What’s Up with the Weather?

The American Meteorological Society (AMS) recently published “Explaining Extreme Events of 2016 from a Climate Perspective.” Scientists have been producing this annual report for the past six years. This is the first time they have found that extreme events could not have happened without human-caused warming of the climate through increases in greenhouse gases.

The report is made up of 27 peer-reviewed analyses of extreme weather across five continents and two oceans during 2016. It presents the 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.

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

The intensity and likelihood of other terrestrial heat events around the world was found to have increased due to human influence. It affected the severity of the El Nino, the severity of coral bleaching in the Great Barrier Reef, and the warmth of the North Pacific Ocean that impacted fisheries and other resources in the Pacific.
An AMS press release highlighted the following findings.

Global heat: 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: “The 2016 extreme warmth across Asia would not have been possible without climate change.” Although El Nino 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” unwarmed by human influences, “even under the influence of a strong El Nino.”

Marine hot spots: 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.

Most of the 2016 studies found effects of human-caused climate change in extreme weather and climate. Listed as examples were:

• 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.

Not all the events studied in this report were found to be linked to human-caused climate change. About 20 percent were not linked including the failure of El Nino to enhance Southern California rains in 2016, the formation of the biggest midwinter snowstorm in the Mid-Atlantic states, and the drought that led to water shortages in Northeast Brazil.

Photo courtesy of NOAA

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