Through the looking glass

The most critical consequences of climate change are arguably its impacts on food production and global food security. A large percentage of the world's food is currently grown as rain-fed annual crops in the tropics, where climate variability plays an important part in determining productivity. Natural climate variability in areas already classified as marginal for agriculture is one of many factors driving people into poverty. Under unmitigated climate change, many more will be at risk.

"Without mitigation, projections to 2100 are an increase in temperature of 1-5ºC, a sea-level rise of up to 80 centimetres, increased variability of the Asian summer monsoon, more intense rainfall with more tropical cyclones, increased drought risk, and more very hot days," reported Professor Martin Parry, co-chair of the IPCC Working Group II on Impacts, Adaptation and Vulnerability.

Modelling the effects of unmitigated climate change began in 1989 and results were published in the First Assessment report of The Intergovernmental Panel on Climate Change (IPCC) in 1990. For the third IPCC report published in 2001, projections included future concentrations of greenhouse gases based on different demographic, social, economic and technological assumptions.

Following the same path

The "business as usual" scenario (i.e. without mitigation and increasing greenhouse gas concentrations equivalent to a 1 per cent rise in carbon dioxide) forecasts a 5-10 per cent reduction in cereal production by 2080 compared with a reference scenario unaffected by climate change. With cereal prices expected to rise by more than 9 per cent, this puts an additional 50 million people at risk of hunger. "This is a global, long-term assessment focusing on average effects over space and time," Parry explained. "But the aggregate disguises regional disparities and airbrushes out the details. It doesn't show how Africa and South Asia are particularly at risk or how severe effects can be at the local level and over short periods."

In 1996, the UK's then Ministry for Agriculture, Forestry and Fisheries (MAFF) began projecting the effects for three time periods (2020s, 2050s and 2080s) of mitigated climate change assuming CO₂ concentrations could be stabilised at 550 or 750 parts per million (ppm). "Stabilisation at 750 ppm achieves some risk reduction, but far less than 550 ppm," concluded Parry. The additional number of people projected to be at risk of water shortage, for instance, in the 2080s is three times higher under the higher level of stabilisation. With this scenario, a far greater number of people are predicted also to be at risk from malaria (25%), hunger (30%) and coastal flooding (50%). Stabilisation at 550 ppm avoids most of these climatic consequences but this would require twenty times more reductions than currently laid down by the Kyoto Protocol.

"Very little of these predicted best set estimates are incorporated into future plans for global food supply," Parry noted. "Ultimately, the impact of climate change and risk of hunger will be greatly influenced by different pathways of development."

More than one fork in the road

For example, one scenario models a world of regional enterprise with high population growth, high but inequitable economic growth, and few global agreements. This corresponds to scenario A2 in the IPCC's Special Report on Emissions Scenarios (SRES). The other models a world of local stewardship with sustainable development, low population growth and moderate economic expansion (SRES B2).

Without climate change, the A2 scenario sees the number of people at risk of hunger reaching about 800 million in 2060-2080; whilst in B2 the number at risk falls steadily to 250 million. Taking climate into account, the number of additional people at risk from hunger is 185 million in A2 compared with only 40 million in B2 by 2080. "These futures are different," observed Parry. "The B2 pathway has much lower risk than A2, largely because of differing levels of income and technology, not differing rates of climate change."

The best strategies to avoid climate change induced hunger, emphasised Parry, combine mitigation with adaptation. "Invest in adaptation to increase resilience to climate change," he advised, citing crop breeding for new conditions, more efficient water use and institutionalised support for adaptation. He stressed that many adaptations can be win-win. Drought proofing for present conditions can increase resilience to a long-term trend in regions that will become hotter and drier. "It is not a question of devising new technologies," he insisted, "but making adequate use of existing ones and investing in the vulnerable regions of Africa, the Indian subcontinent and small island states. The guiding question is what particular investments should be made."