Extreme Weather

Increasing extreme climatic events threaten the functioning of terrestrial ecosystems1,2. Because soil microbes govern key biogeochemical processes, understanding their response to climate extremes is crucial in predicting the consequences for ecosystem functioning3,4. Here we subjected soils from 30 grasslands across Europe to four contrasting extreme climatic events under common controlled conditions (drought, flood, freezing and heat), and compared the response of soil microbial communities and their functioning with those of undisturbed soils. Soil microbiomes exhibited a small, but highly consistent and phylogenetically conserved, response under the imposed extreme events. Heat treatment most strongly impacted soil microbiomes, enhancing dormancy and sporulation genes and decreasing metabolic versatility. Microbiome response to heat in particular could be predicted by local climatic conditions and soil properties, with soils that do not normally experience the extreme conditions being imposed being most vulnerable. Our results suggest that soil microbiomes from different climates share unified responses to extreme climatic events, but that predicting the extent of community change may require knowledge of the local microbiome. These findings advance our understanding of soil microbial responses to extreme events, and provide a first step for making general predictions about the impact of extreme climatic events on soil functioning.

Most studies projecting human survivability limits to extreme heat with climate change use a 35 °C wet-bulb temperature (Tw) threshold without integrating variations in human physiology. This study applies physiological and biophysical principles for young and older adults, in sun or shade, to improve current estimates of survivability and introduce liveability (maximum safe, sustained activity) under current and future climates. Our physiology-based survival limits show a vast underestimation of risks by the 35 °C Tw model in hot-dry conditions. Updated survivability limits correspond to Tw~25.8-34.1 °C (young) and ~21.9-33.7 °C (old)-0.9-13.1 °C lower than Tw = 35 °C. For older female adults, estimates are ~7.2-13.1 °C lower than 35 °C in dry conditions. Liveability declines with sun exposure and humidity, yet most dramatically with age (2.5-3.0 METs lower for older adults). Reductions in safe activity for younger and older adults between the present and future indicate a stronger impact from aging than warming.

ImportanceThe number of extreme heat events is increasing because of climate change. Previous studies showing an association between extreme heat and higher mortality rates generally have been limited to urban areas, and whether there is heterogeneity across different populations is not well studied; understanding whether this association varies across different communities, particularly minoritized racial and ethnic groups, may allow for more targeted mitigation efforts.ObjectiveTo the assess the association between extreme heat and all-cause mortality rates in the US.Design, setting, and participantsThis cross-sectional study involved a longitudinal analysis of the association between the number of extreme heat days in summer months from 2008 to 2017 (obtained from the Centers for Disease Control and Prevention's Environmental Public Health Tracking Program) and county-level all-cause mortality rates (obtained from the National Center for Health Statistics), using a linear fixed-effects model across all counties in the contiguous US among adults aged 20 years and older. Data analysis was performed from September 2021 to March 2022.ExposuresThe number of extreme heat days per month. Extreme heat was identified if the maximum heat index was greater than or equal to 90 °F (32.2 °C) and in the 99th percentile of the maximum heat index in the baseline period (1979 to 2007).Main outcomes and measuresCounty-level, age-adjusted, all-cause mortality rates.ResultsThere were 219 495 240 adults aged 20 years and older residing in the contiguous US in 2008, of whom 113 294 043 (51.6%) were female and 38 542 838 (17.6%) were older than 65 years. From 2008 to 2017, the median (IQR) number of extreme heat days during summer months in all 3108 counties in the contiguous US was 89 (61-122) days. After accounting for time-invariant confounding, secular time trends, and time-varying environmental and economic measures, each additional extreme heat day in a month was associated with 0.07 additional death per 100 000 adults (95% CI, 0.03-0.10 death per 100 000 adults; P = .001). In subgroup analyses, greater increases in mortality rates were found for older vs younger adults (0.19 death per 100 000 individuals; 95% CI, 0.04-0.34 death per 100 000 individuals), male vs female adults (0.12 death per 100 000 individuals; 95% CI, 0.05-0.18 death per 100 000 individuals), and non-Hispanic Black vs non-Hispanic White adults (0.11 death per 100 000 individuals; 95% CI, 0.02-0.20 death per 100 000 individuals).Conclusions and relevanceThese findings suggest that from 2008 to 2017, extreme heat was associated with higher all-cause mortality in the contiguous US, with a greater increase noted among older adults, men, and non-Hispanic Black individuals. Without mitigation, the projected increase in extreme heat due to climate change may widen health disparities between groups.

OBJECTIVE: Across two summers self-report surveys were completed by a total of 130 older adults who were trialling a digital heat early warning system in Southeast Queensland. The purpose of the project was to assess participants’ access to (accessibility), and willingness to use (acceptability) commonly promoted cooling strategies, and to further explore the reasons for reluctance to use. RESULTS: Most participants reported access to all strategies (93–100%). Acceptability (mean response [95%CI]) was high for opening/closing windows or blinds (97 [94–100]%), fans, drinking cool water, sitting quietly, removing excess clothing (all 96 [93–99]%), cold showers (92 [87–96]%), and air-conditioning (90 [84–95] %). Conversely, hand/forearm baths (76 [69–84]%), icepacks (68 [60–76]%), dampened clothing (64 [56–72]%), foot baths (63 [54–71]%), and cold baths (49 [39–60]%) were less acceptable. Key reported barriers included messiness (n = 48), physical discomfort (n = 47), and preference for other strategies (n = 47). Among this sample of older adults, several widely promoted water-based cooling strategies were reported as unacceptable despite high accessibility. These findings highlight an implementation gap between public health recommendations and self-reported willingness to use such strategies, underscoring the need for co-designed heat-health interventions.