If we continue to ignore the danger signs, the world of the future
will be a hotter, poorer, deadlier place. Here's what it might look like.
by Paul Rauber
It starts with heat. Slowly, almost imperceptibly, it starts to get hotter.
The increase in average temperatures is gradual; what we notice are the
scorching spikes, as heat records fall one after another. Winters are milder,
but punctuated by deluges and blizzards. Spring starts early, but too-rapid
snowmelt leads first to floods, and then to summer drought.
Weather becomes more extreme--storms more powerful, hurricanes
more damaging. What once was unusual becomes common; "100-year floods"
become routine. Ecosystems start to shift, subtly at first. Familiar trees,
weakened by drought and disease, brown and burn in the more frequent fires.
Grasslands replace what once were forests, and deserts replace grasslands.
Species accustomed to cooler temperatures move north--if they can find
suitable habitat not covered by malls and housing developments. Fewer songbirds
visit your backyard feeder. Then, none. Species you never heard of are
declared extinct. Then, species you have heard of. Then, familiar favorites
like polar bears and manatees.
Around the periphery, in low-lying coastal areas, storm
surges rush farther inland than ever before. Melting icecaps and glaciers
cause sea levels to rise; beaches erode and then disappear. Cities build
dikes to keep out the rising seas. Inevitably, the dikes sometimes fail.
With warmer winters and earlier springs, mosquitoes are
everywhere. People get sick from diseases you thought occurred only in
the faraway tropics. In those distant places, crops fail year after year
and people take to the roads, looking for food. You don't think much about
those people until they start showing up in your town.
By the end of your life, you realize that everything is
different, that this is not the world you meant to pass on to your children
and grandchildren. And it keeps getting hotter.
Today, global warming is just beginning. It is impossible,
of course, to point at natural events and say that this one is caused by
global warming and that one not. But we can study the past, look at what
is happening around us, and listen to what climatologists say global warming
will mean for our future. Their projections are already being borne out.
Heat
Over the past century, humans have raised our planet's
temperature. We do this through industrial activity and by using internal
combustion engines, generating gases that trap the sun's rays in the atmosphere
and thus greatly enhancing the natural "greenhouse effect." These
gases include methane and nitrous oxide, but especially carbon dioxide.
The inevitable product of the combustion of fossil fuel, CO2 is released whenever we burn oil, coal,
or natural gas. The greater the concentration of CO2 in the atmosphere, the hotter it gets. Before the Industrial
Revolution, the atmosphere contained about 280 parts per million of CO2. Today, that figure is 360 ppm. The Intergovernmental
Panel on Climate Change (IPCC), an assembly of the top climatologists on
the planet, estimates that by the end of the next century, the CO2 level will be somewhere between 480 and
800 ppm. (Most of the projections presented here assume a doubling of preindustrial
concentrations to 560 ppm.)
Not coincidentally, 1995 was the warmest year since global
records started to be kept in 1856. Despite brutal winter storms, 1996
was still among the warmest years, and 1991 to 1995 was the warmest five-year
period in recorded history. Human activity has increased the earth's average
temperature by one degree this century. The IPCC predicts a further increase
of 2 to 6 degrees over the next century. A 2 degree rise would be very
serious; 6 degrees would be catastrophic.
These temperature rises will not be uniform. In the United
States, many areas of the West, Midwest, and Northeast are already 3 degrees
warmer than they were a century ago. In the future, we can also expect
to experience more deadly heat waves like the one that hit Chicago in the
summer of 1995, killing so many people that the morgue couldn't handle
all the bodies.
"Global climate change is here. It is happening
right now."
--Insurance executive Kaj Ahlmann, president of Employers Reinsurance
Corporation, Overland Park, Kansas
Disease
A hotter world means more than higher air-conditioning
bills. It means that vermin will spread to newly suitable habitats, bringing
diseases to afflict newly vulnerable human populations. Mosquito-borne
malaria, for example, is generally restricted to humid regions with average
temperatures above 61 degrees--at present, about 45 percent of the world.
Global warming in the range of 6 to 10 degrees would unleash malaria-carrying
mosquitoes on 60 percent of the globe.
