Is Global Warming Harmful to Health? - Computer models indicate that many diseases will surge as the earth's atmosphere heats up. Signs of the ...
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Is Global Warming
Harmful to Health?
Computer models indicate that many diseases
will surge as the earth’s atmosphere heats up.
Signs of the predicted troubles have begun to appear
by Paul R. Epstein
T
oday few scientists doubt the atmo- and massive bursts of precipitation have be-
sphere is warming. Most also agree come more common. Aside from causing
that the rate of heating is accelerat- death by drowning or starvation, these disas-
ing and that the consequences of ters promote by various means the emergence,
this temperature change could become in- resurgence and spread of infectious disease.
creasingly disruptive. Even high school stu- That prospect is deeply troubling, because
dents can reel off some projected outcomes: infectious illness is a genie that can be very
JEAN-MARC BOUJU AP Photo (above and far right); KAREL PRINSLOO AP Photo (right)
the oceans will warm, and glaciers will melt, hard to put back into its bottle. It may kill
causing sea levels to rise and salt water to in- fewer people in one fell swoop than a raging
undate settlements along many low-lying flood or an extended drought, but once it takes
coasts. Meanwhile the regions suitable for root in a community, it often defies eradica-
farming will shift. Weather patterns should also tion and can invade other areas.
become more erratic and storms more severe. The control issue looms largest in the devel-
Yet less familiar effects could be equally oping world, where resources for prevention
detrimental. Notably, computer models pre- and treatment can be scarce. But the techno-
dict that global warming, and other climate logically advanced nations, too, can fall vic-
alterations it induces, will expand the inci- tim to surprise attacks— as happened last year
dence and distribution of many serious med- when the West Nile virus broke out for the
ical disorders. Disturbingly, these forecasts first time in North America, killing seven
seem to be coming true. New Yorkers. In these days of international
Heating of the atmosphere can influence commerce and travel, an infectious disorder
health through several routes. Most directly, that appears in one part of the world can
it can generate more, stronger and hotter heat quickly become a problem continents away if
waves, which will become especially treacher- the disease-causing agent, or pathogen, finds
ous if the evenings fail to bring cooling relief. itself in a hospitable environment.
Unfortunately, a lack of nighttime cooling Floods and droughts associated with global
seems to be in the cards; the atmosphere is climate change could undermine health in
heating unevenly and is showing the biggest other ways as well. They could damage crops
rises at night, in winter and at latitudes higher and make them vulnerable to infection and in-
than about 50 degrees. In some places, the festations by pests and choking weeds, there-
number of deaths related to heat waves is by reducing food supplies and potentially
projected to double by 2020. Prolonged heat contributing to malnutrition. And they could
can, moreover, enhance production of smog permanently or semipermanently displace en-
and the dispersal of allergens. Both effects tire populations in developing countries, lead-
have been linked to respiratory symptoms. ing to overcrowding and the diseases connect-
Global warming can also threaten human ed with it, such as tuberculosis.
well-being profoundly, if somewhat less di- Weather becomes more extreme and vari-
rectly, by revising weather patterns—particu- able with atmospheric heating in part because
larly by pumping up the frequency and inten- the warming accelerates the water cycle: the
sity of floods and droughts and by causing process in which water vapor, mainly from
rapid swings in the weather. As the atmo- the oceans, rises into the atmosphere before
sphere has warmed over the past century, condensing out as precipitation. A warmed
droughts in arid areas have persisted longer, atmosphere heats the oceans (leading to faster
50 Scientific American August 2000 Is Global Warming Harmful to Health?
Copyright 2000 Scientific American, Inc.PREDICTED CHANGE
IN RISK OF MALARIA
TRANSMISSION
AMOUNT >2
THE RISK 1.7 TO 2.0
WILL 1.4 TO 1.7
MULTIPLY
1.1 TO 1.4
AREAS NEWLY AT RISK
NO CHANGE
DECREASE RISK OF MALARIA TRANSMISSION will have risen in many parts of the
NO SIGNIFICANT RISK world by 2020 (relative to the average risk in the years 1961 to 1990), according
to projections assuming a temperature increase of about two degrees Fahrenheit.
