Tony McMichaelNational Centre for Epidemiology and Population
HealthThe Australian National University
Global Climate Change: Health Risks – and
Preventive Strategies
Climate Change 101• The world’s climate is an integrated system
• Many factors (‘forcings’) influence the atmosphere’s uptake and distribution of energy (heat)
• Energy-trapping gases (esp CO2, water vapour, CH4) absorb outgoing re-radiated infrared radiation
– This raises Earth’s surface temperature
• Human activity is increasing the concentration of these ‘greenhouse’ gases
• CO2 concentration has increased from 275 ppm to 380 ppm over past century
– Current trend: 450 ppm by ~2030 (= + 2oC)
As humanity’s resource consumption increases, World Overshoot Day occurs earlier each year. The first Overshoot Day was Dec 19, 1987. Today, it is on October 9 – i.e., our Ecological Footprint is almost 30% larger than the planet’s biocapacity.
World Overshoot Day = [World biocapacity / World Ecological Footprint ] x 365
This year, in just 282 days, we consume the biosphere’s entire capacity for 2006.
www.footprintnetwork.org/gfn_subphp?content=overshoot
1987
2006
2000
October 9, 2006
Flo o d s
M a lar ia
D ia rr h oea
M a ln u tri tio n
02 04 06 08010 01 2 0 0 2 4 6 8 1 0
Deaths (thousands) DALYs (millions)
2000 2030
Estimated deaths and DALYs attributable to climate changeSelected health outcomes in developing countries
WHO, 2004: Global Burden of Disease
Now (2000)
Future (2030)
Total = 150,000 deaths/yr
Climate Change: Relevance to Med Students
• Professional– Advice to patients and families– Awareness of shifts in differential diagnosis– Contribution to organisational policy/advocacy– Participation in research– Health sector: energy efficiency, technology choices
• Citizen– Participation in public debate and political decisions– Community, family and personal decisions/behaviours
Recent Review Articles
McMichael AJ, Woodruff R, Hales S. Climate change and human health: present and future. Lancet, 2006; 367: 859-69.
Website of Intergovernmental Panel on Climate Change (IPCC) – Working Gp 2: chapter on Health Impacts (McMichael & Githeko)http://www.grida.no/climate/ipcc_tar/wg2/347.htm
Summary of Direction, Magnitude, and Certainty of Projected Health Impacts [IPCC: draft only]
Negative Impact Positive Impact
Very High Confidence
Effects on geographic range & incidence of malaria
High Confidence
Undernutrition & consequent disorders
Extreme events (heatwaves, storms, floods, droughts)
Illness/death due to (amplified) poor air quality
Cold-related deaths
Medium Confidence
Diarrhoeal diseases
Research at NCEPH
• Daily temperature + air pollution mortality & hospital admissions
• Weather patterns and asthma occurrence• Daily/weekly temp and food poisoning• Climatic and environmental influences on Ross
River Virus disease• Drought severity and mental health (suicides)• Modelling future changes in health risks w.r.t.
climate-change scenarios
Variations of the Earth’s surface temperature for the past 1,000 years: 1000-2000 AD
IPCC (2001): SPM 1b
Grey area shows statistical uncertainty range
2000
Past Climate Mean surface temperature, 1855-2004
Climate Research Unit, UEA, 2005
Temperature variation from 1961-90 average oC
Causes of Global Climate Change• Natural variability: wobbles of Earth’s axis and
changes in orbit (20K-100K yrs), solar activity, volcanoes, ENSO cycle
• Human activities: increases in greenhouse gases & aerosols, ozone depletion, land clearing
• IPCC: Most global warming since 1950 due to human activities (incr. greenhouse gas emissions)– Evidence for this:
• land-ocean temperature contrasts• annual cycle of terrestrial temperature• hemispheric temperature contrast• regional warming• height of tropopause (between troposphere/stratosphere) • pattern of ocean heating
Australia: Recent climate change [CSIRO]
• Warming of 0.9oC since 1910, mostly since 1950
• Minimum temperatures have risen twice as fast as maximum temperatures
• 2005 was Australia’s warmest year on record
• More heatwaves, fewer frosts
• More rain in north-west since 1950; less in south and east
Trend in mean temp, 1950-2005 (oC/10 yrs)
Annual total rainfall, 1950-2005 (mm/10 yrs)
Causes of climate change in Australia
• Warming since 1950 mostly due to global increases in greenhouse gases
• Rainfall trends: uncertain causes:– Increases in northwest: ? natural variability and
shift in weather patterns due to increases in northern hemisphere aerosols
