It doesn't really matter...

...what is causing climate change. By the time we definitively identify the cause it may be too late to do anything about it. From a letter to the [UK] Guardian by Piers Corbyn of Weather Action:

The global warmers' claim that current extra CO2 causes warming which gets dangerously magnified through the greenhouse effect of extra water vapour in the atmosphere, consequent to the temperature rise, also fails. The sea absorbs extra CO2. Furthermore, increased transpiration-cooling by enhanced growth of plants, which is caused by extra CO2, cancels out the extra greenhouse warming of that same CO2. Increased greenhouse heating due to doubling CO2 is 3.7 watts per sq metre. This is negated by about the same amount of enhanced transpiration-cooling of plants, all of which grow faster in extra CO2. Therefore there is no CO2 driven net heat flow and surface temperature rise. Temperature and climate change in our epoch is therefore driven by other factors, especially solar particle and magnetic effects.

Fine: there appears to be reasonable doubt about whether greenhouse gas emissions cause climate change. Should we therefore wait several decades before mitigating the effects of climate change or taking steps to stabilise the climate? In general, do we have to find root causes of a problem before we try to solve it? We can do both, but allocating resources between the two courses of action needn't be done at the initial stages. We strongly suspect, for instance, that smoking causes cancer. But we don't give up all research into prevention and cure of cancer until that particular causal relationship has been proven. Similarly with climate change: let's focus on mitigating its worst effects, however caused. And let the market decide, via Climate Stability Bonds, how to allocate scarce resources between prevention and mitigation: something that the market, with its built-in incentives, can do far more adaptively and less divisively than the absurdly expensive, ineffectual bureaucratic testimony to 1990s science that is Kyoto.