Global Warming will perhaps be, in theory, one of the greatest threats to test the capabilities of mankind. Its effects are predicted to be catastrophic: dramatic climate changes, leading to the melting of the polar ice caps and great rises in sea level. This could flood islands and cause major life loss. Diseases are likely to spread more easily due to rises in temperature. Natural systems such as forests and oceans will be affected. Agriculture will be affected, both positively and negatively. .
So what is Global Warming? According to the Oxford Dictionary Global Warming is the "increase in the temperature of the earth's atmosphere caused by the greenhouse effect." Although the concept of global warming had been lightly touched upon during the late 19th Century, only in recent decades has its significance been realized. .
Some parts of the world will probably warm more than others. The warming of 2 to 5 degrees Celsius that scientists predict will occur by the middle of the next century is an increase in the average global temperature. Almost all climate models predict that warming will be greater at higher latitudes (nearer the poles) than at the equator. In fact, the warming that will occur at the North and South poles may be at least twice the global average. .
We can expect patterns of precipitation to change worldwide. On the whole, the total amount of precipitation that falls to the earth each year will probably increase due to global warming. The reason for this is that as air temperatures near the ground get warmer, more water will evaporate from the planet's surface. This evaporated water will eventually return to the earth as rain or snow. Although the total amount of precipitation will probably increase, many areas may become much drier by 2050. .
As climate changes, so will the seasons. On the average, winters will probably be shorter and milder, and summers will be longer and warmer.