U.N. draft cites humans in effects of climate shift
A summary of the working draft of the report was provided to The New York Times yesterday by several people involved in reviewing it. It is a detailed
follow-up to a February report by the United Nations group, the Intergovernmental Panel on Climate Change, which was the fourth assessment since 1990 of the basic science that points to a human hand on the planet’s thermostat. The new report describes the
specific effects of climate changes on people and ecology, identifies those species and regions at greatest risk and describes options for limiting risks. Some of the changes could be beneficial, but most will prove harmful in the long run, the report says.
It finds that global warming caused by humans has most certainly contributed to recent shifts in ecosystems, weather patterns, oceans and icy regions, and that it will have large and lasting effects on human affairs and on the planet’s web of life in this century. It predicts a variety of health effects as well, with “increased deaths, disease and injury due to heat waves, floods, storms, fires and droughts
2”, but also “some benefits to health such as fewer deaths from cold”.
Also in the plus column, higher concentrations of carbon dioxide, the main heat-trapping gas, are contributing to a greener world, according to the draft
3. Based on satellite observations since the early 1980's, there is high confidence that there has been
a trend in many regions towards earlier greening of vegetation in the spring and increased net primary production linked to longer growing seasons and increasing atmospheric CO
2 concentrations. But warming in cool regions can bring mixed results, the draft says.
For example, while temperate and higher latitudes could be friendlier to farming, they are also proving friendlier to weeds4, as well as insect pests and wildfires that are likely to imperil forests.
In the long run, most regions are likely to be more harmed than helped by the changes, the draft says.
For example, projections for coming decades foresee intensifying drought and downpours, as well as a relentless intrusion of rising seas – at an uncertain rate – along crowded coasts and around low-lying islands. Water supplies fed by alpine snows or ice sheets are already experiencing changes and could be greatly disrupted, it said.
Scientists and government officials sparred over the wording of the draft with disagreements on the level of certainty in projections of health and ecological consequences of warming. But over all, the report is expected to provide significant new detail on a world increasingly influenced by human actions, most notably the buildup of carbon dioxide and other greenhouse gases emitted mainly by burning fossil fuels and forests.
ANDREW C. REVKIN
http://college3.nytimes.com
