Mar. 23 -- THURSDAY, June 28 (HealthDay News) -- Sizzling temperatures brought on by global warming will kill more people in the summer months, a new study suggests, and that toll won't be offset by fewer deaths during milder winters.
"The results suggest that mortality [from hot temperatures] won't be compensated by a reduction in mortality in winter," said study author Mercedes Medina-Ramon, a research fellow at the Harvard School of Public Health's department of environmental health.
According to the study, global warming is expected to increase the average temperature of Earth between 1.7 and 4.9 degrees Celsius by the year 2100. It is also expected to result in more scorching summer days and fewer freezing winter ones.
It's no secret that extreme temperatures can kill -- 35,000 people died in the European heat wave of 2003, for example. But scientists don't yet know what the effect of global warming will be on death rates.
"It seems that global warming will increase deaths due to extreme hot temperatures. That we already know," Medina-Ramon said. "What we didn't know was if that would be compensated by a reduction in mortality during the winter because it's less cold."
Medina-Ramon and study co-author Joel Schwartz, also of Harvard, looked at daily death and weather data for more than 6.5 million deaths occurring from 1989 to 2000 in 50 U.S. cities.
During two-day cold snaps, deaths went up 1.59 percent. Many of the deaths were due to heart attacks and cardiac arrest.
But during scorchers, death rates went up by much more: 5.74 percent.
The effect of extreme cold was similar between cities, suggesting that the use of central heating may have prevented some deaths. But the effects of heat were wildly different, with the largest effects seen in cities with milder summers, less air conditioning and denser populations.
The findings were published in the June 28 online issue of Occupational and Environmental Medicine.
"In the U.S., most people have heating in their homes so a change in cold temperature won't make as much of a difference," said Medina-Ramon. "It won't make as much of a difference as hot temperatures because there are more people who don't have an air conditioner at home."
But the answer isn't to install air conditioners in every home, because that just adds to global warming.
"We don't want to say air conditioning is a solution because it's going to have an impact on global warming," Medina-Ramon said. "We should increase the use of air conditioning but stop the abuse. Some places have air conditioning that is so strong it's completely unnecessary. If we had air conditioning everywhere but people didn't abuse it, that would be the best solution, along with investing in technology that is more efficient."
But individual actions, while important, are only part of the picture.
"When you look at global warming as a phenomenon, it clearly has public health, individual health and ecosystem implications, and there is a growing body of evidence that seems to imply that we are a ways from exactly determining how the human-environment interaction will play a role in the ultimate impact of global warming," said Dr. Maureen Lichtveld, chairwoman of the department of environmental health sciences at Tulane University School of Public Health and Tropical Medicine.
"In order for us to deal with the public health implications, it's very critical that we will only have an impact on global warming as a public health issue if we address the policy issue. These are policy issues related to air pollution standards, adhering to them, enforcing them or creating them."
The U.S. Environmental Protection Agency can tell you more about health and global warming.
SOURCES: Mercedes Medina-Ramon, Ph.D., research fellow, department of environmental health, Harvard School of Public Health, Boston; Maureen Lichtveld, M.D., professor and chairwoman, department of environmental health sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans; June 28, 2007, Occupational and Environmental Medicine, online