President Bush appeared to distance himself yesterday from a report by his administration that says human activities are mostly to blame for recent trends in global warming, which many scientists predict will seriously disrupt the environment.

The report, prepared by the Environmental Protection Agency and submitted last week to the United Nations, for the first time put the administration on record as saying that the burning of coal, oil and other fossil fuels is the main cause of heat-trapping greenhouse gases.

Until now, Bush administration officials have insisted there was too much uncertainty in climate change research to accurately assess blame.

The White House opposes the Kyoto protocol, an international treaty that would impose mandatory reductions in carbon dioxide and other greenhouse gas emissions. While the EPA report spotlighted the impact of burning fossil fuels, it suggested nothing beyond the administration's proposals for voluntary actions by industries and others to address the problem.

Asked about the EPA report, Bush replied dismissively, "I read the report put out by the bureaucracy." He said he continues to oppose the international treaty and mandatory controls.

"The Kyoto treaty would severely damage the United States's economy, and I don't accept that," the president told reporters. "I accept the alternative we put out, that we can grow our economy and, at the same time, through technologies, improve our environment."

White House spokesman Ari Fleischer later told reporters there still is "considerable uncertainty" on the scientific causes of global warming.

An EPA spokesman said, "Basically, we have put forth our comprehensive plan for how to deal with this [global warming] issue and the report isn't suggesting anything different from that."

Meanwhile yesterday, Japan ratified the international global warming agreement. It urged the United States and other countries to join efforts to fight global warming by cutting greenhouse gas emissions.

Last Friday, the European Union's 15 members jointly ratified the treaty, and Russia has committed to ratification "as soon as possible." That raises the likelihood that the pact will become law before the end of the year, despite U.S. opposition.

"President Bush is likely to hear some very harsh words from his allies" at an earth summit in South Africa this summer, said Philip J. Clapp, president of the National Environmental Trust. "His efforts to stop Kyoto ratification have all failed, and he still hasn't lived up to his repeated promise to propose an alternative to it."

The EPA report warned that the United States will feel substantial climate change in the next few decades. It said the impact very likely would include the disruption of snow-fed water supplies, more stifling heat waves and the permanent disappearance of Rocky Mountain meadows and coastal marshes, for example.

In describing the rise in the Earth's temperature, the report says, "The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability."

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