The analysis was based solely on temperature threshold and did not assess other
factors that could influence malaria’s spread.
evaporation), and it holds more mois- meal from an infected animal or per- quitoes could expand into formerly for-
BRYAN CHRISTIE; SOURCE: PIM MARTENS Maastricht University
ture than a cool one. When the extra son. Then the pathogen reproduces in- bidden territories, bringing illness with
water condenses, it more frequently side the insects, which may deliver dis- them. Further, warmer nighttime and
drops from the sky as larger downpours. ease-causing doses to the next individu- winter temperatures may enable them
While the oceans are being heated, so is als they bite. to cause more disease for longer periods
the land, which can become highly Mosquito-borne disorders are project- in the areas they already inhabit.
parched in dry areas. Parching enlarges ed to become increasingly prevalent be- The extra heat is not alone in encour-
the pressure gradients that cause winds cause their insect carriers, or “vectors,” aging a rise in mosquito-borne infec-
to develop, leading to turbulent winds, are very sensitive to meteorological con- tions. Intensifying floods and droughts
tornadoes and other powerful storms. ditions. Cold can be a friend to humans, resulting from global warming can each
In addition, the altered pressure and because it limits mosquitoes to seasons help trigger outbreaks by creating breed-
temperature gradients that accompany and regions where temperatures stay ing grounds for insects whose dessicat-
global warming can shift the distribu- above certain minimums. Winter freez- ed eggs remain viable and hatch in still
tion of when and where storms, floods ing kills many eggs, larvae and adults water. As floods recede, they leave pud-
and droughts occur. outright. Anopheles mosquitoes, which dles. In times of drought, streams can
I will address the worrisome health transmit malaria parasites (such as become stagnant pools, and people may
effects of global warming and disrupted Plasmodium falciparum), cause sus- put out containers to catch water; these
climate patterns in greater detail, but I tained outbreaks of malaria only where pools and pots, too, can become incu-
should note that the consequences may temperatures routinely exceed 60 de- bators for new mosquitoes. And the in-
not all be bad. Very high temperatures grees Fahrenheit. Similarly, Aedes ae- sects can gain another boost if climate
in hot regions may reduce snail popula- gypti mosquitoes, responsible for yel- change or other processes (such as al-
tions, which have a role in transmitting low fever and dengue fever, convey terations of habitats by humans) reduce
schistosomiasis, a parasitic disease. High virus only where temperatures rarely the populations of predators that nor-
winds may at times disperse pollution. fall below 50 degrees F. mally keep mosquitoes in check.
Hotter winters in normally chilly areas Excessive heat kills insects as effec-
may reduce cold-related heart attacks tively as cold does. Nevertheless, within Mosquitoes on the March
and respiratory ailments. Yet overall, their survivable range of temperatures,
the undesirable effects of more variable
weather are likely to include new stress-
es and nasty surprises that will over-
mosquitoes proliferate faster and bite
more as the air becomes warmer. At the
same time, greater heat speeds the rate
M alaria and dengue fever are two
of the mosquito-borne diseases
most likely to spread dramatically as
shadow any benefits. at which pathogens inside them repro- global temperatures head upward. Ma-
duce and mature. At 68 degrees F, the laria (marked by chills, fever, aches and
Mosquitoes Rule in the Heat immature P. falciparum parasite takes anemia) already kills 3,000 people,
26 days to develop fully, but at 77 de- mostly children, every day. Some mod-
D iseases relayed by mosquitoes—
such as malaria, dengue fever, yel-
low fever and several kinds of encepha-
grees F, it takes only 13 days. The An-
opheles mosquitoes that spread this ma-
laria parasite live only several weeks;
els project that by the end of the 21st
century, ongoing warming will have en-
larged the zone of potential malaria
litis— are among those eliciting the warmer temperatures raise the odds transmission from an area containing
greatest concern as the world warms. that the parasites will mature in time 45 percent of the world’s population to
Mosquitoes acquire disease-causing mi- for the mosquitoes to transfer the infec- an area containing about 60 percent.
croorganisms when they take a blood tion. As whole areas heat up, then, mos- That news is bad indeed, considering
52 Scientific American August 2000 Is Global Warming Harmful to Health?
Copyright 2000 Scientific American, Inc.that no vaccine is available and that the most 500 feet in the tropics. Marching that dengue and yellow fever may fol-
causative parasites are becoming resist- upward, too, are mosquitoes and mos- low. Dengue fever itself has struck at
ant to standard drugs. quito-borne diseases. the mile mark in Taxco, Mexico. Pat-
True to the models, malaria is reap- In the 19th century, European colo- terns of insect migration change faster in
pearing north and south of the tropics. nists in Africa settled in the cooler moun- the mountains than they do at sea level.
