Washington ? Global warming is caused primarily by humans and “nearly all climate scientists today” agree with that viewpoint, the new head of the National Academy of Sciences – a climate scientist himself – said Wednesday.

Ralph Cicerone’s views contrasted with Bush administration officials’ emphasis on uncertainty about how much carbon dioxide and other industrial gases warm the atmosphere like a greenhouse.

“Carbon dioxide in the atmosphere is now at its highest level in 400,000 years and it continues to rise,” said Cicerone, an atmospheric scientist who left as chancellor of University of California-Irvine to become academy president this month. “Nearly all climate scientists today believe that much of Earth’s current warming has been caused by increases in the amount of greenhouse gases in the atmosphere, mostly from the burning of fuels.”

Cicerone, testifying before a Senate Commerce subcommittee on global climate change, cited data from weather stations and ships indicating the surface of the Earth is generally hotter by about seven-tenths of 1 degree Fahrenheit just since the early 1970s.

The administration officials stressed the $5 billion spent yearly on U.S. climate programs, mostly research. David Conover, a principal deputy assistant energy secretary, said President Bush would lead on the issue though “the scientific and technology challenges are considerable.”

James Mahoney, assistant commerce secretary for oceans and atmosphere, said, “We know that the surface of the Earth is warmer, and that an increase in greenhouse gases caused by humans is contributing to the problem.” But he did not go further than that.

Just three senators – David Vitter, R-La., Frank Lautenberg, D-N.J., and Ted Stevens, R-Alaska – were at the hearing. All three shared concerns about coastlines disappearing.

Among the dire consequences sketched out were surging seas breaking down levees in the Netherlands in 2007, making the Hague “unlivable,” and Europe’s climate becoming “more like Siberia’s” by 2020.

Bush said earlier this month he recognizes that human activity contributes to a warmer Earth. But he continues to reject the Kyoto treaty on global warming that all other G-8 industrialized nations signed, because developing nations weren’t included in it.