NASA names September hottest on record, just barely

Data from the NASA-run Goddard Institute for Space Studies indicates that this past September was the hottest on record, though by a slim margin that falls within the margin of error for the study. 2016 will almost certainly be the hottest year ever recorded, scientists say.

Courtesy of GISS/NASA
A map of the September 2016 LOTI (land-ocean temperature index) anomaly, showing that much of the warmer temperatures occurred in the northern hemisphere.

The latest data from NASA shows that this past September was the hottest on record, making 2016's ranking as the warmest year ever recorded all but inevitable.

The findings come from the Goddard Institute for Space Studies (GISS), a NASA-run laboratory with ties to Colombia University. The laboratory, which specializes in Earth sciences, has been gathering climate data for decades.

While September does seem to be the hottest on record, the margin over the previous September record in 2014 is admittedly slim, about 0.004 degrees Celsius, and falls within the margin of error for the study. As a result, NASA has emphasized that this is a statistical tie, rather than an outright record-breaker. Still, this September came after months of definitively record-breaking temperatures due to historic warming trends, with some help from El Niño weather patterns.

According to a statement released by NASA, 11 out of the 12 previous months have broken heat records. The agency previously reported that June had also been the warmest on record, but newer data from Antarctica drove the global average for that month down to third place.

"Monthly rankings are sensitive to updates in the record, and our latest update to mid-winter readings from the South Pole has changed the ranking for June," said GISS director Gavin Schmidt in the statement. "We continue to stress that while monthly rankings are newsworthy, they are not nearly as important as long-term trends."

That long-term trend, of course, is warming. Even with June turning out cooler than previously thought and September's merely-statistical tie, 2016 is likely to be the hottest ever, at least began keeping accurate global records 136 years ago.

While 2016's heat has certainly been bad news for the climate, this year also marks significant efforts to curb future warming. The UN-sponsored Paris Agreement reached the threshold for ratification earlier this month and will go into force on Nov. 4, marking a historic, global effort to reduce global emissions of greenhouse gases in the coming decades. On Saturday, 197 nations agreed to amend the Montréal Protocol to include a mandatory phase-out of the production of hydrofluorocarbons (HFCs), greenhouse gases with especially high heat-retention capabilities.

According to the NASA statement, the GISS data comes from publicly-available information from 6,300 weather stations around the globe. As more information comes in, it is possible September's status could change, but even if it loses its record status, the month will likely stay on the hot side, about 0.91 degrees Celsius hotter than the average September temperature from 1951-1980.

It is possible that 2016 may see the last of record-breaking temperatures for a little while, as El Niño, a global weather pattern driven by temperatures of currents in the Pacific, drove temperatures up for much of the past year. Scientists had predicted that a La Niña event would occur later this year to cool things down somewhat, but last month brought predictions of neutral conditions. More recent reports indicate that La Niña has become more likely since then, but it is still far from a sure bet.

"Given the background warming has been accelerating ,we will still see an increase in temperature but it won't be as rapid as what we're seeing in 2015 [due to El Niño]," Agus Santoso, senior research associate at the Climate Change Research Centre at Australia's University of New South Wales, told CNN in August. "Next year I would expect the rise to be subdued, but still rising."

Even if La Niña does manage to cool things off, it is important to remember that the overall trend in global temperatures is up, even if weather patterns provide the globe with a brief respite from record-breaking heat.

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