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

Abstract

Heat and discomfort indices are applied to the multimodel ensemble mean of COordinated Regional climate Downscaling EXperiment-Africa regional climate model projections to investigate future changes in heat stress and the proportion of human population at risk under 1.5°C and 2°C global warming scenarios over West Africa. The results show that heat stress of category Extreme Caution is projected to extend spatially (up to 25%) over most of the Gulf of Guinea, Sahel, and Sahara desert areas, with different regional coverage during the various seasons. Similarly, the projected seasonal proportion of human population at discomfort substantially increases to more than 50% over most of the region. In particular, in June-August over the Sahel and the western Sahara desert, new areas (15% of West Africa) where most of the population is at risk emerge. This indicates that from 50% to almost everyone over most of the Sahel countries and part of the western Sahara desert is at risk of possible heat cramp, heat exhaustion, and heat stroke in future climate scenarios. These conditions become more frequent and are accompanied by the emergence of days with dangerous heat stress category during which everyone feels discomfort and is vulnerable to a likely heat cramp and heat exhaustion. In general, all the above features are more extended and more frequent in the 2°C than in the 1.5°C scenario. Protective measures are thus required for outdoor workers, occupational settings in hot environments, and people engaged in strenuous activities.

Intensified hydroclimatic regime in Korean basins under 1.5 and 2°C global warming

“…According to the method suggested by Sylla et al . (), a 30‐year reference period and 30‐year future period experiencing 1.5 and 2.0°C increases in global mean temperature above PI levels (1861–1890) are determined with respect to individual projections (see Section 2.1). Selected global projections are disaggregated to 0.5° (~50 km), a resolution that is employed in the variable infiltration capacity (VIC) hydrological model.…”

“…This agreement aims to keep the increase in global average temperature well below 2.0 C above preindustrial (PI) levels and to pursue ambitious targets to keep the increase to 1.5 C above PI levels. A significant body of recent studies has attempted to quantify the benefits of avoiding an additional 0.5 C increase in temperature by comparing the emerging patterns of climate change induced by global temperature increases of 1.5 and 2.0 C. Although simple thresholds based on the global average temperature are limited in their ability to represent significant regional variations (Harrington and Otto, 2018), many studies recognize the significant impact of a 0.5 C warming increase on regional climate in terms of temperature-related extremes or heat stress worldwide (e.g., King and Karoly, 2017 for Europe; Sylla et al, 2018 for West Africa; Harrington and Otto, 2018 for Southern Asia and Eastern Africa; Lee and Min, 2018;Li et al, 2018 for East Asia). These studies show that temperature responses to enhanced emissions forcings are relatively clear and straightforward.…”

“…To enhance the reliability of future projections based on a multimodel ensemble, five global climate model (GCM) projections participating in the Coupled Model Intercomparison Project phase 5 (CMIP5; Taylor et al, 2012) are carefully selected through a rigorous evaluation procedure. According to the method suggested by Sylla et al (2018), a 30-year reference period and 30-year future period experiencing 1.5 and 2.0 C increases in global mean temperature above PI levels (1861-1890) are determined with respect to individual projections (see Section 2.1). Selected global projections are disaggregated to 0.5 (~50 km), a resolution that is employed in the variable infiltration capacity (VIC) hydrological model.…”

“…The years are selected when the anomalies surpass 0.48 C, 1.5 C, and 2.0 C, and they are considered as the central years for the 30-year reference and future periods with 1.5 and 2.0 C of global warming. While the selection process of the PI period is the same as that of the period used by the International Panel on Climate Change (IPCC), Sylla et al (2018) found a 0.48 C warming for the period 1976-2005, which is set as the reference period by the IPCC (2013) using observational temperature data (HadCRUT.4.6). Table 2 includes the central year and averaged period corresponding to 0.48 C, 1.5 C, and 2.0 C of global warming for individual GCMs.…”

2018 summer extreme temperatures in South Korea and their intensification under 3 °C global warming

“…Since the 2015 Paris Agreement, a significant body of research has quantified the impact of different levels of warming specified by the various thresholds of global average temperature (e.g. 1.5°C, 2°C, 3°C) (King and Karoly 2017, Wang et al 2017, Jacob et al 2018, Li et al 2018, Sylla et al 2018. However, most of these studies applied the GCM projections with relatively coarse resolution, which is not appropriate for investigating detailed features at the regional to local scales.…”