NORFOLK, Va. — Homeowners and businesses are finding it harder to afford, or even obtain, insurance in coastal states after catastrophes such as Hurricane Katrina, and global warming is going to make the situation worse, according to a report released Friday by a nonprofit environmental advocacy group.

Insurance companies faced with record claims after recent active hurricane seasons and predictions of more destructive storms ahead are reducing their risks by walking away from hurricane-prone areas in states along the Southeast coast and Gulf of Mexico or dramatically raising premiums, Environmental Defense found.

The trend will continue until the federal government confronts the growing problem of global warming, contends the group, which works on issues including global warming, oceans and health.

"We need a cap on greenhouse gas emissions" — and to give businesses time to plan how to reduce emissions, Melissa Carey, a climate change policy specialist with the group, told reporters during a conference call.

"Climate change is not something we're going to be able to sort of manage away," Carey said. "At a certain point, you're not going to be able to put the coastal states up on stilts or build a big seawall to protect Florida from sea-level rise."

Environmental Defense has been following the impact of climate change on the insurance industry for a couple years, Carey said.

The report, "Blown Away," examines financial consequences to homeowners, businesses, governments and taxpayers in Florida, Louisiana, Texas, Mississippi, Alabama, Georgia, North and South Carolina, and Virginia.

"If indeed global warming is leading to an era of increased hurricane intensity and possibly more frequent hurricanes, the insurance crisis in these states will only get worse as we move forward," the report said.

Homeowners' insurance rates have climbed between 20 percent and 100 percent since Katrina two years ago, the report said, citing Robert Hartwig, senior vice president and chief economist of the Insurance Information Institute. Increases on the lower end are in relatively low-risk coastal areas like coastal New Hampshire, and the highest increases are in high-risk areas like coastal Mississippi, Florida and Louisiana.

The report also includes previously unpublished data from an ongoing analysis by Georgia State University's Robert W. Klein, director of the Center for Risk Management and Insurance Research. Klein found that insurance premiums nationwide have risen an average 46.3 percent over the past five years; Florida had the highest average, 77.3 percent.

Where insurance is either unavailable or too expensive, more homes and businesses are turning to state-run "insurers of last resort," the Environmental Defense report said. When these FAIR plans (for Fair Access to Insurance Requirements) don't have enough money to cover claims, taxpayers and other policyholders get stuck with the tab.