A new paper by leading authorities on positive feedback loops suggests that even if we could stop all emissions and "only" get to 2°C rise, it likely wouldn't be stable. This is the first paper to suggest 2°C rise is a threshold from which we can't pull back. New positive climate feedbacks, such as weakening carbon sinks and the effect of increased rainfall on carbon sequestration by forest soils, are continually being discovered. We know too far too little about how they will all amplify one another. Ignorance of complex Earth system process interactions will let us in for an ugly surprise.
Rockström and his co-authors are among the world’s leading authorities on positive feedback loops,…
Their new paper asks whether the planet’s temperature can stabilise at 2C or whether it will gravitate towards a more extreme state. The authors attempt to assess whether warming can be halted or whether it will tip towards a “hothouse” world that is 4C warmer than pre-industrial times and far less supportive of human life.
“We note that the Earth has never in its history had a quasi-stable state that is around 2C warmer than the preindustrial and suggest that there is substantial risk that the system, itself, will ‘want’ to continue warming because of all of these other processes – even if we stop emissions,”…
New feedback loops are still being discovered.
Rockström says there are huge gaps in data and knowledge about how one process might amplify another.
… the feedbacks could push the planet to a more extreme state.
“The heatwave we now have in Europe is not something that was expected with just 1C of warming,” Rockström said. “Several positive feedback loops are already in operation, but they are still weak. We need studies to show when they might cause a runaway effect. [emphasis mine]
In sum, my take is that at least 10 positive feedbacks feed back on each other, and we know didly squat. For those of you unfamiliar with complex systems, even small effects which magnify one another become completely unpredictable after 4 or 5 interations. Imagine predicting the patterns a creamer makes as one stir, after a second, then a third.
With the climate, it's like we're not just using one spoon (CO2 emissions) to mix one creamer and trying to predict the outcome (temperature), but ten utensils and ten different creamers. After 5 stirs nobody can predict what patterns will emerge. But you can see how one might think the coffee "wants" to be completely different.image source text from article