Future Projections of Climate Change

Temperature The projections indicate future increases in

average annual temperatures of 1 ºC to 3ºC by the 2050s

By the end of the century (2100) average temperatures are broadly expected to increase in the range of;

1.5°C to 3°C for the lower emission scenario and 3°C to 5°C for the higher emission scenario.

Future Projections of Climate Change

Rainfall The changes in precipitation from the models are more

uncertain. All the climate models show that rainfall regimes will

change, but the degree and even the direction of change differ across the models.

They also vary widely between seasons, regions and rainfall regimes.

Many of the models show the potential for drying signals later in the year in southern and central regions

They show potential increases at other times

Future Projections of Climate Change

Extreme events The information on extreme events (floods and

droughts) is much more uncertain and the model projections vary widely.

Many models indicate an intensification of heavy rainfall in some regions and thus greater flood risks.

Droughts are likely to continue Other models indicate reductions in severity.

Future Climate change and Variability Impacts

Recent studies show that climate change impacts food production systems, particularly in locations with large, vulnerable populations.

Elevated greenhouse gases (GHG), as well as land cover/land use change (LCLUC), can influence regional climate dynamics.

Regional climate model derived from the Regional Atmospheric Modeling System (RAMS) was used To compare the effects of projected future GHG and

future LCLUC on spatial variability of crop yields in East Africa.

Maize yields under current climate conditions ABCDFE

-Precipitation and soils limiting factors-Assume low levels of inputs

Fig. 3 GHG effects: average growing-season differences between 2000–2009 and 2050–2059 in: a mean precipitation, b crop growth duration (CGD), c yield change for the study area, d average maximum temperature, e topography, f a histogram of yield change distribution for the 5 nations.

Source: Moore et al, 2011

Fig. 2. Effect of land cover change on precipitation: the difference in annual precipitation (red decline; blue increase) due to projected land cover change (2050 cover minus current

cover) simulated in RAMS.

Source: Olson et al., 2010

Difference in maize yields due to GHG induced climate change, 2000 to 2050

Average difference in maize yields due to BOTH global climate change and land use change combined, 2000 to 2050

Warmer temperatures, especially Tmin, will enhance maize yields.

Possible shift to maize at the expense of high value tea, coffee.

Reduced incomes?

Highlands, Slopes of Mt. Kilimanjaro

Highlands, Southwest TanzaniaWarmer

temperatures with shorter growing season for maize.

Higher rainfall offsets warmer temperatures, but leads to rapid nutrient leaching from sandy soils and significant yield loss.

Alleviate yield loss with fertilizer?

Central Tanzania Warmer temperatures

lead to accelerated phenology, shortening the growing season and reducing potential yield.

Warmer temperatures combined with reduced rainfall will lead to declining yields.

General impact on cropping systems

Precipitation is the major limiting factor for crops, yet plants will require more water with warmer temperatures.

Warmer temperatures reduce growing season length

Grain yield highly sensitive to length of season.

Crop pests and diseases will increase.

Irrigation water availability may decline.

General impact on herding systems

Warmer temperatures lead to vegetation drying faster and drinking water becoming scarce faster

Livestock forage amount and quality may decline as rangeland plant composition changes due to temperature, rainfall & CO2 concentrations.

Livestock and human diseases more frequent with climatic extremes.

Competition, insecurity?

Impacts of Climate Change Impacts on Impacts of Climate Change Impacts on Water Related SectorsWater Related Sectors

Climate change is expected to hit hard on water sources and availability

Freshwater availability projected to decrease by over half from 1990 levels by 2025

However, impacts will vary geographically

Geographical Variations in Climate Change and Geographical Variations in Climate Change and Variability Impacts on Water SectorVariability Impacts on Water Sector

The projection is that water flow change will be between 5 to 10% decrease in all basins in Tanzania

Ruvu River basin is projected to a 10% decrease in runoff for the whole period of January to December

Runoff in Pangani basin is projected to decrease in between 6-9%

Thus, both social and economic activities will be severely disrupted

Geographical Variations in Climate Change and Geographical Variations in Climate Change and Variability Impacts on Water SectorVariability Impacts on Water Sector

However, there will be increased runoff within the Rufiji basin of 5% and 11% at Mtera and Kidatu dams respectively during the period of November to March

This corresponds well with an increase in rainfall during the same period

Ecological Implications

These changes will have further adverse ecological implications; decreased biodiversity, increased fungal and insect infestations

Ecological Consequences

Increased temperature is agued to influence; Thermal stratification of Lakes Victoria and Tanganyika Increased stratification would reduce water movement

across the thermocline, Thus disrupting water upwelling and mixing that provide

essential nutrients to the food web This would lead to decreased nutrients in the surface

water that could cause damage to fisheries and their ecosystems

Feedback

People respond to altered climate in various ways; Switch crops, Abandon cropping on some land Move to search for jobs and food in towns Increase conflict over water, grazing Develop irrigation where possible Livestock, especially native breeds, maintained since lower

risk. Altered farming systems, Retreat of cropping in some areas and expansion in others. However, responses differ by region, community,

households, and age and gender groups as climate change effects interact with other processes.