Peter Gething, from the malaria atlas project at Oxford, and others have a paper in Nature, Climate change and the global malaria recession (doi:10.1038/nature09098) that examines at changes in global malaria distribution.  While the world warmed in the 20th century, the distribution of malaria shrank.  From their examination of this change they argue that development and public health measures have much stronger impacts on malaria distribution than expected climate change.

Change in P. falciparum malaria endemicity between 1900 and 2007. Negative values denote a reduction in endemicity, positive values an increase.

From looking at these changes and their causes they find that:

1) widespread claims that rising mean temperatures have already led to increases in worldwide malaria morbidity and mortality are largely at odds with observed decreasing global trends in both its endemicity and geographic extent.

2) the proposed future effects of rising temperatures on endemicity are at least one order of magnitude smaller than changes observed since about 1900 and up to two orders of magnitude smaller than those that can be achieved by the effective scale-up of key control measures.

Predictions of an intensification of malaria in a warmer world, based on extrapolated empirical relationships or biological mechanisms, must be set against a context of a century of warming that has seen marked global declines in the disease and a substantial weakening of the global correlation between malaria endemicity and climate.

SciDev.net has a news article that includes some responses from critics of the study.