UN weather office: Why 2015 is the hottest year ever

As world leaders gather to discuss climate change in Paris next week, increasing levels of greenhouse gases in the atmosphere and a strong El Niño weather pattern has caused temperatures to reach record highs.

Michel Jarraud, Secretary-General of the World Meteorological Organization (WMO) holds a graphic during the presentation of the five-year report on the climate from 2011-2015 at the United Nations European headquarters in Geneva, Switzerland, November 25, 2015. This year is set to be the hottest on record, and the current El Nino event is likely to drive up the average temperature further in 2016, the WMO said on Wednesday.

REUTERS/Denis Balibouse

November 25, 2015

Predictions about Earth’s weather patterns reaching a “new normal” appear to be coming true, as 2015 will be the hottest year on record, while 2016 could be even hotter, the United Nations World Meteorological Association (WMO) announced Wednesday.

Man-made global warming and a strong El Niño weather pattern, where warming sea-surface temperatures in the Pacific Ocean can cause flooding, droughts and blazing temperatures, are likely the causes, the organization said.

The report comes as world leaders are set to meet for a climate change summit in Paris, where they will work to keep global temperature increases within 2 degrees Celsius (or 3.6 Fahrenheit) beyond pre-industrial times, a target set in 2010 to try to prevent harmful climate change.

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"...It's still possible to keep to the 2 degree target, but the more we wait for action the more difficult it will be," WMO director-general Michel Jarraud told a news conference, Reuters reports.

"You have scenarios assuming very strong decisions, very quick and sharp reduction of greenhouse gases, and you have other scenarios with business as usual, where you end up with predictions of additional warming of 5, 6 degrees, maybe even more. That will very much depend on the decisions (in Paris),” he added.

While the organization’s report is not surprising, with scientists at the US National Oceanic and Atmospheric Administration and other agencies predicting that 2015 would be the hottest year on record, temperatures will likely reach 1 degree Celsius above those of pre-industrial times, from 1880 to 1899. The organization’s records date to 1880.

That’s a "symbolic and significant milestone,” the WMO says. The organization adds that El Niño, a naturally occurring weather pattern is likely responsible for 16 to 20 percent of the rising temperatures, but longer-term numbers show that temperatures were rising regardless of El Niño (or La Niña, its cooling counterpart), pointing to an urgent need for action to address climate change, Reuters reports.

"This is all bad news for the planet," Mr. Jarraud of the WMO said in a statement.

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Previously, scientists at NOAA, NASA, and Japan’s weather agency have said that 2014 was the hottest year on record, with a global temperature of 14.57 degrees Celsius (58.23 degrees Fahrenheit). 2015 is set to surpass that record, with El Niño peaking between October and January.

"I would call it certain," NOAA's chief climate monitor, Deke Arndt told the Associated Press on Tuesday. "Something game-changing massive would have to happen for it not to be a record."

The WMO’s preliminary estimate based on data from January to October 2015 reveals that the global average surface temperature was around 0.73 degrees Celsius above the average from 1961 to 1990, which was 14 degrees Celsius.

The organization says the years between 2011 and 2015 have been the hottest five-year period on record, while the 10 warmest years have all been since 1998. Temperatures in several land areas, including the continental US, Russia, Australia, South America, and Europe have broken existing records by several margins.

Due to the influence of El Nino, which is set to last into the middle of 2016, and continually rising levels of heat-trapping greenhouse gases, which come from the burning of coal, oil and gas, 2016 may even surpass those levels, the WMO says.