The global warming debate - a personal perspective

Clouds

These are the big unknown. There is no simple physics theory to guide us here as there is in the case of water vapour and albedo. Attempts to prove that clouds provide a negative feedback mechanism have all failed. What evidence there is suggests that temperature induced changes in the nature of cloud cover will result in a small net positive feedback effect.

Stratospheric water vapour

There is some evidence that the concentration of water vapour in the stratosphere declined in the past decade. No one knows why. This by itself could explain the pause in the upward movement of temperature we have observed since 2000, a pause which appears to be coming to an end.

Conclusion

Physics theory implies that adding CO2 to the atmosphere will alter climate. A reasonable inference from the available evidence indicates that this is most likely happening. Therefore there is a decision to be made.

Because CO2 molecules persist in the atmosphere for such a long period prudence suggests that we should start taking steps to reduce CO2 emissions. I shall not put it more strongly than that. Nor am I going to make cheery forecasts about "green jobs". Frankly this is going to be an expensive pain the backside.

It's like spending money on submarines and jet fighters. You don't do it because it's a good thing; you do it because sometimes you have to.