Climate Panel Warns of Major Warming Trend

Predicting that the world’s average temperature could rise as much as six degrees Fahrenheit in the next century, a panel of scientists advising the United Nations on climate change warned Tuesday of dramatic and possibly devastating changes to the Earth’s environment.

In its first comprehensive analysis of global climate change since 1990, the International Panel on Climate Change has painted a harrowing scenario of flood tides, deforestation, desertification and proliferation of tropical diseases.

“Civilization has never experienced the kind of climate that we are moving toward,” said Michael Oppenheimer, an atmospheric physicist with the Environmental Defense Fund and one of the scientists asked by the IPCC to review the report.

“The world hasn’t been as warm for millions of years as it could be at the end of the next century,” Oppenheimer said.

While the report represents the work of about 1,000 scientists worldwide, its conclusions are based on assumptions about warming trends that are not universally shared.

Scientists generally agree that humans are augmenting a 10,000-year-old warming trend by burning fossil fuels that cause heat to be trapped in the Earth’s atmosphere. But whether the atmosphere is warming at a truly alarming rate and whether human activity is contributing heavily to the greenhouse effect are subjects of disagreement.

The average surface temperature of the Earth has risen about one degree in the past century. But because much of that warming occurred during the first half of the century, some scientists remain unconvinced that modern industrial activity is sharply accelerating the warming trend.

The authors, who studied data on environmental trends from all over the world, agree that long-range global forecasting can be a dicey business. “The degree to which climate variability may change is uncertain,” the report says. However, the authors find sufficient basis to assume a range of worldwide temperature increases of two to six degrees Fahrenheit over the next 100 years.

The predicted range of warming is actually slightly lower than the IPCC forecast in its first report five years ago. Moreover, the study suggested that the availability of low-cost energy conservation measures could make it possible to lessen the worldwide temperature increase.

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According to the report, a six-degree increase would imperil some coastal populations, agriculture and ecosystems, raise the risk of famine in arid and semiarid regions and help spread insect-borne diseases such as malaria, yellow fever and dengue fever, from tropical to temperate zones.

If the world is six degrees warmer on average, said Michael Oppenheimer, “there will be significant social and economic disruption that brings into question society’s ability to adapt.”

Oppenheimer added, however, that at the low end of the projected climate change, most societies could adapt.

According to the report, the effects of warming will vary.

“Whereas many regions are likely to experience the adverse effects of climate change--some of which are potentially irreversible--some effects of climate change are likely to be beneficial,” it says.

For example, despite the probability of regional crop failure, global agricultural production is not expected to decline. The same is true, says the report, of worldwide fishery output.

To a great extent, the report says, the vulnerability of human health and socioeconomic systems depends upon the strength of local economies and infrastructure.

“Systems are typically more vulnerable in developing countries,” the authors write. The report also states that “people who live on arid or semiarid lands, in low-lying coastal areas, in water-limited or flood-prone areas, or on small islands are particularly prone to climate change.”

There will be winners and losers in nature, as plants and animals struggle to adapt to climate change. But overall, the report states, “there will likely be reductions in biological diversity. . . . Some systems may not reach a new equilibrium for several centuries after climate reaches a new balance.”

The report estimates that from one-third to two-thirds of existing forested areas will undergo major changes in vegetation. “Entire forest types may disappear while new assemblages of species and hence new ecosystems may be established.” In the United States, forests in the Pacific Northwest, upper Midwest and northern New England would be most vulnerable to climate change.

One-third to one-half of existing mountain glaciers could disappear over the next 100 years, the report states, and the reductions would affect the seasonal river flows and water supplies for hydroelectric power and agriculture.

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The number of people at risk of flooding each year could increase from the current 46 million to as many as 118 million in the next 100 years. Estimated land losses from flooding caused by a rise in sea level range from 1% in Egypt to 6% in the Netherlands, 17.5% in Bangladesh and about 80% for Majuro Atoll in the Marshall Islands.

Flooding also could be devastating to reefs, coral atolls, river deltas, saltwater marshes and a host of coastal ecosystems.

The area of the world in which people are exposed to malaria could expand from 45% to about 60% by the second half of the next century, according to the study.

Scientists who worked on the report cautioned that the effects of climate change over the next century will depend in part on the advances that society makes in protecting human health and the natural environment.

The report is one of three to be issued by the IPCC in coming months on various aspects of global climate change.

Although the final product is not complete, the co-chairman of the report said Tuesday that there is now sufficient evidence for all nations to take the challenge of reducing man-made greenhouse gas emissions more seriously.

“Reductions in greenhouse gases are technically feasible and financially feasible,” said co-chairman Robert Watson, who also is associate director for environment of the White House Office of Science and Technology Policy.

The report maintains that a reduction of 10% to 30% of the expected increase in worldwide greenhouse gas emissions can be achieved over the next 30 years “at little or no net cost in many parts of the world.”