ROG WOOD

Extreme weather such as intense storms, droughts and heat-waves will cause more frequent and severe food production shocks leading to shortages as the global climate and food supply systems change, is the stark warning issued by a recent report.

The study, produced by an independent taskforce of British and American scientists, which included input from Dr Mike Rivington of the Dundee-based James Hutton Institute, outlines key recommendations to safeguard against threats to food supplies.

The Extreme Weather and Resilience of the Global food System report calls for co-ordinated action around the world to mitigate the impacts on people. Recommendations include creating an international contingency plan, adapting agriculture for a changing climate, developing modelling methods that will more accurately predict effects of production shocks, and indentifying international "pinch points" to try and minimise them.

How the climate may change, and what that could do to us, are both highly uncertain. The important thing to understand is that uncertainty is not our friend. There is much more scope to be unlucky than there is to be lucky.

For any pathway of greenhouse gas emissions through time, there are wide ranges of possible increases in global temperature and sea level. On a high emissions pathway where the most likely temperature increase is estimated to be 5 degrees C by 2100, anything from 3 degrees C to 7 degrees C may be possible. However, while on this pathway the chances of staying below 3 degrees C will become vanishingly small over time, the chances of exceeding 7 degrees C will increase, and this extreme outcome could become more likely than not within the following century.

Similarly, there is very little chance that the global sea level rise will slow down from its current rate, and every chance that it will accelerate - the only question is by how much. While an increase of somewhere between 40cm and 1m looks likely this century, the delayed response of huge ice-sheets to warming means we may already be committed to more than 10m over the longer term - we just do not know whether that will take centuries or millennia.

What may appear to be small changes in climate could have very large effects, especially if important thresholds are passed. Crops have limited tolerance for high temperatures, and as the climate warms, these limits are likely to be exceeded increasingly often. This is one reason why a temperature increase of 4 degrees C or more could pose very large risks to global food security.

Climate change is likely to cause even more extreme water scarcity in some regions, while increasing the risks of flooding in others.

Researchers have analysed past events and concluded that the risk of a 1-in-100 year food production shock is likely to increase to 1-in-30 or more by around 2040. Even from 2070 onward, they estimate that severe shocks, in which global food production drops by 10 per cent, could be happening in seven out of ten years. The increasing volumes of international food trade may help dampen the shocks in developed countries but amplify production shocks in developing ones, creating situations of economic and political instability.

Dr Rivington said: "The resilience of the global food system is likely to be impacted by future extreme weather events, posing a threat to food security, particularly for the most vulnerable people in food importing countries. The frequency of droughts, floods and heat-waves. along with additional intensity of storms is likely to increase due to climate change, risking food price shocks and downstream consequences.

"By looking at previous extremes we were able to develop plausible future impacts and response scenarios, showing that the probability of production and price shocks is likely to increase. Previously the risk was in the region of 1 in 100 years, this potentially reduces to 1 in 30 soon, with extreme events being possibly more severe. These shocks have short-term impacts beyond food price rises, such as export restrictions and nations keeping larger reserves leading to shortages elsewhere risking civil unrest and reduced political and economic stability.

"Extreme weather events, along with background climate change and our potential responses to the impacts also have long-term consequences, such as unsustainable intensification of agriculture and degradation of ecosystems. The additional pressure on the global food system from extreme weather occurs whilst food demand is increasing due to diet choices and population growth, and our need to protect our valuable food producing ecosystems."