Presumably she's referring to her first proposal -- a carbon tax. It's my understanding that there's nearly consensus among economists that a carbon tax is the most efficient solution to global warming, but political consensus that it would never happen when framed as a tax.
If you don't know what a carbon tax is, or why it's orders of magnitude more efficient a solution than "eat less meat" I'd encourage you to look into it a bit. Essentially if you create a system where what is best for the planet is also the cheapest course of action (for individuals and businesses), you no longer have to rely on convincing every single individual to change their morality/beliefs.
No sovereign is going to agree to subordinate itself without all others doing the same
Classic prisoners dilemma
They are universally rather timid in their scope, and politically fragile. So maybe they aren’t going to get us there, at least not in their current form.
But it’s going too far to say they just don’t exist or can’t exist.
We have plenty of treaties that inhibit states. Nuclear weapons, slavery, pollutants. Enlightentment and enlightened self-interest isn’t out of the question.
Ask Lybia how nuclear disarmament went
Go count all the slaves supplying the global market for chocolate, cobalt, mica, vanilla etc...
How about prisoners in the US making .20-.50c/hr making license plates or literally picking cotton on a former slave plantation in alabama.
Or how about slave labor in the form of migrant children working in factories for Hyundai in the US south
The concept of self-interested Neoliberalism has utterly failed and it is turning into a global catastrophe
The earth cannot sustain 8 Billion people each living at millionaire consumption standards
In fact, you live better - far better - than anyone in history. It's not even close. It was built by the post-war 'neoliberal' order, on a foundation of human rights and free markets.
For us to quit and complain after all the work our predecessors did, remaining optimistic and working in a much starker situation - after depressions and world wars - would be pathetic abdication of our duties.