The consequences are expected to be most devastating for
less-developed nations in the Tropics. At present, many people living in
tropical highlands are protected by their altitude's cooler weather. In
Rwanda in 1987, a 2 degree increase in temperature led to a 337 percent
rise in malaria rates. At present, malaria kills about 2 million people
annually. According to a study in the Journal of the American Medical
Association, by the middle of the next century global warming could
cause an additional million malaria deaths every year.
Climate change is also increasing the range of Aedes
aegypti, the species of mosquito that carries both dengue and yellow
fever; scientists in New Zealand have already linked outbreaks of dengue
in the South Pacific to global warming. A hot summer in 1995 led to 140,000
cases of dengue fever from Argentina to Texas. Aedes aegypti have
already been identified in Houston and other parts of Texas, as well as
throughout the Southeast. Another dengue-carrying mosquito has reached
Chicago.
The weather extremes caused by global warming can also
lead, indirectly, to outbreaks of deadly hantavirus, the acute, often fatal
respiratory illness that broke out in the Four Corners region of New Mexico
in 1993, eventually killing 76 people nationwide. Hantavirus is transmitted
to humans by rodents, whose populations boom when plentiful rainfall follows
an extended drought--both more frequent occurrences with global warming.
Another deadly threat is the resurgence of cholera, which
thrives in the higher water temperatures of a warmer world; it has already
been found in the Chesapeake Bay. A 1991 cholera epidemic in South America
killed 5,000 people. How many will die next time?
"If tropical weather is expanding, tropical
diseases will expand. We're seeing malaria in Houston."
--Dr. Paul Epstein, Harvard School of Public Health
Vanishing Habitat
As global warming causes low-lying coastal areas to flood
or former cornfields to turn into sandtraps, humans can pack up and move.
It is not so easy for trees, insects, fish, and wildlife, which are dependent
on particular climatic conditions. In the past, climate change has generally
occurred gradually enough for whole populations to migrate. In the 10,000
years following the end of the last ice age, the globe has warmed by about
5 degrees, and ecosystems have gradually adapted. We now face a similar
temperature hike, but this time within the span of only 100 years.
Can plant species keep up with the rapid change? Given
the right conditions, fast-growing trees like spruce can move up to 100
yards a year. For most species, however, progress is measured in feet per
decade. A shift of 40 miles north (or 60 yards in altitude) has already
been necessary to compensate for the one-degree rise in temperature. On
the West Coast, Edith's checkerspot butterfly has shifted its range 100
miles to the north, and entire populations of sea life in Monterey Bay
have moved north in response to a water temperature 4 degrees warmer than
it was 60 years ago.
Freshwater fish don't have the luxury of such mobility.
Species dependent on cold water--salmon, trout, walleye, pike, and muskie,
to name a few--are in big trouble. A 5 degree rise in average water temperatures
would devastate many trout populations; an EPA study last year concluded
that 24 states could lose 50 to 100 percent of their cold-water fish populations.
The future belongs to the omnivores and the opportunists,
fast-moving creatures who aren't too particular about what they eat. Slow-moving
plants--and the animals that depend on them--may lose the race. Alpine
species that must move up mountainsides in order to find cooler temperatures
will eventually run out of mountain. Species already stressed by loss of
habitat to human development may run out of luck.
The forests of the next century will be dramatically different.
The sugar maple, for example, could virtually disappear from the United
States. (Good-bye Vermont maple syrup!) With a doubling of atmospheric
CO2, the ranges of birch, hemlock,
and beech trees could also shift 300 to 600 miles to the north. This would
mean, of course, huge areas of dead and dying trees left behind, fuel for
catastrophic fires that would further contribute to the atmosphere's heavy
carbon burden, deforming even more habitat. University of California researchers
estimate that global warming could render 20 to 50 percent of the state's
natural areas unsuitable for their current species.
Climate change is already playing havoc with the seasons.
Worldwide, from 1981 to 1991, the start of springtime plant growth has
advanced by eight days; major changes in vegetation are occurring over
one-eighth of the planet. Migrating red-winged blackbirds now arrive in
Michigan 21 days earlier than they did in 1960. Migratory birds who depend
on solar cues to know when to move on may find that local temperatures--and
thus vital local food sources--are no longer in sync. Shorebirds migrating
through Delaware Bay, for example, depend on the eggs of horseshoe crabs
to fuel their flight; if global warming means the birds arrive before the
crabs lay their eggs, they might not make it to their arctic breeding grounds.
