What we learned about Earth's climate in the hottest of years
In many ways, climate change this year was no different to all the other years since the turn of the century. Early data from the World Meteorological Organization shows global temperatures to be simmering away at 1.2° C (2.2° F) above pre-industrial levels, on track to make 2016 the hottest on record.
If that phrase sounds familiar, it is because it would mean 16 of the 17 hottest years recorded have occurred since 2000, the other being 1998. But the year threw up plenty of surprises too, an Arctic heatwave, massive coral bleaching and the election of a certain unpredictable leader, just to name a few. Here's a look at the key events to shape the year in climate science, and what they might mean as we sweat into 2017 and beyond.
About midway through the year, NASA scientists studying Arctic sea ice found that it was melting at a record-breaking rate, with levels declining by about 13.4 percent per decade. Its total coverage at the height of the melting season in September is now 40 percent less than in the late 1970s.
"I would say that perhaps the most spectacular sign of climate extremes this year was indeed the exceptional warmth in the Arctic – beginning with temperatures just around the freezing point in January 2016 (when normally these are between -25 and -40°C/-13 and -40° F) and the repeated warmth in the last few weeks," Martin Beniston, Director of the Institute for Environmental Sciences at the University of Geneva, tells New Atlas. "This is also linked to record low surface areas of sea ice in the Arctic Ocean recorded in September."
What normally happens is that September passes and the sea ice coverage builds again. But 2016 was different. The freakishly warm weather meant that ice coverage has remained at record low levels since late October as winter approaches (despite the best efforts of migrating birds, whose poop help keep it cool, it was revealed in November). Scientists studying this trend say that the record November and December temperatures do not occur in modeling that leaves out human-driven climate factors.
The disappearing habitat of polar bears is one well-known consequence of climate change in the Arctic, but earlier this month researchers discovered another animal that is having a hard time up top. The warmer temperatures mean more rainfall on the Norwegian archipelago of Svalbard, which freezes on top of the snow and seals reindeer food below a sheet of ice. The animals have experienced a 12 percent decrease in average body mass over 16 years as a result.
"The changes in the arctic are scary because no one knows what they portend," says Dr Tim Barnett, an emeritus research marine geophysicist at Scripps Institution of Oceanography.
So what about the other end of the globe? In November, evidence arising from the logbooks and journals of early 20th century explorers suggested that Antarctic sea ice coverage is fluctuating over decades-long cycles, rather than a steady downward trend, and therefore appears less vulnerable to climate change than the Arctic.
But nonetheless, scientists are increasingly concerned with the state of the West Antarctic ice sheet. In 2015, a nearly 225 sq mi (582 sq km) iceberg broke off the region's Pine Island Glacier. Researchers were unsure of the cause of the event until in November, some new imaging software revealed that a rift had formed at the base of the ice shelf, around 20 mi (32 km) inland.
This rift propagated upwards over two years until it burst through the ice surface and sent the iceberg on its merry way out to sea. In simple terms, the ice sheet is breaking up from the inside out. This could bring more melted ice into the ocean and flood coastlines the world over. For Dr. Virginia Burkett, who was a lead author on the Intergovernmental Panel on Climate Change's Nobel Peace Prize-winning fourth assessment report, and is now Associate Director of Climate and Land Use Change at the United States Geological Survey, 2016's climate revelations didn't come any bigger.
"The most significant science news in my mind is the new understanding we have gained on the vulnerability of the West Antarctic ice sheet," Burkett tells New Atlas. "I am a coastal ecologist and the latest observations and process-oriented studies reveal that the ice sheet may be much more vulnerable than previously thought. This has serious implications for low-lying coastal and island communities around the world."
Record-breaking heat wasn't the only landmark event when it comes to the climate in 2016. We also saw carbon dioxide concentrations in the atmosphere over the South Pole tip over 400 parts per million (ppm) for the first time in four million years. Experts say 350 ppm is a concentration that is safe. But we are well beyond that now, with the South Pole the final location to surpass this symbolic but dangerous threshold.
"The far Southern Hemisphere was the last place on earth where CO2 had not yet reached this mark," Pieter Tans, the lead scientist of NOAA's Global Greenhouse Gas Reference Network, said at the time. "Global CO2 levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer."
While the greenhouse gases emitted through human activity are enough on their own, research published in early December revealed that the Earth may be about to make its contribution of its own. Scientists studying the carbon stored in the planet's soil found that as temperatures rise, it will escape into the atmosphere as a result of heightening microbial activity. So much so, that it would be the same as adding another United States to the planet's carbon footprint by mid-century.
Last year's Paris Agreement on climate action is intended to put the brakes on these trends. A total of 195 countries have signed the accord, pledging to cut greenhouse gas emissions in order to keep global temperatures from rising 2° C (3.6° F) above pre-industrial levels this century.
"The Paris accord is the first global recognition that there is a problem," says Burkett. "The treaty is weak and full of holes, but it is a start."
But only one year on the UN has declared the need to go well beyond the initial commitments. According to current projections, to keep warming below 2° C, greenhouse gas emissions in the year 2030 need to be kept to 42 gigatons. But the UN's annual Emissions Report released in November found we are currently on track for 54 to 56 gigatons, a figure that would put us on a path to temperature rises of 2.9 to 3.4° C (5.22° F to 6.12° F) by the end of the century.