If 100 million Americans woke up tomorrow, slapped their heads, and voluntarily cut their greenhouse gas emissions in half, I predict the effect on climate change would be negligible. Nothing short of global greenhouse gas regulation can curb climate change.
Part of the explanation is economics. If for example, 100 million more people doubled their MPG overnight, the demand on gas would drop, and thus so would the price.
The decrease in price in turn would result in increased consumption by the remaining crowd that is not voluntarily environmentally conscientious.
And so economics is a negative feedback mechanism that works against all voluntary savings.
The very observant reader may notice that the offset from economic forces will only be partial; otherwise a paradox results. If the ‘ungreen’ folk consumed 100% of the energy saved by the ‘green’, then the result would be no change in the demand on energy, and thus no change in the cost, and so the ‘ungreen’ would have to increase spending in this scenario. That’s a paradox, so the economic argument deminishes less than 100% of all voluntary savings. (But determining the exact quantity requires some calculation that is beyond the scope here.)
The same axioms are true across other fields where greenhouse gas is relevant; farming, heating and air conditioning, etc. And it is true across the world, given the global nature of energy economies.
For the second piece of my argument, we know that two thirds of the existing known oil reserves must be left in the ground in order to limit climate change to the 2 degrees C goal. This means that in order to succeed, we must reach a very low demand notwithstanding a glut of supply. Economics, without the aid of regulation, will not permit this to happen.
So any ‘solution’ that stops short of global regulation will fail.