The U.S. has long been home to An- tains to escape the dangerous swamp Those alterations can thus serve as indi-
opheles mosquitoes, and malaria circu- air (“mal aria”) that fostered disease in cators of climate change and of diseases
lated here decades ago. By the 1980s the lowlands. Today many of those ha- likely to expand their range.
mosquito-control programs and other vens are compromised. Insects and in-
public health measures had restricted sect-borne infections are being reported Opportunists Like Sequential Extremes
the disorder to California. Since 1990, at high elevations in South and Central
however, when the hottest decade on
record began, outbreaks of locally trans-
mitted malaria have occurred during hot
America, Asia, and east and central Af-
rica. Since 1980 Ae. aegypti mosquitoes,
once limited by temperature thresholds
T he increased climate variability ac-
companying warming will proba-
bly be more important than the rising
spells in Texas, Florida, Georgia, Michi- to low altitudes, have been found above heat itself in fueling unwelcome out-
gan, New Jersey and New York (as well one mile in the highlands of northern breaks of certain vector-borne illnesses.
as in Toronto). These episodes undoubt- India and at 1.3 miles in the Colombian For instance, warm winters followed by
edly started with a traveler or stow- Andes. Their presence magnifies the risk hot, dry summers (a pattern that could
away mosquito carrying malaria para-
sites. But the parasites clearly found
friendly conditions in the U.S.—enough
warmth and humidity, and plenty of
mosquitoes able to transport them to
Changes Are Already Under Way
victims who had not traveled. Malaria
has returned to the Korean peninsula,
parts of southern Europe and the for-
C omputer models have predicted that global warming would produce sever-
al changes in the highlands: summit glaciers (like North Polar sea ice) would
begin to melt, and plants, mosquitoes and mosquito-borne diseases would mi-
mer Soviet Union and to the coast of grate upward into regions formerly too cold for them (diagram).All these predic-
South Africa along the Indian Ocean. tions are coming true. This convergence strongly suggests that the upward ex-
Dengue, or “breakbone,” fever (a se- pansion of mosquitoes and mosquito-borne diseases documented in the past 15
vere flulike viral illness that sometimes years (list at bottom) has stemmed,at least in part,from rising temperatures.
causes fatal internal bleeding) is spread-
ing as well. Today it afflicts an estimat-
BEFORE 1970 TODAY
ed 50 million to 100 million in the Cold temperatures Increased warmth has
tropics and subtropics (mainly in urban caused freezing at high caused mountain glaciers
areas and their surroundings). It has elevations and limited to shrink in the tropics and
broadened its range in the Americas mosquitoes, mosquito- temperate zones
over the past 10 years and had reached borne diseases and
many plants to low
down to Buenos Aires by the end of the altitudes
1990s. It has also found its way to north-
ern Australia. Neither a vaccine nor a
specific drug treatment is yet available.
Although these expansions of malar-
ia and dengue fever certainly fit the pre-
dictions, the cause of that growth cannot
be traced conclusively to global warm-
ing. Other factors could have been in- DENGUE FEVER MOSQUITOES
volved as well—for instance, disruption OR MALARIA
of the environment in ways that favor Some mosquitoes,
mosquito proliferation, declines in mos- mosquito-borne
quito-control and other public health diseases and plants
have migrated upward
programs, and rises in drug and pesti-
cide resistance. The case for a climatic
contribution becomes stronger, howev- PLANTS
er, when other projected consequences
of global warming appear in concert
with disease outbreaks. WHERE DISEASES OR THEIR CARRIERS HAVE REACHED HIGHER ELEVATIONS
Such is the case in highlands around
Malaria Dengue fever Aedes aegypti mosquitoes
the world. There, as anticipated, warmth Highlands of Ethiopia, Rwanda, San Jose, Costa Rica (can spread dengue
is climbing up many mountains, along Uganda and Zimbabwe Taxco, Mexico fever and yellow fever)
with plants and butterflies, and summit Usamabara Mountains,Tanzania Eastern Andes Mountains,
BRYAN CHRISTIE
glaciers are melting. Since 1970 the ele- Colombia
Highlands of Papua New Guinea
vation at which temperatures are al- and West Papua (Irian Jaya) Northern highlands of India
ways below freezing has ascended al-
Is Global Warming Harmful to Health? Scientific American August 2000 53
Copyright 2000 Scientific American, Inc.become all too familiar as the atmo-
sphere heats up) favor the transmission El Niño’s Message and parts of Southeast Asia and Australia suf-
fer droughts.Atmospheric pressure changes
of St. Louis encephalitis and other in- over the tropical Pacific also have ripple ef-
fections that cycle among birds, urban
mosquitoes and humans.
