Outline

• Background– Human energy balance– Strategies to temperature changes

• Morbidity– Heat Waves– Flooding– Famine

• Disease– Malaria

IPCC (2007) Working Group 2 Report

How climate change affects health

Heat Waves

• Associated with short-term increases in mortality

• Have been increasing in frequency

• Mortality displacement is a factor– People close to death will die sooner in a heat

wave– Drop off in deaths after the heat wave

Human Adaptability to Heat

• Humans maintain near constant core temperature through various adaptive strategies:– Physiological (sweating)– Acclimatization (adjustment to new conditions

over time)– Alteration of food intake– Changing when you do things– Migration– Clothing– Use energy for A/C or heating

Human Energy Balance

• Storage change = 0 over time to maintain temperature balance

SECRQM )(

Metabolic Rate

Incoming shortwave

Longwave Radiation

Convection

Evaporation

Storage

Clothing Impact

• The “private climate”• Quantified by estimating the resistance to

thermal transfer:

T

DT

T

ASCL hM

AqQM

M

TTI

/

Body Temp.Air Temp. Body Area

Incoming shortwave

Metabolic Rate Dry Heat Flux = 6.6+8.7(wind speed)0.5

Simplified Clothing Index

Acclimatization

• Evidence that some populations have become less sensitive to temperature extremes– USA (1964-1988)– South Carolina (since 1970s)

• Physiological responses include:– More efficient heat loss through sweat– Readjustment of temperature preference toward the

extreme values

• Leads to less discomfort, better work performance, sense of better well being

Flooding and Health Effects

• Large numbers of fatalities from the events themselves– Bangladesh

• Post-event impacts– Digestive diseases– Chemical contamination

(e.g. Katrina)– Mental disorders

(anxiety, depression)• Higher impacts on poor

– More live in flood prone areas

Drought

• Diminishes diversity in diet and reduces overall food consumption

• Malnutrition– Increases risk of acquiring and dying from

infectious disease

• May cause mass migration (rural to urban)– Increase in communicable disease

Climate Model Projections

Food Safety

• Studies have shown a linear increase in food poisoning with increase in temperature

• Higher temperatures increase contact between food and pests (flies, cockroaches, rodents)

• More ocean toxins (Harmful Algal Blooms) contaminate shellfish

Water Supply

• Water access already a global concern– 2 billion + do not

have access to clean water

– Leads to disease, malnutrition, infant mortality

Water Supply

• Climate extremes (projected to increase) stress water supply systems

• Lower river flows increases pathogen proportion

• Extreme rain/runoff events may increase water borne disease– Curriero et al. 2001

Vector Borne Diseases

• Transmitted through bites– Mosquitoes, ticks, bugs,

some flies

• Tick populations have shifted north (Sweden, Canada) and up (Czech Republic)

• Evidence of earlier arrival of mosquitoes

Malaria

• 515 million cases each year in tropics and subtropics– 1-3 million deaths

• Conflicting results on malaria trends and how they relate to climate– Some evidence that high minimum temperatures in

preceding months mean more malaria (Ethiopia)

Future Vulnerability to Climate Change

• Factors– Existing burden of disease and disability– Aging of the population– Population explosion

• From 6.4 bil to 9 bil by mid-21st century• Highest in poor countries

– Urbanization• Heat island effect, more efficient disease transfer

– Socio-economic• Rich get richer, poor get poorer