By Karla Gale

WESTPORT, CT (Reuters Health) – A higher frequency of disease outbreaks, increasingly prolonged heat waves, and escalating rates of asthma may break through the American public's denial regarding the reality and extent of global climate change. If nothing else, insurance company documentation of the aggregate costs of catastrophic weather events will surely lead that way.

So reported a panel of medical experts in a teleconference regarding the United Nation's Intergovernmental Panel on Climate Change's Third Assessment Report–Climate Change 2001.

"We now have polls indicating that the public believes global warming is happening, despite years of doubt," Dr. Robert K. Musil, executive director of Physicians for Social Responsibility in Washington, DC, told Reuters Health.

"Along with that, we have spectacular stories cropping up all over the place, from chunks of Antarctica falling into the ocean to Inuit gravesites bubbling up from the permafrost" as it has thawed, he added.

Another noticeable measure of change, Dr. Musil noted, is a doubling or tripling of 4-day heat waves over recent years, which has led to increasing numbers of heat strokes and heat-related deaths, particularly in inner cities.

According to the report, it is very likely that the 1990s was the warmest decade, and 1998 the warmest year, since 1861. The authors of the report believe that the increase in surface temperature over the 20th century in the northern hemisphere has been greater than that for any other century in the last thousand years.

"Just as we underestimated the rate of change, we vastly underestimated the way biologic systems would respond," Dr. Paul R. Epstein, of Harvard Medical School in Boston, pointed out. "Over 80 studies show shifts in the range of butterflies, birds, plant movement, insect movement–even glacier movement."

Scientists have observed a direct effect of carbon dioxide and prolonged growing seasons on ragweed pollen, Dr. Epstein said. Higher pollen counts, as well as synergistic effects from increased ground-level ozone related to higher temperatures, may have been significant contributors to the doubling of asthma over the last few decades, he suggested.

A primary result of climate change has been more extensive droughts and flooding due to alterations in the hydrologic cycle, Dr. Jonathan Patz, of Johns Hopkins School of Public Health in Baltimore, maintained. The public health repercussions are illuminated by the finding that "more than two thirds of waterborne disease outbreaks in the US have been preceded by rainfall in the upper 20th percentile," he said, an association found to be "highly statistically significant."

Examples in recent years include the largest known outbreaks of cryptosporidiosis and Escherichia coli poisoning attributed to heavy rainfall.

In addition, Dr. Patz noted, "according to the US National Assessment, many communities still maintain combined sewer/storm water systems." As a result, during periods of excess rainfall the systems fail to handle excess runoff, allowing frequent sewage overflow.

According to Dr. Patz, "To the extent we are living in a globalized world with international travel, food importation, and tourism, not only is our country at risk, any country in the world is at increased risk. And that will affect us, as masses of people migrate and refugee populations expand. We all need to be concerned."