***In a warmer world, scientists predict that more people will get sick or die from heat stress, due less to hotter days than to warmer nights (giving the sufferers less relief). Diseases now found in the tropics, transmitted by mosquitoes and other animal hosts, will widen their range as these animal hosts move into regions formerly too cold for them. Today, 45% of the world's people live where a mosquito carrying the parasite that causes malaria might bite them; that percentage may increase to 60% if temperatures rise. ***

GLOBAL warming means increase in the average temperature of the atmosphere, oceans, and landmasses of the earth. The planet has warmed (and cooled) many times during the 4.65 billion years of its history’. At present, earth appears to be facing a rapid warming, which most scientists believe results, at least in part, from human activities.

The chief cause of this warming is thought to be the burning of fossil fuels, such as coal, oil, and natural gas, which releases carbon dioxide and other substances known as greenhouse gases into the atmosphere. As the atmosphere becomes richer in these gases, it becomes a better insulator, retaining more of the heat provided to the planet by the sun.

Scientists use elaborate computer models of temperature, precipitation patterns, and atmosphere circulation to study global warming. Based on these models, they have made several predictions about how global warming will affect weather, sea levels, coastlines, agriculture, wildlife.

and human health.

Weather

Some experts predict that an increase in global warming will result in unpredictable weather patterns, including storm surges in which the wind piles jp water in low-lying areas. The rurved arms of the New Waterway Storm Surge Barrier n the Netherlands protect Rotterdam and other inland rities from flooding during arge storms in the North Sea.

Normally, the large, curved irms are retracted to allow ships rom the North Sea to travel to jorts along the New Waterway. Alien a dangerous storm is antic-pated, the arms are swung out to jlock off the waterway and present large waves from pushing loodwaters inland

Scientists predict that during global warming, the northern egions of the Northern femisphere will heat up more han other areas of the planet, lorthern and mountain glaciers rill shrink, and less ice will float in northern oceans. Regions that low experience light winter nows may receive no snow at all.

In temperate mountains, nowlines will be higher and

mow-packs will melt earlier. Growing seasons will be longer in >ome areas. Winter and nighttime emperatures will tend to rise nore than summer and daytime ines.

The warmed world will be ’enerally more humid as a result if more water evaporating from he oceans. Scientists are not jure whether a more humid itmosphere will encourage or iiscourage further warming. On he one hand, water vapour is a greenhouse gas, and its ncreased presence should add o the insulating effect. On the ithcr hand, more vapour in the itmosphere will produce more :louds, which reflect sunlight lack into space, which should low the warming process (see Vater Cycle).

Greater humidity will ncrease rainfall, on average, ibout 1% for each Fahrenheit legree of warming. (Rainfall iver the continents has already increased by about 1% n the last 100 years.) Storms re expected to be more fre-|uent and more intense, iowever, water will also evaporate more rapidly from the oil, causing it to dry out faster

ictween rains.

Some regions might actually iccome drier than before. Winds rill blow harder and perhaps in lifferent patterns. Hurricanes, riuch gain their force from the vaporation of water, are likely to ie more severe. Against the back-;round of warming, some very old periods will still occur. Veather patterns are expected to ie less predictable and more Xtreme.

>ea levels

m increase in global warming rill likely result in a rise in sea

evcls, which could threaten nany coastal areas around the ,vorld. Experts predict that parts jf Bangladesh may become completely submerged if sea levels rise.

As the atmosphere warms, the surface layer of the ocean warms is well, expanding in volume ind thus raising sea level, banning will also melt much of :he glacier ice, especially around Greenland, further swelling the sea. Sea levels worldwide rose 10 to 25 cm (4 to 10 in) during the 20th century, and IPCC scientists

iredict a further rise of 9 to 88 m (4 to 35 in) in the 21st cen-ury.

Sea-level changes will compli-atc life in many coastal regions, i 100-cm (40-in) rise could sub-nerge 6% of the Netherlands, 7.5% of Bangladesh, and most or ill of many islands. Erosion of liffs, beaches, and dunes will ncrease. Storm surges, in which vinds locally pile up water and aise the sea, will become more requent and damaging. As the ea invades the mouths of rivers, looding from runoff will also

ncrease upstream.

Wealthier countries will spend inge amounts of money to pro-ect their shorelines, while poor ountries may simply evacuate pw-lying coastal regions.

Even a modest rise in sea level dll greatly change coastal cosystems. A 50-cm (20-in) ise will submerge about half of he present coastal wetlands of he United States. New marshes dll form in many places, but >ot where urban areas and levelopcd landscapes block the vay. This sea-level rise will :over much of the Florida Everglades.

Agriculture

l warmed globe will probably iroduce as much food as lefore, but not necessarily in he same places. Southern Canada, forexample, maybene-it from more rainfall and a onger growing season. At the ame time, the semiarid tropi-:al farmlands in some parts of Africa may become further mpoverished.

Desert farm regions that bring n irrigation water from distant nountains may suffer if the win-er snow-pack, which functions is a natural reservoir, melts lefore the peak growing months. 2rops and woodlands may also ie afflicted with more insects and plant diseases.

Animals and plants

Animals and plants will find it iifficult to escape from or adjust o the effects of warming because mmans occupy so much land. Jnder global warming, animals

rill tend to migrate toward the ides and up mountainsides oward higher elevations, and Hants will shift their ranges, eeking new areas as old habitats 'row too warm.

In many places, however, mman development will prevent his shift. Species that find cities >r farmlands blocking their way iorth or south may die out. Some ypes of forests, unable to propa-;ate toward the poles fast inough, may disappear.

Tuman health n a warmer world, scientists iredict that more people will get iick or die from heat stress, due ess to hotter days than to varmer nights (giving the sufferers less relief). Diseases now bund in the tropics, transmitted ly mosquitoes and other animal wsts, will widen their range as hese animal hosts move into egions formerly too cold for hem.

Today, 45% of the world's people live where a mosquito carrying the parasite that :auses malaria might bite them; hat percentage may increase to 50% if temperatures rise. Other ropical diseases may spread similarly, including dengue ever, yellow fever, and encephalitis. Scientists also predict rising incidence of allergies and espiratory diseases as warmer iir grows more charged with pollutants, mold spores, and lollens.

Zd Badsha Mia writes from the Dept of Environmental Science and Resource Management, Mawtana Bhashani Science and technology Unrversty. Santosh, Tangait