Climate change is an area where science and engineering – across all disciplines, from the physical to the social sciences – has a crucial role in informing decisions by policy makers.
The Intergovernmental Panel on Climate Change (IPCC) published the first instalment of its Fifth Assessment Report last September. This summarised the latest scientific understanding of how the climate is changing and the contribution of human activities. The second instalment of the IPCC Fifth Assessment Report, published today, looks at the evidence relating to the impacts of climate change and some of the potential consequences for natural and human systems.
The September IPCC report found that, without concerted efforts to reduce greenhouse gas emissions, global temperatures are likely to rise by more than 2°C over the next century and could rise by as much as 5°C. The messages from today’s report are clear: even at the low end of this range of warming there are considerable risks, and at the top end of the range these become widespread and very serious.
At lower levels of warming there may be some positive effects, for example the effects of a warmer climate and higher levels of CO2 in the atmosphere could increase crop yields in some parts of the world. But at higher levels of warming the impacts are expected to be overwhelmingly negative. Risks of water scarcity, flooding, and food insecurity all increase with temperature. The report highlights that at warming of more than 4°C some of the impacts will be very unpleasant, including risk of substantial species extinction. In some areas of the world, for parts of the year, human habitation could become very difficult.
As temperatures increase so too does the risk of abrupt or irreversible changes in the climate system. Accelerated melting of the Greenland or West Antarctic Ice Sheets would significantly increase sea levels. Release of large stores of the greenhouse gas methane from thawing permafrost would further amplify global warming. These are currently considered low probability events, but the potential consequences are sobering.
Our current and future vulnerability to climate-related risks depends not just on the physical impacts themselves but on the context in which they occur. Climate change will interact with other socio-economic factors, including economic and population growth, demographic change and urbanisation. Taking account of climate-related risks as part of development decisions is a fundamental part of managing the risks. By understanding the risks better, we understand choices for policy makers more clearly.
If we are to protect future generations from the most serious risks of climate change we must take decisive action now to reduce emissions. If we wait for the impacts to happen, it will already be too late. The transformation to a low carbon future is one of the greatest technological challenges of the twenty first century, but it also brings with it important opportunities for sustainable growth and prosperity.