but doubts that the world's governments will be able to agree on effective action to halt it

Supporters of worldwide drastic action always talk as if all countries will be losers. Some countries, including Russia, think they will be winners. And that doesn't even take into account the fact that humans tend to see things in relative terms, and might well accept a loss if their enemies suffer a greater loss. And countries which feel, rightly or wrongly, that their relative prosperity is unfairly low might like to just roll the dice. So if you want to get anywhere you need to:

• Get the countries that want strong action to unite and agree that, at the very least, they will form a trading block and not allow the export of CO2 pollution to industry outside the block. This will involve abrogating many existing treaties. Chance of war high.
• Not be sidetracked and delay action by negotiation with countries outside the block

But all this is fanciful. Consider the suggestion that we reduce emissions by 25% (or even 5%) by purely financial means (trade or tax). This means imposing huge pain until the market does its magic trick of producing an alternative. Politically impossible. The right answer is for the government to do a bit of winner picking (not a good idea in general), build some huge power infrastructure THEN bring in the carbon price that will make that infrastructure cost effective. If you don't prepare alternative infrastructure then the only way to get the reductions you want is demand destruction. You can call it an efficiency dividend, but you still can't sell it to the voters.
And indeed we see that the peak oil economic collapse is hitting NSW before the other states, and what does the government do in the face of falling revenue: shelve plans for more electric public transport. We're doomed.