Definition of Global Warming

Simply put, Global warming is the observed and projected increases in the average temperature of Earth's atmosphere and oceans. The Earth's average temperature rose about 0.6° Celsius (1.1° Fahrenheit) in the 20th century. Scientists believe that by the year 2100, the average temperature will have grown by 1.4 to 5.8 degrees Celsius (2.5 degrees F. to 10.5 degrees F.).

TEMPERATURE CHANGES - PAST 100 YEARS 

Avg. Temperature increase during the past 100 years. (Global Temp. in °C)

The black line is the annual global mean. The red line is the 10-year running mean. The grey area is the 95% confidence interval of the same data, calculated for the 50 years up to and including each year's measurement. The diagram illustrates several aspects of global warming, the most obvious of which is the increase in mean temperature. However, also the confidence interval has increased both in value (i.e., warmer climate) and in width (i.e., more variable temperature).

TEMPERATURE CHANGES - PAST 1000 YEARS 

Avg. Temperature increase during the past 1000 years. (Global Temp. in °C)

 The black line is the smoothed global mean. The grey area is the smoothed 95% confidence interval of the estimates. The blue line is the regression line for the period 1000–1899. The red line is the regression line for the period 1900–2004.The diagram illustrates several aspects of global warming. The rapid increase (as well as the earlier slow decrease) is statistically highly significant. One can also see that the 1990s most probably have been the last millenium's warmest decade.