AcknowledgmentsReferences

Abstract• The summer of 2015 has experienced

major heat waves on 4 continents, and heat stress left ~4000 people dead in India and Pakistan. The International Organization for Standardization (ISO) uses Wet Bulb Globe Temperature (WBGT)—an empirical metric this is calibrated with temperature, humidity, and radiation—for determining labor capacity during heat stress. Unfortunately, limited number of studies use the combination of temperature and humidity. Recent global assessments use WBGT, yet omit the radiation component without recalibrating the metric.

GC23H-1204

Methods • We use RCP8.5 (Taylor et al., 2012)

output to drive the Community Land Model 4.5 (Oleson et al., 2013) (CLM4.5).

• We implemented the HumanIndexMod into CLM4.5 to calculate wet bulb temperature (Buzan et al., 2015), and also implement solar and thermal radiation fluxes to calculate globe thermometer.

• We used 1°x1° resolution, and years 2005-2100, to output 4x daily and analyze the characteristics of the full Wet Bulb Globe Temperature (WBGT).

2. Background2.1 What is Heat StressHeat stress occurs when the human body loses the ability to internally regulate heat balance. An increase of internal temperatures of ~3C can be lethal (Simon, 1993). Heat balance is modulated by many different mechanisms within the human/environment system. There are four different methods of heat transport at the exterior of a human body (Figure 1): radiation, convection, conduction, and evaporation (Simon 1993; Daniela 2004; Gaughan et al, 2009). Heat is generated within the core body dependent on levels of activity; from a minimum at rest up to ~8x the heat production due to strenuous activity from work. As external temperatures increase, the primary method of removing excess heat is through evaporation, controlling ~75% of heat loss (Daniela 2004). Future climate scenario show that when wet-bulb temperatures (the lowest temperature the environment cools to from latent heat release from evaporation) reaches 35C, the human body can no longer use sweat to remove heat, and cannot survive without air conditioning (Sherwood and Huber, 2010).

~75%Evaporation

~10%Convection

~0-20%Work

~1%Conduction

Radiation(Dependent on Environment)

SensibleHeat

~5%Respiration

2.2 Human Adaptation to Heat Stress

Figure 1

Heat balance in the human body. The red arrows represent a hot environment, with the flux of

heat into humans. The blue arrows are heat dissipation mechanisms and their relative

contributions humans: Evaporation, Respiration, Convection, Conduction (conduction could add

heat, and thus is purple), and Work. The dissipation mechanisms are variable due to thermal

inertia, and may not reach steady state (quantities may not equal 100%).

• J. R. Buzan thanks NRESS, EPSCoR, and NCAR for ongoing support. • Support for the NH EPSCoR Program is provided by the National Science Foundation's

Research Infrastructure Improvement Award # EPS 1101245.

• Computing resources from Information Technology at Purdue University supported this research.

• NCAR is sponsored by the National Science Foundation.

Jonathan R Buzan1,2 and Matthew Huber1,2

1.Department of Earth Sciences, University of New Hampshire, Durham, NH, United States.

2.Earth Systems Research Center; Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, United States.

Correspondence: jonathan.buzan@unh.edu

Influence of Solar and Thermal Radiation on Future Heat Stress Using CMIP5 Archive Driving the Community Land Model Version 4.5

Future Work• Explore sensitivity to each CMIP5 model

2026-2045 baseline. • Dynamically downscale results for

EPSCoR Ecosystems and Society Project.• Dunne, J. P., R. J. Stouffer, and J. G. John (2013), Reductions in labour capacity from heat stress under climate warming, Nature Climate Change,

doi:10.1038/nclimate1827.• Oleson, K.W., D.M. Lawrence, G.B. Bonan, B. Drewniak, M. Huang et al., (2013), Technical Description of version 4.5 of the Community Land

Model (CLM), 1–435, doi:DOI: 10.5065/D6RR1W7M.

• Taylor, K., R. Stouffer, and G. Meehl (2012), An overview of CMIP5 and the experiment design, Bulletin of the American Meteorological Society, 93(4), 485–498.

• Buzan, J. R., K. Oleson, and M. Huber (2015), Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5, Geosci. Model Dev., 8(2), 151–170, doi: 10.5194/gmd-8-151-2015.

BCC-CSM1 ESM2G

IPSL-CM5A-IR CCSM4

99th Percentile ΓWBGT Above Veg

ΓWBGT Above VegBCC-CSM1 ESM2G

IPSL-CM5A-IR CCSM4

75th Percentile ΓWBGT Above Veg

ΓWBGT Above Veg

BCC-CSM1 ESM2G

IPSL-CM5A-IR CCSM4

75th Percentile ΓWBGT Above Veg

ΓWBGT Above Veg

Figure 2: Slope Parameter and zonal average for 99th and 75th percentile threshold WBGT Above Vegetation and zonal means.

2026–2045WBGT Above Veg

WBGT (unitless)

2081–2100

75th

Per

cent

ile99

th P

erce

ntile

Green F

lag

Yello

w Flag

Red Fl

ag

Black F

lag

WBGT Above Vegetation Ensemble Mean

Figure 1: Ensemble mean with zonal average of WBGT Above Veg for two . Stipple pattern is inter-model spread greater than ±2.

WBGT Above Vegetation Change Scaled by Global Mean Surface Temperature Change (Slope Parameter Γ )

Labor Capacity at 75th WBGT Above Vegetation Scaled by ΓWBGT Above Veg

DiscussionEnsemble mean inter-model spreads are small (figure 1), and spatial patterns are nearly identical between time slices for each threshold. Slope parameters are spatially uniform except for the Middle East for both thresholds (figure 2). Spatially uniform slope parameters, and small inter-model spreads are consistent with quasi-equilibrium theory. This allows global calculations of labor reductions that are dependent on global mean surface temperature uncertainties, not inter-model uncertainties (figure 3).

Figure 3: Labor capacity (Dunne et al., 2013) at 75th WBGT Above Veg scaled by global mean surface temperature change using the ΓWBGT Above Veg for CCSM4. Reference values of 2026-2045. Global mean surface temperature changes are +1°C – +8°C.

What is Heat Stress?• Heat stress is the measure of thermal

load on humans (and animals). For mammals, there are 4 methods for d i s s i p a t i n g h e a t : C o n v e c t i o n , Conduction, Radiation, and Evaporation. In hot climates, ~75% of heat dissipation occurs through Evaporation. A sustained change of 3˚C in core temperature in humans, can be lethal. Heat dissipation may not be in equilibrium.

Sally Heat Stress