Earlier, a report issued by the Earth Policy Institute, had stated that 2007 was the second warmest year on record since 1880, with a global average of 14.73 degrees Celsius. Now, the record for the warmest year would be shared with the year 1998. For confirming the new record, Goddard Institute researchers used temperature data from weather stations on land, satellite measurements of sea ice temperature since 1982 and data from ships for earlier years.
This also established the fact that the eight warmest years in the GISS record have all occurred since 1998, and the 14 warmest years in the record have all occurred since 1990.
As for warming trends in 2007, the greatest level of warming occurred in the Arctic and neighboring high latitude regions.
Global warming has a larger affect in polar areas, as the loss of snow and ice leads to more open water, which absorbs more sunlight and warmth. Snow and ice reflect sunlight; when they disappear, so too does their ability to deflect warming rays.
The large Arctic warm anomaly of 2007 is consistent with observations of record low geographic extent of Arctic sea ice in September 2007.
"As we predicted last year, 2007 was warmer than 2006, continuing the strong warming trend of the past 30 years that has been confidently attributed to the effect of increasing human-made greenhouse gases," said James Hansen, director of NASA GISS.
Although 2007 did not post a new record high, the year stands out as being extremely warm despite several factors that usually cool the planet.