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#466 - Climate and Infectious Disease, Part 1, 01-Nov-1995

Inside a greenhouse, it is the glass roof that creates the warmth. The
glass lets sunlight stream in. When the sunlight strikes a surface and
turns into heat energy, the heat then radiates back toward the sky. The
radiated heat strikes the glass, which has the peculiar property of
allowing light to pass through much better than it lets heat pass
through. Therefore, some of the heat is reflected back down into the
greenhouse, and the greenhouse warms up.

For at least 100 years, physicists and chemists have known that carbon
dioxide (CO2) in the atmosphere acts like glass covering the earth.[1]
CO2 lets sunlight in, but does not let heat out nearly so well. Since
1850, the carbon dioxide content of the atmosphere has increased 30%
because of humans burning coal and oil. There is nearly universal
agreement among scientists that this will warm the earth.[2] It's only
a question of when.

Now evidence is accumulating steadily, indicating that the warming has

** AIR IS WARMING: Global average air temperature over the last century
has risen about 0.8 degrees Fahrenheit (F.), which is 0.45 degrees
Celsius (C.), according to the Intergovernmental Panel on Climate
Change (IPCC). The IPCC is made up of about 200 of the world's leading
scientists who specialize in climate studies. In some areas, such as
Australia and New Zealand, the increase in air temperature has exceeded
the average; in New Zealand, average air temperature has risen between
0.7 and 1.4 degrees F. (or between 0.4 and 0.8 degrees C.).[3]

** OCEANS ARE WARMING: In November, 1994, researchers announced finding
a 0.9 degree F. (0.5 degree C.) rise in the temperature of the deep
waters of the Indian Ocean, compared to measurements taken 20 years
ago. This was the third ocean observed to be warming. In 1992 Nathan
Bindoff reported that the subsurface temperature of the southwestern
Pacific Ocean had increased at about the same rate (0.9 degrees F. [0.5
degrees C.] over 20 years).[4] In early 1994, a group led by Gregorio
Parrilla of the Spanish Oceanographic Institute reported that the North
Atlantic was also warming.[5]

** In December, 1994, Ed Carmack of the Institute of Ocean Sciences in
Sidney, British Columbia, Canada, reported that the waters 200 to 1000
meters (660 to 3280 feet) beneath the Arctic Ocean have warmed 1.8
degrees F. (1.0 degrees C.) "compared to a few years ago." "There is
clear evidence that the arctic is warming," Carmack reported.[6] The
Arctic is thus the fourth ocean found to be measurably warming. In
June, 1995, researchers used a new technique to measure temperature
beneath the Arctic ice cap. They measured the speed of sound through
Arctic waters, and from that calculated a warming of 0.9 degrees F.
(0.5 degrees C.) compared to thermometer data from a decade ago.[7]

** GLACIERS ARE MELTING. For example, on Mount Jaya in New Guinea,
three glaciers have shrunk by 6.2 square miles (16 square kilometers)
since 1936, and now only 1.1 square miles (3 square kilometers) of ice
remain. "The region has heavy snow showers," says Geoff Hope of the
Australian National University in Canberra, "so the shrinking must be
due to a rise in temperature."[8]

RESPONSE TO RISING TEMPERATURES. For example, 45 species of
invertebrates were surveyed along the California coastline in 1930 and
again in 1993-94. A definite shift northward in the range of these
species was observed over the 60-year period. During the period, annual
average (mean) ocean temperature at the shoreline increased 1.35
degrees F. (0.75 degrees C.), and average summer maximum air
temperatures increased 3.9 degrees F. (2.2 degrees C.).[9]

** In 1994, researchers reported a study of plants on 26 mountain tops
in the Alps in western Austria and eastern Switzerland. From

"12 very precise historical records" the researchers were able to show
that 9 species of plants have been moving upward at the rate of 4
meters (12 feet) per decade since the original measurements were made
70 to 90 years ago.[10] These species are in danger of becoming extinct
as they move upward because eventually they will run out of mountain.

