Climate Change

Some extreme weather events in 2016 would never have happened without human-caused warming: studies

Extreme heat across Asia in 2016 and unusually warm waters in the Bering Sea would not have been possible without human-induced climate change

 
By Vineet Kumar
Last Updated: Wednesday 20 December 2017 | 15:51:48 PM
Extreme rains, like the record-breaking 2016 event in China, are 10 times more likely in the present climate than they were in 1961. Credit: Wikimedia Commons
Extreme rains, like the record-breaking 2016 event in China, are 10 times more likely in the present climate than they were in 1961. Credit: Wikimedia Commons Extreme rains, like the record-breaking 2016 event in China, are 10 times more likely in the present climate than they were in 1961. Credit: Wikimedia Commons

A new research report “Explaining Extreme Events in 2016 from a Climate Perspective” has been published recently in the Bulletin of the American Meteorological Society (BAMS) on December 12, 2017. This annual report has been produced continuously for the past six years by scientists and this is the first time that they have found that some of the extreme events could not have happened without human-caused warming.

The IPCC 5th Assessment Report, 2014 already observed that human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise and in changes in some climate extremes. It says that evidence of human influence has grown since IPCC 4th Assessment Report, 2007. According to the report, it is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the increase in greenhouse gas concentrations due to anthropogenic causes.

This BAMS report takes forward the climate attribution science by assessing most recent peer-reviewed research papers. It points out that record global heat in 2016, extreme heat over Asia, and unusually warm waters in the Bering Sea would not have been possible without human-induced climate change.

"This report marks a fundamental change," says Jeff Rosenfeld, editor-in-chief of BAMS. “For years, scientists have known humans are changing the risk of some extremes. Finding multiple extreme events that weren’t even possible without human influence makes clear that we're experiencing new weather because we've made a new climate.”

This report presents 27 peer-reviewed analyses of extreme weather across five continents and two oceans during 2016. It features research of 116 scientists from 18 countries looking at both historical observations and model simulations to determine whether and by how much climate change may have influenced particular extreme events. Twenty-one of the 27 papers in this edition identified climate change as a significant driver of an event. Of the 131 papers now examined in this report over the last six years, approximately 65 per cent have identified a role for climate change, while about 35 per cent have not found an appreciable effect.

This year’s report reveals that the influence of human-caused climate change has become strong enough to push some heat events beyond the bounds of natural variability alone. In addition, scientists are reporting increasing confidence in their findings that human-caused climate change is impacting temperature-related events on land and in the oceans.

Some of the major findings of the report:

Global heat in 2016: The record mean surface temperature for the world in 2016 was found to be “only possible due to substantial centennial-scale anthropogenic warming.”

Asia heat in 2016: “The 2016 extreme warmth across Asia would not have been possible without climate change,” the report observes. Although El Niño (warming tropical Pacific waters) was expected to warm Southeast Asia in 2016, the heat in the region was unusually widespread. Another study produced evidence suggesting that a deadly April heat in Thailand, which devastated crops and broke records for energy usage, “would not have occurred in the natural climate” without human influences, “even under the influence of a strong El Niño.”

Marine hotspots: Ocean temperatures in the Gulf of Alaska, Bering Sea, and off northern Australia were the most elevated in 35 years of satellite records, leading to massive bleaching of the Great Barrier Reef and one of the largest harmful algal blooms ever off the Alaska shore. Natural climate variations played a part but studies find it “extremely unlikely that natural variability alone led to the observed anomalies,” and suggest that the blob of sub-Arctic 2016 warmth “cannot be explained without anthropogenic climate warming.”

Human-caused climate change

Like previous years, most of the studies conducted this year found role of human-caused climate change in extreme climate events.

  • Human-caused warming likely exacerbated impacts of warm waters on marine life in the California Current.
  • Highly anomalous Arctic warmth during November–December 2016 most likely would not have been possible without human-caused warming.
  • Human influences quintupled the risk of dry air conditions in western North America that exacerbates wildfires such as those from the 2016 fire season.
  • Flash droughts over southern Africa, like the one in 2015/16, have tripled in the last 60 years mainly due to human-caused climate change.
  • Extreme rains, like the record-breaking 2016 event in Wuhan, China are 10 times more likely in the present climate than they were in 1961.

El Niño, the periodic warming in the eastern and central tropical Pacific waters, figured prominently in 2016 weather patterns and cross-global atmospheric connections. While the main cause of “the longest, most widespread, and most damaging global coral bleaching event on record” on the Great Barrier Reef was ocean warming caused by human influence, the impact of El Niño also exacerbated the bleaching. According to a study published in the American Meteorological Society, human-caused climate change strengthened El Niño in the central equatorial Pacific Ocean. Another study found that the climate change-enhanced 2015/16 El Niño exacerbated South Africa’s drought and food scarcity.

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