Even if they did make it to the Arctic, they might find
a dangerously unfamiliar environment. Spruce forests are already advancing
into what is now tundra; a doubling of CO2 is expected to reduce the tundra's size by 30 percent. In 1990,
caribou migrating to the coastal plain of northern Alaska found that the
earliest spring in nearly 40 years had caused their principal forage to
go to seed, depriving them of crucial nourishment. In the High Arctic,
unseasonable warmth could collapse the snow dens of the ringed seal, leaving
the pups vulnerable. Together with a reduction in the extent of pack ice,
this decline in the seal population could spell the end for the king of
the north, the polar bear.
"Eskimo hunters are falling through the
arctic ice as a result of global climate change."
--Rosemarie Kuptana, chair of the Inuit Circumpolar Conference
Extreme Weather
"Everyone talks about the weather but no one does
anything about it," claims the old joke. Now we are doing something
about it: we are making it worse. A warmer atmosphere means the evaporation
of more water from the oceans, leading to greater precipitation. It also
means the exchange of more energy, leading to greater atmospheric violence.
According to the National Climatic Data Center, weather
extremes are becoming more and more frequent: hurricanes, tornadoes, blizzards,
flooding, droughts. So far this century, extreme weather events have increased
by 20 percent. Annual precipitation is up 6 percent since 1900, and total
winter precipitation is up 8 percent. What used to be "100-year"
events are now commonplace. "I talked with one mayor who said his
community had had six hundred-year floods in the last ten years,"
reported Vice President Al Gore, after his visit to flood-stricken North
Dakota in April.
North Dakotans should keep their sandbags ready. Rather
than the light rains and gentle snowfalls of the past, future precipitation
is increasingly likely to come in the form of deluges or blizzards, both
of which are more likely to lead to floods. Last winter, a couple of major
blizzards buried California's Sierra Nevada, but a New Year's warm spell
melted much of it, resulting in massive flooding in the Central Valley,
causing 36 deaths and billions of dollars in damage. Despite such extreme
storms, the overall snowpack is expected to be much reduced in the future,
leading to summer droughts.
Warmer ocean temperatures in the Atlantic might also spawn
more frequent and intense hurricanes. While these storms have always varied
widely, hurricanes in the past two years have been as strong as or stronger
than any this century. A Japanese government study predicts a 60 percent
increase in the number of hurricanes hitting the eastern United States.
Hotter seas might also result in widespread flooding of
coastal areas, not to mention the complete inundation of low-lying island
nations like the Maldives in the Indian Ocean. One reason is simply that
the warmer the water, the greater its volume. In addition, large amounts
of the world's moisture currently trapped as ice are melting. The world's
glaciers have shrunk 11 percent in the past century (those in the Alps
by 50 percent); in the next, according to the IPCC, one-third to one-half
of all mountain glacier mass could disappear.
Another major contributor to ocean mass could be the antarctic
ice shelves, which are deteriorating at a rapid rate; two huge chunks,
each the size of Rhode Island, have fallen off in the past two years. The
mean temperature in Antarctica has risen by 2 degrees since 1950, and the
enormous Larsen B ice shelf is riven with cracks, leading some scientists
to predict its demise within two years.
The IPCC predicts that sea level will rise by as much
as three feet by the end of the next century. At that rate, most East Coast
beaches would vanish within 25 years (they are already disappearing at
a rate of two to three feet per year). The Everglades and Atchafalaya swamps
would be totally under water. Storm surges and hurricanes would subject
areas far inland to catastrophic flooding, including much of southern Florida,
New Orleans, and the San Francisco Bay Area. Chesapeake Bay and the Sacramento
Delta would be inundated by saltwater, drastically changing their roles
as marine-life nurseries. Huge dikes would have to be constructed to protect
low-lying metropolitan areas--at a cost, based on Dutch experience, of
$1 billion per mile.
Like the vision shown to Ebenezer Scrooge by the ghost
of Christmas Yet to Come, this nightmare need not come to pass. Given current
CO2 levels, some warming is bound
to occur, but the worst can still be prevented. Humankind has demonstrated
the awesome power to heat the entire globe; now we must demonstrate the
wisdom to turn the thermostat down.
"Climate is an angry beast, and we are poking
it with sticks."
--Wallace Broecker, Lamont-Doherty Earth Observatory
