The Effects of Global Warming on Food Security

By Kate Godden

Kate is a Senior Lecturer in the Centre for Public Health Nutrition at the University of Westminster where she teaches food security, programme planning and emergency nutrition. She has over 10 years experience within the emergencies sector.

With so many reports on climate change coming out from different quarters, it can be hard to know which are based on reliable information. Those of us who work in the food and nutrition sector do have real cause for concern, as it is highly probable that there will be a general increase in food insecurity in many of our most vulnerable populations over the coming years. Additionally, it is very likely that there will be an increased frequency of natural disasters caused by extreme weather, including flooding, heat waves and drought.

Sourcing objective information

The Intergovernmental Panel on Climate Change (IPCC) was set up in 1988 to review objectively and consolidate the latest scientific literature on the subject. In 2007, they released their Fourth Assessment Report (AR4)¹ based on 29,000 observational data series from 75 studies around the world (though data from developing countries are seriously lacking). The AR4 reflects that global warming is a reality, the average air temperature has warmed by 0.74o C (0.56-0.9 o C) over the past 100 years. This is an average global figure and doesn't truly reflect localised temperature variations. It is also feared that the rate of global warming is increasing - eleven of the twelve years to 2006 rank among the twelve warmest years on record since 1850. Land regions are warming faster than the oceans and the northern latitudes are warming faster than southern ones with the average arctic temperature increasing at twice the global rate. There are also increased sea levels (global average 1.8, 1.3-2.3 mm per year 1961-2003). The rate of increase of the sea level accelerated in the last decade of the century but it is not yet clear if this was due to decadal variation or not. The world's third largest natural disaster of recent years, (after the tsunami of 2004, Pakistan earthquake of 2005) was, in fact, a heatwave that killed over 64,000 people² in southern Europe in July/Aug of 2003.

Observed changes in the climate

'Warming of the climate is unequivocal as is now evidenced from observations of increases in global average air and ocean temperatures, widespread melting of the snow and ice caps, and rising global average sea level ' (IPCC, 2007).

Warm air is able to hold more water vapour than cooler air and this means that warm air is less likely to provide rainfall until it cools. Cooling, however, results in very heavy, localised rainfall coming from the water laden skies. Simplistically, this means hot regions become hotter and drier whilst cooler ones become warmer, wetter and with a higher potential for flooding. The rate of global warming is thought to be increasing at a rate of 0.2 degrees centigrade/ decade.

The AR4 observes that trends in precipitation have changed, with eastern parts of North and South America, northern Europe and northern and central Asia having significantly higher rainfall in contrast to lower rainfall in the Sahel, Mediterranean, southern Africa and parts of southern Asia. Globally, the area affected by drought has almost certainly increased since the 1970s.
There has also been an increase in the frequency and/or intensity of extreme weather events over the past 50 years. Hot days and nights have become more frequent and cold days and nights less common. It is likely that heat waves are more frequent over most land areas, that the frequency of heavy precipitation has increased over most areas, and that the incidence of extremely high sea level has increased at a wide range of sites worldwide.

What does this mean for food security?

Naturally, these climate changes have direct effects on agricultural production. It is anticipated that for moderate global average temperature increases (estimated between 1-3oC), there will be an overall increase in global food production. Additional temperature increases, however, would cause an o v erall fall in food production.

So who are likely to be the winners as the climate changes and who are likely to lose out? In very general terms, some regions at lower latitudes will become hotter and drier with a shortened growing season. Small scale and subsistence farmers will be at particular risk. The AR4 has also confidently predicted that by 2020, rain fed agricultural production will fall by 50% in many African countries. A number of arid and semi-arid areas may simply fall out of agricultural production. In contrast, other regions, in higher latitudes and including parts of Europe and the western USA, will become warmer and wetter with an extended growing season. This provides the potential of an increased level of production, though producers may need to adapt and change their agricultural techniques and the types of crops grown. The ability of a country to respond to this may well depend on its preparedness and wealth.

Future changes in the climate

If predictions based on the current levels of global warming are realised, between 75 and 250 million people will be exposed to increased water stress due to climate change. By 2030, production from agriculture and forestry is projected to decline over much of southern and eastern Australia due to increased drought and fire. By 2050, freshwater availability will be decreased in Central, South, East and S E Asia. Coastal areas will be at increased risk of flooding from the sea or the river megadeltas.

Overall, this means that we can expect malnutrition levels to increase in some of the worlds most vulnerable populations. Additionally, we need to anticipate more droughts, heat-waves and floods. This article has focused on the impact of climate change upon food security through agricultural production effects alone. However, the impact of climate change on other sectors like human health through changes in infectious disease vectors will also impact food security but are difficult to quantify.

To contact the author, email: K.Godden@westminster.ac.uk.

Additional information, including the entire IPCC report series, can be found at http://www.ipcc.ch

¹IPCC 2007. Climate Change 2007. Synthesis Report. A Report of the Intergovernmental Panel on Climate Change. World Meteorological Organisation (WMO) and the United Nations Environment Programme (UNEP). Available at http://www.ipcc.ch

²Centre for Research on the Epidemiology of Disasters. (CRED), http://www.cred.be