Fed up with controversy

If we're agreed that global warming does exist, how much difference does it really make whether it's human-caused or not?  After all, most technological optimists (often known as "cornucopians" or "browns") willingly accept that humanity can and does influence nature on a global scale, just not in this particular way.  Given that we have this kind of power, and given the catastrophic consequences of letting the climate continue to warm, shouldn't we try to do something to counteract the change, no matter what's causing it?