FRIDAY, Feb. 2 (HealthDay News) -- Global warming not only poses significant threats to the Earth's ecology, it may also unleash unprecedented health risks, experts say.

On Friday, an international panel of scientists released a report predicting that global warming due to greenhouse-gas emissions will continue for centuries, no matter what's done to check pollution. The result will be killer heat waves, devastating droughts, rising sea levels and fiercer storms.

Saying it was acting with 90 percent confidence, the Intergovernmental Panel on Climate Change of the United Nations said carbon dioxide and other greenhouse gases produced by human activity are the main cause of the global warming that has taken place since 1950.

Michael A. McGeehin, director of the U.S. Centers for Disease Control and Prevention's Division of Environmental Hazards and Health Effects, said, "There are some health effects from climate change that we are comfortable in predicting. We will see an increase in the intensity, duration and frequency of heat waves around the world. We will see more severe precipitation events, both heavy rainfall and severe droughts."

That flooding and drought with bring attendant health problems, McGeehin said. "There are health effects secondary to flooding, such as contaminated water supplies, that could result in the spread of infectious diseases," he said.

Droughts, which are becoming more common and longer lasting, can lead to starvation and the destruction of entire ways of life, particularly in regions -- such as sub-Saharan Africa -- that are least equipped to deal with such catastrophes.

McGeehin also foresees the possible spread of mosquito-borne illnesses such as malaria, dengue fever, yellow fever and encephalitis. "As the climate warms, we may see a change in the range of vector-borne diseases," he said.

Dr. Paul Epstein, associate director of Harvard Medical School's Center for Health and the Global Environment, said the effects of climate change are already apparent, as some of these mosquito-borne diseases are spreading to new areas as the world warms and precipitation increases.

"There is a whole range of infectious diseases like malaria, dengue fever and water-borne diseases whose range is restricted by temperature," Epstein said. "We are seeing malaria changing in its altitude. It is moving into higher altitudes in Africa, Asia and Latin America.

"In the very places where glaciers are retreating, we are also seeing a lengthening of the season of transmission of the disease in parts of Africa," Epstein added. In Africa, there has been an increase in Rift Valley Fever, which affects animals and people, as well as cholera, he said.

Epstein noted that even in the United States, ticks, mosquitoes and other insects that carry disease -- such as West Nile Virus, Rocky Mountain Spotted Fever, Eastern Equine Encephalitis and Lyme disease -- are already spreading to areas once considered too cold for them to survive.

In addition, increasing air pollution from the continued burning of fossil fuels will cause higher rates of respiratory and cardiovascular disease, McGeehin said.

"With warming, there are also increases in pollen and mold spores," Epstein added.

The best way to deal with the new health threats posed by a changing climate is to improve on the methods currently in place to combat disease, McGeehin said.

"Everything we are seeing as likely coming out of climate change from a public health standpoint, particularly in the developed nations, can be dealt with by improving what we already do," McGeehin said. "What we are seeing is things we have seen before. So, if we improve the public health infrastructure in the United States and other developed countries and improve surveillance and people's access to health care, we can blunt a lot of the effects of this," he said.

In response to the threat of climate change, the CDC is creating an "action plan" to address the health risks posed by global warming, The Atlanta Journal-Constitution reported last month.

Of particular concern, McGeehin said, are developing nations, where health-care systems are under-equipped to deal with the changes that global warming might bring.

"Climate change will affect, at a much greater level, the populations that are least able to deal with it," he said. "In the developed world, it will affect the poor more than the rich. In the developing world, it will affect the nations least able to respond to these stresses and these threats."

Public health efforts can only do so much, Epstein said, adding that "the real driver of climate" is the burning of fossil fuels.

"Ultimately, public health officials and physicians all have to be bringing attention to the politicians and call for clean energy -- it's fundamental for public health. Our energy is fundamental to air pollution, acid rain to its impact on our health and the health of our environment," he said.

"Without changing that, we are going to have a very polluted, sick future," Epstein said.

More information

The U.S. Environmental Protection Agency can tell you more about health and global warming.