http://video.nationalgeographic.com/video/101-videos/global-warming-101
the earths climate has evolved over many years from extreme cold to extreme heat, but in the last century the climates temperature has risen about 1.2 to 1.4 degrees farenheit. its believed that human activity has been the main reason of this occurrence. ever once the industrial revolution factories and cars have greatly increased the use of fossil fuels oil and coal releasing massive amounts of carbon dioxide into the atmosphere. these "greenhouse gases" become trapped in the eath and heats up the temp of the earth. the green house effect has been being intensified by the use of more green house gases. arctic sea ice has been decreasing due to the excess trapped heat. weather patterns could change and cause worse hurricanes and tsunamis as well as worse droughts in the future.
