With more greenhouse gases trapping heat, average annual global temperatures are rising. This is known as global warming. While temperatures have risen since the end of the Pleistocene, 10,000 years ago, this rate of increase has been more rapid in the past century, and has risen even faster since 1990. The nine warmest years on record have all occurred since 1998, and the 10 of the 11 warmest years have occurred since 2001 (through 2012). The 2000s were the warmest decade yet. Annual variations aside, the average global temperature increased about 0.8 degrees C (1.5 degrees F) between 1880 and 2010, according to the Goddard Institute for Space Studies, NOAA.

The amount CO2 levels will rise in the next decades is unknown. What will this number depend on in the developed nations? What will it depend on in the developing nations? In the developed nations it will depend on technological advances or lifestyle changes that decrease emissions. In the developing nations, it will depend on how much their lifestyles improve and how these improvements are made. Computer models are used to predict the effects of greenhouse gas increases on climate for the planet as a whole and also for specific regions.

Whatever the temperature increase, it will not be uniform around the globe. A rise of 2.8 degrees C (5 degrees F) would result in 0.6 degrees to 1.2 degrees C (1 degree to 2 degrees F) at the equator, but up to 6.7 degrees C (12 degrees F) at the poles. So far, global warming has affected the North Pole more than the South Pole, but temperatures are still increasing at Antarctica.

The timing of events for species is changing. Mating and migrations take place earlier in the spring months. Species that can are moving their ranges uphill. Some regions that were already marginal for agriculture are no longer farmable because they have become too warm or dry.