NEW YORK, Feb. 10 (UPI) -- National Aeronautics and Space Administration scientists say 2004 was the fourth warmest year on average since the late 1800s.
To determine if the Earth is warming or cooling, scientists look at average high and low temperatures on land and on surfaces of the oceans and calculate the Earth's readings for an entire year.
Globally, 1998 has proven to be the warmest year on record, followed by 2002, 2003 and 2004.
NASA spokesman James Hansen said the 2004 average temperature at Earth's surface around the world was 0.48 degrees Celsius or 0.86 Fahrenheit above the average temperature from 1951 to 1980.
Compared to the average temperatures from 1951 to 1980, the largest unusually warm areas over all of 2004 were in Alaska, near the Caspian Sea, and over the Antarctic Peninsula. Compared to the previous five years, the United States as a whole was quite cool, particularly during the summer.