** MOSQUITOES ARE SPREADING: Plants are not the only creatures moving
northward and to higher elevations. Mosquitoes that carry diseases such
as malaria, yellow fever, dengue fever, and encephalitis are also
extending their range, and moving to higher elevations --thus
threatening larger human populations with exposure to serious
infectious diseases. Dengue fever --also known as "breakbone fever"
because it is so painful --appeared in Texas this past summer.

In May, 1995, researchers in the Netherlands and in England estimated
the increase in malaria that could occur if the IPCC's projection for
global warming proves correct. They concluded that, in tropical
regions, the "epidemic potential of the mosquito population" would
double; on the other hand, in temperate climates, the epidemic
potential would increase 100-fold (in other words, it would become 100
times as great as it is today). Furthermore, they said, "There is a
real risk of reintroducing malaria into nonmalarial areas, including
parts of Australia, the United States, and southern Europe." All told,
they estimated that climate change of 5.4 degrees F. (3 degrees C.) in
the next century could cause an additional 50 million to 80 million new
cases of malaria each year around the globe.[11] Today, about 110
million new cases of malaria occur each year, globally.

The increase of malaria is not merely theoretical. A recent study of a
1987 malaria outbreak in Rwanda showed that 80% of the outbreak could
be explained by unusually high temperatures, and abundant rainfall
(both of which are expected to increase with global warming).[12] A 1.8
degree F. (1.0 degree C.) temperature increase led to a 337% increase
in malaria. Furthermore, there is evidence of a 5-to-8-year cycle of
malaria outbreaks in various parts of the world, and these can be shown
to correlate with the El Nino Southern Oscillation (ENSO), a periodic
warming of the southern Pacific ocean surface, which usually occurs
about twice each decade. ENSO ordinarily appears at Christmastime and
affects patterns of temperature, rainfall, and drought worldwide for
about a year.[13] Since 1980, ENSO events have occurred more
frequently, and have lasted longer than they used to. As a writer in
SCIENCE magazine said recently, "Recent data suggest that warming in
the deep oceans may be driving El Nino conditions...."[14] During the
period 1991-1994, El Nino recurred each year --an event without
precedent in the historical record.[15] Paul Epstein of the Harvard
School of Public Health explains the importance of recent El Nino
events this way: Warmer seas evaporate quickly, yielding greater
precipitation over some areas and drought in others. The strength of
the 1992/1993 El Nino was unexpected, and the endurance of +2 to 3
degree C. (3.6 to 5.4 degree F.) increases in ocean temperatures into
summer was unprecedented. As a result of the extended El Nino event of
the last 4 years, weather patterns have become particularly erratic and
volatile (i.e., unstable), Epstein writes.

** Partly as a result of El Nino events, marine ecosystems around the
globe have begun to experience enormous unnatural blooms of algae.
Algae are tiny floating plants that photosynthesize, which is to say
they use energy from sunlight to combine carbon dioxide and hydrogen
(from water) into carbohydrates. Thus algae form the bottom of the
oceans' food chains. According to researchers from Harvard University
and from the University of Maryland, recent algae blooms threaten the
health of marine ecosystems,[16,17] and of humans.

Algae blooms are promoted by many human activities:

** Algae growth is promoted by nitrogen-rich waste waters, by
fertilizers, by acid rain, and by nutrient-carrying soil that runs off
the land when it rains.

** Wetlands and mangroves ("nature's kidneys") filter out nitrates and
phosphates (chemicals which act as fertilizers and promote algae

** While nutrient sources are increasing, the filtration systems are
being lost to coastal development, to aquaculture (fish farming), to
diking (a response to rising sea levels, caused by global warming), and
to drilling.

