The 1994 agricultural sample survey indicates that the average yield of all crops at the national level was about 1000kgs (10 quintals) per hectare, while the average yield of cereals, pulses and other crops was about ten, nine and three quintals per hectare respectively (CSA 1995). Crop production has been poor for the last three and half decades. Food grain per capita has registered a downward trend for several years. Once self-sufficient in food production and a net exporter of food grains, Ethiopia has since 1981/82 become a net grain importer (MEDaC 1999).

# **_2.2 Livestock_**

Ethiopia has the largest livestock population in Africa and the tenth largest in the world. Livestock is an integral part of the farming systems in the country. It is the source of many social and economic values such as food, power, fuel, cash income, security and investment in both the highland and the lowland pastoral farming systems. The livestock sector contributes approximately 12 to 15% to total GDP and about 25 to 30% to the agricultural GDP (MEDaC 1999). It is also a major source of foreign exchange, second only to coffee.

In general the country’s livestock resources are characterized by low productivity. Average yields per animal slaughtered or milked are estimated at 110kg of beef, 10kg of mutton and 213kg of cow’s milk. At present the per capita consumption of milk and meat is estimated to be 16 kg and 10 kg per annum respectively. Compared with its neighbors, Ethiopia has the lowest consumption rates of these two products because of the low income level of the majority of its population (MEDaC 1999).

Inadequate food and nutrition, the low level of veterinary care, the high occurrence of diseases, poor genetic structure, inadequate budget allocation, limited infrastructure, limited research on livestock, insecure land tenure and recurrent drought are the main constraints in this subsector (Befekadu & Nega, 1999/2000).

# **3. Review of literature on climate change impact studies and methodologies employed**

# **_3.1 Climate prediction models_**

Human activities such as the burning of fossil fuels and deforestation increase the concentration of carbon dioxide (CO2) and other trace gases in the atmosphere, which in turn alters the energy balance of the earth (Rosenzweig 1989). The gases do this by absorbing long wave radiation emitted by the earth to balance the incoming short wave solar radiation. In the long run, if the absorbed solar radiation is not balanced by outgoing thermal radiation, global warming will occur. The warming caused by the trapping of the long wave radiation is known as the ‘greenhouse effect. and the trace gases responsible are known as ‘green house gases’ (Rosenzweig 1989).

The behavior of a climate system, its components and their interactions are studied and simulated using climate prediction models. These models are designed mainly for studying climate processes and natural climate variability, and for projecting the response of climate to human induced forces. The most complex climate prediction models developed and used are called the global climate models or general circulation models (GCMs). These are mathematical representations of the atmosphere, ocean, and land surface processes involving mass, momentum, energy and water and their interactions. They are based on physical laws describing the dynamics 6