2005 is warmest year on record for Northern Hemisphere, scientists say
by: Patrick O'Driscoll 16 December 2005
The Earth's average temperature reached a near-record high in 2005, international and U.S. climate agencies reported Thursday.
While some scientists said it indicates that human-caused global warming is growing worse, others said it is more likely natural climatic change that is not connected to human activity.
The World Meteorological Organization and the National Climatic Data Center said the global average of 58.1°F is the second highest ever recorded, one-tenth of a degree behind 58.2°F in 1998. The years from 1997 to the present rank as the nine hottest since record-keeping began in 1861.
The agencies said 2005 also was the warmest on record for the Northern Hemisphere, where Arctic sea ice has shrunk to record low amounts and major glaciers are retreating several miles a year. In some northern latitudes this year, average temperatures were 5°F above normal, said Jay Lawrimore, the U.S. center's chief of climate monitoring.
Lawrimore said there is concern that the loss of sea ice and snow cover in the north also will reduce the region's ability to deflect solar radiation, which could raise temperatures more.
This year's average U.S. reading of 53.8°F is the 20th highest on record, roughly one degree from the high of 54.9°F in 1998. Lawrimore said the year might have ranked No. 10 if not for the unusual cold this month.
Some scientists said the world temperature reading is more evidence that global warming, heating of the atmosphere aggravated by the burning of fossil fuels, is growing worse. "Could these changes arise from natural climate fluctuations alone? The answer is no," said physicist Ben Santer of Lawrence Livermore National Laboratory.
That belief isn't universally held. "I don't know how Ben Santer can say what he said," said Richard Lindzen, professor of atmospheric sciences at the Massachusetts Institute of Technology.
Lindzen said normal weather cycles may account for this year's average temperature. "Natural, normal fluctuations can be this big," he said. "It fluctuates tenths of a degree from year to year."
The record global high in 1998 was influenced by a major El Niño, the periodic warming of the Pacific Ocean near the equator that affects weather globally. This year was almost as warm even without El Niño.
"The trend has been sharp enough that ... we're already back up to the temperatures we experienced during that remarkable (El Niño) period," Lawrimore said.
The global average is based on readings from more than 7,200 ground weather stations around the world and from ships at sea.
The climate center's analysis also showed 2005 was much warmer than average in 22 states and warmer than normal in 23 others. No state was cooler than average. This summer was the second hottest for the Northeast, where New Jersey and New Hampshire set summer highs. The July heat wave broke more than 200 daily records in six Western states.