Despite a winter-long coming-out party for the polar vortex and the record snows around here, for the planet 2014 was the warmest in 135 years of record-keeping, U.S. climatologists said Friday.
Averaged for the entire year, temperatures were 1.24 degrees Fahrenheit above the 20th century average of about 57, according to the National Climatic Data Center, nudging out 2005 and 2010 by a mere 0.07 degrees.
At a joint morning briefing, NASA also said that 2014 was the warmest on its database, although its method of calculation is slightly different. As other scientists have been saying, NASA's Gavin Schmidt said greenhouse gases have been stoking the heat engine, even if the rate of warming has slowed a bit.
Computing Earth's annual temperature is a bit more complicated, say, than sticking a thermometer into random points in the globe. It requires analyzing data from hundreds of thousands of stations at varying locations, correcting for biases and more sparsely observed regions of the planet, and then averaging the numbers for an entire year.
The margin of error for the 2014 NCDC temperature was 0.16 degrees, but center director Thomas R. Karl said it was highly likely that it was warmer than either 2005 or 2010.
The NASA and NCDC temperature figures have been in line with those of other global databases. The Japanese already had declared 2014 to be the warmest.
While "the attribution of these long-term trends is a complicated fingerprinting exercise," said Schmidt, deputy director of NASA's Goddard Institute for Space Studies in New York, greenhouse gases appear to be the leading cause.
A paper published this week in the journal Science said that human activity also is having an effect on the oceans and "already powerfully changed virtually all major marine ecosystems."
While "meaningful rehabilitation" still was possible, the paper said, warming would worsen the problems and possibly lead to significant marine-life extinctions. NCDC said Friday that ocean temperatures last year were the warmest on record.
While the rate of global warming has slowed somewhat since 1998, climatologists said, temperatures have continued to creep upward.
The slowdown evidently is related to a decadal pattern in the Pacific Ocean, said Kevin E. Trenberth, scientist at the National Center for Atmospheric Research in Colorado. However, that pattern shows signs of reversing, and an uptick in warming might result.
The warming hasn't been at the same intensity everywhere, and Arctic temperatures have been rising faster than elsewhere. Melting has accelerated temperature rises there because snow and ice repel solar energy.
Recent warming in Philadelphia evidently has been a bit more robust than in the rest of the world. Officially, Philadelphia's average temperature since 2001 has been about two degrees above the 20th century average; the world's has been just over a degree in the same period. Philadelphia's "normal" January daily high now is 40, up from 38 in the 1990s.
The year was only the 34th warmest in the contiguous United States, NCDC said. Karl noted that parts of North America, with an assist from the polar vortex that emerged from eons of obscurity last winter, finished the year below normal.
However, that was overpowered by warming elsewhere.
Historically, worldwide temperatures have changed ponderously from year to year, never more than 0.47 degrees Fahrenheit in either direction.
Assuming that trend continues, in all likelihood 2015 also would finish among the warmest on record.