** Simultaneously, fish stocks (which eat the creatures that eat algae)
are being depleted (14 of 17 major world fisheries are in serious

** Simultaneously, climate-related warmer sea-surface temperatures also
increase growth of algae by: (1) increasing photosynthesis and speeding
up the algae's metabolism; (2) increasing nutrient-rich coastal
upwelling (upward flows of water); and (3) shifting the community of
organisms toward more toxic species ("red tides," fish and shellfish
poisonings) which are in turn less palatable to creatures that eat

Why should humans care? For one thing, algae provide a home for the
microbe that causes cholera --an illness that kills humans by a violent
diarrhea, if not promptly and expertly treated. In 1991, El Nino and
algae blooms contributed to a massive outbreak of cholera in Latin
America in which 500,000 people fell ill and 5000 died.[16]

In sum, "The spread of infectious diseases will be the most important
public health problem related to climate change," says Jonathan Patz, a
microbiologist at Johns Hopkins University.[14]

--Peter Montague


[1] Svante Arrhenius, "On the Influence of Carbonic Acid in the Air
Upon the Temperature of the Ground," PHILOSOPHICAL MAGAZINE (1896)
cited in Douglas Cogan, THE GREENHOUSE GAMBIT (Washington, D.C.:
Investor Responsibility Research Center, 1992), pg. 63.

[2] Kathy Maskell, Irving M. Mintzer, and Bruce A. Callendar, "Basic
science of climate change," THE LANCET Vol. 342, No. 8878 (October 23,
1993), pgs. 1027-1031.

[3] Tim Thwaites, "Are the Antipodes in hot water?" NEW SCIENTIST
November 12, 1994, pg. 21.

[4] Nathan L. Bindoff and others, "Warming of the water column in the
southwest Pacific Ocean," NATURE Vol. 357 No. 6373 (May 7, 1992), pg.

[5] Gregorio Parrilla and others, "Rising temperatures in the
subtropical North Atlantic Ocean over the past 35 years," NATURE Vol.
369 No. 6475 (May 5, 1994), pgs. 48-51.

[6] John Travis, "Taking a Bottom-to-Sky 'Slice' of the Arctic Ocean,"
SCIENCE Vol. 266 (December 23, 1994), pgs. 1947-1948.

[7] Antonio Regalado, "Listen Up! The World's Oceans May Be Starting to
Warm," SCIENCE Vol. 268 (June 9, 1995), pgs. 1436-1437.

[8] Helen Goss, "Meltdown warning as tropical glaciers trickle away,"
NEW SCIENTIST June 24, 1995, page unknown.

[9] J.P. Barry and others, "Climate-Related, Long-Term Faunal Changes
in a California Rocky Intertidal Community," SCIENCE Vol. 267 (February
3, 1995), pgs. 672-675.

[10] Georg Grabherr and others, "Climate effects on mountain plants,"
NATURE Vol. 369 (June 9, 1994), page unknown. See also Carol Kaesuk
Yoon, "Warming Moves Plants Up Peaks, Threatening Extinction," NEW YORK
TIMES June 21, 1994, pg. C4.

[11] Willem J.M. Martens and others, "Potential Impact of Global
103, No. 5 (May 1995), pgs. 458-464.

[12] Michael E. Loevinsohn, "Climatic warming and increased malaria
incidence in Rwanda," THE LANCET Vol. 343 (March 19, 1994), pgs. 714-

[13] M.J. Bouma and others, "Climate change and periodic epidemic
malaria," THE LANCET Vol. 343 (June 4, 1994), page unknown.

[14] Richard Stone, "If the Mercury Soars, So May Health Hazards,"
SCIENCE Vol. 267 (February 17, 1995), pgs. 957-958.

[15] Paul R. Epstein, "Emerging Diseases and Ecosystem Instability: New
Threats to Public Health," AMERICAN JOURNAL OF PUBLIC HEALTH Vol. 85,
No. 2 (February 1995), pgs. 168-172.

[16] Paul R. Epstein and others, "Marine Ecosystems," THE LANCET Vol.
342 (November 3, 1993), pgs. 1216-1219.

[17] Elizabeth Culotta, "Red Menace in the World's Oceans," SCIENCE
Vol. 257 (September 11, 1992), pgs. 1476-1477.

Descriptor terms: greenhouse effect; greenhouse gases; carbon dioxide;
air pollution; atmosphere; coal; oil; fossil fuels; air temperature;
global warming; oceans; glaciers; mosquitoes; dengue fever; yellow
fever; malaria; encephalitis; rwanda; el nino southern oscillation;
paul epstein; algae; eutrophication; fertilizer; nutrients; mangroves;
wetlands; aquaculture; fish; cholera; infectious diseases;

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