Friday, September 16, 2011

Temperature and Malaria Trends in Highland East Africa

Our article: "Temperature and Malaria Trends in Highland East Africa" is published today in PLoS ONE. I've noted some of the key points already in a series of posts as the article developed. The key points are:

  • In 2002 we (Hay et al., 2002) could find little evidence of significant increase in temperature or precipitation in the East African highlands in a period of a surge in malaria cases. It, therefore, seemed most likely that the increased malaria was mainly due to other causes such as increased drug resistance.

  • This was a very controversial finding, which has been discussed by various other researchers who generally find that there has been a significant increase in temperature in these areas and that, therefore the increase in malaria was likely due to this.

  • We have now tested the more recent versions of the UEA CRU database as well as the temperature series from Kericho in Kenya prepared by Omumbo et al. (2011) using a new robust test for trends in series.

  • Using the new test, we find that there is no significant trend in the data we originally tested but that there is a significant increase in mean temperature in the newer versions of the CRU database for the same pre 1995 period. This change in data explains the results of several of our critics.

  • When the post 1995 data is included in our tests the results show an even more significant increase in temperature.

  • We do not find a significant increase in temperature in the Kericho data for the period up to 1995 but there is a significant trend when post 1995 data is included.

  • We conclude that there is now clear evidence of increased temperatures in highland East Africa especially in the last 15 years.
  • The twist is that malaria incidence has now declined. So it's still not clear if climate change was the main cause of the surge in malaria and despite recent warming malaria has radically reduced and, therefore, other factors appear to be more important than climate in malaria incidence.

Press release version.

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