Last updated September 11, 2019

Marine heatwaves under global warming

  • States that marine heatwaves (MHWs) are periods of extreme warm sea surface temperature that persist for days to months and can extend up to thousands of kilometres
  • Uses satellite observations and a suite of Earth system model simulations to show that MHWs have already become longer-lasting and more frequent, extensive and intense in the past few decades, and that this trend will accelerate under further global warming
  • Detects a doubling in the number of MHW days between 1982 and 2016
  • Projects this number will increase on average by a factor of 16 for global warming of 1.5°C relative to preindustrial levels and by a factor of 23 for global warming of 2.0°C
  • Notes that current national policies for the reduction of global carbon emissions are predicted to result in global warming of about 3.5°C by the end of the twenty-first century
  • Shows that today, 87% of MHWs are attributable to human-induced warming, with this ratio increasing to nearly 100% under any global warming scenario exceeding 2°C