As climate extremes hit land don’t forget those in the ocean

Dr Carol Turley, Dr Phil Williamson and Professor Ric Williams explain why we must pay attention to the climate extremes in the ocean. 

The damage to society is clearly greatest when weather extremes occur on land, such as the ferocious heat and deadly floods that recently shattered records across the northern hemisphere.

The evidence linking these extremes to changes in the atmosphere, primarily due to burning fossil fuels, is now overwhelming.

Yet the ocean is also undergoing profound change, with equally crucial consequences for the planet. Both long-term warming and local heatwaves disrupt marine systems, with many impacts that make matters worse for marine life. And for us.

The ocean is both Earth’s central heating system and air conditioner, with its large-scale circulation patterns determining future climate on both regional and global scales.

The ocean is also where more than 90% of recent global warming has occurred, increasing its heat content as thermal energy. Whilst ocean warming – and its rate of increase – is greatest in near-surface waters, where marine life is most abundant, all water depths are affected.

Coral Bleaching in American Samoa, Before (Dec 2014) & After (Feb 2015). Photo Credit – The Ocean Agency / Ocean Image Bank

Over the past 50 years, the global frequency of marine heatwaves has doubled.

They have also become longer-lasting, more intense and extensive. The extraordinary heat that hit North America over the past few weeks killed hundreds of millions of marine animals along the Pacific Coast. Marine heatwaves have also had a devastating effect on coral reefs, which harbour amazing biodiversity, and on coastal vegetation, such as mangroves and seagrass meadows, releasing their carbon stores that have accumulated over many centuries.

As well as soaking up the heat, the ocean has taken up around a quarter of the current man-made carbon dioxide emissions.

Together these removal processes have greatly mitigated the rate of climate change on land. Yet these benefits have come at a price: not only causing ocean warming but also ocean acidification from CO2 increase; loss of oxygen; and a near-doubling of the rate of sea-level rise, through volume expansion.

We all now know that serious political action is needed; what is not so well known is that direct and indirect ocean protection is needed to avoid continued climate breakdown and its unfolding consequences.

To learn more about why the ocean matters in climate negotiations, visit:

Environment Journal, 4 August 2021. Full article.

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