Malaria in Kenya - It's Your Fault This Time
Global warming has caused a seven-fold increase in cases of malaria on the slopes of Mount Kenya, a British-funded research team has found.
A DfID spokesman said the research had also concluded that emissions from human activity, rather than natural climate variability, were responsible for the change in temperature. He said: “The seven-fold increase is directly attributable to man-made climate change. One of the problems in making the link between climate change and malaria is that natural factors usually have a part to play.
IRIN Africa | KENYA: Climate change and malaria in Nairobi | Feature
The third assessment report, published in 2001, by the Intergovernmental Panel on Climate Change, paid special attention to highland malaria. The report states that due to the life-cycle of the mosquito and its role as host of the malaria parasite, "at low temperatures, a small increase in temperature can greatly increase the risk of malaria transmission" and "future climate change may increase transmission in some highland regions, such as in East Africa".
However, the IPCC report continues, "there are insufficient historical data on malaria distribution and activity to determine the role of warming, if any, in the recent resurgence of malaria in the highlands of Kenya, Uganda, Tanzania, and Ethiopia".
Furthermore, two subsequent studies drawing on weather records at several highland locations in Africa, including tea estates in Kenya's Kericho region, published in Nature and Proceedings of the National Academy of Sciences, reach differing conclusions about whether temperatures were increasing and the occurrence of malaria.
The award-winning film by former US vice-president Al Gore, An Inconvenient Truth, says Nairobi used to be too cold for malaria-carrying mosquitoes, but now climate change is causing the disease to occur.
Paul Reiter, a malaria expert now with the Pasteur Institute, has taken issue both with the film and some of the IPCC reporting. In the International Herald Tribune in January, he wrote, "Gore's claim is deceitful on four counts. Nairobi was dangerously infested when it was founded; it was founded for a railway, not for health reasons; it is now fairly clear of malaria; and it has not become warmer."
HEALTH-KENYA: Malaria Rises to Highland Areas
"There is a clear correlation between climatic variations and malaria epidemics," says Dr Willis Akhwale, head of Kenya's National Malaria Control Programme. He referred to a 1998 investigation by his department into the breakout of epidemics in Kericho, a district in the southwestern highlands known for its tea production and cool climate. The study determined that the El Nino effect had raised temperatures by 2.2 - 4.5 degrees celsius between January and March 1997 and by 1.8-3.0 degrees celsius in February-April 1998, leading to the sudden occurrence of epidemics.
The science of this phenomenon is simple: the mosquito-transmitted parasite requires an 'ambience temperature' - usually a quarterly mean of over 18-19 degrees celsius - which occurs in the highlands only in unusually warm years, as in 1997-98 due to El Nino. Such years are becoming more frequent now.
Previous records in East Africa's highlands show, said Akhwale, that "the epidemics of the 1940s, for example, and some in 1905 were also the times when high temperatures were recorded internally and globally."
But has the climate changed that much in the first place?
Christy et al (J Clim 2009), Surface Temperature Variations in East Africa and Possible Causes, is a detailed study of station records from Kenya and Tanzania in East Africa an area which more or less covers nine 5-degree gridcells from 10S to 5N and from 30E to 45E.
For the 100-yr period from 1905 to 2004 in this grid cell, the trends were near zero for both TMax and TMin, but confidence in these results is low because of the relatively sparse data in the years before 1946. Beginning with 1946 and ending in 2004, near-zero trends were found for TMax. The TMin trends were more positive, and significantly so based on both measurement error and temporal sampling error. It is difficult to assess the measurement error of these trends, but using the spread of 20 realizations in which the construction parameters were varied, the range of +/- 0.10 Degree C per Decade is plausible.