One of the great features of climate science is that you always learn new things. It is the story of how our planet evolved, changed, and arrived where we are, silly naked apes as we are. One of the most fascinating moments of this long history is the "Snowball Earth" period. Some 700 million years ago, in the Sturtian period, at the end of the Proterozoic Eon, the whole planet got frozen, covered by an ice sheet. Yes, Earth was all white, ice-covered, and nicely frozen. The great holobiont that some call "Gaia" nearly died. It may have survived, barely, because some small areas, maybe volcanic hot springs, remained ice-free.
Why this event? An ongoing research effort is aimed at unraveling the story. The latest results show that the great freezing was preceded by the "Franklin Large Igneous Province" (Franklin LIP). It was another spectacular event but for the opposite reasons. It involved a gigantic volcanic eruption that spread molten lava over a huge region that went from the regions now called Alaska and Greenland. It lasted about one million years. Earth's history is never boring!
Great, but one moment. There have been several Large Igneous Provinces, LIPs, in the later history of Earth. In most cases, the result was warming, not cooling. The "great dying" of the end of the Permian, about 250 million years ago (at the "Permian-Triassic" boundary) was caused by a giant LIP in the region called Siberia today. The demise of the dinosaurs (apart from birds) was caused by another huge LIP taking place in the Deccan region in what is now India (an asteroid may have helped, but the LIP was probably the main cause). Smaller LIPs also caused havoc in the ecosystem.
The basic idea is that these huge eruptions inject large amounts of CO2 into the atmosphere, generating a rapid and catastrophic warming that, in turn, causes a dieoff in the ecosystem. So, what did the Franklin LIP have that is different from the more recent LIPs? Is this a new demonstration that climate science is all wrong, actually a hoax created by the appliance industry to force us to cook on induction stoves?
Well, no. If you know the basic mechanisms that control CO2 concentrations and consequently Earth's temperature, the story makes plenty of sense. The Franklin LIP was not different (not so much, at least) from the later LIPs. But the world in which these eruptions took place was completely different.
Let's start from the beginning: How do LIPs emit CO2? It is because the volcanic lava contains carbonates, compounds that can decompose, producing CO2 and oxides. As for all chemical reactions, the equilibrium between CO2 release and uptake depends on temperature. At the high temperatures of molten lava, carbonates tend to decompose, but, when the lava cools down, the reverse reaction occurs. Now, CO2 reacts with silicates to form carbonates. If the mass of lava is truly huge, as it was in the Franklin LIP, then it is no surprise that the CO2 drawdown is massive. If the temperature is hot enough, but not too hot, the drawdown is also rapid, at least on the geological time scale. Starved of CO2, the atmosphere doesn't act any longer as a blanket to keep the Earth warm. Bang! It is snowball Earth.
Now, there comes the fundamental point: at the time of the Franklin LIP, the interplay between CO2 release and uptake took place in a relatively simple world: There was no life on land; it only appeared a couple of hundred million years later. So, since the LIP took place mainly on land, it didn't interact with the land biosphere. Then, fast forward 400 million years in the future, and you are now seeing the huge, gigantic, enormous, appalling lava landscape that we call the Siberian LIP. Same thing as before, but with a profound difference. By then, life had spread on land and had plenty of time to create huge reservoirs of carbon that resulted from the decomposition of living matter. This carbon we call "coal." In addition, there were also reservoirs of kerogen (solid hydrocarbons dispersed in the soil) and those hydrocarbons that the naked apes living today on Earth call "fossil fuels."
Imagine the lava spewing out from the Siberian LIP going through this mass of fossil carbon, and you see that there was a factor that didn't exist with the Franklin LIP: coal was burned by the hot lava and turned into CO2. The same thing happened some 190 million years later with the Deccan LIP. Huge amounts of carbon were turned into CO2 and the resulting warming wrecked the whole ecosystem. Bang! Another mass extinction (the poor dinosaurs were boiled alive). That was the rule with all the Phanerozoic LIPs; their correlation with mass extinctions is reasonably well established, although the details can be complicated. You can find more information in this paper by Ernst and Youbi.
And there we stand: the story of life on Earth is an incredible adventure that sees the geosphere, the atmosphere, and the biosphere interacting with each other, usually resulting in a certain degree of stability but sometimes leading to great upheavals. It is what's happening now, with a large tribe of naked monkeys having taken control of the biosphere and playing the role of a Large Igneous Province by burning the huge reserves of fossil hydrocarbons built over the Phanerozoic Eon. For sure, this new "artificial LIP" will not lead to cooling but to warming. A huge and rapid warming. Gaia will probably survive it, but the monkeys... well, it all to be seen
A simple discussion of the recent results on the Franklin LIP can be found on Anton Petrov's blog.
How Gaia survived Snowball Earth is described in this post by Ugo Bardi https://theproudholobionts.blogspot.com/2022/12/how-gaia-saved-earth-from-cold-death.html
The paper on the Franklin LIP by Dufour et al. that stimulated this post can be found at https://www.sciencedirect.com/science/article/pii/S0012821X23002728
The link to the paper by Ernst and Youbi on mass extinctions is: https://www.sciencedirect.com/science/article/pii/S0031018217302857
If you cannot access these papers, ask me for a copy
