Damage to the ocean nearly doubles economic cost of climate change

Scientists have factored damage to the ocean into the social cost of carbon for the first time, finding it nearly doubles the economic impact from climate change.

Ocean damage from climate change, dubbed the "blue" social cost of carbon, causes the global cost of carbon dioxide emissions to society to nearly double, according to new findings by researchers at the Scripps Institution of Oceanography at the University of California San Diego.

The researchers calculated an additional $46.2 per ton of carbon dioxide, amounting to a total of $97.2 per ton of carbon dioxide, a 91% increase, according to the study, published Thursday in Nature Climate Change. Global carbon dioxide emissions were estimated to be 41.6 billion tons in 2024, according to the Global Carbon Budget, implying nearly $2 trillion in ocean-related damages in one year that are currently missing from standard climate cost estimates.

The ocean has never been accounted into the economic harm caused by greenhouse gas emissions before, the researchers said. The ocean was largely overlooked in the standard accounting of the social cost of carbon, despite widespread degradation to coral reef ecosystems, losses from fisheries and damage to coastal infrastructure – all of which are "well documented" and have impacted millions of people globally.

In addition, the distribution of impacts is "highly unequal" across the globe, according to the paper. Islands and small economies will be disproportionately affected, given the regions' dependence on seafood and nutrition, according to the study.

Scripps researchers felt the need to put a price tag on the harm that climate change causes to the ocean in order to properly inform key decision-makers with a cost-benefit analysis, said environmental economist and assistant professor at the National Autonomous University of Mexico Bernardo Bastien-Olvera, who led the study during a postdoctoral fellowship at Scripps Oceanography.

"The ocean was the big missing piece in these models that calculate the climate impacts on humans," Bastien-Olvera told ABC News.

Human-amplified climate change damages oceans by warming temperatures and altering its chemistry, according to the Scripps researchers. The changes then alter the distribution of species and damages ecosystems such as reefs, mangroves, seagrass beds and kelp forests.

Coastal infrastructure, such as shipping ports, can also be damaged by increased flooding and stronger storms.

The social cost of carbon is an economic metric used in climate policy to estimate the damages that a ton of carbon dioxide causes to humans today, Bastien-Olvera said.

The researchers estimated the social cost of carbon by using integrated assessment models to run different future scenarios of how people and the economy might behave during the next century, also incorporating the potential climate impacts on systems such as coral reefs, mangroves, fisheries and seaports, Bastien-Olvera said.

The accounting was further developed by looking at straightforward market-use values, such as decreased fisheries revenue or diminished trade, as well as non-market values such as health impacts of reduced nutrition availability from impacted fisheries and recreational opportunities at the ocean, according to Scripps.

The research accounted for reduced availability of key nutrients in seafood, including calcium, omega-3 fatty acids, protein and iron – the loss of which can be linked to increases in disease risk and additional deaths.

The economic cost is caused by losses in the fishing industry, damage to coastal communities and impacts to systems that help fortify those communities, like mangroves and reefs.

The social cost of carbon is considered a more accurate accounting of harm from climate change than other calculations used as the basis of carbon credits or carbon offsets to travelers, according to Scripps.