Earth's recent climate spiral.

[The Grand Nudger]

There's a strong correlation between co2 and gdp. Which is to say that in a current use scheme those developing areas with larger contributions to the fund based on co2 would also tend to have a gdp to match, and, at least ostensibly, an economic motivation to participate in any massively funded global program. It could easily be the case that the contributors get a bigger infrastructure or funding return on their climate mitigation dollar than they pay in.

It may be useful to point out that it's not that The Solution™ would cost 60t according to economists - it's the problem itself that is costing us as much, at present. That number is, itself, based on a very specific subset of all emissions. Arctic ice drilling. The number of developing countries drilling the arctic ice is...well, let's call it slim. This is very much the global norths lane. Which will not, in mere reality, fare well under any climate change scenarios. That misunderstanding is based on wishful projections of marginal improvement in agricultural productivity - dwarfed by the yawning chasm of global economic destruction. Simply put - one day in my lifetime the place I'm at will strongly remind me of florida. I'll have a longer growing season, and I'll be able to plant more tender crops (we're just about there already, to be honest). That'll be convenient for when I have to grow all of my own food in the dystopian shithole created by our stubborn insistence on fucking this all up. It'll all be worth it - the flash floods, the 60deg temperature swings, the 60mph winds....provided that some guy in the south pacific had to pay an extra half cent for every hundred dollars to cover for their contribution to that scenario.