouse gases and sulfate aerosols) and another that accounted only for natural influences on climate. They then calculated the change in risk of extreme heatwaves that can be attributed to the increase in greenhouse gases.

Stott and his colleagues compared the model's simulations with actual observed climate records to ensure that it accurately portrayed the natural variability of European summers、and their analysis allowed for uncertainties in the nature and extent of human-induced climate change.

Researchers estimate that the summer of 2003 was the hottest in Europe since at least the year 1500、leading to 22,000-35,000 heat-related deaths across the continent and more than $12 billion in crop losses.

資料來源：U.S. EPA、2004