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.
The temperature analysis produced at GISS is compiled from weather data from more than 1,000 meteorological stations around the world, satellite observations of sea surface temperature and Antarctic research station measurements. A publicly available computer program is used to calculate the difference between surface temperature in a given month and the average temperature for the same place during 1951 to 1980. This three-decade period functions as a baseline for the analysis.
The resulting temperature record is very close to analyses by the Met Office Hadley Centre in the United Kingdom and the National Oceanic and Atmospheric Administration's National Climatic Data Center in Asheville, N.C.
Hansen said he expects record-breaking global average temperature in the next two to three years because solar activity is on the upswing and the next El Nio will increase tropical Pacific temperatures. The warmest years on record were 2005 and 2010, in a virtual tie.
"It's always dangerous to make predictions about El Nio, but it's safe to say we'll see one in the next three years," Hansen said. "It won't take a very strong El Nio to push temperatures above 2010."
|Contact: Leslie McCarthy|
NASA/Goddard Space Flight Center