source: Roy Spencer, Ph.D
Over at Reason magazine, Ron Bailey reprints the UAH team's notes on the data:
The end of November 2011 completes 33 years of satellite-based global temperature data, according to John Christy, a professor of atmospheric science and director of the Earth System Science Center (ESSC) at The University of Alabama in Huntsville. Globally averaged, Earth’s atmosphere has warmed about 0.45 Celsius (about 0.82° F) during the almost one-third of a century that sensors aboard NOAA and NASA satellites have measured the temperature of oxygen molecules in the air.Agreed, though see the later back-and-forth between the WaPo's Andrew Freedman and John Christy's and Roy Spencer's reply.
This is at the lower end of computer model projections of how much the atmosphere should have warmed due to the effects of extra greenhouse gases since the first Microwave Sounding Unit (MSU) went into service in Earth orbit in late November 1978, according to satellite data processed and archived at UAHuntsville’s ESSC.
"While 0.45 degrees C of warming is noticeable in climate terms, it isn’t obvious that it represents an impending disaster," said Christy. "The climate models produce some aspects of the weather reasonably well, but they have yet to demonstrate an ability to confidently predict climate change in upper air temperatures."
The atmosphere has warmed over most of the Earth’s surface during the satellite era. Only portions of the Antarctic, two areas off the southwestern coast of South America, and a small region south of Hawaii have cooled. On average, the South Pole region has cooled by about 0.05 C per decade, or 0.16 C (0.30° F) in 33 years. The globe’s fastest cooling region is in the central Antarctic south of MacKenzie Bay and the Amery Ice Shelf. Temperatures in that region have cooled by an annual average of about 2.36 C (4.25° F).
The warming trend generally increases as you go north. The Southern Hemisphere warmed 0.26 C (0.46° F) in 33 years while the Northern Hemisphere (including the continental U.S.) warmed by an average of 0.65 C (1.17° F).
The greatest warming has been in the Arctic. Temperatures in the atmosphere above the Arctic Ocean warmed by an average of 1.75 C (3.15° F) in 33 years. The fastest warming spot is in the Davis Strait, between the easternmost point on Baffin Island and Greenland. Temperatures there have warmed 2.89 C (about 5.2° F).
While Earth’s climate has warmed in the last 33 years, the climb has been irregular. There was little or no warming for the first 19 years of satellite data. Clear net warming did not occur until the El Niño Pacific Ocean "warming event of the century" in late 1997. Since that upward jump, there has been little or no additional warming.
"Part of the upward trend is due to low temperatures early in the satellite record caused by a pair of major volcanic eruptions," Christy said. "Because those eruptions pull temperatures down in the first part of the record, they tilt the trend upward later in the record."
Christy and other UAHuntsville scientists have calculated the cooling effect caused by the eruptions of Mexico’s El Chichon volcano in 1982 and the Mt. Pinatubo volcano in the Philippines in 1991. When that cooling is subtracted, the long-term warming effect is reduced to 0.09 C (0.16° F) per decade, well below computer model estimates of how much global warming should have occurred.