Stanford University climatologist Stephen Schneider discusses what we know and don’t know about the future of the Earth’s climate, and whether it is worth spending trillions of dollars to fight climate change.
What's the old joke? Prediction is hard, especially about the future. What do you have to do to predict the climate of 2100? Well, you have to know how much CO2, methane, nitrous oxide, aerosols - that's dust and smoke - are going to be there, because that changes what we call the forcing - the pressures on the climate system - to be warmer or colder. We know it's going to be warmer. That's virtually certain.
But you don't know what those are going to be on the basis of any history. There's never been a time before when there was six to ten billion people on the Earth, when they're demanding dramatic increases in their standards of living, and when they're using the cheapest available technology - usually coal and oil burning, big cars - to get there. So, before you can forecast how warm it will be in 2100 - and whether it's worth a trillion-dollar investment not to have that outcome - you've got to know a bunch of social factors.
What kinds of social factors?
How many people are in the world? What standards of living do they have? That's population times GDP per capita - a typical measure of standard of living. Then you have to multiply that by how much energy per unit of GDP they consume. We call that energy intensity. It's critically important. And how do we know if people are going to take this problem seriously?
"It seems that the climate in the next century would really be different, we might not know how different it is."
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