Grade school science howler from Ken Caldeira: 'CO2…forms carbonic acid (the same thing that makes soda fizz)'

From the Carnegie Institution , where soda pop science is like a carbonic acid trip, they say (thanks to modeling) we have to make big changes:  “To save coral reefs, we need to transform our energy system…” while equating natural dissolution of CO2 into seawater with carbonation of soda pop, done under pressure and reduced temperature, making it supersaturated. The process is described as:

The amount of a gas like carbon dioxide that can be dissolved in water is described by Henry’s Law. Water is chilled, optimally to just above freezing, in order to permit the maximum amount of carbon dioxide to dissolve in it. Higher gas pressure and lower temperature cause more gas to dissolve in the liquid. When the temperature is raised or the pressure is reduced (as happens when a container of carbonated water is opened), carbon dioxide comes out of solution, in the form of bubbles.

While weak carbonic acid does get formed with CO2 dissolution in water [CO₂ + H₂O H₂CO₃ ] the majority of the carbon dioxide is not converted into carbonic acid, remaining as CO₂ molecules, which is why it outgasses so easily when a non-chemical catalyst is applied, like vibration. Carbonic acid does not make the soda pop “fizzy”; it is the fact that it is supersaturated, and stored in a way to seal pressure preventing gas escape and maintaining the supersaturation. It is pressure and temperature that drive the main outgassing process, as anyone who as left an open can of soda pop in their car during a hot summer can attest.

Major changes needed for coral reef survival

Washington, D.C.—To prevent coral reefs around the world from dying off, deep cuts in carbon dioxide emissions are required, says a new study from Carnegie’s Katharine Ricke and Ken Caldeira. They find that all existing coral reefs will be engulfed in inhospitable ocean chemistry conditions by the end of the century if civilization continues along its current emissions trajectory. Their work will be published July 3 by Environmental Research Letters. 

Coral reefs are havens for marine biodiversity and underpin the economies of many coastal communities. But they are very sensitive to changes in ocean chemistry resulting from greenhouse gas emissions, as well as to coastal pollution, warming waters, overdevelopment, and overfishing.

Ricke and Caldeira, along with colleagues from Institut Pierre Simon Laplace and Stanford University, focused on the acidification of open ocean water surrounding coral reefs and how it affects a reef’s ability to survive.

Coral reefs use a mineral called aragonite to make their skeletons. It is a naturally occurring form of calcium carbonate, CaCO3. When carbon dioxide, CO2, from the atmosphere is absorbed by the ocean, it forms carbonic acid (the same thing that makes soda fizz), making the ocean more acidic and decreasing the ocean’s pH. This increase in acidity makes it more difficult for many marine organisms to grow their shells and skeletons, and threatens coral reefs the world over.

Using results from simulations conducted using an ensemble of sophisticated models, Ricke, Caldeira, and their co-authors calculated ocean chemical conditions that would occur under different future scenarios and determined whether these chemical conditions could sustain coral reef growth.

Ricke said: “Our results show that if we continue on our current emissions path, by the end of the century there will be no water left in the ocean with the chemical properties that have supported coral reef growth in the past. We can’t say with 100% certainty that all shallow-water coral reefs will die, but it is a pretty good bet.”

Deep cuts in emissions are necessary in order to save even a fraction of existing reefs, according to the team’s results. Chemical conditions that can support coral reef growth can be sustained only with very aggressive cuts in carbon dioxide emissions.

“To save coral reefs, we need to transform our energy system into one that does not use the atmosphere and oceans as waste dumps for carbon dioxide pollution. The decisions we make in the next years and decades are likely to determine whether or not coral reefs survive the rest of this century,” Caldeira said.

The World Climate Research Programme’s Coupled Model Intercomparison Project is provided support from the U.S. Department of Energy, which developed a software infrastructure in partnership with the Global Organization for Earth System Science Portals.