Ocean's Hidden Cost in Climate Economics

The ocean has been getting a free ride in climate economics for decades. While policymakers debate the true cost of carbon emissions, they've largely ignored what happens when that carbon wreaks havoc on the world's seas. A new study published this week changes that calculation dramatically—and the numbers should worry anyone who cares about climate policy.

The Hidden Cost of Ocean Damage

Researchers have introduced something they call the "blue social cost of carbon." It's the first comprehensive attempt to put a dollar value on climate damage to ocean ecosystems. The figure they arrived at? An additional $48 per tonne of CO₂.

That might sound abstract, but here's what it means: the economic cost of carbon emissions is nearly double what current policy frameworks assume. For decades, climate-economy models have effectively assigned a value of zero to ocean impacts. As lead researcher Bernardo Bastien-Olvera from UC San Diego's Scripps Institution of Oceanography puts it, "We've been estimating the economic cost of climate change while effectively assigning a value of zero to the ocean."

This isn't a small oversight. The ocean covers more than 70% of Earth's surface and produces more than half the oxygen we breathe. Yet marine ecosystems have been largely absent from the models that underpin carbon pricing and policy decisions worldwide.

What the Ocean Actually Does for Us

The study, published January 15, 2026, in Nature Climate Change, captures damage to four critical areas: coral reefs, mangroves, fisheries, and global seaports. These aren't just environmental concerns—they're economic powerhouses.

Coral reefs alone provide ecosystem services worth hundreds of thousands, and sometimes millions, of dollars per hectare. They protect coastlines from storms, support tourism industries, and nurture fish populations that feed hundreds of millions of people.

Mangrove forests act as natural barriers against storm surges while storing massive amounts of carbon. They're nurseries for commercially important fish species and provide livelihoods for coastal communities across the tropics.

The researchers found that health impacts linked to fisheries account for nearly half of ocean-related climate damages. When fish stocks decline because of warming waters and ocean acidification, people go hungry. Climate-driven declines in fish populations translate directly into higher mortality and poorer health outcomes, especially in lower-income countries and island states.

The Human Cost Isn't Evenly Spread

Ocean damages cost the global economy nearly $2 trillion annually, according to the study. But that burden doesn't fall equally on everyone.

In some economies, ocean damages account for 20-30% of total climate-related welfare losses. Small island developing states and lower-income countries face disproportionately large impacts. These are places where people depend on marine ecosystems for food, tourism revenue, and transportation networks.

The study brings together research from Scripps Oceanography, the Euro-Mediterranean Center on Climate Change, Leibniz University, University of British Columbia, UC Santa Barbara, and University of Oxford. Their integrated framework accounts for both market impacts—like reduced fishing catches and port disruptions—and non-market values such as nutrition, health, biodiversity, and recreation.

Francesco Granella from CMCC captures the challenge well: "Losing a coral reef or a mangrove forest isn't just an environmental loss, it's a loss to human wellbeing that can't be easily compensated for with money or manufactured alternatives."

Why Current Carbon Prices Fall Short

Current carbon prices in major markets like the European Union hover around €70-80 per tonne. That's well below the levels justified when ocean damages are included in the calculation.

Johannes Emmerling, also from CMCC, explains the long-term nature of the problem: "Because CO₂ stays in the atmosphere for centuries, each tonne has long-lasting impacts on societies worldwide."

The social cost of carbon is supposed to represent the total economic damage from emitting one additional tonne of CO₂. It's used to set carbon taxes, evaluate regulations, and guide investment decisions. Getting this number right matters enormously for climate policy.

Amy Campbell, a UN climate advisor and former British government COP negotiator, calls the social cost of carbon "one of the most efficient tools we have for internalizing climate damages into economic decision-making."

When that number is too low, it systematically undervalues climate action. Companies and governments make decisions based on incomplete information about the true costs of emissions.

What This Means Going Forward

The findings suggest that carbon prices should be significantly higher to reflect the full scope of climate damages. This strengthens the economic case for faster emissions reductions.

Massimo Tavoni, Director of CMCC, notes that "the standard accounting of the socio-economic costs of climate change has ignored nature." This study corrects that oversight for ocean ecosystems, but it also raises questions about what else might be missing from our climate-economy models.

Climate disasters cost the world over $320 billion in 2024 alone. Those are just the immediate, visible costs—fires, floods, hurricanes. The new research reveals that slower-moving ocean changes carry their own massive economic burden.

The blue social cost of carbon isn't just an academic exercise. It's a tool for better decision-making. When businesses evaluate whether to invest in clean energy, when governments decide how strictly to regulate emissions, when international bodies negotiate climate agreements—all of these decisions rest on assumptions about what climate change actually costs.