Greenhouse gas emissions: Ultimately, stabilisation - at whatever level - requires that annual emissions be brought down to more than 80% below current levels

A diet that relies heavily on meat production results in higher emissions than a typical vegetarian diet. Different individuals will make different choices. However, the debate about climate change should not be dumbed down to a single slogan, such as 'give up meat to save the planet.

The greenhouse effect is something you can observe experimentally - and most people have observed the greenhouse effect themselves, in greenhouses. Yes?

Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world's resources. A vegetarian diet is better.

As an undergraduate, I did maths and physics. That doesn't make me a scientist. So I try to read and understand and talk to scientists.

How is it that, in the face of overwhelming scientific evidence, there are still some who would deny the dangers of climate change? Not surprisingly, the loudest voices are not scientific, and it is remarkable how many economists, lawyers, journalists and politicians set themselves up as experts on the science.

Looking back, I underestimated the risks. The planet and the atmosphere seem to be absorbing less carbon than we expected, and emissions are rising pretty strongly. Some of the effects are coming through more quickly than we thought then.