K.R. Tanaka and K.S. Van Houtan. The recent normalization of historical marine heat extremes. PLOS Climate. Published February 1, 2022. doi: 10.1371/journal.pclm.0000007.

 

Climate Change is catching up to us

Human activities have been the main driver for climate change since the 1800s. Climate change is currently causing a range of consequences such as severe droughts, melting glaciers, erratic weather patterns, and higher temperatures. The fast speed and massive scale of these events reflect how quickly the climate is changing. A recent report analyzing sea surface temperatures (SST) from the last 150 years uncovers that in 2019, 57 percent of the ocean’s surface experienced extremely high temperatures compared with historical averages.

 

Tracking the heat through history

Global warming is not new. The average SST have risen about 1.5 degrees Fahrenheit since 1901 and continues to rise, contributing to the frequency, intensity, and duration of marine heat waves in the ocean. Kisei Tankaka and Kyle Van Houtan analyzed monthly SST data from 1870 to 2019, picking out extreme marine heat wave events lasting at least 5 days to provide historical context for modern heat waves.

Major marine heatwaves have been occuring across the globe. Source: Frölicher and Laufkötter, Nature Communications 2018.

What we’re facing

Most reports look at temperature changes on an annual or decadal scale, so more frequent monthly observations provide a clearer picture of ocean changes. The results clearly show that extreme heat events became more common. In 2014, 50 percent of the world’s ocean experienced extreme heat events, making marine heat waves the ‘new normal’. Today’s extreme events are also more severe, with heatwaves recorded in 2014 far surpassing anything recorded in the 1920s.

 

Consequences

Many ocean regions will continue to be hit with severe heat on a more regular basis, damaging ecosystems and causing major shifts in marine animal populations. Consequently, many organisms will be unable to survive the excessive heat. Large coral bleaching events and changes in economically important fish migration patterns are already happening around the world. Climate change is becoming impossible to ignore as extremes have become the ‘new normal’. This research provides valuable historical evidence of climate change in a time where action must be taken to reduce the world’s carbon emissions.



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