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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
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
Fig. 3 GHG effects:
average growing-season
differences between
2000–2009 and 2050–
2059 in:
a mean precipitation,
b crop growth duration
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
Highlands, Slopes of Mt. Kilimanjaro
Warmer temperatures, especially Tmin,
will enhance maize yields.
Possible shift to maize at the expense of
high value tea, coffee.
Reduced incomes?
Highlands, Southwest Tanzania
 Warmer
temperatures with
shorter growing
season for maize.
 Higher rainfall offsets
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
shortening the
growing season and
reducing potential
 Warmer temperatures
combined with
reduced rainfall will
lead to declining
General impact on cropping systems
 Precipitation is the
major limiting factor
for crops, yet plants
will require more
water with warmer
 Warmer temperatures
reduce growing
season length
 Grain yield highly
sensitive to length of
 Crop pests and
diseases will increase.
 Irrigation water
availability may
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
Water 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
Variability 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
Variability 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
 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
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.