Climate change has serious, long-term, and far-reaching negative consequences for our ocean.

Burning fossil fuels, raising livestock, and clearing forests are just three examples of human activities that release billions of tons of CO2 and other heat-trapping gases into our atmosphere every year, making our planet warmer. The ocean has buffered us from the worst impacts of climate change—absorbing more than 25 percent of the excess CO2 and more than 90 percent of the excess heat. But these climate services come at a significant cost for marine ecosystems and result in harmful impacts including:

  • Increasing ocean temperature: bleaches coral reefs, shifts where fish can live, and decreases ocean wildlife,
  • Ocean acidification: causes a depletion of carbonate ions, which are critical for shell-forming animals like oysters, crabs, and shrimp,
  • Decreasing oxygen: creates areas that suffocate marine animals, shrinks their habitats, and forces them to swim into places where they are more vulnerable to predators,
  • More intense tropical storms and higher sea level: puts coastal communities in harm’s way and destroys coastal wetland habitats which include mangroves and salt marshes.
Climate Change Ocean Infographic

These and other negative impacts are documented and summarized in the Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate—released on September 25, 2019, in Monaco. It is the first IPCC report to focus specifically on the marine realm.

In order to protect the ocean and slow the impacts of climate change, the science indicates we need to take action on two fronts:

  • Cut net carbon dioxide emissions to zero by 2050;
  • Increase ocean health—by reducing pollution, overfishing and safeguarding critical marine and coastal habitats.

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Climate change facts

From the Intergovernmental Panel on Climate Change report, The Ocean and Cryosphere in a Changing Climate:

Carbon dioxide uptake

It is very likely that the ocean has taken up between 20 to 30 percent of total anthropogenic carbon since the 1980s.

Loss of oxygen

The open ocean is losing oxygen overall with a very likely loss of 0.5 to 3.3 percent between 1970 and 2010 from the surface to depths of 1,000 meters. The oxygen minimum zones are likely expanding by 3 to 8 percent, most notably in tropical areas.

Heat

The ocean has taken up more than 90 percent of the excess heat in the climate system since 1970. The rate of ocean warming has more than doubled since 1993.

Fisheries

In many regions, declines in the abundance of fish and shellfish stocks due to direct and indirect effects of global warming have already reduced fisheries catches.

Coastal wetlands

Nearly 50 percent of coastal wetlands have been lost over the 20th century since pre-industrial time, as a result of the combined effect of localized human pressures, sea level rise, warming and extreme climactic events. Nearly 50 percent of coastal wetlands have been lost over the 20th century since pre-industrial time, as a result of the combined effect of localized human pressures, sea level rise, warming and extreme climactic events.

Harmful algal blooms

Harmful algal blooms show range expansion and increased frequency in coastal areas since the 1980s in response to both climatic and non-climatic drivers. The observed trends are attributed partly to the effects of ocean warming, acidification, and loss oxygen as well as eutrophication and pollution.

Climate change in Monterey Bay

Temperature

The surface of Monterey Bay has warmed about 0.8°C (1.4°F) since 1930.

Acidity

10 percent increase in acidity near the surface over the last 20 years.

Oxygen

The minimum oxygen zone is getting bigger.

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Carter, B.R., N.L. Williams, W. Evans, A.J. Fassbender, L. Barbero, C. Hauri, R.A. Feely, and R.A. Sutton. 2019. Time-of-detection as a metric for prioritizing between climate observation quality, frequency, and duration. Geophysical Research Letters, 46: 3853–3861. https://doi.org/10.1029/2018GL080773

Russell, J. L., I. Kamenkovich, C. Bitz, R. Ferrari, S.T. Gille, P.J. Goodman, R. Hallberg, K.S. Johnson, K. Khazmutdinova, I. Marinov, M.R. Mazloff, S.C. Riser, J.L. Sarmiento, K.G. Speer, L.D. Talley, and R. Wanninkhof. 2018. Metrics for the evaluation of the Southern Ocean in coupled climate models and Earth system models. Journal of Geophysical Research: Oceans, 123: 3120–3143. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JC013461

Woodson, C.B., F. Micheli, C.A. Boch, M. Al-Najjar, A. Espinoza, A. Hernandez, L. Vazquez-Vera, A. Saenz-Arroyo, S.G. Monismith, and J. Torre. 2018. Harnessing marine microclimates for climate change adaptation and marine conservation. Conservation Letters, e12609. https://doi.org/10.1111/conl.12609

Chavez, F.P., J.T. Pennington, R.P. Michisaki, M. Blum, G.M. Chavez, J. Friederich, B. Jones, B. Herlien, B. Kieft, B. Hobson, A.S. Ren, J. Ryan, J.C. Sevadjian, C. Wahl, K.R. Walz, K. Yamahara, G.E. Friederich, and M. Messié. 2017. Climate variability and change: Response of a coastal ocean ecosystem. Oceanography, 30: 128–145. https://doi.org/10.5670/oceanog.2017.429

Stewart, J.S., E.L. Hazen, S.J. Bograd, J.E.K. Byrnes, D.G. Foley, W.F. Gilly, B.H. Robison, and J.C. Field. 2014. Combined climate- and prey-mediated range expansion of Humboldt squid (Dosidicus gigas), a large marine predator in the California Current System. Global Change Biology, 20: 1832–1843. http://dx.doi.org/10.1111/gcb.12502

Hoving, H.J.T., W.F. Gilly, U. Markaida, K.J. Benoit-Bird, Z.W. Brown, P. Daniel, J.C. Field, L. Parassenti, B. Liu, and B. Campos. 2013. Extreme plasticity in life-history strategy allows a migratory predator (jumbo squid) to cope with a changing climate. Global Change Biology, 19: 2089–2103. http://dx.doi.org/10.1111/gcb.12198

Smith Jr., K.L., H.A. Ruhl, M. Kahru, C.L. Huffard, and A.D. Sherman. 2013. Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean. Proceedings of the National Academy of Sciences, 110: 19838–19841. https://doi.org/10.1073/pnas.1315447110

Doney, S.C., M. Ruckelshaus, J.E. Duffy, J.P. Barry, F. Chan, C.A. English, H.M. Galindo, J.M. Grebmeier, A.B. Hollowed, N. Knowlton, J. Polovina, N.N. Rabalais, W.J. Sydeman, and L.D. Talley. 2012. Climate change impacts on marine ecosystems. Annual Review of Marine Science, 4: 11–37. http://dx.doi.org/10.1146/annurev-marine-041911-111611

Zeidberg, L.D., and B.H. Robison. 2007. Invasive range expansion by the Humboldt squid, Dosidicus gigas, in the eastern North Pacific. Proceedings of the National Academy of Sciences, 104: 12948–12950. http://dx.doi.org/10.1073/pnas.0702043104