I'm reading "The Ends of the World: Supervolcanoes, Lethal Oceans, and the Search for Past Apocalypses" by Peter Brannen. Most of the book focuses on past mass extinction events, but there's a bit of discussion and comparison to what's going on in the world now. It's written in a fairly popular-science-y style, but there's lots of references to further reading. Some quotes:

> [...] humanity has not yet come anywhere even remotely close to the death tolls of the major mass extinctions of the past half-billion years ... yet. In the past 400 years, there have been documented extinctions of some 800 species. This is a tragedy, to be sure, and likely a massive undercount, but when divided by the 1.9 million species known, 800 extinct species amounts to an extinction of less than one-tenth of 1 percent - a far cry from the End-Permian, during which, generously rounding up, almost 100 percent of complex life on earth was killed.

re: the End-Permian mass extinction

> "Five hundred million years is a really, really, _really_ long time. And [the End-Permian mass extinction] is the single worst event in the last 500 million years of earth history. So your scenario should not be sort of a bad-day scenario. [...] It's closer to a one-in-a-billion event."

> [...] End-Permian sites across the planet from the ancient ocean [...] similarly recorded a carbon cycle jackknifing. Where did all this extra light carbon in the atmosphere come from? One way is to kill all the plants, plankton, and animals in the world. [...] But the carbon isotope swing at the End-Permian mass extinction is so severe that many other scientists think that the collapse of the biosphere isn't enough to explain it.

> [...] At the end of the Permian, Siberia briefly turned inside out as the Traps covered Russia in more than 2 million square miles of lava.

> [...] "Basically the entire global economy rests on how quickly we can get carbon out of the ground and put it in the atmosphere", Ridgwell told me. "That's basically the global enterprise. And there's a lot of people doing it. Geologically, it's a really impressive effort."

> But as exceptional as humans are, estimates of the carbon released in the End-Permian mass extinction range from an utterly catastrophic 10,000 gigatons of carbon -- twice as much as we could ever burn -- up to a mind-meltingly unfathomable 48,000 gigatons.

> [...] "So taking the modern ocean and adding 40,000 gigatons of carbon -- like in the End-Permian -- it would take you from, say, 300 ppm to 30,000 ppm CO_2," Payne said. We both started laughing. This number is incomprehensible.

> [...] For now, typical estimates place End-Permian atmospheric carbon dioxide somewhere around 8,000 parts per million [...]

> [...] In the long term the oceans can keep up with a huge buildup of carbon dioxide in the atmosphere, as long as it happens slowly enough. The gradual process of weathering breaks down rocks on land, washing them into the ocean and, in doing so, buffer the seas against acidification [...]"

> "Well, the rate at which we're injecting CO_2 into the atmosphere today, according to our best estimates, is ten times faster than it was during the End-Permian. And rates matter. So today we're creating a very difficult environment for life to adapt, and we're imposing that change maybe ten times faster than the worst events in Earth's history".

For reference, the human endeavour is injecting roughly 40 gigatons of CO_2 into the atmosphere every year.