Exposure to excessive heat and impacts on labour productivity linked to cumulative CO2 emissions

Yann Chavaillaz,H Damon Matthews,Laurent Da Silva,Diane Chaumont,Antti-Ilari Partanen,Philippe Roy,Émilie Bresson,Nadine Mengis

doi:10.1038/s41598-019-50047-w

Abstract

Cumulative CO2 emissions are a robust predictor of mean temperature increase. However, many societal impacts are driven by exposure to extreme weather conditions. Here, we show that cumulative emissions can be robustly linked to regional changes of a heat exposure indicator, as well as the resulting socioeconomic impacts associated with labour productivity loss in vulnerable economic sectors. We estimate historical and future increases in heat exposure using simulations from eight Earth System Models. Both the global intensity and spatial pattern of heat exposure evolve linearly with cumulative emissions across scenarios (1% CO2, RCP4.5 and RCP8.5). The pattern of heat exposure at a given level of global temperature increase is strongly affected by non-CO2 forcing. Global non-CO2 greenhouse gas emissions amplify heat exposure, while high local emissions of aerosols could moderate exposure. Considering CO2 forcing only, we commit ourselves to an additional annual loss of labour productivity of about 2% of total GDP per unit of trillion tonne of carbon emitted. This loss doubles when adding non-CO2 forcing of the RCP8.5 scenario. This represents an additional economic loss of about 4,400 G$ every year (i.e. 0.59 $/tCO2), varying across countries with generally higher impact in lower-income countries.

Highlights

Excessive heat exposure has many potential socioeconomic impacts, including health effects, loss of labour productivity, higher death rates and higher energy demand [e.g.1]
Heat exposure above the extreme and deadly thresholds increases with cumulative emissions, by 55.30 ± 53.31 and 18.44 ± 28.37 K-days per trillion tonne of carbon (TtC), respectively; given the small signals and high inter-model spread, we were not able to demonstrate a statistically robust linear relationship with cumulative CO2 emissions (CCE)
Across all Wet-Bulb Globe Temperature (WBGT) thresholds, the RCP scenarios show a more rapid and more robust increase in heat exposure compared to the 1% CO2 scenario as a result of additional positive non-CO2 forcing

Summary

Introduction

Excessive heat exposure has many potential socioeconomic impacts, including health effects, loss of labour productivity, higher death rates and higher energy demand [e.g.1]. Previous analyses have developed relationships between heat exposure thresholds and health recommendations with respect to recommended rest time during labour[2,3,4,5]. We assess to what extent cumulative CO2 emissions are linked to increased extreme heat exposure and resulting labour productivity loss across future climate change scenarios. We use here a simplified version of the WBGT, which is calculated using average solar irradiation and wind speeds This version is easy to reproduce from climate model outputs[23]. From this indicator, we define the annual total heat exposure as the integral of daily WBGT values in a year above six pre-defined thresholds, labelled as light, medium, strong, very strong, extreme and deadly (see Methods). We quantify the response of heat exposure to CCE in eight CMIP5 Earth system models (ESMs, i.e. models which include a dynamic carbon cycle24) across a range of emission pathways

Methods

Results

Discussion

Conclusion