Nature reports that extant strains of Yersinia pestis are very similar to the Black Death bacterium that wiped out half of Europe in the 14th century — meaning that environment ought to be at the forefront of concern for the plague’s potential return.
The article specifically cites climate as a factor that could mediate a return of the Black Death. The citation for this claim is this paper, recently published in the Proceedings of the National Academy of Sciences.
The PNAS paper examined the plague breakouts in China from 1850 to 1964 and correlated them with climatic conditions (i.e., wetness/dryness) and concluded:
In northern China, plague intensity generally increased when wetness increased, for both the current and the previous year, except for low intensity during extremely wet conditions in the current year (reflecting a dome-shaped response to current-year dryness/ wetness). In southern China, plague intensity generally decreased when wetness increased, except for high intensity during extremely wet conditions of the current year. These opposite effects are likely related to the different climates and rodent communities in the two parts of China: In northern China (arid climate), rodents are expected to respond positively to high precipitation, whereas in southern China (humid climate), high precipitation is likely to have a negative effect. Our results suggest that associations between human plague intensity and precipitation are nonlinear: positive in dry conditions, but negative in wet conditions.
We take this to mean that any change in precipitation levels could prompt a plague breakout. So expect the take-home message for alarmists to be: climate change, as accelerated by man, could bring back the Black Death. You heard it here first.