George Monbiot is correct in his praise of Thomas Piketty's proposal for a wealth tax to counteract the insane levels of inequality now generated in our world, and in pointing out that only the Green party is prepared to back this obvious idea. However, we should be careful not to let Piketty's helpful intervention in the debate blind us to the severe limits of his own stance in political economy.

Some people think the rhetoric of climate change is too emotive. But faced with a global catastrophe it would be unwise to tone down our language.

We are all familiar by now with the shrill voices of climate change deniers. But with every passing week they become more and more irrelevant, as their 'scepticism' about the reality of man-made climate change is exposed as risible. The issue now is not whether we are certain that dangerous climate change is real and is happening - the issue is only how we are going to tackle it. So how do we motivate people to act? How do we persuade them not to seek refuge in psychological defence mechanisms of the kind Leo Hickman chronicled in the Guardian last week?