"It's fair to say that it probably is the warmest since we have modern meteorological records," said Drew Shindell of the NASA institute in New York City. "Using indirect measurements that go back farther, I think it's even fair to say that it's the warmest in the last several thousand years."
1998 was an unusually warm year due to a record El Nino. 2005 was even warmer without an El Nino, indicating that warmer temperatures are becoming the norm--not the anomaly.
This is one in the series of "Decade in Review" posts on this blog that began in January 2010. These posts present climate-change-related events that occurred during the 00's, the warmest decade in recorded history.