The Ocean-Climate Nexus
The oceans have literally spared the terrestrial world from the extreme effects of climate disruption so far, absorbing some 90% of all the excess heat caused by our greenhouse gas pollution. Without oceans the earth’s surface temperatures would be unlivable.
Oceans have also absorbed a significant portion (some 30%) of the carbon dioxide pollution we have put in the atmosphere, and as a result are becoming more acidic.
Ocean warming has already resulted in deoxygenation, interrupted circulation and mixing, species shifts, marine heatwaves, coral bleaching, increased storm intensity and sea level rise.
Ocean chemistry has been affected as well, and the Ocean is now some 30% more acidic than pre-industrial periods. Ocean acidification affects the ability of some ocean organisms to create shells, and the potential impacts on the oceanic food web is enormous, from the Arctic to the tropics.
ROLE OF THE OCEANS IN CLIMATE RESTORATION
The oceans have an enormous potential role to play in climate restoration. And while this role is ramped up, we need an oceans’ systems life support plan if we are to ultimate win on climate restoration.
The needed focuses and actions fit into the three main action areas of the portfolio.
First, the oceans have an important role to play in global decarbonization, with the largest contribution coming from the scaling of ocean-based renewable energy (offshore wind, wave and geothermal amongst others), followed by decarbonizing shipping,fishing and other ocean sectors, and developing new foods from ocean plants to replace more carbon-intensive food sources.
Second, the oceans have a significant role to play in the needed negative emissions portfolio. As the largest area of the planet (71% of the globe’s surface), they have the potential to capture significant amounts of atmospheric carbon; and to do so in a way that is far less damaging than some of what is being proposed on land.
There are a number of promising approaches that need to be significantly ramped up; with accelerated testing, development and deployment in the next decade. The oceanic element of the negative emissions portfolio is significantly underinvested at the moment; the world continues to focus most of that attention on land-based solutions.
We are unlikely to be able to win at negative emissions without active utilization of the oceans.
Ecoystem Life Support
Lastly, some of the most critical components of the global climate system are in the oceans and cryosphere. These include:
Arctic sea ice, which has been lost at an escalating pace, is responsible for a significant fraction of total warming to date as a result of changed global albedo. Arctic ice extent also affects weather patterns around the world.
Greenland and Antarctic ice sheets whose melting is changing sea levels, currents and salinity, with a high potential for acceleration of these impacts.
Tundra (permafrost) which stores enormous amounts of carbon and methane and which threatens to break the global greenhouse gas budget completely if it continues to melt.
Ocean warming and the amount of additional heat the ocean can withstand before dangerous changes in oxygen levels and impacts to key systems like coral reefs.
Ocean alkalinity, which is increasingly moving to acidic (corrosive) as more carbon is deposited and absorbed into the water. This threatens shell-forming organisms, many of which are at the base of the food web.
These key parts of the global climate system cannot be allowed to pass tipping points, which would in turn fuel further climate disruption. Passing tipping points in these systems is clearly an unacceptable outcome.
The hedges element of the portfolio is about a rigorous research program on potential intervention approaches on different critical systems to see whether, how and with what impacts we might be able to slow the loss of these critical foundational systems.
Slowing these changes down, if even possible, will require an ocean’s focus on design, testing, development and deployment.