Extreme weather, drought, heavy rainfall and increasing temperatures are a fact of life in many parts of the U.S. as a result of human-induced climate change, according to a new report released Tuesday. These and other changes will continue and likely increase in intensity into the future, the scientists found.

Researchers representing 13 U.S. government science agencies, major universities and research institutes produced the study, " Global Climate Change Impacts in the United States." Commissioned in 2007, it is the most comprehensive report to date on national climate change, offering the latest information on rising temperatures, heavy downpours, extreme weather, sea level changes and other results of climate change in the U.S.

The 190-page report is a product of the interagency U.S. Global Change Research Program, led by the National Oceanic and Atmospheric Administration (NOAA). It is written in accessible language, intended to better inform members of the public and policymakers about the social, environmental and economic costs of climate change. It focuses on effects by region and details how the nation's transportation, agriculture, health, water and energy sectors will be affected in the future.

"This report provides the concrete scientific information that says unequivocally that climate change is happening now and it's happening in our own backyards and it affects the kind of things people care about," Administrator of NOAA Jane Lubchenco said Tuesday at a White House briefing.

Some of the key findings of the report are that global warming is unequivocal and primarily human-induced. Climate changes are underway and include increased stresses on water supplies, challenges to livestock and crop production, risks to coastal areas from rising sea levels and storm surges, health risks, quality of life issues in urban areas and permanent changes to entire ecosystems.

One area of focus in the report is the southwestern U.S., where warming has been as rapid as anywhere in the country.

"It is becoming clear that the Southwest is the front line of ongoing climate change in the country, and the projections are for a much more serious set of problems if climate change isn't slowed dramatically," said Jonathan Overpeck in a press release from the University of Arizona (UA).

Overpeck is a professor of geosciences and atmospheric sciences at the UA. He is also the lead author on the Southwest section of the report.

The report also highlighted several key issues. Scarcity will increase demand for water and likely generate conflicts over who gets a share. Warmer, drier conditions also make the region more susceptible to wildfires and invasive species, which not only threaten property owners but biological diversity in sensitive areas. Those conditions also increase the dangers associated with flooding.

"The greatest warming and impacts on water supplies are projected to affect the Colorado River Basin with a bulls-eye on Arizona. As a state, we have as much at stake as any other state in the country," Overpeck said.

A phenomenon known as the urban heat-island effect is also projected to exacerbate summertime temperature increases, which the report said are projected to be greater than the annual average. Droughts, which are frequent in the Southwest, could become more severe. The cycle of increasing temperatures and decreased water supplies represent a challenge to the region which continues to lead the country in population growth.

Demand also for air conditioning in warmer weather increases the demand for electricity and the risks for brownouts and blackouts as utilities strain to keep up.

Farmers and ranchers also face risks. Besides less water for crops and herds, warmer temperatures also are detrimental to some specialty crops that depend on a period of colder temperatures in order to set fruit for the next harvest.

Recreation and tourism, two vital components to the regional economy, could also take a hit. Ski resorts, especially those on the southern parts of the western U.S., would have substantially shorter seasons. Hunting, fishing and boating activities could also feel the pinch.

In a press conference on Tuesday, University of Illinois Professor of Atmospheric Sciences Don Wuebbles, a contributor to the report, outlined the current and predicted effects of climate change in the Midwest U.S.

Average temperatures have risen in the Midwest in recent decades, Wuebbles said, especially in winter. The growing season has been extended by one week. Heavy downpours are now twice as frequent as they were a century ago, he said, and the Midwest has experienced two, record-breaking floods in the past 15 years.

These trends are expected to continue into the future. Average annual temperatures are expected to increase by about two degrees Fahrenheit over the next few decades, and by as much as seven to 10 degrees by the end of the century, he said, with more warming projected for summer than winter.

As temperatures and humidity increases, heat waves, reduced air quality and insect-borne diseases are more likely to occur. Heavy downpours can overload drainage systems and water treatment facilities, increasing the risk of waterborne diseases, he said.

The Great Lakes, which contain 20 percent of the planet's fresh surface water, will also be affected by the changing climate, Wuebbles said. Depending on the extent of climate change, average water levels in the Great Lakes could drop by as much as two feet in this century. This would affect beaches, coastal ecosystems, fish populations, dredging requirements and shipping.

The report focuses primarily on the impacts of climate change, but it also addresses activities that could potentially mitigate those effects and adapt to changes as well. Measures in populated areas include rainwater harvesting and better urban planning to reduce urban heat island effects. In rural areas, more effective planning and management would help to slow the growing wildfire risk.

"The report lays out what is ahead for our country if we fail to act to curb climate change, and if we fail to act aggressively, " Overpeck said. "Time is running out."

(Xinhua News Agency June 17, 2009)