Climate Change and the Ocean: A Stark Message from the IPCC

This week, the Intergovernmental Panel on Climate Change (IPCC) released a jaw-dropping report that laid bare the choices that we must make to ensure a livable and equitable future in the face of climate change. Make no mistake: climate change is here now—we are living with it as more powerful hurricanes, worsening drought, melting glaciers and rising sea levels are affecting populations around the world at an ever faster pace. While nations have now stepped up to reduce greenhouse gas emissions under the Paris Accord, the new UN requested report makes it abundantly clear that we must do more.

The report, drafted in response to a request by the United Nations Framework Convention on Climate Change (UNFCCC), evaluates the differences between a 1.5°C and a 2°C future and whether different emissions trajectories can achieve a future with less warming.  It makes clear that we need a global commitment to move away from fossil fuels and also focus on the removal of carbon dioxide that is already in the atmosphere (not just reduction of future emissions) to prevent irreversible effects that would have devastating consequences across the globe. Such an approach is especially vital to the ocean, where achieving a 2°C future (the official goal of the Paris Accord) would still result in destructive changes to the ocean and coastal areas around the world. We can and must do better.

To date, human activities have caused approximately 1°C of global warming since the Industrial Revolution; this warming will likely reach 1.5°C between 2030 and 2052 if current activities continue. While these differences seem small, the consequences are not. Scientists now predict large differences between current conditions and those likely to occur between 1.5°C and 2°C. By 2100, average global sea level rise would be around 0.1 meter lower with global warming of 1.5°C compared to 2°C. This seemingly small difference means that up to 10 million fewer people would be exposed to the related risks of flooding, storm damage and coastal displacement. This is especially relevant for the millions of people living on small islands and in low-lying coastal areas and deltas.

For the ocean, the risks are also projected to be substantially lower at 1.5°C than at 2°C. Most striking, coral reefs suffer a 70–90% loss at 1.5°C, but are entirely destroyed at 2°C. Studies have shown that, at the lower loss level, with continued decreased temperatures, corals can still recover. The risk of irreversible loss of many other marine and coastal ecosystems increases sharply with rate of warming, and becomes especially stark at 2°C or more.

Risks to marine biodiversity, fisheries, ocean ecosystems, and the vital functions and services they provide to humans, also increase substantially at 2°C. Should we fail to secure a 1.5°C future, acidification and warming are predicted to act synergistically—producing stronger effects working together than they could alone—to decrease the growth, development, calcification, survival and abundance of a broad range of species, from algae to fish. For example, at 2°C, loss of global annual catch for marine fisheries would be twice that predicted under a 1.5 °C world. These types of differences would be catastrophic for both the ocean and people alike.

We shouldn’t be afraid of this truth. We should confront it head on and let this new climate reality be a motivator to work together to secure the future we want.

The IPCC report was a massive undertaking, comprising three years of work by more than 130 authors, synthesizing over 6,000 scientific references and fielding over 42,000 comments during the extensive peer review process. The report is also a global testament to the importance of research, observations, modeling, synthesis, review and analysis and to the numerous scientists around the world who have donated their time to summarize this information for the benefit of all of us.

While the ocean is often cast simply as a victim of climate change and a bystander in our climate future, it can, in fact, be an active and important part of our climate solutions as well. Blue carbon habitats sequester large amounts of carbon, making their protection and restoration important parts of a global greenhouse gas reduction strategy. The ocean itself is an important site for the expansion of renewable energy, enabling the ocean to play a role in the clean energy transition. Protection of ocean habitats and marine species through networks of marine protected areas, sustainable fisheries management and pollution reduction are critical strategies to adapt to the changes that will still manifest even under a 1.5°C future. As global citizens, what are our options to ensure a more stable future? The IPCC report explores a range of emissions scenarios that would put the planet on a path to 1.5°C, and we need decision-makers to prioritize those options to ensure a reality.

Enhanced climate ambition is vitally needed at the international level. Carbon dioxide is raising average global temperature and driving acidification of the ocean.  As the UN Framework Convention on Climate Change grapples with the urgency of the findings in this week’s report, we must set global emissions targets that incorporate the needs of the ocean as well as the critical role that the ocean can play in meeting those targets.  It’s up to each and everyone one of us to take individual action by urging decision-makers in Congress, the Executive branch, and across the world to take immediate action. We need to reduce fossil fuels and cut carbon emissions—our ocean depends on it.

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