Projected trends in high-mortality heatwaves under different scenarios of climate, population, and adaptation in 82 US communities

Abstract

Some rare heatwaves have extreme daily mortality impacts; moderate heatwaves have lower daily impacts but occur much more frequently at present and so account for large aggregated impacts. We applied health-based models to project trends in high-mortality heatwaves, including proportion of all heatwaves expected to be high-mortality, using the definition that a high-mortality heatwave increases mortality risk by ≥20 %. We projected these trends in 82 US communities in 2061-2080 under two scenarios of climate change (RCP4.5, RCP8.5), two scenarios of population change (SSP3, SSP5), and three scenarios of community adaptation to heat (none, lagged, on-pace) for large- and medium-ensemble versions of the National Center for Atmospheric Research's Community Earth System Model. More high-mortality heatwaves were expected compared to present under all scenarios except on-pace adaptation, and population exposure was expected to increase under all scenarios. At least seven more high-mortality heatwaves were expected in a twenty-year period in the 82 study communities under RCP8.5 than RCP4.5 when assuming no adaptation. However, high-mortality heatwaves were expected to remain <1 % of all heatwaves and heatwave exposure under all scenarios. Projections were most strongly influenced by the adaptation scenario- going from a scenario of on-pace to lagged adaptation or from lagged to no adaptation more than doubled the projected number of and exposure to high-mortality heatwaves. Based on our results, fewer high-mortality heatwaves are expected when following RCP4.5 versus RCP8.5 and under higher levels of adaptation, but high-mortality heatwaves are expected to remain a very small proportion of total heatwave exposure.

Temporal Trends in Heat-Related Mortality: Implications for Future Projections

“…However, this method would only capture short-term acclimatization or inter-annual behavioral adaptations. A recent study modeled adaptation based on the mortality risk on "heat wave days" falling above the 99th percentile of temperature [49]. For future projections, a "no adaptation" scenario used the threshold temperatures observed in the historical baseline period to define heat wave days and associated mortality risk in the 2061-2080 period.…”

“…These findings warrant replication using other national datasets. Heat wave-based mortality models are also amenable to simple adaptation adjustments, as in [49].…”

Projected Heat Stress Under 1.5 °C and 2 °C Global Warming Scenarios Creates Unprecedented Discomfort for Humans in West Africa

“…Such temperature increase is expected to continue in the future with a projected global temperature change of about 1.4°C to 4.8°C (Intergovernmental Panel on Climate Change, 2014) and a regional response over the Sahel of about 2°C to 6°C (Sylla, Nikiema, et al, 2016) when considering the Representative Concentration Pathway 4.5 and 8.5 concentration scenarios (Moss et al, 2012). As a result, hot extremes will become more common and deadly in many regions across the world (Gasparrini et al, 2017;Im et al, 2017;Lee & Kim, 2016;Mora et al, 2017) and in tropical Africa (Giorgi et al, 2014;Liu et al, 2017;Russo et al, 2014), with their frequency, duration, and magnitude depending on the underlying forcing scenario (Anderson et al, 2018;Dosio, 2017;Linares et al, 2014;Russo et al, 2016). Such hot extremes can have widespread impacts on human and natural systems, thereby challenging the adaptive capacity and resilience of local populations and activities (Ceccherini et al, 2017;Fontaine et al, 2013;Pal & Eltahir, 2016;Sultan & Gaetani, 2016;Zougmoré et al, 2016).…”

An introduction to the special issue on the Benefits of Reduced Anthropogenic Climate changE (BRACE)

“…Anderson et al (2016b) test the sensitivity of heat-related mortality to adaptation, but no explicit adaptation options are modeled. Rather, the study quantifies the consequences of generic adaptation actions that lessen vulnerability at a hypothetical pace over time.…”