20 january 2016

The hottest year

2015 was hot.
2016 will likely be hotter.

by Andrew Freedman, Mashable, January 20, 2016

It wasn't even close.

In all of recorded history back to the mid-19th century, we haven’t seen a year warmer than 2015. Everywhere scientists looked, from Siberia to northern South America, to all of the world's major ocean basins, they found record to near-record warmth.

This was the announcement the National Oceanic and Atmospheric Administration (NOAA) and NASA jointly made on Wednesday, using their databases of global surface temperatures dating back to 1880. The warmest year news was also echoed by independent findings from the UK’s Hadley Center, which keeps its own global temperature records.

According to NASA, globally averaged surface temperatures in 2015 shattered the previous mark set in 2014 by 0.13 degrees Celsius, or 0.23 degrees Fahrenheit. "Only once before, in 1998, has the new record been greater than the old record by this much," NASA said in a press release.

Taking uncertainties regarding surface temperature data into account, NASA noted that its scientists have 94 percent certainty that 2015 was the warmest year.

“It was much much warmer than 2014, and 2014 itself was a record,” said Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies, in an interview with Mashable.

NASA's analyses incorporate surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. The space agency analyzes these raw measurements using an algorithm that takes into account the varied spacing of temperature stations around the world.

NOAA scientists use much of the same raw temperature data, but they look at a different baseline period and methods to analyze Earth’s polar regions and global temperatures.

NOAA found that the global average temperature was 0.90 degrees Celsius, or 1.62 degrees Fahrenheit, above the 20th century average. This ranks as the hottest year since 1880, as well as the largest margin by which a previous record has ever been exceeded — with the year coming in at 0.16 degrees Celsius, or 0.29 degrees Fahrenheit, above the previous record warm year, which occurred in 2014.

Image images//import_0aa43ff48484321b06ebca03917ed7b0_Warmest-Year-on-Record.jpg

In NOAA's data set, 10 out 12 months in the year set monthly global temperature records, and the five highest monthly temperature departures from average for any month all occurred during 2015 as well.

In a testament to how mild 2015 was, some of the records were milestones themselves. For example, according to NASA, the monthly average temperature records that were set in December, November and October were the top three largest monthly temperature departures from average ever recorded, NASA found.

In December 2015, the global average surface temperature was 1.12 degrees Celsius, or 2.012 degrees Fahrenheit, above the 1951-1980 average, dwarfing any other month in NASA's database stretching back to 1880. (Typically, monthly records are exceeded by a few tenths of a degree.)

Separate data from the Japan Meteorological Agency confirms the 2015 ranking. Each center tends to differ in its rankings and specific temperature anomalies, owing to its independent way of analyzing what are essentially similar data.

But this year the verdict was unanimous, which is unusual.

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