Background
The authors report "there has been much recent speculation that global warming may allow the reestablishment of malaria transmission in previously endemic areas such as Europe and the United States."  In particular, they note that "the British Chief Medical Officer's recent report [Getting Ahead of the Curve: A Strategy for Combating Infectious Diseases (Including Other Aspects of Health Protection), Department of Health (2002), London] asserted that 'by 2050 the climate of the UK may be such that indigenous malaria could become re-established'," which is the same mantra that is incessantly chanted by the world's climate alarmists.

What was done
To investigate the robustness of this hypothesis, the authors analyzed the determinants of temporal trends in malaria deaths within England and Wales from 1840-1910.

What was learned
With respect to temperature changes over the period of study, it was determined that "a 1°C increase or decrease was responsible for an increase in malaria deaths of 8.3% or a decrease of 6.5%, respectively," which explains "the malaria epidemics in the 'unusually hot summers' of 1848 and 1859."  Nevertheless, the long-term near-linear temporal decline in malaria deaths over the period of study, in the words of the authors, "was probably driven by nonclimatic factors," among which they list increasing livestock populations (which tend to divert mosquito biting from humans), decreasing acreages of marsh wetlands (where mosquitoes breed), as well as "improved housing, better access to health care and medication, and improved nutrition, sanitation, and hygiene."  They additionally note that the number of secondary cases arising from each primary imported case "is currently minuscule," as demonstrated by the absence of any secondary malaria cases in the UK since 1953.

What it means
Although model simulations suggest that the increase in temperature predicted for Britain by 2050 is likely to cause an 8-14% increase in the potential for malaria transmission, the authors say "the projected increase in proportional risk is clearly insufficient to lead to the reestablishment of endemicity."  Expanding on this statement, they note that "the national health system ensures that imported malaria infections are detected and effectively treated and that gametocytes are cleared from the blood in less than a week."  For Britain, therefore, they conclude that "a 15% rise in risk might have been important in the 19th century, but such a rise is now highly unlikely to lead to the reestablishment of indigenous malaria," since "socioeconomic and agricultural changes" have greatly altered the cause-and-effect relationships of the past.