Research
Climate change in southern Africa
Northern Botswana, western Zimbabwe and southern Zambia (Region 8)
22 August 2007
Long-term fluctuations
This is a transition zone between the semi-arid Kalahari-extension in
the south and the wetter climate to the north. It is an elevated
plateau at about 1000m above mean-sea-level. The time series plots
show that rainfall shortages
were experienced in this area
during the last few decades of the 20th century, in common with other regions in this proximity.
The
models project a regular downward precipitation trend over this area during
the 21st century. Droughts are projected to become more severe here.
Region 8 precipitation differences from the 1901-1950 mean [σ] with a ten-year running mean in the observations (black bars) and
selected climate models. The blue line shows the multi-model ensemble mean. The darker (lighter) shading show 1σ (2σ) from the mean.
Annual cycle
The observed annual cycle for this region
show a peak of about 5mm/day during summer with
a typical dry winter. Without exception, the models show
a notable reduction in precipitation amounts from October to November.
From December, some outliers (CNRM-CM3, CGCM3.1 and ECHO-G) give indications
for an increase in mean monthly precipitation. Otherwise, there is evidence
for either no change or a slight reduction in precipitation.
Region 8 annual cycle. The observations are shown by bars.
Model simulated annual cycle is shown by the dotted line (open diamond) for the 20th century (around 2100). For each model, the line segment displays the simulated deviation (from its 20th century) in mean monthly rainfall. Positive (negative) deviations are indicated by line segments pointing upwards (downwards) from the dotted line.
|
|
