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Heat Stress In Australia (final)

How bad is heat stress in Australia in summer? Some methods of quantifying heat stress.
by

bruno lemke

on 19 August 2013

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Transcript of Heat Stress In Australia (final)

WBGT
Heat Stress
at work:
Australia

Skel-*
Economics
collaboration
Heat gained by human:
mainly from radiation & energy generated by working
Heat loss (at higher temperatures):
mainly by sweat evaporation & being sensible

Heat gain = heat loss + heat stored
Stored heat  --> core temperature increase

Core temperature over 40C causes heat stroke & death.
Heat balance
Sometimes sensibility is over-ridden
Lack of knowledge
Hunger
Company profits
Cairo
Competition
Fashion
Older age
Sun protection vs sweat evaporation
Thermometer, wet wick, and black globe:
WBGT = 0.7Tw + 0.2Tg + 0.1 Ta
Simple model
Aims: To quantify the potential impacts of climate change on workplace heat exposures and related health, productivity and economic effects
Global partnership program: Research activities that develop methods, test these in field studies in different parts of the world (with different vulnerability), and encouraging and supporting local studies and preventive actions; collaboration with experts in different institutions.
Hothaps research program approaches
For each WBGT level we calculate impacts per million working people at three different levels of work intensity (heavy, moderate and light) for the four time points 1975, 2000, 2030 and 2050.
Then we calculate the number of people affected by multiplying with the working age population sizes (ages 15-64 years) for each region at the four time periods.
We estimate potential impacts of changing workforce patterns and heat exposure by applying different workforce distributions (agriculture-industry-services).
We estimate impacts on clinical health by calculating DALYs by assuming that being unable to work gives a disability fraction of 0.5,
The DALY equivalent impact of reduced work capacity (DAWYs) was also calculated to give an indication of the economic impact of the heat induced loss of work capacity (or productivity) in groups of working people.
Process
DALYs (Disability-Adjusted Life Years lost) based on fatal heat stroke deaths and non-fatal clinical effects of heat
Theory
Temperature
WBGT
UTCI
AT
UTCI mathematical model
Where do we want accuracy?
Mean Radiant Temperature
Comparison
Apparent Temperature
AT = Ta + VP/3 - 0.7WS + 4
Solar version available
Steadman, Rational
Which model would you use?
US Military
Most people use temperature
Humidex, BoM, HI also add humidity
WBGT, UTCI, AT also add solar radiation and wind speed
Index summary
Index
Comparison

Methodology
z normalise then do rmse
RMSE(Ta-UTCI) = 0.03
RMSE(TMax-UTCI) = 0.04
RMSE(WBGT-UTCI) = 0.10
RMSE(AT-UTCI) = 0.03
RMSE(BoM-UTCI) = 0.09

Meaning?
All Australia
RMSE(Ta-UTCI) = 0.02
RMSE(TMax-UTCI) = 0.05
RMSE(WBGT-UTCI) = 0.05
RMSE(AT-UTCI) = 0.05
RMSE(BoM-UTCI) = 0.14

Meaning?
Northern Australia
Multitude of health effects....
Heat stress at work --> time off, illness, death
Reduced work output or hours --> loss in productivity, social effects
Effects on Health & Productivity
Consequences
Health
Quantitative studies:
Ethics?
Marathons
Wyndham
Productivity
Max. core temperature
Protective clothing
Acclimatisation
0.5X0.5 degree grid squares based on CRU3.1 data
Heat indexes calculated for each latitude and longitude grid square then exported to Quantum GIS.
GIS display
GIS Data
WBGT Shade
(january)
1975
2030
2050
2005
WBGT Sun
(january)
2050
1975
Different
Indexes
(january)
WBGT
AT
HI
Tw
Tmax
Humidex
UTCI
AT
Humidex
BoM WBGT
Tmax
Tw
UTCI
WBGT
Loss of productivity calculated using the ISO standard for how much work it is safe to do per hour at each WBGT level.
Calculation
Possible
Moderate work in sun
Moderate work in shade
Tave, Tmax, Tdew daily or hourly from 1000s of weather stations can be freely downloaded from NOAA.
GIS display
Station
Data

Daily
Data
HothapSoft
Trendlines
Percentiles
Days over
Hourly
Data
What we need for heat stress
WBGTmax
WBGTmean
WBGThalf
Difference between indoor and outdoor WBGT for a location
Collecting
Data

Skel-*
equipment
About US$2000
Measuring climatic parameters
How we make $70 equipment
Measuring climatic variables
People understand temperature
Heat indexes unfamiliar
and too complex
Humidity is not easily sensed
Why are heat stress indexes not used?
Future
Predictions

Major project by Tord & Liz measuring heat stress at work in Australia
WHO supplied 0.5X0.5 gridded data from GCM for 2030 & 2050
Three GCM
Ensembles work in Europe:
BCM, EGMAM & IPCM
Model must have humidity related data
Model must be on 0.5X0.5 grids
Employed method of "field change" to achieve this
Use the work loss calculation and multiply it by the working population from Sedac database: approx 2/3 Australian population 15-65
Calculation
Heat stress
Impact

(january)
Sun Moderate Work
Sun Moderate 90% work loss
Heat stress indexes not used because ...
Eurocentric and USAcentric
Do we really need them?
Biggest problem is in the tropics.
When temperature is greater than 34C you can only cool down by .....
Many indexes have significantly different scales
Climate change is already responsible for nearly 400,000 deaths annually and costs the world more than $1.2 trillion, reducing the global GDP by 1.6% annually.
DARA report 2012:
Climate Vulnerability Monitor: A Guide to the Cold Calculus of A Hot Planet
(january)
Moderate work in sun
(80percentile)
Moderate work in sun
(90percentile)
WBGT = 0.7Tw + 0.2Tg + 0.1 Ta
Sun Moderate 80% work loss
Issue isn't likely to be the same as in SE Asia and Africa and Central America.
It is likely that rather than 3 high heat January days now, there will be 6 in future.
Future heat stress in Australia
Where to?
Presenter
Bruno Lemke
PhD in physics but teach physiology at NMIT
(Nelson NZ)
...evaporation of sweat.

So humidity is critical.
60% humidity can lose 350W
90% humidity can lose 88W
work
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