This sequence seems to have abetted
S cientists often gain insight into the work-
ings of complicated systems by studying
subsystems. In that spirit, investigators
fects throughout the globe, generally yield-
ing milder winters in some northern regions
the surprise emergence of the West Nile concerned about global warm-
virus in New York City last year. No ing’s health ef-
one knows how this virus found its way fects are assess-
into the U.S. But one reasonable expla- ing outcomes
nation for its persistence and amplifica- of the El Niño/
tion here centers on the weather’s effects Southern Oscillation
on Culex pipiens mosquitoes, which ac- (ENSO), a climate process that
counted for the bulk of the transmis- produces many of the same me-
sion. These urban dwellers typically lay teorological changes predicted
their eggs in damp basements, gutters, for a warming world. The find-
sewers and polluted pools of water. ings are not reassuring.
The interaction between the weather, “El Niño” refers to an oceanic
the mosquitoes and the virus probably phenomenon that materializes
went something like this: The mild win- every five years or so in the trop-
ter of 1998–99 enabled many of the ical Pacific. The ocean off Peru
mosquitoes to survive into the spring, becomes unusually warm and
which arrived early. Drought in spring stays that way for months be-
and summer concentrated nourishing fore returning to normal or go-
organic matter in their breeding areas ing to a cold extreme (La Niña).
and simultaneously killed off mosquito The name “Southern Oscillation”
predators, such as lacewings and lady- refers to atmospheric changes Disease Outbreaks
bugs, that would otherwise have helped that happen in tandem with the Accompanying Extreme
Pacific’s shifts to warmer or cool- Weather during the
limit mosquito populations. Drought 1997– 98 El Niño
would also have led birds to congregate er conditions.
more, as they shared fewer and smaller During an El Niño,evaporation
watering holes, many of which were fre- from the heated eastern Pacific
can lead to abnormally heavy Extreme Weather
quented, naturally, by mosquitoes.
rains in parts of South America Abnormally wet areas
Once mosquitoes acquired the virus,
the heat wave that accompanied the and Africa; meanwhile other ar- Abnormally dry areas
drought would speed up viral matura- eas of South America and Africa
tion inside the insects. Consequently, as
infected mosquitoes sought blood meals,
they could spread the virus to birds at a
rapid clip. As bird after bird became in- 1993, were long-lasting drought inter- because people have learned to be more
fected, so did more mosquitoes, which rupted by intense rains. careful about avoiding the animals’
ultimately fanned out to infect human First, a regional drought helped to re- droppings. But the disease has appeared
beings. Torrential rains toward the end duce the pool of animals that prey on in Latin America, where some ominous
of August provided new puddles for the rodents—raptors (owls, eagles, prairie evidence suggests that it may be passed
breeding of C. pipiens and other mos- falcons, red-tailed hawks and kestrels), from one person to another.
quitoes, unleashing an added crop of po- coyotes and snakes. Then, as drought As the natural ending of the first han-
tential virus carriers. yielded to unusually heavy rains early in tavirus episode demonstrates, ecosys-
Like mosquitoes, other disease-con- 1993, the rodents found a bounty of tems can usually survive occasional ex-
veying vectors tend to be “pests”— op- food, in the form of grasshoppers and tremes. They are even strengthened by
portunists that reproduce quickly and piñon nuts. The resulting population seasonal changes in weather conditions,
thrive under disturbed conditions unfa- explosion enabled a virus that had been because the species that live in change-
vorable to species with more specialized either inactive or isolated in a small able climates have to evolve an ability to
needs. In the 1990s climate variability group to take hold in many rodents. cope with a broad range of conditions.
