This is one of the key sentences: > Policymakers and the public, however, remain largely unaware of the risks posed by such a practically irreversible transition Most people still underestimate what it means for the earth system to change from the current stable state into another state, which might need many years to become stable again. And that new stable state might be a lot less favourable for us humans.
People really fail to grasp the significance of this part.
One of our most common apocalyptic fantasies lays this out quite well: nuclear annihilation. The common narrative is about the post-apocalyptic world and rebuilding. But this presumes a new normal has been established.
With climate change we will continue to experience more extreme changes at a faster rate over time with no chance of a "new normal" in our lives.
It took hundreds of thousands of years for humans to develop agriculture. It's no coincidence that this development happened during one of the most stable periods of climate the planet has ever seen. People love to wax poetic on human adaptability, but we were effectively playing on "easy" mode.
While the other side of climate change might be a more hostile earth, the transition period will be worse because you can't adapt. In our lifetimes we may live to see a period of record heat waves in Europe, followed by a transition of Europe to that is dramatically colder (and who knows, maybe back again).
The other major problem is as stability decreases so does our ability to predict the future. It's hard to even know what we might be facing in the coming years, but high variance is usually not great for complex life.