New Era

- An economist's point of view...

The following article is the second part of a series of four. The third article is about costs and benefits of anti-climate change actions, while the fourth and last part assesses the meager results of the recent Copenhagen Conference and tries to forecast the way forward.

Increase of temperature
Africa is no exception to the global rise in temperature. During the last century, average surface temperature rose by around 1 degree C.

One can distinguish three separate periods of different tendencies: first a period of rising, then one of falling, and again one of rising temperatures. The last period seems to show a specifically steep increase in temperatures.

Rainfall
The long-term development of rainfall is much more volatile and much less predictable than that of temperature.

The Sahel region, for example, experienced volatile but, taken together, favorable rainfall from 1900 to 1965.

From 1965 onwards there was a sharp downturn in rainfall, which improved a bit only 25 years later.

There are opinions that the decrease of rainfall in the Sahel is at least partly man-made - by overgrazing and destruction of the plant cover.

Rainfall forecasts for the Sahel for the period 2000 to 2100 are much diverging but not too bad. They range from -10% to +35% in 2100.

East Africa, by contrast, had historically not only much more rainfall than the Sahel but the rainfall variability was also lower.

Rainfall forecasts are relatively good for East Africa. Six out of 7 models indicate an increase in rainfall over the next 100 years between +15% and +20%.

This contrasts of course to the current drought crisis in Kenya and Ethiopia. But it should be understood that one can never be sure beforehand whether a current development signifies a new trend or is part of the usual variability.

For South East Africa, there is very much rainfall variability in the historical data, even more so than for the Sahel.

Unfortunately, the prospects are less positive: 5 out of 7 models indicate a decrease in rainfall over the next 100 years by between -5% and -35%.

Namibia
Compared to many other African countries, Namibia is rich in long-term, detailed and regionalized data on temperature and rainfall - of which I can only present a small fraction here.

(I would like to thank Mr Sepiso Mwangala from Namibia's Meteorological Service for providing me with a large set of data and well-prepared and ready-to-use charts.)

Chart 2 shows the development of temperature in Windhoek over 100 years, from 1909 to 2008. There is a clear rising trend. The dotted line, the long-term trend, calculated by the colleagues of the Meteorological Service, indicates a rise by around 1.5 degrees C. This is even more than the global and All-African development of temperature.

Quite different is the development of rainfall, again in Windhoek. Chart 3 shows the development over nearly 120 years, from 1892 to 2009.

As the dotted line (again the calculated trend line) indicates, there is neither a decrease nor an increase in the long run. Instead, there is very large variability from year to year.

Some people think that there is a cyclical pattern in Namibia's rainfall data. But it is difficult to detect.

One could say, perhaps, that there is a certain upward trend in rainfall over the past 20 years - besides all variability.

But one should be careful and not take a series of some consecutive good rainy seasons as a proof for a change of a trend to the better - as the current drought in Kenya should not be prematurely interpreted as a change to the worse.

Variability was always there and will be there.

Another inconvenient truth
Unchecked global warming may turn out to be catastrophic for all of us, specifically for poor low-latitude countries. But this is not the only "inconvenient truth" (Al Gore).

Another one is that a continent of mainly poor countries, Africa, also contributes to global climate change.
42% of global biomass burning happens in Africa. Burnt biomass is an important source of methane which has a much higher heat storage capacity than CO2.

Plant cover destruction, while not limited to Africa, is a source of CO2 emissions and mainly man-made.

Moreover, plant cover is also relevant on the regional level, because it may stabilize regional rainfall.

Climate change adaptation pressure: on top
Looking at Africa as a whole, there are many different climatic regimes. Even within countries, for example within Namibia, climates differ.

Generally, one can say that agricultural and social techniques are adapted to these different climates.

However, population growth and the goals of economic and social development demand a continuous change of agricultural and social techniques - meaning that there is already a considerable adaptation pressure.

The adaptation pressure exerted by climate change comes on top of the existing adaptation pressure.

Dr Rigmar Osterkamp is at Unam, Faculty of Economics and Management Science, Economics Department.

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