This story has been updated.
In a powerful testament to the warming of the planet, two leading U.S. science agencies Wednesday jointly declared 2016 the hottest year on record, surpassing the previous record set just last year — which itself had topped a record set in 2014.
Average surface temperatures in 2016, according to the National Oceanic and Atmospheric Administration, were 0.07 degrees Fahrenheit warmer than 2015 and featured eight successive months (January through August) that were individually the warmest since the agency’s records began in 1880.
The average temperature across the world’s land and ocean surfaces was 58.69 Fahrenheit, or 1.69 degrees above the 20th-century average of 57 degrees, NOAA declared. The agency also noted that the record for the global temperature has now successively been broken five times since the year 2000. The years 2005 and 2010 were also record warm years, according to the agency’s data set.
NASA concurred with NOAA, also declaring 2016 the warmest year on record in its own data set that tracks the temperatures at the surface of the planet’s land and oceans, and expressing “greater than 95 percent certainty” in that conclusion. (In contrast, NOAA gave a 62 percent confidence in the broken record.)
NASA found a bigger leap upward of temperatures in 2016, measuring the year as .22 degrees Fahrenheit higher than the prior record year of 2015. The agency also noted that since the year 2001, the planet has seen “16 of the 17 warmest years on record.”
Last year “is remarkably the third record year in a row in this series,” said Gavin Schmidt, who directs NASA’s Goddard Institute of Space Studies, in a statement. “We don’t expect record years every year, but the ongoing long-term warming trend is clear.”
The record comes two days before Donald Trump, who has tweeted that global warming is a “hoax,” assumes the presidency and, with it, control over the two science agencies that announced these records. It is also the same day that Scott Pruitt, Trump’s controversial nominee for the Environmental Protection Agency, is appearing before the Senate in an often-tense confirmation hearing in which he has been questioned about climate change. Pruitt has previously written that the “debate” over climate change is “far from settled.”
Trump’s other nominees, such as State Department nominee Rex Tillerson and Interior Department nominee Ryan Zinke, have been less dismissive of climate change in their confirmation hearings, acknowledging at least some human contribution to the phenomenon but also raising questions either about the extent to which it is human-caused or about our capacity to predict the consequences. On Wednesday, Pruitt acknowledged that climate change is not a “hoax” and said that “the climate is changing, and human activity contributes to that in some manner.”
Scientists have been far less guarded. “2016 is a wake-up call in many ways,” Jonathan Overpeck, a climate scientist at the University of Arizona, said of the year’s temperatures. “Climate change is real, it is caused by humans, and it is serious.”
NASA and NOAA produce slightly different records using somewhat different methodologies, but have now concurred on identifying 2014, 2015 and 2016 as, successively, the three warmest years in their records. There was a noticeable difference this year, however, in how much two agencies judged 2016 to have surpassed 2015. NASA was more bullish — a difference that Schmidt, in a press call Wednesday, attributed to different ways of measuring the Arctic.
“The warming in the Arctic has really been exceptional, and what you decide to do when you’re interpolating across the Arctic makes a difference,” Schmidt said.
But the differences between NOAA and NASA aren’t that significant, Schmidt further argued, in the context of the bigger picture. “Getting hung up on the exact nature of the records is interesting, and there’s lots of technical work that can be done there, but the main take-home response there is that the trends we’ve been seeing since the 1970s are continuing and have not paused in any way,” he said.
Here’s a NASA figure showing that long term trend, now updated through 2016:
Last year’s warmth was partly enhanced by a strong weather pattern known as El Niño, but the federal scientists underscore that this was not the only cause. For example, 1998 was also, at the time, the warmest year on record, thanks in part to a strong El Niño — but the 2016 planetary temperature now far surpasses the temperature of that year, as you can see above. The reason is that Earth has been warming since then, allowing another El Niño event, unlocking heat from the vast Pacific Ocean, to push overall temperatures to new heights.
