Signs of a warming world

Global warming: no day at the beach

November 27, 1997

(CNN) -- Anyone who thinks the most notable effect of rising global temperatures would be the advent of soft spring breezes from Siberia to the Tierra del Fuego is sorely mistaken, if scientists' models are to be believed.

The preponderance of scientific thought today sees the next 100 years as a time of traumatic environmental change. The United Nations Intergovernmental Panel on Climate Change (IPCC) projects a rise in average global temperature of about 1-3.5 degrees Celsius by the year 2100. Warming in this range is cause for concern, if not alarm.

Scientific modeling produced by some of the world's most advanced supercomputers has depicted a series of scenarios that might result from global warming. Here's a look at what some scientists say might happen:

Impact on land

The current boundaries of year-round farming are pushed farther to the north and south as temperatures moderate. But the lands today considered the bread baskets of the world are left with reduced crop yields.

Factoid

The U.N. World Health Organization reported in 1996 that malaria and dengue fever could reach epidemic levels and spread farther from the equator as a result of a warmer climate. Source: Union of Concerned Scientists

That's because moisture in the soil evaporates at higher rates as the overall temperature rises, and soil moisture is a key to plant growth. So more rain should be falling somewhere, but it's unlikely to make up for the lost moisture in what had been the planet's most fertile fields.

The deserts found in the mid-latitudes are also expected to expand, even as regions of arable land move north and south. The growth of desert areas can already be observed in North Africa's voracious Sahara.

Range of arable land expands south and north Soil drier due to higher evaporation rates Increased CO2 aids some plant growth Habitats for some animals shrink Range of insects likely to expand

Impact on water

Rising waters, the result of melting polar ice caps and water expansion from increasing warmth, are the most widely anticipated consequence of a warming world. The U.N.'s IPCC projects that the world's oceans will rise anywhere from 15 to 95 centimeters by the year 2100.

Factoid

The Reinsurance Assocation of America, the trade group for the companies which insure insurance companies, have urged strong action on global warming. The five costliest years for U.S. insurance payouts for floods and storms have happened in the 1990s. Source: Union of Concerned Scientists

This may not sound like much, but figures at the high end of that scale would rob a low-lying nation like Bangladesh of over 20 percent of its arable land. And it could put the city of New Orleans underwater. At the low end of the scale, rising waters would increase coastal erosion and heighten the damaging effects of hurricanes and other coastal storms.

Encroaching salt water has the potential to contaminate the water supplies that coastal cities and farms depend on. The rising ocean finds it easier to make its way inland as the level of coastal rivers and streams drop with the drying of the soil. Aside from the outright loss of land to the ocean, the threat of contaminated water supplies is perhaps the most serious problem posed by rising sea levels.

Sea level rises due to melting ice caps, warming water High water eats away at, or submerges, coastal land Sea water contaminates some drinking water supplies Water levels drop in some rivers, streams

Impact on air

What will happen to the atmosphere itself during global warming is unclear. Cloud cover should increase with the higher rates of evaporation, but scientists are unsure where the moisture will go.

Clouds closer to the earth's surface reflect sunlight, producing an overall cooling effect. Clouds higher up in the atmosphere, however, have the effect of trapping heat and warming the planet. Where the extra moisture in the atmosphere ends up -- high or low -- could determine how much of an impact of global warming has on the environment.

Cloud cover increases Levels of the greenhouse gas methane may increase Hurricanes range farther north, south on warmer water

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