ABC News' Clayton Sandell reports:
Scientists at NASA's Goddard Institute for Space Studies tell ABC News that 2007 is on track to be the second-warmest year globally since measurements have been taken in the late 1800s. (2005 holds the current record for warmest global temperature.) NASA says this means the six warmest years on record have all occurred since 1998, and the 15 warmest years have all occurred since 1988.
The analysis by NASA climate scientists James Hansen, Reto Ruedy, Makiko Sato and Ken Lo says that 2007 "continues the strong warming trend of the past 30 years that has been confidently attributed to the effect of increasing human-made greenhouse gases."
The greatest warming anomalies in 2007 have been in the Arctic, which has reached 6.84 degrees Fahrenheit in some areas. The scientists say this "is consistent with observations of record-low Arctic sea ice cover in September this year."
Scientists point out the warming occurred in spite of the fact that several known natural cycles are currently in their "cool" phase -- solar radiation is now at a minimum, and equatorial Pacific waters are cooler than normal thanks to La Nina conditions.
A final analysis on 2007 will come in mid-January when the December numbers are in. (And if December is unusually cold, 2007 might slip to third place, says NASA.)