What difference does it make if temperature rise by a few degrees?

Researchers have developed various mathematical models to simulate the effect of greenhouse gases on the earth. The warming will not be uniform. It will be greater at higher latitudes than in equatorial regions, and it will produce significant changes in sea level, precipitation, and vegetation. The sea level is expected to rise 1 to 4 feet as a result of ice-cap and glacial melting and thermal expansion of the water. Most coastal marshes and swamps would be inundated by salt water; coasted erosion would increase. Water quality would decline as aquifers became polluted by salt. Such low-lying regions as the North American Gulf Coast, the Netherlands, the Nile Delta, Bangladesh, and much of Southeast Asia could lose substantial amounts of land. Many major ports might be flooded.

Warming of lakes and oceans would speed evaporation, causing more active convection currents in the atmosphere and thus fiercer storms. Important regional changes in precipitation would occur, with some areas receiving more precipitation, others less. Polar and equatorial regions might get heavier rainfall, and the mid-latitudes become drier.

Changes in temperature and precipitation would affect soild and vegetation. The composition of forests would change as some areas became less favorable for certain species of plants and more hospitable to others. Hotter, drier weather would reduce crop yields in some areas, such as the corn and wheat belts of the Midwest. Conversely, more northerly agricultural regions, such as parts pf Canada and the USSR, might become more productive.