Propelled in part by extreme heat in North America, last year was one of the globe’s 10 warmest on record, according to numbers released Tuesday by NASA and the National Oceanic and Atmospheric Administration.
The earth-space agency ranked the year ninth warmest, while the climate-weather administration pegged it at No. 10, with the difference being that NASA folded in temperatures at the poles while NOAA didn’t.
Global warming is making its most obvious mark at the earth’s poles, and because NASA factors in that warming, its 2012 ranking edged up a notch.
James Hansen, director at NASA’s Goddard Institute for Space Studies and Tom Karl, director, NOAA’s National Climatic Data Center, discussed the 2012 climate analysis in a national teleconference.
With the bull’s-eye of the Earth’s abnormal heat centered over North America last year, the United States saw its warmest year on record. Nebraska was among 19 of 48 states that saw their warmest years.
As a consequence, North America caught up with the rest of the world’s recent history of extreme heat, Karl said.
“Eventually your turn comes around,” Karl said. “Now our trends are pretty much reflective of a fairly rapid increase in temperatures in other parts of the globe.”
Every year since 1976 has been warmer than the 20th century average, according to Karl.
In terms of decades, each decade has been warmer than the previous since the mid-1970s, Hansen said.
Hansen said the warmup has slowed this decade, probably because of a weaker solar cycle and perhaps the cooling effect from aerosols in air pollution released by the world’s developing economies.
“We can predict with confidence that the next decade is going to be warmer than the last — this standstill is a temporary one,” Hansen said. That’s because the earth’s energy balance is out of whack, more heat is coming in from the sun than is being released back into space.
The warming of the Earth’s climate has “conclusively” been linked to the effect of increasing greenhouse gases, primarily carbon dioxide, Hansen said.