So, by 2030 even if the US cuts emissions by 30%, aren't there going to be 2-3 billion people in emerging markets moving up the economic ladder who will use a lot more energy.
Sure 300 million Americans are currently using a lot of energy but we're going to be much smaller part of the problem by 2030.
How does it help being smaller part of the problem? Sure, there are many ways to be smaller part of the problem - from reducing economic output to increasing the overall problem - but that doesn't seem to be a worthy target. If it does not lead to contraction of the whole problem - e.g. if strict regulations would just make manufacturing move to countries with weaker regulations - then why do it? Just to say "it's not us, it's those guys" - does not sound very helpful.
By that point renewables will be substantially cheaper.
I suspect that at that point, since many countries will be experiencing the effects of climate change full-force (especially the Chinese), there will be economic treaties which will tax according to emissions per capita or a similar metric.
That wasn't my point, at all. It's great that we're committed to reducing our usage by 30%. The problem is that 10x the number of people are going to increase their usage by a lot more than that amount.
Sure 300 million Americans are currently using a lot of energy but we're going to be much smaller part of the problem by 2030.