WASHINGTON - Climate scientists released a grim portrait yesterday of likely effects of global warming on the United States and Canada.

More droughts, floods, heat waves, infectious diseases and extinctions are possible, according to the North American section of the latest report by the Intergovernmental Panel on Climate Change. Poor countries in tropical Africa and Asia will be hit even harder.

In the United States, the Southwest, California, Alaska, and the Atlantic and Gulf coasts are the most seriously threatened areas, the authors of the report said at a Washington news conference.

"The impacts are faster and larger than we ever anticipated," said Anthony Janetos, a climate researcher at the Pacific Northwest National Laboratory. "Things are happening much more quickly than the science community imagined. It's profoundly concerning."

Another author, Kristi Ebi, an epidemiologist in Alexandria, Va., said matters were even worse than they appeared in the panel's report, which is based on data published in peer-reviewed scientific journals.

"The scientific literature is behind what people on the ground are seeing," Ebi said. She cited, for example, accounts of accelerated thawing of Alaskan tundra and melting of Himalayan glaciers.

"It's not just global warming, it's local warming. It's happening where we live," Larry Schweiger, the president of the National Wildlife Federation, said in a statement.

Also yesterday, 11 retired U.S. generals and admirals said worldwide water shortages caused by global warming were a "serious threat to America's national security" and might drag the nation into fights over shortages of natural resources.

The United Nations Security Council prepared to hold its first discussion of global warming today in New York City.

A 23-page summary of the 1,000-plus-pages report on the worldwide impact of global warming by the Intergovernmental Panel on Climate Change was released in Brussels, Belgium, on April 6.

The North American section, Chapter 14, describes what is happening and what the authors think will occur. These are some developments it forecasts as likely or very likely:

By 2039, average temperatures across North America will rise by 1.8 to 5.4 degrees Fahrenheit. By 2100, the warming will be 3.6 to 5.4 degrees in the west, south and east, but more than 9 degrees in the far north.

Trends in hurricane frequency and intensity are uncertain, but there will be more intense mid-latitude storms and extreme wave heights.

Growing seasons will lengthen for most of the 21st century. Forests will increase 10 percent to 20 percent. As much as a third of plant and animal species may be doomed to extinction.

Sea levels will rise 9 to 18 inches by 2100 along U.S. coasts, higher in Canada and Alaska. Up to 21 percent of coastal wetlands in the Mid-Atlantic region will be lost. Higher seas and accompanying storm surges will harm transportation along the Gulf and Atlantic coasts.

For more on the global warming report, go to http://go.philly.com/earthEndText