If there is to be any hope of avoiding civilization-threatening climate disruption, the U.S. and other nations must act immediately and aggressively on an unprecedented scale. That means moving to emergency footing. War footing. "Hitler is on the march and our survival is at stake" footing. That simply won't be possible unless a critical mass of people are on board. It's not the kind of thing you can sneak in incrementally.
And it isn't happening. Indeed, one major political party denies climate change at all, and wants to double down on carbon. The gains made under Obama – largely through the stimulus and through the new gas mileage moves – are not enough. Which is why one thinks of geo-engineering as a last resort. I still hope that technology will eventually save the planet from too drastic a change (like the experiments in genetically saving the Great Barrier Reef). I just don't know whether it will happen in time to save entire ecosystems.