Arctic ice melted to new lows in 2016, temperatures soared to scorching highs and extreme weather rocked all parts of the planet.
The World Meteorological Organization (WMO) released its annual State of Global Climate report on Tuesday, noting a year of broken records and extreme weather events—climate change trends that are continuing into 2017.
"This report confirms that the year 2016 was the warmest on record—a remarkable 1.1 degrees Celsius above the pre-industrial period," said WMO Secretary-General Petteri Taalas. That temperature rise marks a 0.06 degrees Celsius increase over the record set in 2015. The Paris climate agreement commits the world's nations to holding the atmospheric temperature increase to below 2 degrees Celsius, to try to stave off the most catastrophic global warming impacts.
Much of that increased warmth was centered in the Arctic in 2016, where mean temperatures hit at least 3 degrees Celsius above the average from 1961-90 in some areas. Norway's Svalbard Airport, in the high Arctic, reported an average temperature of -0.1 degrees, which was 6.5 degrees above the 1961-90 average and 1.6 degrees above the previous record.
Beyond the extremes of the Arctic, the year's warming was exceptional because of its consistency, the report said, rather than being the result of spikes in a few locations.
Average atmospheric carbon dioxide levels hit a record high, at 400 parts per million, and projections for 2017 are even higher. The U.K. Met office recently forecast that this year's monthly CO2 level at Mauna Loa could reach nearly 410 parts per million in May, and the 2017 average could be 2-3 parts per million higher than last year.
"The influence of human activities on the climate system has become more and more evident," wrote Taalas in the report's foreword. "This influence is increasingly being demonstrated by attribution studies for some of the most critical weather and climate extremes, in particular extremes related to heat."
Record high sea-surface temperatures and high ocean temperatures in general contributed to significant coral bleaching, particularly in the Great Barrier Reef. A study recently released in the journal Nature found that despite conservationists' longtime hope that the corals could be saved by measures like stopping pollution or overfishing, those efforts are unlikely to help stave off bleaching in periods of extreme warmth like last year.
While severe droughts brought food insecurity to millions across southern and eastern Africa and Central America, Hurricane Matthew was the first category 4 storm to make landfall since 1963. It ravaged parts of Haiti and caused significant damage in the United States.
The report noted that based on early signs, 2017 will bring more broken records and extreme weather.
The Arctic has seen three heatwaves this winter, thanks to powerful Atlantic storms that bring warm, moist air the region. At the very time when the sea ice should have been refreezing on its way to the maximum extent in March, there were days when it was close to the melting point, according to the WMO report. And while Antarctic sea ice was growing in recent years, that's no longer the case. It reached a record low.
In February, 11,743 warm temperature records were broken or tied in the U.S. alone, according to NOAA.
"Even without a strong El Niño in 2017, we are seeing other remarkable changes across the planet that are challenging the limits of our understanding of the climate system," said David Carlson, the director of the WMO-sponsored World Climate Research Program. "We are now in truly uncharted territory."