Ignoring climate change will cost countries billions and lead to food scarcity

The Stern Review, commissioned by the UK's chancellor in July last year and published last week, is the most comprehensive study ever on the economics of climate change.

Pre-industrial levels of greenhouse gases in the atmosphere were 280ppm CO2 equivalent (CO2e). The current concentration is 430ppm CO2e. Unabated climate change, caused by CO2 emissions, risks raising average temperatures by over 5C from pre-industrial levels.

Such changes will transform the physical geography of our planet. Agricultural practices would be catastrophically altered beyond recognition in many parts of the world, as the UN's current climate change conference in Nairobi confirms.

A temperature increase of just 2C would dramatically decrease productivity in many parts of the world. Such a rise might raise agricultural productivity in colder climates no one really knows for sure. But the net effect would likely be a decline in output especially in the poorer south.

What's more, low-lying agricultural areas will increasingly be more susceptible to flooding. This will pose a significant challenge to farmers especially as most attention will be focused on protecting built-up areas rather than the countryside.

The Stern review estimates that the costs of action to reduce greenhouse gas emissions to avoid the worst impacts of climate change can be limited to around 1 per cent of global GDP each year. People would pay a little more for carbon-intensive goods, but economies could continue to grow strongly.