(c) The average increase in the earth’s temperature during the last century is 0.8 degree Celsius.According to an ongoing temperature analysis conducted by scientists at NASA’s Goddard Institute for Space Studies (GISS), the average global temperature on the earth has increased by about 0.8 degree Celsius (1.4 degree Fahrenheit)since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20 degree Celsius per decade.