2015 was hot.
2016 will likely be hotter.

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.

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. 



Road markings appear distorted as the asphalt starts to melt due to the high temperature in New Delhi, India on May 27, 2015.


This is manmade warming

There’s virtually no scientific doubt about why last year was so mild.

A record-strong El Niño event in the Pacific Ocean may have helped a bit, but the majority of the warmth this year was caused by manmade emissions of greenhouse gases, like carbon dioxide and methane, from the burning of fossil fuels.

“Generally speaking you have a warm year in the year following an El Niño,” Schmidt said in an interview in his office on the Upper West Side of Manhattan. The Goddard Institute, known by its acronym, GISS, is a small NASA laboratory that sits incongruously above the famed deli whose exterior was a fixture on the TV series Seinfeld.

Schmidt cited 1998 as an example of a year that started out with an El Niño and wound up being a record warm year. The same thing happened in 2005 and 2010, which are both in NASA’s current list of the top 10 warmest years, he said.

But 2015 is different...

Director of NASA's Goddard Institute for Space Studies, Gavin Schmidt, sat down with Mashable to explain the official analyses from NASA and other agencies of 2015 global temperature and climate conditions.

“What we have here is something else. The El Niño that we’re seeing is starting at the end of 2015, and so there hasn’t been enough time for that to really have an impact on the annual mean temperatures,” Schmidt said.

“So 2015 was warm even though there was an El Niño, and it would’ve been a record year even if you abstract out the El Niño affect, 2015 would’ve been a record warm year by a long chalk,” Schmidt said, using a British term meaning “by far.” 

A before-and-after image of coral bleaching in American Samoa. The first image was taken in December 2014. The second was taken in February 2015.


The lag effect that El Niño has on the atmosphere means that 2016 is also likely to set another warmest year record, or come close to it, Schmidt said.

“We expect 2016 to be if not the warmest then one of the top five as well,” he said.

Katharine Hayhoe, a climate scientist at Texas Tech University in Lubbock, Texas, said we have now entered a period in Earth's history when, thanks to ever growing amounts of greenhouse gases in the atmosphere, breaking warm temperature records have become the norm. In 2015, the amount of carbon dioxide in the atmosphere routinely eclipsed 400 parts per million for the first time.

She cited a new study showing that twice as much heat is now in the world’s oceans since the last big El Niño in 1997-98, largely because of manmade emissions of greenhouse gases. 

According to an Associated Press report about the study, since 1997, the Earth's oceans have absorbed enough manmade heat energy to be the equivalent to a Hiroshima-style bomb being exploded every second for 75 straight years.




Studies of pre-1880 temperatures, using ice cores, tree rings and other sources, have shown that 2015 was very likely the warmest year for at least the past 4,000 years.

According to NASA, the month of December was particularly extraordinary, with the highest departure from average of any month on record. The temperature anomaly for the month was 1.12 degrees Celsius, or 2.01 degrees Fahrenheit. This beat out October and November for the top spot on the most unusually mild month list.

The warmest year record adds yet another rung to the extraordinary string of warm years seen since the year 2000. Nine of the 10 warmest years on record have occurred since the year 2000, with 15 of the 16 hottest years on record globally all occurring since 2001, based on NASA data.

The planet’s average surface temperature has risen about 1 degree Celsius, or 1.8 degrees Fahrenheit, since the late-19th century. Most of this warming has occurred in the past 35 years.


Skiers slalom through patches of dry ground at Squaw Valley Ski Resort, March 21, 2015 in Olympic Valley, Calif. MAX WHITTAKER/GETTY

The long-term trend is what's concerning

In the context of the long-term climate history of the planet, the significance of an individual year is relatively minor. What climate scientists are so concerned with is the overall trend, and the fact that this trend is steepening.

“Records can be broken for all sorts of reasons," Schmidt said. "But these records are being broken because the planet itself is warming. And it’s going to continue to warm because we continue to burn fossil fuels.”

Schmidt said the 2015 record is really “the odometer moment” that people tend to be fascinated by, though scientists are focused on the continuous, overall warming trend that is now playing out largely as they predicted.

“We like to mark things in steps rather than continuously, and when you’ve got a continuous process, once it marks a step, then people pay attention,” he said. “These are steps, records are steps.”

People wade through a flooded road in Chennai, Tamil Nadu, India on Dec. 2, 2015. Weeks of torrential rains left tens of thousands of people stranded in their homes. AP

Climate scientists say that unless emissions of greenhouse gases such as carbon dioxide and methane are not drastically curtailed in the next few decades, the world will see warming of far greater than 2 degrees Celsius, or 3.6 degrees Fahrenheit, compared to preindustrial temperatures.

That is the level of warming that world leaders have agreed would be "dangerous" based on a 1992 U.N. climate treaty. In the Paris Agreement struck in December, world leaders pledged to trying to keep the warming to “well under” 2 degrees Celsius.

“This record is a vivid and immediate reminder that climate is changing, that our future is in our hands and that we have some serious choices to make that will determine whether we will continue to see these records being broken with increasing frequency,” Hayhoe told Mashable, “or whether we will choose a safer pathway where we act to reduce the risks that we’re facing today.”

“Climate change is the challenge of our generation, and NASA’s vital work on this important issue affects every person on Earth,” said NASA Administrator Charles Bolden, in a press release. 

Bolden called Wednesday's announcement "a key data point that should make policy makers stand up and take notice.

"Now is the time to act on climate.” 

“There’s a reason why people keep hearing warmest month, warmest month, warmest year,” Schmidt said. “It’s because it’s warming up.”

According to Jason Smerdon, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, the temperature record is "alarming" while being unsurprising.

"The trend has been predicted for decades, and all the consequences associated with it have been predicted as well. If you know about gravity, it’s not that hard to predict what will happen if a cup falls out of your hand,” he said in a press release.

The Rhone Glacier was wrapped in insulating foams that protected it from the sun on July 14, 2015 near Gletsch.



Surface data vs. satellites

Climate skeptics often point to the satellite-based temperature record as a more accurate measure of Earth's temperature, since surface stations can be affected by urban heat island effects and other biases. Generally speaking, the satellite record does not show as much warming as the surface data does.

However, studies have consistently shown that the urban heat island and other trends that could affect the surface record have been accurately adjusted for in the surface records that NASA, NOAA and other agencies use.

“The interesting thing about the weather stations and the ocean records that come along with it is that there’s enough redundancy, there’s enough different spots and different stations that you can basically take half of it, throw it away and see what the other half gives,” Schmidt said. “And there’s enough redundancy in the pattern of station data that we know that we’re actually capturing what’s actually going on.”

“The errors in the surface records are actually pretty well characterized at this point,” he said.

The Los Angeles Reservoir is covered with more than 90 million black plastic on Aug. 12, 2015. The "shade balls" protect water quality by blocking sunlight from penetrating the 175-acre surface of the reservoir, preventing chemical reactions that can cause algae blooms and other problems. DAMIAN DOVARGANES/AP

Satellites are good for measuring average conditions in Earth's atmosphere, rather than at the surface where we live, and there is a long history of data corrections that had to be made to adjust for orbital drift and other quirks of the satellite record, too.

Also, the satellite data does not stretch back as far as 1880, which makes it even more imperfect as an indicator of long-term climate change.

The 2015 temperature for the lower troposphere (roughly the lowest five miles of the atmosphere) was the third-highest in the 1979-2015 record, measured against the 1981-2010 average, as analyzed by the University of Alabama Huntsville (UAH). Another satellite measuring group, Remote Sensing Systems, found the year was the third-warmest on record as well.

by: Andrew Feedman


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by Andrew Freedman

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