> The scientific community was so wrong. Begging the government to solve it wasn't going to happen.

Which government?

Rewind to 1990. Suppose the U.S. government takes the hard-line position that climate change risks being a civilization-ending nightmare and has to be stopped ASAP. Other countries are going to know that going into negotiations. What exactly is the proposition to other countries to get them to dramatically decrease emissions? If we even got them to agree to it, they'd stripmine the U.S. economy in return, and wouldn't even leave us with our shirts. That's on top of the severe short-term self-imposed economic hardship of cutting hydrocarbon usage.

Granted, I don't believe for a moment that most conservative politicians have the appropriate level of concern for global warming, or the broader environment, or the wide variety of failure modes of capitalism in the realms of non-excludable and "club" (excludable but non-rival) goods in general. But assume for the sake of argument that they did have sufficient concern, or better yet, let's say the Green Party controls the House, Senate, and Executive. I don't understand what strategy the environmental left would have the U.S. use in international relations 10, 20, 30 years ago to try to mitigate environmental damage.

The US government obviously. I suppose as the biggest polluter by far you are bound to lose out most but how is that everyone else's problem? And what an argument - 'oh yeah I would have but I knew nobody else would so I just did even worse'. Plenty of other governments signed up for Kyoto in 1990 and pushed for higher levels. Anyways, what sort of economy were you planning to have without a habitable planet? The strategy, and potentially a highly lucrative one given US lead in required green tech, would have been less denying the uncomfortable truth, less pandering to big oil lobby and more educating the willfully ignorant and more investment in renewables and a bit of using your market influence to push the agenda. Hardly ever going to be likely though with GWB et al in charge although he did correctly say that there needed to be a technological solution. Trump omgwtf - they should call that thing the Bigly Berg in his dishonour.

I have 100ha trees btw. Used to be veggie but as that means GM and worse soya i.e. bad and very, very bad, eat and fly fewer miles now.

I'm not sure if these are the best data to use but can we go with this?

1990: http://cait2.wri.org/historical/Country%20GHG%20Emissions?in...

    (Mt CO2 emissions  direct / with land-use)
    U.S.: 5,866 / 5,550
    China: 3,154 / 2,833
    India: 1,188 / 1,142
    Brazil: 556 / 1,447
    World: 23,541 / 33,823

2013: http://cait2.wri.org/historical/Country%20GHG%20Emissions?in...

    U.S.: 6,279 / 6,213 
    China: 11,735 / 11,422
    India: 2,909 / 3,031
    Brazil: 1,017 / 1,317
    World: 48,257 / 46,445

Of course the U.S. is worst per capita, both then and now, but the U.S. could have cut emissions to zero in 1990 and CO2 emissions would be higher now than they were then.

How could a 1990s U.S. put substantially more pressure on other countries to curb hydrocarbon use when their economies were (and many still are) "developing"?

If the US cut emissions by investing in new technology that technology would be available to purchase to everyone in the world.