Climate Change and Malaria in Canada: A Systems Approach
Figure 3
(a) Annual number of consecutive days 18˚C, Toronto. Bars indicate the number of consecutive days per year that temperatures
18˚C. A trendline (solid line) shows the 10-year moving average for the
data. The trendline suggests that in the last few years, we have begun to
experience sufficiently prolonged summer warm periods to support parasite
replication and malaria transmission potential. In 2002 and 2005, the number of
days above 18˚C was sufficient to support 2 cycles of P. vivax replication. These data should be considered conservative
since each degree-day 18˚C will reduce the remaining time required for
parasite replication. Additionally, breaks in consecutive warm days 18˚C do
not necessarily prohibit continued development once temperatures rise [35]. Source of climate
data: Environment Canada [46]. (b) Annual
number of consecutive days 18˚C projected for 2010–2099, Chatham
(ON). Bars indicate the number of consecutive days per year that temperatures
are projected to reach or exceed 18°C. Error bars indicate the range of values
during each time period. The climate change projections were obtained from
interpolation (for Chatham, Ontario) of output from the CGCM2 (Canadian Coupled
Global Climate Model 2) [47] that were
downscaled using LARS-WG stochastic weather generator. LARS-WG was calibrated
with 30 years of daily weather observations at Chatham (and its predecessors)
obtained from the Environment Canada database. The output used here was
obtained using emissions scenario A2 (business as usual). The data and
methodology used here are the same as described in Ogden et al. [49]. The projected
trend shown here indicates increasingly extended summer warm periods sufficient
to support multiple parasite replication cycles.
