Will the Oceans Absorb 80% of All Human Carbon Dioxide Emissions From the Atmosphere?

Check out this answer from Consensus:

While the oceans play a vital role in absorbing CO2 emissions, current research suggests that they absorb about 25-30% of anthropogenic CO2, not 80%. The idea that the oceans could absorb 80% of all human CO2 emissions is not supported by existing data. Further research and more recent measurements are necessary to refine our understanding of the ocean’s capacity to act as a carbon sink.

The role of the oceans in absorbing carbon dioxide (CO2) emissions is a critical component of the Earth’s carbon cycle. As human activities continue to release significant amounts of CO2 into the atmosphere, understanding the capacity of the oceans to absorb these emissions is essential for predicting future climate change scenarios. This article explores whether the oceans can absorb 80% of all human CO2 emissions, drawing on recent research findings.

Current Oceanic Carbon Dioxide Absorption

Research indicates that the oceans currently absorb a substantial portion of anthropogenic CO2 emissions. According to one study, the ocean is a significant sink for CO2, taking up about a third of the emissions from fossil-fuel use and tropical deforestation1. Another study supports this, noting that the world ocean has absorbed around 25% of human-caused CO2 emissions over the past few decades, thereby playing a crucial role in mitigating climate change2.

Historical Data and Uncertainties

The estimates of oceanic CO2 absorption are primarily based on research conducted in the 1990s. Recent studies suggest that approximately 30% of anthropogenic CO2 emissions were absorbed by the oceans during this period3. However, there are uncertainties in these measurements, and more recent data is needed to provide a clearer picture of the current state of oceanic CO2 absorption.

Potential for Increased Carbon Uptake

There is ongoing research into methods to enhance the ocean’s natural ability to absorb CO2. By increasing the ocean’s carbon uptake, it may be possible to boost this natural climate service. However, the feasibility and potential environmental impacts of such interventions are still under investigation2.

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Katsumi Matsumoto has answered Near Certain

An expert from University of Minnesota in Oceanography, Palaeoclimatology, Geochemistry

On ten to thousand year timescales, anthropogenic CO2 has three places to go : (1) remain in the atmosphere; (2) absorbed by the ocean; and (3) absorbed by the terrestrial biosphere. Most will end up in the ocean, because it is by far the largest carbon reservoir. The ocean holds 50-60 times more carbon than the atmosphere. The terrestrial biosphere (land plants and soils) holds a few times more carbon than the atmosphere. The oceans thus have a large capacity to absorb carbon. Seawater is a bit basic (pH~8), so it can naturally absorb more CO2, which is essentially an acid. But it takes time for the oceans to mop up the excess carbon humans are emitting, because the time scale of vertical mixing of the oceans is centennial to millennia. Vertical mixing takes surface waters that become more saturated with anthropogenic CO2 down into the deep ocean and brings up deep waters that are not saturated with anthropogenic CO2. Eventually, the CO2 that is absorbed by the oceans can get neutralized by CaCO3 on the sea floor… On timescales of continental weathering and movement (i.e., tectonics), the huge carbon reservoir of the rocks come into play. But they are much too long for humans.

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Martine Lizotte has answered Unlikely

An expert from Université Laval in Oceanography

No, not in the short term. However, on millennial scales and if anthropogenic CO2 emissions are abated, the percentage of oceanic uptake of total human-derived CO2 emissions could increase as carbon is mixed deeper into the ocean. There remains, however, much uncertainty as to the overall percent of potential oceanic uptake.