contributed to the appearance in hu- When drought returned in summer, the But long-lasting extremes and very wide
mans of a new rodent-borne ailment: animals sought food in human dwellings fluctuations in weather can overwhelm
the hantavirus pulmonary syndrome, a and brought the disease to people. By ecosystem resilience. (Persistent ocean
highly lethal infection of the lungs. This fall 1993, rodent numbers had fallen, heating, for instance, is menacing coral
infection can jump from animals to hu- and the outbreak abated. reef systems, and drought-driven forest
mans when people inhale viral particles Subsequent episodes of hantavirus fires are threatening forest habitats.)
hiding in the secretions and excretions pulmonary syndrome in the U.S. have And ecosystem upheaval is one of the
of rodents. The sequential weather ex- been limited, in part because early-warn- most profound ways in which climate
tremes that set the stage for the first hu- ing systems now indicate when rodent- change can affect human health. Pest
man eruption, in the U.S. Southwest in control efforts have to be stepped up and control is one of nature’s underappreci-
54 Scientific American August 2000 Is Global Warming Harmful to Health?
Copyright 2000 Scientific American, Inc.of the U.S. and western Canada. During a La Niña years,especially in areas hit by floods or University have shown that regions stricken
Niña, weather patterns in the affected areas droughts. Long-term studies in Colombia, by flooding or drought during the El Niño of
may go to opposite extremes. Venezuela, India and Pakistan reveal, for in- 1997–98 (the strongest of the century) often
The incidence of vector-borne and water- stance, that malaria surges in the wake of El had to contend as well with a convergence
borne diseases climbs during El Niño and La Niños. And my colleagues and I at Harvard of diseases borne by mosquitoes, rodents
and water (map). Addition-
ally, in many dry ar-
eas, fires raged out
of control, pollut-
ing the air for miles
around.
ENSO is not merely a
warning of troubles to come;
it is likely to be an engine for
those troubles. Several climate
models predict that as the atmo-
sphere and oceans heat up, El Niños
themselves will become more com-
mon and severe—which means that
the weather disasters they produce
and the diseases they promote could
become more prevalent
as well.
Indeed, the ENSO
pattern has already
begun to change.
Since 1976 the inten-
sity, duration and
pace of El Niños have
increased. And dur-
Disease Outbreaks
ing the 1990s, every
year was marked by
Mosquito-borne: Dengue fever Rodent-borne: Hantavirus pulmonary syndrome
an El Niño or La Niña ex-
Encephalitis Waterborne: Cholera treme. Those trends bode ill for
Malaria Noninfectious: Respiratory illness resulting human health in the 21st century.
Rift Valley fever from fire and smoke
— P.R.E.
ated services to people; well-functioning lack of clean water during a drought in- Indian Ocean to the Horn of Africa in
ecosystems that include diverse species terferes with good hygiene and safe re- 1997 and 1998 offer an example of how
help to keep nuisance organisms in hydration of those who have lost large people will be affected as global warm-
BRYAN CHRISTIE; SOURCES: NOAA CLIMATE PREDICTION CENTER; http://chge2.med.harvard.edu/enso/disease.html
check. If increased warming and weath- amounts of water because of diarrhea ing spawns added flooding. The down-
er extremes result in more ecosystem or fever. pours set off epidemics of cholera as
disturbance, that disruption may foster Floods favor waterborne ills in differ- well as two mosquito-borne infections:
the growth of opportunist populations ent ways. They wash sewage and other malaria and Rift Valley fever (a flulike
and enhance the spread of disease. sources of pathogens (such as Crypto- disease that can be lethal to livestock
sporidium) into supplies of drinking wa- and people alike).
Unhealthy Water ter. They also flush fertilizer into water To the west, Hurricane Mitch stalled
supplies. Fertilizer and sewage can each over Central America in October 1998
B eyond exacerbating the vector-borne
illnesses mentioned above, global
warming will probably elevate the inci-
combine with warmed water to trigger
expansive blooms of harmful algae.