“This El Niño might have contributed about a quarter or a third” of the record in 2016, said Deke Arndt, chief of the global monitoring branch at NOAA’s National Centers for Environmental Information, on a press call Wednesday.
Thus do natural wobbles of the planet’s temperature interact with an overall warming trend to produce records on a regular basis. At present, that means that while scientists would expect 2017 to be quite warm, relative to, say, a year in the 1990s, there has been little talk of a fourth record year in a row. And, indeed, El Niño has subsided.
Two other global agencies, the Japan Meteorological Agency and Britain’s Hadley Center, also track global temperatures. On Wednesday, the Hadley Center also announced that 2016 was the warmest year on record, albeit only “nominally” because it was very close to 2015 in the agency’s data set. The center reported that while 2016 was .77 degrees Celsius above the temperature average between 1961 and 1990, 2015 was very close at .76 degrees Celsius higher.
The difference between the Hadley Center and NASA once again comes down to the treatment of the Arctic, Schmidt explained.
“Our analysis demonstrates that the Arctic is warming around two to three times as fast as the global mean,” he said. “So that will be the cause of continuing divergences between the groups, and it ‘s something I think we all need to be thinking about.”
NASA further noted in its analysis that compared with the late 19th century, the planet has now warmed about 1.1 degrees Celsius, or 2 degrees Fahrenheit. That’s significant because the global community has been striving to limit overall warming to considerably below a 2 degree Celsius rise, and even, if possible, to hold it to a 1.5 degree Celsius increase. That is now about .4 degrees away, in Celsius, based on these figures.
“It is the second year in a row that the annual global temperature has been more than 1 Celsius degree higher than the pre-industrial level, and shows that the world is moving ever closer to the warming threshold of 1.5 Celsius degrees, beyond which many scientists have concluded the impacts of climate change will be unacceptably dangerous,” said Bob Ward, who is director of policy and communications director at the Grantham Research Institute on Climate Change and the Environment, part of the London School of Economics and Political Science.
Last year’s warmth was manifested across the planet, from the warm tropical ocean waters off the coast of northeastern Australia, where the Great Barrier Reef experienced its worst coral bleaching event on record and large scale coral death, to the Arctic, where sea ice hit regular monthly record lows and overall temperatures were also the warmest on record, at least from January through September 2016.
Among major 2016 events, the devastating bleaching of the Great Barrier Reef did not stand alone. In a catalogue of some of the extremes the planet witnessed during the year, NOAA also noted the megafire that engulfed Fort McMurray, in Alberta, Canada, at the beginning of May, relatively early in the year for wildfires. That event was certainly consistent with a warming climate, as well as with the role of El Niño, although scientists are reluctant to formally say that climate change has played a role in an individual event without conducting extensive analysis.
Extreme high temperatures were seen from India — where the city of Phalodi recorded temperatures of 51 degrees Celsius (123.8 Fahrenheit) in May, a new national record — to Iran, where a temperature of 53 degrees Celsius (127.4 F) was recorded in Delhoran on July 22.
For the contiguous United States, 2o16 was merely the second-warmest year on record, but for Alaska, it was the warmest yet recorded, underscoring once again the sharpness of Arctic warmth, in particular.
The particular signature of warming in 2016 was also revealing in another way, Overpeck said, noting that the stratosphere, the layer of the planet’s atmosphere stretching from about 8.5 to 13.5 miles above us, saw record cold temperatures last year.
“The pattern of record warmth in the lower atmosphere, coupled with record cold in the stratosphere, provides a clear fingerprint of the cause of the unprecedented warming — greenhouse gases trapping heat in the lower atmosphere instead of letting it escape to the stratosphere, and then to space. No doubt about it anymore — humans, mainly by burning fossil fuels, are cooking the planet,” Overpeck said.
All of that said, because of the extreme warmth that occurred early in 2016, the record just announced does not come as much of a surprise to weather and climate watchers. On April 15, NASA’s Schmidt tweeted: “Too soon? I estimate >99% chance of an annual record in 2016 in @NASAGISS temperature data, based on Jan-Mar alone.”
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