The Stern Review is regarded as the most comprehensive review ever carried out on the economics of climate change. The review finds that all countries will be affected by climate change, but it is the poorest countries that will suffer earliest and most. However, there is still time to avoid the worst impacts of climate change, if we act now and act internationally. Strong, deliberate policy choices by governments are essential to motivate change. The first half of the review focuses on the impacts and risks arising from uncontrolled climate change, and on the costs and opportunities associated with action to tackle it. A sound understanding of the economics of risk is critical here. The review emphasises that economic models over timescales of centuries do not offer precise forecasts – but they are an important way to illustrate the scale of effects we might see.
The review finds that all countries will be affected by climate change, but it is the poorest countries that will suffer earliest and most. Unabated climate change risks raising average temperatures by over 5°C from pre-industrial levels. Such changes would transform the physical geography of our planet, as well as the human geography – how and where we live our lives. Adding up the costs of a narrow range of the effects, based on the assessment of the science carried out by the Intergovernmental Panel on Climate Change in 2001, the Review calculates that the dangers of unabated climate change would be equivalent to at least 5% of GDP each year.
The review goes on to consider more recent scientific evidence (for example, of the risks that greenhouse gases will be released naturally as the permafrost melts), the economic effects on human life and the environment, and approaches to modelling that ensure the impacts that affect poor people are weighted appropriately. Taking these together, the review estimates that the dangers could be equivalent to 20% of GDP or more. In contrast, the costs of action to reduce greenhouse gas emissions to avoid the worst impacts of climate change can be limited to around 1% of global GDP each year. People would pay a little more for carbon-intensive goods, but our economies could continue to grow strongly.
If we take no action to control emissions, each tonne of CO2 that we emit now is causing damage worth at least $85 – but these costs are not included when investors and consumers make decisions about how to spend their money. Emerging schemes that allow people to trade reductions in CO2 have demonstrated that there are many opportunities to cut emissions for less than $25 a tonne. In other words, reducing emissions will make us better off. According to one measure, the benefits over time of actions to shift the world onto a low-carbon path could be in the order of $2.5 trillion each year. The shift to a low-carbon economy will also bring huge opportunities. Markets for low-carbon technologies will be worth at least $500bn, and perhaps much more, by 2050 if the world acts on the scale required. Tackling climate change is the pro-growth strategy; ignoring it will ultimately undermine economic growth.