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Recent studies indicated that the internal climate variability plays an important role in various aspects of projected climate changes on regional and local scales. Here we present results of the spreads in projected trends of wintertime North American surface air temperature and extremes indices of warm and cold days over the next half-century, by analyzing a 50-member large ensemble of climate simulations conducted with CanESM2. CanESM2 simulations confirm the important role of internal variability in projected surface temperature trends as demonstrated in previous studies. Yet the spread in North American warming trends in CanESM2 is generally smaller than those obtained from CCSM3 and ECHAM5 large ensemble simulations. Despite this, large spreads in the climate means as well as climate change trends of North American temperature extremes are apparent in CanESM2, especially in the projected cold day trends. The ensemble mean of forced climate simulations reveals high risks of warm days over the western coast and northern Canada, as well as a weakening belt of cold days extending from Alaska to the northeast US. The individual ensemble members differ from the ensemble mean mainly in magnitude of the warm day trends, but depart considerably from the ensemble mean in spatial pattern and magnitude of the cold day trends. The signal-to-noise ratio pattern of the warm day trend resembles that of the surface air temperature trend, with stronger signals over northern Canada, Alaska, and the southwestern US than the midsection of the continent. The projected cold day patterns reveal strong signals over the southwestern US, northern Canada, and the northeastern US. In addition, the internally generated components of mean and extreme temperature trends exhibit spatial coherences over North America, and are comparable to their externally forced trends. The large-scale atmospheric circulation-induced temperature variability influences these trends. Overall, our results suggest that climate change trends of North American temperature extremes are likely very uncertain and need to be applied with caution. [ABSTRACT FROM AUTHOR]

Previous studies have detected an effect of earlier temperatures on the incidence of campylobacteriosis in humans, but without adjustment for earlier numbers of cases of the disease. We estimated the effect of temperature on the number of cases notified by week in Montreal, Canada, from 1 January 1990 to 26 March 2006, simultaneously with the effect of the numbers of cases notified in the preceding weeks. The current campylobacteriosis count (week 0) was modelled by negative binomial regression, with earlier weekly average temperatures and earlier counts as predictors. Secular trends were accounted for by cubic spline functions and seasonal variations by sine-cosine functions. Indicator variables identified weeks with fewer than 5 working days. In the final statistical model, a 1°C increase in temperature above 10°C during any of weeks −1 to −6 was associated with a 0.8% (95% CI: 0.3% to 1.3%) increase in the current count. For each additional notified case during any of weeks −1 to −5 or −9 to −12, the increase in the current count was approximately 0.5% (95% CI: 0.2% to 1.0%). Thus, earlier temperatures and earlier counts have independent effects, that of temperatures being the larger one. The temperature effect is too small to require short term public health planning. However, in Montreal, an increase in average temperature of the order of 4.5°C, forecast by some for 2055, could produce a 23% increase in incidence, resulting in about 4,000 excess cases per year. [ABSTRACT FROM AUTHOR]

Climate change has important implications for mental health globally. Yet, few studies have quantified the magnitude and direction of associations between weather and mental health-related factors, or assessed the geographical distribution of associations, particularly in areas experiencing rapid climatic change. This study examined the associations between air temperature variables and mental health-related community clinic visits across Nunatsiavut, Labrador, Canada, and the place-specific attributes of these associations. Daily de-identified community clinic visit data were collected from the provincial electronic health recording system and linked to historical weather data (2012–2018). A multilevel, multivariable negative binomial regression model was fit to investigate associations between temperature variables and mental health-related community clinic visits across the region, adjusting for seasonality as a fixed effect and community as a random effect. A multivariable negative binomial model was then fit for each Nunatsiavut community, adjusting for seasonality. Mental health-related visits contributed to 2.4% of all 228,104 visit types across the study period; this proportion ranged from 0.6% to 11.3% based on community and year. Regionally, the incidence rate of mental health-related community clinic visits was greater after two weeks of warm average (i.e. above -5ᵒC) temperatures compared to temperatures below -5ᵒC (IRR -5≤5ᵒC = 1.47, 95% CI = 1.21–1.78; IRR 6≤15ᵒC = 2.24, 95% CI = 1.66–3.03; IRR >15ᵒC = 1.73, 95% CI = 1.02–2.94), and the incidence rate of mental health-related clinic visits was lower when the number of consecutive days within −5 to 5ᵒC ranges (i.e. temperatures considered to be critical to land use) increased (IRR = 0.96; 95% CI = 0.94–0.99), adjusting for seasonal and community effects. Community-specific models, however, revealed that no two communities had the same association between meteorological conditions and the incidence rate of daily mental health-related visits. Regionally, longer periods of warm temperatures may burden existing healthcare resources and shorter periods of temperatures critical to land use (i.e. −5 to 5ᵒC) may present enjoyable or opportunistic conditions to access community and land-based resources. The heterogeneity found in temperature and mental health-related clinic visits associations across Nunatsiavut communities demonstrates that place quantitatively matters in the context of Inuit mental health and climate change. This evidence underscores the importance of place-based approaches to health policy, planning, adaptation, and research related to climate change, particularly in circumpolar regions such as Nunatsiavut where the rate of warming is one of the fastest on the planet. • Longer periods of warm temperatures significantly increased mental health clinic visits in Nunatsiavut. • Temperature-mental health associations aligned with community participation in land-based activities. • Results suggest that place will modify the impact of climate change on mental health. [ABSTRACT FROM AUTHOR]