Jan 14, 2016

Explaining Extreme Events of 2014 from a Climate Perspective

Stephanie C. Herring, Martin P. Hoerling, James P. Kossin, Thomas C. Peterson, and Peter A. Stott
American Meteorological Society, Bulletin of the American Meteorological Society
  • States that understanding how long-term global change affects the intensity and likelihood of extreme weather events is a frontier science challenge
  • States that this fourth edition of explaining extreme events of the previous year (2014) from a climate perspective is the most extensive yet with 33 different research groups exploring the causes of 29 different events that occurred in 2014
  • A number of this year’s studies indicate that human-caused climate change greatly increased the likelihood and intensity for extreme heat waves in 2014 over various regions
  • States that for other types of extreme events, such as droughts, heavy rains, and winter storms, a climate change influence was found in some instances and not in others
  • States that this year’s report also included many different types of extreme events
  • Specific report findings include:
    • The tropical cyclones that impacted Hawaii were made more likely due to human-caused climate change
    • Climate change decreased the Antarctic sea ice extent in 2014 and increased the strength and likelihood of high sea surface temperatures in both the Atlantic and Pacific Oceans
    • For western U.S. wildfires, no link to the individual events in 2014 could be detected, but the overall probability of western U.S. wildfires has increased due to human impacts on the climate.
  • States that attribution assessments face challenges that include the often limited observational record and inability of models to reproduce some extreme events well
  • Notes that, in general, when attribution assessments fail to find anthropogenic signals this alone does not prove anthropogenic climate change did not influence the event
  • States that researchers also considered other human-caused drivers of extreme events beyond the usual radiative drivers, for example:
    • Flooding in the Canadian prairies was found to be more likely because of human land-use changes that affect drainage mechanisms
    • The Jakarta floods may have been compounded by land-use change via urban development and associated land subsidence
  • States that these types of mechanical factors reemphasize the various pathways beyond climate change by which human activity can increase regional risk of extreme events