It's Kyoto all over again.
The United Nations Framework Convention on Climate Change embraced ''binding targets'' for emissions reductions in 1997 only to discover some years later that they weren't binding at all. But they felt good.
The G20 finance ministers' communique is actually weaker than the Kyoto Protocol.
It doesn't even use the word ''target'' - preferring the weaker word ''aim'' - and, whereas each of the signatories to the Kyoto Protocol agreed to individual targets, it is not yet clear that's what will happen when the world's 20 leading economies regroup in Brisbane in November.
Agreeing to the sum of the parts without agreeing to the parts themselves would be like agreeing to let other nations do all the work.
It's one of the arguments that was used against Australia signing the Kyoto Protocol. What would it matter what Australia did? The other bigger nations would have to do the heavy lifting.
This time, the conference chairman, Joe Hockey, was having none of that argument. Australia had an important, pivotal role to play in demonstrating to the world what can be done to boost growth. Each of the G20, regardless of size, had to do its part.
Behind the scenes, big advances were made in sharing information about tax, reorienting and refinancing the International Monetary Fund and ensuring central bankers work together rather than in opposition.
The summit was brilliantly organised and the brainpower assembled in the conference room was awesome.
It might have achieved even more if it had lasted more than two days and it might achieve more still if it happened several times each year. But just assembling so many leaders and officials in one room was an astounding achievement. Hockey and the Treasury served Australia and the world well.