Most climatologists now believe that the Earth's atmosphere is warming, but no one knows how high, or how fast, temperatures may rise. And even though several national and international studies this year predicted that tropical diseases such as malaria and dengue may extend their ranges as the world warms -- and that disrupted storm and rainfall patterns may raise threats of everything from crop failures to cholera -- no scientific consensus exists on precisely what ecological upsets will hit which countries, where, in the coming decades. Climate computer models cannot fine-tune their projections to regional levels that could tell local officials, for example, whether to prepare for droughts, or floods, or both.
But several major conclusions are clear. "What needs to be recognized is that there is very little doubt among leading scientists [who have taken part in recent studies] that climate change is a reality," says WHO environmental health expert Dr Carlos Corvalan. "We don't yet know how severe the impacts are going to be or how accurate the predictions of environmental change are, but the evidence is accumulating, and ecological and human health impacts are expected. We are also concerned that the health impacts of global warming will strike hardest at developing nations, particularly the poorest."
A nation's ability to adapt to climate change "depends on such factors as wealth, technology, education, information, skills, infrastructure, access to resources, and management capabilities," says the Third Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC), released early this year. "The developing countries, particularly the least developed countries, are generally poorest in this regard."
It is also clear that preparing for global warming is going to be an immensely complex task. Global warming "will require attention on many fronts," says Dr Jonathan Patz, director of the programme on health effects of global environmental change at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, USA.
In particular, global warming will place huge new demands on public health officials and governmental health ministries, says Dr Bettina Menne, global change officer of the WHO European Centre for Environment and Health in Rome. Up until now, she says, most studies of the multiple, interlocking risk factors posed by warming have been driven "not by the public health people but by [computer] modellers, mathematicians and climatologists or economists." The public health community must become more deeply involved in these assessments, she says.
At least, the modellers, mathematicians and climatologists have filled in the background. The IPCC's report projected that unless world governments take steps to stabilize emissions of carbon dioxide and other greenhouse gases, the global average surface temperature will rise by 1.4 [degrees] C to 5.8 [degrees] C (2.5 [degrees] F to 10.8 [degrees] F) between 1990 and 2100 -- a pace of warming that the report said is "very likely" unprecedented over the past 10 000 years.
The IPCC's Working Group I, which involved nearly 1000 scientists, predicted these changes: land areas will warm more rapidly than the oceans, particularly at high latitudes; precipitation will increase globally, with heavy precipitation over most land areas; in some areas precipitation will decline; and the sea level will rise by 9-88 centimetres between 1990 and 2100. "Extreme weather events" -- such as heatwaves, heavy rains, floods, droughts, more ferocious hurricanes and typhoons, and drying out of soil at mid-latitudes -- will likely increase, but current climate models cannot tell precisely where they will strike, the IPCC report said.
These projections are based on computer models that still have some gaps and uncertainties, but the scientific consensus supporting the forecast of a warmer world has become overwhelming. …