What is being won is a changed world. How much change, we don't know, we have not been down this road before. What are the total effects going to be? We don't know that, either. And, what will be the time scale that the effects take hold on? We don't know that, also. We do know that some of the effects predicted, such as the regression of the Arctic Sea Ice have progressed far faster than any thought possible. And we know that there are some unknowns, the rate of discharge of CO2 and CH4 by the Arctic Ocean clathrates and Arctic permafrost, that could drastically change the equation.
In the face of all these unknowns, and with the knowledge that GHGs do increase the heat in the atmosphere, the deniers continue to insist we can go on as we have before. Either denying observed effects, or denying the basic physical science. And when they can no longer deny either, they will deny that they ever did, or that the scientists told them of the trouble ahead.