CLIMATE CHANGE IMPACTS
The ocean is extremely vulnerable in the face of climate change
Ocean life is largely accustomed to stable temperatures, and is vulnerable to related changes. Coral reefs, for example, which can house millions of species, are being bleached from overheating. Back-to-back extreme ocean heat waves in 2016 and 2017 caused massive bleaching of the Great Barrier Reef off the coast of Australia, killing half of its coral. Potential related economic impacts, not to mention environmental impacts, are significant - a 2013 Deloitte study found that the Great Barrier Reef was generating about $7 billion in revenue for Australia, largely via tourism.
Since the first industrial revolution, the acidity of the ocean has increased by roughly 30% as carbon dioxide dissolves in marine waters; this makes it more difficult for organisms to form healthy skeletons and shells.
The ocean is being hit hard by climate change in the form of warming, acidification, and oxygen depletion. The 2019 Intergovernmental Panel on Climate Change (IPCC) special report on the ocean and cryo-sphere found that all of these effects were intensifying.
A future ocean that is hotter, more acidic, and a more difficult place to breathe presents serious challenges. The ocean has absorbed more than 90% of the heat produced via greenhouse gas-associated warming since the 1970s - and, according to the National Oceanic and Atmospheric Administration, 2019 was the second-warmest year on record.
As the ocean warms, its oxygen levels drop. Oxygen content in the ocean declined by an estimated 2% global average between 1960 and 2010, according to a study published in the journal Nature, and IPCC scientists predict there could be a further 3% to 4% decrease by the end of the 21st century.
Scientists from the University of British Columbia's Institute for the Oceans and Fisheries have predicted that if climate change continues unchecked, global fisheries may suffer $10 billion in annual revenue loss by 2050. Global warming-driven sea level rise may be the most impactful form of ocean-related climate change. Scientists predict that half the population in cities with more than 10 million inhabitants will be affected by sea level rise if climate change is not slowed; Miami, Shanghai, and dozens of other cities have already suffered related effects.
Climate change must be aggressively checked in order to enable natural adaptation and evolution, and the best way to do this is to confront the difficult task of directly reducing global carbon emissions.