Some of these blooms are directly toxic
for three days. Fueled by a heated Carib-
bean, the storm unleashed torrents that
killed at least 11,000 people. But that
dence of waterborne diseases, including to humans who inhale their vapors; oth- was only the beginning of its havoc. In
cholera (a cause of severe diarrhea). ers contaminate fish and shellfish, which, the aftermath, Honduras reported thou-
Warming itself can contribute to the when eaten, sicken the consumers. Re- sands of cases of cholera, malaria and
change, as can a heightened frequency cent discoveries have revealed that algal dengue fever. Beginning in February of
and extent of droughts and floods. It blooms can threaten human health in this year, unprecedented rains and a se-
may seem strange that droughts would yet another way. As they grow bigger, ries of cyclones inundated large parts of
favor waterborne disease, but they can they support the proliferation of various southern Africa. Floods in Mozambique
wipe out supplies of safe drinking water pathogens, among them Vibrio cholerae, and Madagascar killed hundreds, dis-
and concentrate contaminants that might the causative agent of cholera. placed thousands and spread both chol-
otherwise remain dilute. Further, the Drenching rains brought by a warmed era and malaria. Such events can also
Is Global Warming Harmful to Health? Scientific American August 2000 55
Copyright 2000 Scientific American, Inc.greatly retard economic development, gy would have multiple components. at-risk populations and to deliver prompt
and its accompanying public health ben- One would include improved surveil- treatments.
efits, in affected areas for years. lance systems that would promptly spot This past spring, efforts to limit the
the emergence or resurgence of infec- West Nile virus in the northeastern U.S.
Solutions tious diseases or the vectors that carry followed this model. On seeing that the
them. Discovery could quickly trigger virus had survived the winter, public
T he health toll taken by global
warming will depend to a large ex-
tent on the steps taken to prepare for
measures to control vector proliferation
without harming the environment, to
advise the public about self-protection,
health officials warned people to clear
their yards of receptacles that can hold
stagnant water favorable to mosquito
the dangers. The ideal defensive strate- to provide vaccines (when available) for breeding. They also introduced fish that
Weather and the West Nile Virus
T his diagram offers a possible explanation for how a
warming trend and sequential weather extremes helped
the West Nile virus to establish itself in the New York City area
in 1999. Whether the virus entered the U.S. via mosquitoes,
birds or people is unknown. But once it arrived, interactions
between mosquitoes and birds amplified its proliferation.
MILD WINTER
More mosquitoes than usual survived Mosquito population
1 the winter in sewers, damp basements flourished in spring
and other sources of still water and summer
DRY SPRING AND SUMMER
2
As water in breeding sites
evaporated, organic compounds
became concentrated, nourishing
mosquito larvae
Lack of rain killed
predators of mosquitoes
(frogs, lacewings, ladybugs)
Many birds congregated at
dwindling water sources
MOSQUITO
POPULATION
JULY HEAT WAVE GREW LARGE
3 Once mosquitoes infected
with the West Nile virus
appeared, the heat caused DRENCHING AUGUST RAINS
the virus to proliferate Downpours formed new breeding
rapidly inside them sites for mosquitoes, yielding
a new crop of the insects
VICIOUS CYCLE
BEGAN 4
INFECTED MOSQUITO
Infected mosquitoes
transmitted the virus to
initially uninfected birds
UNINFECTED MOSQUITO
INFECTION SPREAD TO PEOPLE
As more and more mosquitoes became
infected, they spread the virus to still
Initially uninfected
more birds and ultimately to people
mosquitoes picked up
BRYAN CHRISTIE
the virus from infected birds
56 Scientific American August 2000 Is Global Warming Harmful to Health?
Copyright 2000 Scientific American, Inc.eat mosquito larvae into catch
basins and put insecticide pel-
lets into sewers.
Sadly, however, comprehen-
sive surveillance plans are not
yet realistic in much of the
world. And even when vaccines
or effective treatments exist,
many regions have no means
of obtaining and distributing
them. Providing these preven-
tive measures and treatments
should be a global priority.
