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No big decisions have a 100% confidence level, that's an absurd criteria. Catastrophic events are also a bad thing to look at because researchers tend to just s
by AlanSE 7y ago
No big decisions have a 100% confidence level, that's an absurd criteria. Catastrophic events are also a bad thing to look at because researchers tend to just stop the detailed simulations beyond a certain horizon (specifically 100 years) because so much changes in the human world on those time frames that people don't take it seriously. The vast majority of truly terrible things that will happen as global warming continues will happen past that time frame. At some point, the metabolism of the plant will draw down the CO2 concentration (if we stop emitting), and this is >1,000 year frame. 100 years tends to not be enough for terrible (and I mean like really truly truly terrible) things to happen due to thermal inertia.
We're going to have to engineer the climate directly if we still want to have an industrial society in 200 years. We will probably do it much sooner. The effects of the combination of more CO2 + artificially decreased sunlight are going to be bad, but are not well understood.
It is true, it's not a question of whether we have consequences or not, just a question of "how bad". That is extremely strongly a function of how much emissions we emit until, say 2050. It's hard for me to even imagine how we can continue using fossil fuels for energy much beyond then, so not reducing emissions also strikes me as kind of... needless self-inflicted harm.
- agent008t 7y agoI am not setting a threshold, I just want to estimate the objective confidence level in our predictions. When you say 'It is not a question of whether we have consequences or not, just a question "how bad"', it sounds like 100% confidence, but then you say that it is not 100%. So is it more like >99%? Or 70%? Or 10%? Or <1%? And more specifically, what is the probability that reducing anthropogenic emissions to a certain target would result in us averting the predicted catastrophic scenario that otherwise would not have been averted?
- AlanSE 7y agoMaybe a problem of units? Sea levels are rising due to the melting of land ice. That's a historic fact, but predicts are concerned with how much it will rise. There is a chance that it will reverse, and before 100 sea level will actually fall. How much probably depends on what factors you allow yourself to consider. For example, I think the most likely reasons this would happen would be due to human geo-engineering or nuclear war. For that, maybe I'd give 0.01% chance. But for it to change course due to natural factors... I'll give 1.0e-6%. Because you know, about every 100M years sounds reasonable for a sudden violent and unprecedented climate movement in Earth's history. The reason this is so tremendously unlikely is because the climate is already hot enough to melt most of the ice, only reason it hasn't is because it takes time. It's a system that's moving on (an abstract form of) inertia. > reducing anthropogenic emissions to a certain target would result in us averting the predicted catastrophic scenario that otherwise would not have been averted? I honestly can't read this. Rising sea levels affects people... the more it rises the worse it is. At some point, the rise is catastrophic. The English language is not going to help say "at exactly 1.65 meter rise it becomes catastrophic". Climate scientists can, and do, connect emissions scenarios to a sea level. It's a much more human activity to connect the change in environment given by a numerical metric to a moral judgement.