NASA illustrates the global warming since 1880

The first 11 years of the 21st century experienced notably higher temperatures compared to the middle and late 20th century. The only year from the 20th century in the top 10 warmest years on record is 1998.
Higher temperatures today are largely sustained by increased atmospheric concentrations of greenhouse gases, especially carbon dioxide. These gases absorb infrared radiation emitted by Earth and release that energy into the atmosphere rather than allowing it to escape to space. As their atmospheric concentration has increased, the amount of energy "trapped" by these gases has led to higher temperatures.
The carbon dioxide level in the atmosphere was about 285 parts per million in 1880, when the GISS global temperature record begins. By 1960, the average concentration had risen to about 315 parts per million. Today it exceeds 390 parts per million and continues to rise at an accelerating pace.
Further information and an animation map about global temperatures since 1880 at:
http://www.giss.nasa.gov/research/news/20120119/