By the end of this century, each hemisphere can expect severe water stress and unless governments prepare, rising temperatures are likely to cause "heat-related mortality, pollution, storm-related fatalities and infectious disease," the Intergovernmental Panel on Climate Change (IPCC) warns.

With much of its population located on or near coasts, the United States is exposed to extreme weather events -- as Hurricane Katrina showed in 2005 -- and drought may affect cities that have sprung up in its deserts.

In Latin America, global warming is melting Andean glaciers and threatening the Amazonian forest, swathes of which may gradually become savannas in the worst scenarios.

The report, which deals with the impacts of global warming, is the second in a three-volume review of the evidence for climate change, the most recent since 2001.

A final draft of the 1,400-page document obtained by AFP says that even if dramatic measures are taken to reduce the carbon dioxide (CO2) emissions that drive warming, temperatures worldwide will continue to climb for decades to come, unleashing unwelcome changes across the planet.

And if nothing at all is done to mitigate climate change, the impact in some of the world's regions could be catastrophic by century's end.

By 2080, the report says, it is likely that 1.1 to 3.2 billion people worldwide will experience water scarcity, 200 to 600 million will suffer from hunger, and each year, an additional two to seven million people will be victims of coastal flooding.

The human toll will be heaviest, experts say, in Africa and Asia, where hundreds of millions in low-lying "mega-river deltas" are threatened by rising sea levels, and tens of millions more by the spread of infectious disease.

Some regions of north America -- especially the northernmost reaches of Canada and Alaska -- will likewise be severely challenged. But overall the continent is less vulnerable than others, because it has the resources and skills to adapt more easily than poorer counterparts.

Latin America may have between 100 and 400 million inhabitants struggling to procure fresh water by 2080, according to the report, and tens of millions at risk of hunger. Even in the United States, climate change will put tremendous pressure on the country's heavily utilized water resources.

Over the two last decades, Alaska and Siberia have been among the fastest-warming spots on the planet. As a result, native Inuit say their way of life is now in peril.

In some areas, melting permafrost -- today a misnomer -- is wrecking the foundations of their homes, while shorter seasons of ice cover and thinner ice make fishing and hunting for seals difficult and dangerous.

Farther south, if global temperatures rise no more than 2 C (3.6 F) compared to 1990 levels, parts of the United States and Canada may actually enjoy higher crop yields, milder winters and expanding forests.

But as the 21st century unfolds, those benefits are very likely to be swamped by the negative impact of warming.

Rising sea levels in both North and Latin America will place enormous stress on low-lying and heavily populated delta regions, swamping delicately-balanced mangroves in Brazil, Ecuador and Colombia while accelerating shoreline erosion and flooding in the United States.

In the first volume of its report, issued in February, the IPCC predicted world temperatures would rise by 1.8 C to 4.0 C (3.2-7.2 F) by 2100, depending on how much greenhouse gas is emitted into the atmosphere. A third volume, issued at the end of April, will look at ways of reducing those emissions.

In the Brussels meeting next week, the second volume will be issued on Friday after delegates hammer out a "summary for policy makers," distilling in a couple of dozen pages their most important findings.

The draft summary concludes that global warming is "unequivocal," that human activity is the main driver, and that "changes in climate are now affecting physical and biological systems on every continent."

Across the planet, 20 to 30 percent of animal and plant species face extinction if temperatures rise 1.5 C to 2.5 C (2.7 F to 4.5 F).

Increases greater than 4 C (7.2 F) above 1990-2000 levels would lead to "major increases in vulnerability" that would exceed "the adaptive capacity of many systems," the report says.

Email This Article

Related Links
Learn about Climate Science at TerraDaily.com