Walt Kelly, the
originator of
Pogo, didn’t
know about
global warming,
but the
sentiment fits.
Water supplies and global warming.
Water supplies are already limiting many human
societies. Shortages are likely to become
increasingly frequent as global warming
interacts with growing populations and
increasingly developed societies that demand
more water for agriculture, manufacturing, and
personal use.
Water pollution is also a major problem. More than five million
people die from waterborne diseases each year - 10 times the
number killed in wars around the globe.
Global warming is likely to increase these problems by increasing
the frequency of both floods and droughts and changing the
seasonal pattern of runoff from snowpacks and glaciers. In
addition, salt water incursion into low lying coastal areas and river
deltas will restrict agriculture, reduce availability of fresh water,
and endanger fresh water wildlife.
The amount of water on Earth is fixed.
Less than 0.01% of the planet's 1.4 billion cubic
kilometers is easily accessible freshwater in
lakes and rivers.
About a fifth of the water used worldwide comes
from the 30% of the world's freshwater which is
stored in groundwater.
Soaring demand
The world's population has tripled in the last 100
years, but water use has increased sixfold.
Agriculture now consumes 70 % of the water used
worldwide.
Much more will be needed if we are to feed the
world's growing population - predicted to rise from
6.8 billion today to 8.9 billion by 2050.
Water use is very uneven. Just like
energy, Americans are by far the largest
consumers.
Water consumption will soar further as
more people expect Western-style
lifestyles and diets - one kilogram of
grain-fed beef needs at least 15 cubic
meters of water, while a kilo of cereals
needs less than three cubic meters.
An estimated third of the world's population currently
lives in water-stressed countries. This will likely increase
to two-thirds within 25 years. Africa and Asia are already
hard-hit by water stress. Increasing populations will
create more pressure in the coming decades.
Of the many possible examples of
anticipated water shortages, I’ll
talk briefly about just one: the
watershed of the Himalayas.
Nearly all the great rivers of Asia begin in the Tibetan Plateau
The Himalayas contain the largest store of
water outside the polar ice caps, and feed
seven great Asian rivers.
Two billion people in the river basins depend
on the Himalayan glaciers for their water
supply,
The rapid melting of Himalayan glaciers will first
increase the volume of water in rivers by 20-30
percent, causing widespread flooding. Hundreds
of millions live on flood plains that are highly
vulnerable to raised water levels.
There is also the risk of sudden flash floods as rapidly expanding glacial
lakes burst through their natural dams.
There are 3,300 glaciers in the Nepalese Himalayas and 2,300 of them
contain glacial lakes. These lakes are quietly growing because of rising
temperatures, but nobody knows how many are close to bursting, and there
are no early warning systems for the villages downstream.
A glacier lake catastrophe happened once in a
decade 50 years ago,' said UK geologist John
Reynolds, whose company advises Nepal. 'Five years
ago, they were happening every three years. By
2010 there will be one every year.'
An example of the impact is provided by Luggye
Tsho, in Bhutan, which burst its banks in 1994,
sweeping 10 million cubic meters of water down the
mountain. It struck Panukha, 50 miles away, killing
21 people.
Now a nearby lake, below the Thorthormi glacier, is in imminent danger of
bursting. That could release 50 million cubic meters of water, a flood
reaching to northern India 150 miles downstream.
But in a few decades the glaciers will be largely gone and the
water level in rivers will drastically decline, meaning massive
eco and environmental problems for people in China, Nepal,
India, and Bangladesh. Without the glaciers, drinking and
irrigation water will be drastically reduced, especially during
the dry season. Crops will die. Hundreds of millions of people
will be affected.
These disruptions are quite likely to trigger major conflicts
locally and internationally, as people clash over water and land.
People will be forced to migrate away from their dry or
flooded land. Governments will bicker over who will get the
remaining water and who will pay the economic costs.
Global warming is also changing the distribution
of diseases, particularly tropical diseases.
Dengue Fever
Dengue, or "breakbone", fever is a mosquito
borne disease related to yellow fever. Unlike its
relative, however, there is no vaccine against
dengue. One strain of the disease, hemorrhagic
dengue fever, is often deadly, and doctors in the
U.S. and other areas into which it is expected to
spread have little experience diagnosing or
treating it.
The range of Aedes aegypti, the mosquito that carries dengue fever, is limited
by temperatures. Frost kills both adults and larvae. Previously, the disease
could not spread out of the tropics, but rising temperatures are changing that.
It has moved steadily north in recent decades, and to higher elevations. Nepal
and Bhutan saw their first cases in recent years and in South America it is
climbing up the Andes. In the United States A. aegypti has reached as far
north as Chicago. This means that many people who have not previously been
exposed to Dengue fever virus are now at risk.
Malaria
Like dengue fever, malaria is a mosquito borne
illness normally limited by temperatures. Rising
temperatures have expanded its range, and
exposed new populations to infection. IPCC
scientists project that as warmer temperatures
continue to spread north and south from the
tropics and to higher elevations, malaria-carrying
mosquitoes will spread with them. They project
that global warming could put as much as 65
percent of the world’s population at risk of
infection by malaria.
Here in the United States malaria infections are already on the rise.
Houston has experienced a malaria outbreak in each of the last two years.
In the last three years malaria cases have occurred as far north as New
Jersey, Michigan and Queens, New York. In 1997 an outbreak occurred in
Florida, striking the Disney World theme park, and mosquitoes carrying the
illness were discovered in New York.
To make matters worse, the Asian Tiger
Mosquito, Aedes albopictus, is an invasive
species that has spread from its native range
in Asia to all the other continents (except
Antarctica). It is an aggressive daytime flier
that bites rapidly, thereby avoiding most
attempts to swat it. It can spread several
diseases, including dengue fever and malaria.
Because it can be
transmitted by the
common household
mosquito, Culex
pipiens, West Nile
virus spread rapidly
after it was
introduced at La
Guardia airport in
New York.
Heat waves
The IPCC projects that one lethal effect of global warming will be more
frequent and more severe heat waves. Deadly stretches of hot days, where
nighttime temperatures remain high, will become more common.
One such event killed over 700 people in Chicago during the summer of 1995.
By the year 2020, global warming could cause up to a 145% rise in mortality
in New York City. Other major cities could suffer similar problems.
A record heat wave scorched Europe in August 2003, claiming an estimated
35,000 lives. In France alone, 14,802 people died from the searing
temperatures—more than 19 times the death toll from the SARS epidemic
worldwide. In the worst heat spell in decades, temperatures in France soared
to 104 degrees Fahrenheit (40 degrees Celsius) and remained unusually high
for two weeks.
August 2003 was the warmest August on record in the northern hemisphere,
but according to the projections of the IPCC, even more extreme weather
events lie ahead. By the end of the century, the world's average temperature
is projected to increase by 2.5-10.4° F (1.4-5.8° C). As the mercury climbs,
more frequent and more severe heat waves are in store.
Though heat waves rarely are given adequate attention, they claim more
lives each year than floods, tornadoes, and hurricanes combined.
Heat waves are a
silent killer,
mostly affecting
the elderly, the
very young, or
the chronically
ill.