The 2010s almost certainly will be the warmest decade on Earth since instrument temperature data began to be gathered in the 19th century (and very likely long before that), according to new data released this week from the World Meteorological Organization. “Since the 1980s, each successive decade has been warmer than the last,” the WMO stated in its provisional state of the climate report.
The WMO also found that the past five years have been the warmest such period on record, as 2019 careens toward the second- or third-warmest year.
The past month tied for the warmest November on record globally, according to the Copernicus Climate Change Service, in a statistical dead heat with November 2016 and just behind November 2015. The global average temperature in 2019 (January through October) was about 1.96 degrees Fahrenheit above the preindustrial period.
The magnitude of recent warming is noteworthy, since under the Paris Climate Agreement, countries pledged to hold global warming to “well below” 3.6 degrees Fahrenheit of warming, and to aspire to keep it to 2.7 degrees Fahrenheit. Reporting by The Washington Post has shown that numerous hot spots exist around the planet that have already soared past the 3.6-degree threshold.
What’s remarkable about the warmth this year is that there has been no strong El Niño present in the tropical Pacific Ocean, as there was in 2015-2016. Such events tend to boost global average surface temperatures and can reconfigure weather patterns from the United States to Africa and Australia. Typically, the hottest years of a given decade occur when an El Niño is present, but 2019 illustrates the increased role played by human-caused climate change in driving temperatures ever higher.
In a stark report delivered to negotiators gathered for U.N. climate talks in Madrid on Wednesday, the secretary general of the WMO, Petteri Taalas, laid out the new findings.
One trend the WMO pointed to is a sharp uptick in ocean heat content, which is leading to more pervasive marine heat waves.
The oceans are the world’s main heat sponge, absorbing more than 90 percent of the added energy building up in the climate because of increasing concentrations of greenhouse gases.
“In 2019, ocean heat content in the upper 700 meters (in a series starting in the 1950s) and upper 2000 meters (in a series starting in 2005) continued at record or near-record levels, with the average for the year so far exceeding the previous record highs set in 2018,” the WMO found.
Satellite monitoring of sea surface temperatures show that in 2019, the ocean has on average seen about 1.5 months of unusually warm temperatures. Nearly 40 percent of the global oceans had a marine heat wave ranked as “strong,” along with about one-third of the oceans seeing moderate marine heat waves. The area that stands out as experiencing a severe marine heat wave this year is in the northeast Pacific, the WMO said.
Marine heat waves can have a cascading effect on marine ecosystems, bleaching or even killing coral reefs, driving out cold water fish species, and causing mass mortality events in iconic marine species such as gray whales.
The effects of warming were observed far and wide. The Greenland ice sheet shed an unusually large amount of ice in 2019, the WMO found, amounting to a loss of 329 billion tons. This was not a record but was well above the long-term average of 260 billion tons per year. Ice melt from land-based ice sheets, including Greenland, are the largest contributor to sea level rise.