It's all a matter of opinion. One could argue that the pollution generated from cultivating agriculture is worthy of the x amount of tons of CO2 emitted, because the lives prevented from starving from that food are worth more than the .000001 degree they raise the temperature.
By the same argument, one could say that the satisfaction or benefit one person gains from driving a hummer is not worth as much as the negative impact it has on the environment.
But regardless, if society as a whole set a certain amount of pollution as acceptable (this is all theoretical), then society would find more efficient ways to produce products so that more can be produced in the same amount of pollution