According to an article from the Associated Press, we are in the warmest decade (2000-2009).
The last few decades are the warmest period in at least 400 years and probably 1,000 years, based on evidence from tree rings, retreating glaciers and other scientific methods to track climate before record-keeping, according to a 2006 report by the U.S. National Academy of Sciences.
Although temperatures have fluctuated, the causes were natural. The difference now is that they are being driven up by human activity, that modern civilization has many more coastal cities and needs to feed far more people, and that scientists believe humans can head off such dangerous warming.
Many parts of the world are already feeling the effects of global warming. Melting polar ice caps are causing sea levels to rise in some places, as result people in many countries losing their homes and businesses close to the coastline. Since what one country does affects the whole world, developing countries are paying for the waste and huge carbon emissions that other countries have released into the air.
Although we are seeing the warmer decades, that does not mean that all is over. We can work to reduce our carbon emissions. Most people and cities are trying to go green and hopefully going green continues to be cool and be just what we need to slow down global warming.