Earth's warming climate is estimated to contribute to more than 150,000
deaths and 5 million illnesses each year, according to the World Health Organization,
a toll that could double by 2030.
The data, being published today in the journal Nature, indicate that climate
change is driving up rates of malaria, malnutrition and diarrhea throughout
Health and climate scientists at the University of Wisconsin at Madison, who conducted
one of the most comprehensive efforts yet to measure the impact of global warming
on health, said the WHO data also show that rising temperatures disproportionately
affect poor countries that have done little to create the problem. They reached
their conclusions after entering data on climate-sensitive diseases into mapping
"Those most vulnerable to climate change are not the ones responsible
for causing it," said the study's lead author, Jonathan Patz, a professor
at the university's Gaylord Nelson Institute for Environmental Studies and its
department of population health sciences. "Our energy-consumptive lifestyles
are having lethal impacts on other people around the world, especially the poor."
The regions most at risk from climate change include the Asian and South American
Pacific coasts, as well as the Indian Ocean coast and sub-Saharan Africa. Patz
said that was because climate-sensitive diseases are more prevalent there and
because those regions are most vulnerable to abrupt shifts in climate. Large
cities are also likely to experience more severe health problems because they
produce what scientists refer to as the urban "heat island" effect.
Just this week, WHO officials reported that warmer temperatures and heavy rain
in South Asia have led to the worst outbreak of dengue fever there in years.
The mosquito-borne illness, which is now beginning to subside, has infected
120,000 South Asians this year and killed at least 1,000, WHO said.
Senior U.S. and international officials said they now regard climate change
as a major public health threat. In an interview this week, Howard Frumkin,
who directs the National Center for Environmental Health at the Centers for
Disease Control and Prevention, called it "a significant global health
Diarmid Campbell-Lendrum, a scientist at WHO's Department of Protection of
the Human Environment, said its initial estimates of global warming-related
deaths are conservative in light of Europe's massive 2003 heat wave and new
research linking climate change to more intensive hurricane activity.
"Climate change makes it even more important to combat diseases of the
poor, many of which are highly climate-sensitive," said Campbell-Lendrum,
who wrote the Nature paper with Patz. "We already have good evidence that
there are a series of significant risks to health, which makes it even more
important to curb greenhouse gas emissions in a short period of time."
Some experts, however, questioned whether it was fair to attribute death and
illness in the developing world to global warming.
"Wealth is the number one factor in determining vulnerability or adaptability
of a country to any of the threats out there," said John R. Christy, a
climatologist who directs the Earth System Science Center at the University
of Alabama in Huntsville. Christy, who lived in Kenya in the mid-1970s, added,
"Thugocracies and other non-democratically accountable governments . .
. have no real incentive to create a healthy populace with free markets and
therefore free people."
Climate change can contribute to such diseases as diarrhea, malaria and infectious
illnesses in a number of ways. In warmer temperatures the parasite that spreads
malaria via mosquitoes develops more quickly, for example, and a 2000 study
conducted in Peru found that when the periodic El Nio phenomenon boosted temperatures
there, hospital admissions of children with diarrhea increased exponentially.
Researchers have also documented an association between rising temperatures
and deaths stemming from air pollution, since warmer, sunnier days trigger atmospheric
reactions that worsen harmful smog.
Patrick L. Kinney, a professor at Columbia University's Mailman School of Public
Health, was the co-author of a study last year in the journal Environmental
Health Perspectives that predicted global warming alone could prompt the rise
of smog-related deaths in the New York City region by 4.5 percent by the middle
of this century, compared with the 1990s.
The study of the health impacts of climate change, Kinney said, "is at
a very early research field, but I sense it's beginning to grow rapidly."
Much remains uncertain about the impact of climate change: Harvard Medical
School's Center for Health and the Global Environment issued a report this month
outlining two possible scenarios with varying degrees of extreme weather events.
In one, warming would simply strain the world's resources; the second "would
involve blows to the world economy sufficiently severe to cripple the resilience
that enables affluent countries to respond to catastrophes."
The center's associate director, Paul Epstein, who helped write the study,
said the ecosystems that are now undergoing climate change will shape our future
health because they are "our life support systems. They're our food, our
air and our water."
Researcher Madonna Lebling contributed to this report.