For people in their 30s, climate change has already reshaped the world into which they were born.

By the time they reach retirement, the changes will be far more dramatic and perhaps life-threatening on a massive scale, an authoritative UN study will say this week.

Today, the Intergovernmental Panel on Climate Change (IPCC), a network of more than 2,000 scientists, will open a five-day meeting in Brussels, Belgium, to finalize a report on how warming will affect the globe and whether humans can do anything about it.

The panel will paint a bleak picture of increasing poverty, paucity of drinking water, melting glaciers and polar ice caps, and a host of vanishing species by mid-century unless action is taken to curb emissions of carbon dioxide and other heat-trapping gases.

Among the gloomy forecasts, the report predicts that glaciers in the Himalayas, the world's highest mountain range, will melt away, affecting hundreds of millions of people.

"If current warming rates are maintained, Himalayan glaciers could decay at very rapid rates, shrinking from the present 500,000 square kilometers to 100,000 square kilometers by 2030s," according to a draft technical summary.

Some regions, like parts of North America and northern Europe, will see some benefits, at least in the short term, from longer growing seasons and milder winters.

Even the most optimistic forecasts say the climate will continue to change and the planet will be irrevocably damaged. The question is, how much?

"We are going into a realm the Earth has not seen for a very long time... over the past 800,000 years," said Camille Parmesan, a University of Texas biologist who has studied the effects of climate change on wildlife and was a reviewer of the upcoming report.

Guideline for governments

Policymakers will go over the IPCC document line-by-line this week before unveiling the final text on Friday. It will then become a guideline for governments to determine policies and draft legislation.

About 285 delegates from 124 countries are attending, along with more than 50 of the scientists who compiled the report and dozens of observers from nongovernment, mostly environmental, organizations.

The closed-door talks are likely to focus on predictions of how many people will be at high risk from changing ecosystems and water cycles, and whether such specific weather events like Hurricane Katrina should be attributed to global warming.

"Do you use examples? And do you use ones that are relatively positive or highly negative?" said Rik Leemans, a co-author from Wageningen University in the Netherlands. "You can tone it down or strengthen it by including examples, and that's always an issue in these discussions."

The summary's final wording must be adopted by consensus among the diplomats, with the approval of the scientists.

While there may be editing for the sake of nuance, the underlying premise of the draft report will not change. "A decade ago, climate impacts were largely hypothetical," said James J. McCarthy, a Harvard University oceanographer who was a main author of the 2001 IPCC report. "That's no longer a question."

It is the second of four reports by the IPCC. The first, issued in February, updated the science of climate change, concluding with near certainty that global warming is caused by human behavior.

That report galvanized the European Union to adopt an ambitious goal of reducing carbon emissions by at least 20 percent from 1990 levels by 2020.

Snow covers mountain peaks in the Himalayas in May 2003. Global warming could cause more hunger in Africa and melt most Himalayan glaciers by the 2030s, a draft UN report says.Reuters

The IPCC's work will be presented at a summit in June of leaders from the world's richest countries, including US President George W. Bush whose administration has declined to take coordinated action with other nations to limit greenhouse gases.

The latest report was six years in the making. Since the IPCC's 2001 assessment, knowledge about climate change has become more precise, and studies have tracked specific shifts on the ground to changing temperatures and weather patterns.

"Many natural systems on all continents and in some oceans are being affected by regional climate changes, particularly temperature increases," reads the final draft.

Parmesan said storms and floods have become more severe in some places, coastlines have eroded and deserts have expanded. Diseases common in the tropics have spread. In the Northern Hemisphere, spring is coming an average two weeks earlier, disrupting bird migrations and causing flowers and trees to bloom too early. At least 70 species have become extinct so far because of global warming, Parmesan said in a telephone conference with reporters.

'Highway to extinction'

The report will offer stark warnings for the future.

Within 25 years, hunger and death from diarrhea will threaten poor countries where crops fail and water becomes more scarce. Later in the 21st Century, warmer seas will likely destroy coral reefs and the fish that feed off them, and may lead to the poisoning of shellfish. Tens of millions of people in coastal cities and river basins will likely be affected by flooding, and fresh water supplies will likely be inundated with salt water from sea surges. Small islands will probably be submerged by rising sea levels. Beetles and other pests are expected to infest forests even more, with forest and wild fires more frequent and widespread.

University of Victoria climate scientist Andrew Weaver said the chart of results from various temperature levels is "a highway to extinction, but on this highway there are many turnoffs. This is showing you where the road is heading. The road is heading toward extinction."

Weaver is one of the lead authors of the first report in February.

While humanity will survive, hundreds of millions, maybe billions of people may not, according to the chart if the worst scenarios happens.

The report says global warming has already degraded conditions for many species, coastal areas and poor people. With a more than 90 percent level of confidence, the scientists in the draft report say man-made global warming "over the last three decades has had a discernible influence on many physical and biological systems."

And as the world's average temperature warms from 1990 levels, the projections get more dire. Add 1 degree centigrade and between 400 million and 1.7 billion extra people cannot get enough water, some infectious diseases and allergenic pollens rise, and some amphibians go extinct. But the world's food supply, especially in northern areas, could increase. That is the likely outcome around 2020, according to the draft.

Add another 1.8 degrees and as many as 2 billion people could be without water and about 20 percent to 30 percent of the world's species near extinction. Also, more people start dying because of malnutrition, disease, heat waves, floods and droughts all caused by global warming. That would happen around 2050, depending on the level of greenhouse gases from the burning of fossil fuels.

At the extreme end of the projections, the chart predicts: "Up to one-fifth of the world population affected by increased flood events... 1.1 to 3.2 billion people with increased water scarcity... "major extinctions around the globe."

Agencies

(China Daily 04/02/2007 page6)