According to recent and revised estimates of ocean-atmosphere CO2 fluxes, the oceans may have taken up as much as 500 Gt CO2 from the atmosphere out of the total 1300 Gt CO2 anthropogenic emissions over the last 200 years (Watson et al. 2020; IPCC Special Report on Carbon dioxide Capture and Storage 2018). In other words, about 38% of all human-derived CO2 from fossil fuel burning, cement manufacturing and land-use changes may now have entered the ocean from the surface. The fraction of excess CO2 entering the oceans has likely fluctuated since the Industrial Revolution and may keep changing in the future, for a number of reasons. Firstly, as CO2 dissolves into a given volume of water, there is growing resistance to adding more CO2. This aspect of the relationship between the changing composition of seawater and the overlying atmosphere is known as the Revelle Factor (described by the late Roger Revelle more than 50 years ago). Secondly, human use of fossil fuels is also the root cause of a general warming trend in the oceans, observed over the past 50 years, that increases the resistance to CO2 uptake (warmer waters decrease the solubility of CO2). In addition, as oceans are warming, water column stability is increasing, slowing down the transfer of CO2 from the ocean surface deeper into the ocean depths. Ocean mixing is a crucial process in changing the water at the surface of the ocean where it meets the air and can dissolve CO2. Slower mixing also has implications for the transport of nutrients from deeper waters to the surface, nutrients which are essential to the growth of phytoplankton, photosynthetic organisms that participate in the capture of carbon and to its potential removal from the surface via the sinking of biomass to depths.

The slowing down of all these oceanic carbon capturing processes, combined with increases in the rate of fossil fuel use by humans, may lead to a gradual shrinking of the relative oceanic CO2 sink in the short term. The oceans, as a whole, have a large capacity to store CO2, but ocean mixing is too slow to keep up with the current pace of CO2 accumulation in the atmosphere. At present, ocean waters deeper than 500 m still hold the capacity to absorb CO2. If anthropogenic CO2 emissions are abated in the future, oceans will continue absorbing excess CO2 emitted in the past, naturally equilibrating with the atmosphere, and the excess CO2 will eventually reach deeper layers of the ocean over several hundreds of years. When expressed as a percent of the total emissions, the ocean’s proportional uptake will increase over millennia, potentially reaching 50-80% of the cumulative anthropogenic CO2 emissions.

Watson, A.J., Schuster, U., Shutler, J.D. et al. Revised estimates of ocean-atmosphere CO2 flux are consistent with ocean carbon inventory. Nat Commun 11, 4422 (2020). https://doi.org/10.1038/s41467-020-18203-3

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Robert  Steneck has answered Uncertain

An expert from University of Maine in Oceanography, Marine Biology

I cannot confirm that. CO2 in the worlds oceans is making them more acidic but what percent of emissions do that is not known by me.

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Megan Cook has answered Uncertain

An expert from Ocean Exploration Trust in Oceanography

Oceans do absorb carbon dioxide and also excess heat trapped by human greenhouse gas emissions. Over the past 150 years, the amount of carbon dioxide in the atmosphere has been increasing over time due to human emissions. As a result, the ocean is absorbing increasing amounts of carbon dioxide from the air. However, as carbon dioxide enters the ocean, it reacts with water to form carbonic acid which makes many animals’ lives more challenging. You can learn more about the impacts of ocean acidification here: https://oceanservice.noaa.gov/facts/acidification.html Additionally, more than 90% of the excess heat from the atmosphere is stored in the ocean. Heat absorbed by the ocean is moved from one place to another, but it doesn’t disappear. The heat energy eventually re-enters the rest of the Earth system by melting ice shelves, evaporating water, or directly reheating the atmosphere. 

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Anna Zivian has answered Unlikely

An expert from Ocean Conservancy in Oceanography

No – the ocean has absorbed about 30% of human CO2 emissions and about 90% of the heat created by anthropogenic climate change. In addition, absorbing increasing heat and CO2 is having devastating effects on the ocean.

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Will the oceans absorb 80% of all human carbon dioxide emissions from the atmosphere?

Jessica Meeuwig has answered Uncertain

An expert from University of Western Australia in Ecology, Marine Science

There is some suggestion that ultimately, the ocean can or will absorb between 50% and 80% of CO2 emissions. But the real question is what does that ocean look like? As CO2 is absorbed by the ocean, the ocean’s pH decreases, with seawater becoming more acidic. If you like eating lobster and oysters and snorkelling on coral reefs, you should care as acidic water makes it difficult for these animals to thrive.