Sooner or later things have got to change. It just can’t carry on being the case that the companies posting record profits from selling a product that we now know is contributing to a potential climatic disaster, have so far escaped any firm policy to make them pay for their pollution.

I don’t really mean to pick on Shell – it’s just that my inbox this week contained three stories relating to them that got to me once again. Firstly, they are reported to be pulling out of the offshore wind farm development in the Thames Estuary – as ever good at talking the talk but when it comes to actually doing something, it’s all too difficult….. Secondly there’s the record profits issue – and thirdly, their submission to an Australian review of how to implement emissions trading over there has been made public. In it they claim that emissions trading won’t work to solve emissions from transport. And they are not the only ones – even many green NGOs adopt this line.

The whole point of trading is that it doesn’t actually matter where emissions reductions are made as long as someone makes them. Capping emissions from transport and making petrol companies responsible is a very sensible way of making sure that we are able to progressively reduce the amount of pollution entering into the atmosphere. Transport makes up a significant and rising portion of global emissions – it has to be capped if we’re to stand any chance of controlling the situation. If the caps mean companies like Shell paying for emissions reductions elsewhere that’s perfectly ok.

The alternatives that are often suggested of encouraging improvements in vehicle efficiency and incentivising alternative fuels are not incompatible with a cap – they can sit very easily alongside. But at least with a cap in place, if it turns out that the more efficient vehicles are just being used more or being sold to more people, and the alternative fuels are actually using more energy to be produced than they are saving, then the cap provides a safety net. And that’s what we need – we only have one chance at solving this problem and a belt and braces approach is absolutely essential.