A second component would
focus on predicting when cli-
matological and other envi-
ronmental conditions could
become conducive to disease
outbreaks, so that the risks
could be minimized. If climate models man activities that contribute to the heat- to pay for these solutions. Climate, eco-
NASA (http://pao.gsfc.nasa.gov/gsfc/earth/rvalley/rvalley.htm)
indicate that floods are likely in a given ing or that exacerbate its effects must logical systems and society can all re-
region, officials might stock shelters be limited. Little doubt remains that coup after stress, but only if they are
with extra supplies. Or if satellite im- burning fossil fuels for energy is playing not exposed to prolonged challenge or
ages and sampling of coastal waters in- a significant role in global warming, by to one disruption after another. The
dicate that algal blooms related to spewing carbon dioxide and other heat- Intergovernmental Panel on Climate
cholera outbreaks are beginning, offi- absorbing, or “greenhouse,” gases into Change, established by the United Na-
cials could warn people to filter con- the air. Cleaner energy sources must be tions, calculates that halting the ongo-
taminated water and could advise med- put to use quickly and broadly, both in ing rise in atmospheric concentrations
ical facilities to arrange for additional the energy-guzzling industrial world of greenhouse gases will require a
staff, beds and treatment supplies. and in developing nations, which can- whopping 60 to 70 percent reduction
Research reported in 1999 illustrates not be expected to cut back on their en- in emissions.
the benefits of satellite monitoring. It ergy use. (Providing sanitation, hous- I worry that effective corrective mea-
showed that satellite images detecting ing, food, refrigeration and indoor fires sures will not be instituted soon enough.
heated water in two specific ocean re- for cooking takes energy, as do the Climate does not necessarily change
gions and lush vegetation in the Horn pumping and purification of water and gradually. The multiple factors that are
of Africa can predict outbreaks of Rift the desalination of seawater for irriga- now destabilizing the global climate sys-
Valley fever in the Horn five months in tion.) In parallel, forests and wetlands tem could cause it to jump abruptly out
advance. If such assessments led to vac- need to be restored, to absorb carbon of its current state. At any time, the
cination campaigns in animals, they dioxide and floodwaters and to filter world could suddenly become much
could potentially forestall epidemics in contaminants before they reach water hotter or even much colder. Such a sud-
both livestock and people. supplies. den, catastrophic change is the ultimate
A third component of the strategy The world’s leaders, if they are wise, health risk— one that must be avoided
would attack global warming itself. Hu- will make it their business to find a way at all costs. SA
The Author Further Information
PAUL R. EPSTEIN, an M.D. trained The Emergence of New Disease. Richard Levins, Tamara Auerbuch, Uwe Brinkmann, Irina
in tropical public health, is associate Eckardt, Paul R. Epstein, Tim Ford, Najwa Makhoul, Christina dePossas, Charles Puccia, Andrew
director of the Center for Health and Spielman and Mary E. Wilson in American Scientist, Vol. 82, No. 1, pages 52–60; January/
the Global Environment at Harvard February 1994.
Medical School. He has served in med- Climate Change and Human Health. Edited by Anthony J. McMichael, Andrew Haines,
ical, teaching and research capacities Rudolf Slooff and Sari Kovats. World Health Organization, World Meteorological Organiza-
in Africa, Asia and Latin America and tion, United Nations Environmental Program, 1996.
has worked with the Intergovernmen- The Regional Impacts of Climate Change: An Assessment of Vulnerability, 1997. Edited
tal Panel on Climate Change, the Na- by R. T. Watson, M. C. Zinyowera and R. H. Moss. Cambridge University Press, 1997. Sum-
tional Oceanic and Atmospheric Ad- mary from the Intergovernmental Panel on Climate Change available at www.ipcc.ch/pub/
ministration, and the National Aero- reports.htm
nautics and Space Administration to Biological and Physical Signs of Climate Change: Focus on Mosquito-Borne Diseases.
assess the health effects of climate Paul R. Epstein, Henry F. Diaz, Scott Elias, Georg Grabherr, Nicholas E. Graham, Willem J. M.
change and to develop health applica- Martens, Ellen Mosley-Thompson and Joel Susskind in Bulletin of the American Meteorological
tions for climate forecasting and re- Society, Vol. 79, pages 409–417; 1998.
mote-sensing technologies. Other Web sites of interest: www.heatisonline.org and www.med.harvard.edu/chge
Is Global Warming Harmful to Health? Scientific American August 2000 57
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