WASHINGTON – The Bush administration released a long-overdue climate change report last week that reinforces what Alaskans have long known – warming temperatures are having dramatic effects on the environment across the state.

The report documents numerous changes occurring as a result of warming, including coastal erosion; rising sea levels; receding Arctic sea ice; and an increase in the incidence and intensity of wildfires.

The changes are expected to have the greatest economic and cultural impacts on Alaska Native coastal communities, which depend on marine mammals for subsistence and are at a greater risk from coastal erosion.

In the Interior, longer, hotter summers will likely increase the threat of wildfires, the report stated.

The report, which focused on the impacts climate change is expected to have on the United States in the coming decades, argues that adaptation to global warming will be required in the short-term as some changes to the environment are now inevitable.

“Warming is very likely to continue in the United States during the next 25 to 50 years, regardless of reductions in greenhouse gas emissions, due to emissions that have already occurred,” the report said.

All of North America is “very likely” to warm during this century, with the largest increases expected to occur in northern Alaska during the winter, the report found. Average warming in the U.S. will likely exceed 3.6 degrees Fahrenheit, and could surpass 7.2 degrees Fahrenheit, increasing the number of abnormally hot days, the report said.

The 271-page report has no new science in it, but it provides a comprehensive summary of dozens of different U.S. studies and localizes international reports into a single document for Congress to refer to when considering measures to address climate change. It’s the first such overview compiled by the federal government in eight years.

The comprehensive report breaks with President George W. Bush’s previous position on climate change, and could undermine efforts by his administration to limit federal regulation of greenhouse gas emissions.

The U.S. Senate is set to take up sweeping climate change legislation later this week that would establish a mandatory cap on the amount of carbon dioxide and other greenhouse gases polluters could release into the atmosphere. The legislation seeks to reduce emissions by 19 percent by 2020, and 71 percent by 2050.

Critics of the measure, including the Bush administration, say it will harm the economy. Most analysts believe climate change legislation has little chance of passing while President Bush is in office.

However, the federal report, which was released Thursday, is expected to undermine opposition among some lawmakers to imposing stricter limits on polluters.

“I think this long-awaited scientific report by the Bush administration will lay to rest the global-warming skeptics who don’t believe human activity is causing global warming,” said Pam Miller, Arctic coordinator for the Northern Alaska Environmental Center.

The assessment concludes that “most of the recent global warming is very likely due to human-generated increases in greenhouse gas concentrations” and that it is likely that there has been “substantial human contribution to surface temperature increases in North America.”

The Bush administration put off releasing the report for four years. It took a court order to finally force the administration to produce the assessment.

Under a 1990 law, the government is required to produce a report to Congress on global warming every four years. The last one was issued in 2000, during the Clinton administration.

Kassie Siegel, climate program director of the Center for Biological Diversity, said the report represents a “major turning point” in the Bush administration’s resistance to acknowledging the human contribution to global warming.

“This assessment is an example of what federal scientists can and should be doing when they are freed from political interference and allowed to actually do their jobs,” Siegel said.

In November 2006, the Center For Biological Research, Greenpeace and Friends of the Earth sued the administration for failing to issue the assessment.

“Administration officials have spent nearly eight years trying to deny and downplay the science,” Siegel said. “They just cannot do it anymore. They are boxed in by court order.”

The assessment found global warming has been particularly intense in boreal and Arctic regions. In northern parts of the Alaska, scientists have observed snow melting about eight days earlier than it did in the mid-1960s.

Ecosystems will have a difficult time dealing with climate change while species will continue to migrate toward the poles, the report stated.

The report found the most vulnerable areas are likely to be rural Alaska Native communities that rely on subsistence hunting and fishing of climate-sensitive species. Communities on the coast and along rivers are also endangered by an increased risk of floods and erosion.

The report estimates the Arctic Ocean could be ice-free in the summer as soon as the end of this century, with some scientific modeling suggesting it could happen as soon as 2040.

The loss of sea ice increases the threat of shoreline erosion by creating more open water allowing winds to generate stronger waves.

Climate change is reducing the predictability of whether conditions, affecting travel safety and presenting “serious challenges to human health, food security and possibly even survival of some cultures,” the report said.

Warming temperatures are also affecting the oil and gas industry. While reductions in sea-ice cover will make offshore exploration and development easier, equipment will have to be designed to withstand increased wave forces and ice movement.

Thawing permafrost also poses a risk to natural gas and oil pipelines and natural gas processing plants.

The assessment shows large decreases in Arctic summer sea ice between 1978 and 2005. Summer sea ice melt in 2007 was roughly 23 percent lower than the previous all-time minimum observed in 2005.

Among other findings in the report:

• Climate change has likely increased the size and number of insect outbreaks, increasing tree mortality which help fuels forest fires.

• Thawing ground is destabilizing transportation, buildings and other facilities, putting tens of billions of dollars worth of infrastructure at risk.

• Permafrost has been thawing at a rate of up to 1.6 inches annually since 1992.

• Lakes and rivers are freezing later and breakup is coming about six days earlier on average then in past years.

• Arctic sea ice has declined 2.7 percent per decade since 1978, with larger declines – 7.4 percent – in summer.

• Average sea ice thickness in the central Arctic has likely decreased up to 3 feet between 1987 and 1997.

• The sub-Arctic tree line has crept six miles northward.

• 2 percent of tundra on the Seward Peninsula has been replaced by forest in the past 50 years.

• Global warming is also reducing snow pack, increasing the chance of drought and wildfires. Snow cover is projected to decrease by as much as 20 percent by 2070, with the greatest declines in spring.

• Glaciers are projected to continue to lose mass as increases in summertime melting outweigh increases in winter precipitation.

• Storm surge levels are expected to increase due to sea levels, which are projected to rise between 7 and 23 inches this century.

• Stream temperatures are likely to increase as the climate warms, affecting aquatic ecosystems and water quality.

• Shifts in the range of marine mammals and other species used for subsistence in rural areas is increasing.

The report is available online at www.climatescience.gov.