Science Seen Time One author Colin Gillespie helps you understand the physics of your world.

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Capping Climate Change?

Limits of survival are set by climate, those long drifts of change which a generation may fail to notice.
And it is the extremes of climate which set the pattern.

Frank Herbert

Can we set a limit on how bad climate change can get? A new paper by ten European geoscientists seems to say so. What does it tell us about today’s concerns? It tells us to look to the oceans. It says extreme weather events are not the whole, or maybe even the main, story. The research is a big achievement—but the limit is a big mistake! There’s reason for despair and room for hope; let’s sort them out.

The geoscientists looked at a limestone bed that trillions of shells made on the sea bottom long ago. They focused on certain isotopes (elementsPermian Mass Extinction LPI image with different numbers of neutrons per atom, and so similar chemistry but different atomic weights) in the deposit. They looked at new data for boron isotopes and previous data for carbon isotopes. They used them to decode the state of oceans 252 million years ago, at the time of the Great Dying (aka the Great Permian Extinction). Knowing the basic chemistry, they asked what conditions would create the observed proportions of isotopes in the limestone. Their method was like reverse engineering a long-lost environmental disaster with a computer.

Their work shows how increased carbon dioxide (CO2) in the atmosphere led to the Great Dying. The CO2 likely came from vast volcanoes, whose lava beds covered much of Siberia and can still be seen today. Most species of land animals and 95% of sea creatures disappeared; this is the most catastrophic loss of species ever, in a geologic record of three billion years.

It was ocean acidity not air temperature that caused most of the Dying. CO2 dissolves in water to make carbonic acid. High CO2 drove ocean acidity up. Acidity is measured by pH. The study shows the pH of the oceans dropping by 0.6 or 0.7 pH units. Doesn’t sound like much. But this means a four- to five-fold increase in concentration of hydrogen ions (the bearers of acidity). Could climate change be doing this today? The authors seem to say: Perhaps, but not as badly.

The carbon release required to drive the observed acidification event must have occurred at a rate comparable with the current anthropogenic perturbation but exceeds it in expected magnitude.

That is, we may be going to hell in a handcart at about the same rate but it should be a lesser hell. How do they get to that conclusion? Their reverse engineering tells them how much carbon was released (as CO2) 252 million years ago.  The authors say that even if we burn the world’s entire supply of fossil fuels (which is the present plan) this would likely release less carbon than those volcanoes did.

Let’s be clear that less-than-the-Great-Dying, if true, is cold comfort. Even a smaller increase in acidity (i.e., less than 0.6 decrease in pH) from the oceans’ current pH of around 8.0 could mean: Goodbye coral reefs, farewell to all the fish that live and breed in them. Farewell to some one-hundred million tons of fish caught in the seas each year to nourish billions of people. And let’s not forget the economic loss, about a trillion dollars per annum.

Let’s be clear on this too: There is no scientific basis in the study for its comment on ‘expected magnitude’. The comment assumes that climate impact is proportional to the amount of fossil fuels burned. We know that it is not. Climate today (and likely back then too) is highly non-linear, with many interlocking feedback loops.

For example, climate change warms glaciers which melt and raise sea level, which erodes shorelines, which releases organics trapped in permafrost, which rot and release greenhouse gases, thus increasing climate change. Once you start this kind of system it may not stop until it gets to where it’s going pretty much regardless of what else you do. On the other hand, warmer seas may mean more water vapour in the atmosphere, which makes more clouds, which reflect more of the Sun’s heat into space, which cools the planet, thus reducing climate change. Fact is, nobody yet understands the feedback loops that are already starting to decide our fate.

Bottom line: this study and many others underline the urgent need to understand the feedback in the climate system. Should we stop eating meat (the main source of greenhouse gas today) or should we move to higher ground?


Frank Herbert (1976), Children of Dune, New York: G.P. Putnam’s Sons, p. 335;

Matthew Clarkson et al. (2015), “Ocean Acidification and the Permo-Triassic mass extinction”, Science, Washington: AAAS, vol. 348, p. 229;

Other Reading:

Hillel Hoffman (2000), “When Life Nearly Came to an End”, National Geographic,

Image credit: Universities Space Research Association, Lunar and Planetary Institute (2015),

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