From
reading my previous blog post hopefully you now have an understanding of
how climate variability, and more specifically precipitation variability, effects
water availability across Africa. An example of this precipitation variation can
be seen in the comparison of Malawi and Sudan. Malawi has a mean annual rainfall
of approximately 1250mm, whereas Sudan’s mean annual rainfall does not even
reach 200mm. It is now a generally accepted notion that climate change exists
and this is having an impact on the global climate. In this blog post I will
explain the effects of climate change on temperature and precipitation, and
then briefly discuss the impacts on a change in climate on to the population of
Africa.
As we are
becoming increasingly concerned with the potential effects of climate change on
Africa, more and more climate change models are being developed to try and understand
the implications on water resources (see Kingston and Taylor 2010 for an
example). Climate change scenarios are projecting an increase in temperature and therefore
an increase in evaporation. Warming in Africa (and other Tropic regions) will
be approximately 1.5x the global mean. This is because Africa has a
considerable amount of land mass around the tropics meaning the continent will
warm at a faster rate than other parts of the world (Joshi et al 2011).
Graph showing the Clausius-Clapeyron relation.
The Clausius-Clapeyron relation demonstrates that as
temperatures increase, the capacity of air to hold moisture also increases
which causes an intensification of the hydrological cycle (Owor et al 2009).
However this graph shows that the relationship between temperature on the x axis and vapour pressure on the y axis – with vapour
pressure increasing more rapidly when temperature has passed a certain
threshold. This means that warming in the tropics where temperatures are already high leads to a greater ability of
the air to hold moisture and therefore when it rains, it draws from a greater
amount of moisture in the air. This explains how an increase in temperature
will intensify precipitation, with the occurrence of low and medium intensity
precipitation events decreasing but the occurrence of extreme precipitation
events increasing (Allan and Soden 2008).
This does however mean that rainfall will occur less frequently, which will
increase the incidence of droughts. In areas of already low rainfall (see previous blog post) this will have devastating effects on their water
resources. In a study by de Wit and Stankiewicz (2006), they found that there
was a non-linear response of drainage to rainfall. They ultimately found that a
10% decrease in precipitation in unstable regions of Africa (defined as those
receiving less than 500mm of precipitation annually) could experience a 50%
decrease in surface drainage. This would then have significant implications
upon river discharge and any activities along the river that that rely on
sustained levels of discharge such as agriculture.
The IPCC Fifth Assessment Report chapter on Africa summarises that a 2°C mean annual rise in temperature is
likely to occur in Africa but some scenarios estimate this increase could reach
6°C by 2100. Any increase in
temperature will have a variety of effects on Africa due to the high
variability in Africa’s climate. The closest universal rule that we have for
understanding how climate change will affect different regions is that wet
regions will become wetter and dry regions will become drier (Liu and Allan 2013).
But with Africa’s ecosystems ranging from desert to tropical rainforests, there
will be significant dissimilarities in the way that climate change will
effect Africa.
The blog features some very well written posts. I also very much like the photo in your opening post. There is some very good detail in your posts reviewing critical insights gained from the literature. The frequency of your posts could certainly be increased and it is not necessary to have long posts. It may be that you raise questions or make brief commentary on your reading and investigations. Try to encourage greater interaction on your blog by getting some GEOG3038 fellow students to comment and you can comment on theirs in return. The exchanges can be very good for developing your further and more critically.
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