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Climate variability and change currently place significant stresses on food production and availability. Global climate change is expected to increase over the next century. Human-induced global warming is likely to cause increased risk of hunger and famine, especially amongst the world's poor. Improved adaptation of food production, particularly to current climate variability, which is large, holds the key to improving food security for the global population.

Food Security and the Risks of A Changing Climate

MANY FACETS of food security depend directly on environmental conditions including weather and climate; among them are food production and efficient distribution systems.

The growth in agriculture this century is unprecedented due to the development of new technologies to increase crop yields. However, climate variability causes considerable fluctuations in crop yields and productivity. On top of that, day-to-day variations in weather which manifest themselves in the form of hurricanes and typhoons, floods and dry spells often lead to mass displacement of populations and cause damage to food production systems, resulting in food shortages and famine.

Beyond regional, seasonal and year-to-year climate variability, global warming is predicted to strongly affect agricultural production in some areas, especially in the tropics and subtropics.

There are potentially serious consequences on a regional scale for food security because of climate variability and change. Many models also predict a considerable increase in extreme weather conditions as a consequence of climate change. There may be increased risk of hunger and famine in some locations. Many of the world's poorest people are most at risk, especially those living in subtropical and tropical areas, and dependent on food production systems in semiarid and arid regions. These areas are found in sub-Saharan Africa, south, east and south-east Asia, tropical parts of Latin America and in some Pacific island nations

Atmospheric and oceanic conditions determine the breeding grounds for fish generally and fish production. Globally, climate change is unlikely to affect marine fish production but will probably produce changes at the regional level. Principal changes will be longer growing seasons and lower winter fish mortality. Oceanic changes could lead to migrations in species and affect migration routes, with subsequent changes in fish stocks in the economic zones of some nations.

Climate Change

The threat of climate change over decades to centuries caused by human-induced (anthropogenic) increases in greenhouse gases in the atmosphere is a matter of global concern. This concern is being addressed by the UN Framework Convention on Climate Change through which nations have committed themselves to achieve stabilization of greenhouse gas concentrations in the atmosphere "at a level that will prevent dangerous anthropogenic interference with the climate system

The Impact of Climate Variability on Food Production

CLIMATE variability has always had a significant impact on food production. Reliable climate records have been kept for many regions of the globe only over the last 100 years. Around the mean global surface temperature increase of between 0.3°C and 0.6°C since the late 1 9th century, considerable variability occurs. About 20-30 per cent of the temperature variability from the global trend, especially in the southern hemisphere, is linked to the Southern Oscillation, an irregular variation in the tropical oceans and atmosphere between the Pacific and Indo-Australian areas.

Rainfall in the Sahel from the late 1 960s to 1993 was well below amounts received earlier in the century, about half that of the wet 1 950s.

Food production is well adjusted to the mean climatic conditions of the region, and can cope with moderate variations. However, climatic variability creates hazards to which agricultural ecosystems are not well adapted. High temperatures exacerbate the effects of drought, damage crops and their establishment, and reduce yields. Low temperatures, frost and heavy snowfall curtail yields and destroy crops. Heavy rainfall and flooding cause inundation and waterlogging of productive land. Drought directly impacts on agricultural yields by reducing plant growth and animal production. High winds cause mechanical damage to crops, soil erosion and land degradation.

A phenomenon that is related to the occasional warming of the eastern part of the Pacific Ocean is the El Niño/Southern Oscillation. El Niño events affect the global climate, particularly in the southern hemisphere.

Indicative annual values of precipitation anomalies for the Sahel

Northern Hemisphere Winter

El Niño and Its Impacts

The El Niño phase of the Southern

Oscillation causes lower agricultural yields and major variations in temperature (both land and marine) and rainfall.

El Niño episodes have strong correlations with:

The Toll of Chronically Poor and Erratic Rainfall

A ALTHOUGH catastrophic weather phenomena receive wide media coverage, it should be noted that far more agricultural production is lost in pockets of chronically poor rainfall or other adverse weather during otherwise average years. In addition, climate is characterized by persistence, i.e. a tendency for "good" or "bad'' years to occur in runs, which highlights the need for storage of food, and particularly affects livestock (see graph at right).

Finally, due to population growth, agriculture had to expand more and more into marginal land, including those with soils with poor water storage capacity. Such areas are more vulnerable to irregular rainfall, resulting in more frequent "drought" even under relatively stable climatic conditions. This increases even further vulnerability to climate change.

Rainfall index and milk production
Mean values of Niger, Mali and Chad

Adaptation Strategies

The impacts of climate variability and change require a number of strategies to make food security more robust:

Global Warming and Future Climate

DURING THE PAST CENTURY human activities have changed the atmospheric concentrations and distributions of greenhouse gases and aerosols.

Concentrations of carbon dioxide, methane and nitrous oxide have grown by about 30, 145 and 15 per cent, respectively. These increases have been from the burning of fossil fuels, land-use changes and agriculture. Greenhouse gases have a warming effect on surface temperatures. In contrast, tropospheric aerosols, resulting from fossil fuel combustion and burning of biomass, have a cooling effect on climate. The balance of evidence now suggests a discernible human influence on global climate and that the warming effect of greenhouse gases is outweighing the cooling effect of aerosols.

It is now believed that global temperatures could increase at a faster rate than they have up to now. Results of advanced computer models project a "best estimate" increase of global mean surface air temperatures by about 2°C, relative to 1990, by 2100 AD. General warming is expected to lead to an increase in high temperature extremes, with decreases in extremes of cold with repercussions on the hydrological cycle with changes in the occurrence of severe droughts and floods. Most climate models indicate an increase in rainfall intensitv leading to more extreme rainfall events.

Project global mean temperature changes from 1990 to 2100

This fact sheet was prepared by the World Meteorological Organization, in collaboration with the Food and Agriculture Organization

For further information, please contact:
Information and Public Affairs Office, World Meteorological Organization, 41, avenue Giuseppe-Motta, Case postale 2300, Geneva 2, Switzerland. Tel: (41-22) 730 83 15: Fax: (41-22) 733 28 29; E-mail:; Internet:
Information Division, (Press Office) Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy Tel: (39-6) 5225-7276/5225-4241 Internet: or

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