Global warming will bring increased summer heat waves nationwide that are especially harmful to low-income and minority populations in urban areas and the elderly, according to a new report by environmental and public health groups.

"This is another reason why we must take steps to curb global warming pollution as much and as quickly as possible," said Amanda Staudt, a climate scientist with the National Wildlife Federation, which released the report today with Physicians for Social Responsibility.

The report, citing the U.S. Global Change Research Program, notes projected increases in the number of days on which temperatures exceed 100 degrees Fahrenheit.

The report says urban areas, with their asphalt and concrete, are as much as 10 degrees hotter than more rural regions.

More than 3,400 people died in the United States from exposure to excessive heat between 1999 and 2003, the study states, adding that heat accounts for more weather-related deaths than any other single source.

Heat waves will worsen ozone pollution when temperatures soar, the report warns, citing a 2008 paper in the Journal of Geophysical Research that found global warming could increase eight-hour ground-level ozone levels in coming decades in the Northeast and Midwest, especially during heat waves.

This "climate penalty" will make it tougher for cities to meet the eight-hour U.S. EPA ozone standard of 75 parts per billion, the report states.

It cites several public health risks associated with very high temperatures. Heat waves can be deadly, due to heat stroke, and can exacerbate underlying health problems, the report says, making the elderly particularly vulnerable. Extreme heat boosts risks of heart attacks, strokes and asthma, it notes.

Children also face increased risks, it adds. "The increased air pollution that typically accompanies heat waves can especially harm children, who have a higher risk of developing asthma, have lungs that are still developing and growing, and have higher exposure because they breathe at a higher rate than adults and spend more time outdoors engaging in vigorous physical activity."

Peter Wilk, the executive director of Physicians for Social Responsibility, cited the 1995 Chicago heat wave that killed more than 700 people as a sign of things to come. Such events require short-term medical and emergency responses, such as access to cooling centers, he said on a conference call this morning.

But cutting emissions linked to global warming is needed to limit increases in heat waves, Wilk added.

"The most cost-effective and preferred approach is to take actions that will prevent the problem or reduce its scope in the future," he said. "Cutting greenhouse gas emissions may be difficult, but it is a medical necessity."

The report lists 30 cities that face increased health risks from heat waves worsened by global warming, based on a combination of four factors: average number of summer days with "oppressive" summer heat, the percentage of households without central air conditioning, ground-level ozone levels, and the percentage of households below the poverty line.

Cities in the top tier of risk include Boston, Houston, Phoenix, New York and Los Angeles.

The report says heat waves are especially harmful to black people, who live in urban areas in higher percentages than whites, and who are also more likely to be low-income than other Americans and already suffer from higher asthma rates than whites.

"Our concern here I think is fairly obvious. Black folks are both more likely to live in the places where heat waves are the most severe, and when they occur, we are more likely to face grave consequences," said Benjamin Todd Jealous, the CEO of the National Association for the Advancement of Colored People, on the call with reporters today.

The report, which also warns of major wildlife extinctions and risks to crops from extreme heat, calls for reducing emissions 80 percent from current levels by 2050, which is consistent with the targets in major climate legislation moving through Congress.

But it also calls for specific steps to make cities "cooler and greener," such as more reflective and light-colored roofing to help reduce the "urban heat island" effect, as well as more green space such as parks, trees and "green roofs."

Other recommendations include better urban preparation and response to heat waves, such as improved public notification and outreach to the elderly, poor and homeless.

To help wildlife, the report calls for habitat restoration and wildlife management approaches that can help shield species from extreme heat, such as stream-shading vegetation to help cool waters and protect fish.

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC., 202-628-6500