– Decreases in south: ? natural variability plus greenhouse gas increases
– Decreases in east: ? increase in El Niño events since 1975 (uncertain cause)
131900 21002000
20
15
14
16
17
18
19Earth’s Average Surface Temp (OC)
Year205019501860
Central estimate:
2.5 oC increase
Band of 1200-yr historical climatic variability
Most of warming since 1950 is due to human actions (IPCC, 2001)
IPCC (2001) estimate:+ 1.4-5.8 oC by 2100
Climate Change ProjectionsInstead of simple extrapolation, CSIRO uses computer models of
the climate system, driven by future emissions scenarios for greenhouse gas and aerosols (and ozone depletion)
Emission scenarios (e.g. IPCC ‘SRES’) make assumptions about future demographic, economic & technology changes
Global CO2 Emissions Atmospheric CO2 Concentrations
Changes in Earth’s temperature over past 80 m years, and upper/lower estimates for next several centuries
Millions of years
2100
Barrett, Nature, 2003
Hundreds of years
Hominins appear
Now
Homo genus
PAST
FUTURE
Greenland Ice Sheet: Increase in Area Melted in Summer, from 1992 to 2002 (Arctic Climate Impact Assessment, 2004)
Orange area = melt-zone
1992 2002
Two Important Perspectives
• Health risks are influenced by both ‘natural climate variability’ and by (human-induced) climate change
• Climate change typically acts in concert with other environmental changes
Worldwide Capture-Fisheries
Global fisheries harvest has declined since late ’80s
Global fisheries
Grand Banks cod fishery
Fish account for a high proportion of animal protein in the world’s diet – especially in many developing-country coastal communities.
Global marine fish harvest
25% of commercially exploited marine fish stocks are now seriously over-harvested (Millennium Ecosystem Assessment, 2005)
“… the distributions of both exploited and non-exploited North Sea fishes have responded markedly to recent increases in sea temperature…over 25 years. … Further temperature rises are likely to have profound impacts on commercial fisheries…”
Climate Change and Ocean Acidity Report by (UK) Royal Society, 30 June 2005
Increase in atmospheric carbon dioxide has significantly increased ocean acidity.
Report chairman: "Failure to cut CO2 emissions may mean that there is no place in the oceans of the future for many of the species and ecosystems that we know today.“
(Calcification – zooplankton, crustaceans, shellfish – is very sensitive to pH. These species are base of marine food web. )
That is, in combination:
• Over-fishing
• Ocean warming
• Ocean acidification
… are all impairing the food web and the future productivity of ocean fisheries
Illustrates problem of emerging global non-sustainability
Climate change
Social, economic, demographic disruptions
Biological changes: processes, timing
Changes to ecosystem structure and function
Direct impact
Mediating processes(indirect)
Health impacts
e.g. heatwaves, floods, fires
e.g. fisheries; constraints on microbes; nutrient cycles; forest productivity
Changes to physical systems/processes
e.g. urban air pollution
e.g. mosquito numbers,range; photosynthesis crop yields
Climate Change and Health: Pathways1
2
3
Three Types of Study
Past FuturePresent
Learn DetectEstimation, modelling
Empirical studies
Natural climate variation:- identify ‘effect’ - quantify risks
Current climate change:- detect effects- quantify effects- attribute burden
Future climate change:- estimate risks- est. attrib burden
Monthly cases of Salmonella food-poisoning in relation to monthly temperature
Australian cities, 1991-2001 (modelled best-fit graphs)
0
10
20
30
40
50
60
70
80
90
100
10 15 20 25 28
Temperature oC
Salmonella cases / month Perth
Brisbane
Adelaide
Melbourne
Sydney
D’Souza, Hall, et al., NCEPH/ANU, 2003
12-day Heatwave, 3-14 Aug, 2003
Maximum Temperature, Aug 10Excess Mortality:
France: 14,800
Italy: 10,000
Spain & Portugal: 5,000
Etc.
Total = 30,000+
Paris, Heatwave (Aug 2003): Daily Mean Temps and Deaths
30Mean daily temp, 2003
Mean daily temp 1999-2002
~12oC above season norm 25
15 oC
20
35 oC
~900 extra deaths during heatwave
350
300
250
200
150
100
0
Daily deaths
50
+8 oC
+12 oC
Based on: Vandentorren S, et al. AJPH 2004;94:1518-20.
Daily death rate
Average Warm Hot Extremely hot
We already have sufficient observations within this ‘normal’ temperature range
Daily temperature
?
c
b
a
Young adults
Old adults
Impact of Europe 2003 heat-wave suggests graph c, not b, applies at unusually hot
temperatures
Daily temperature and deaths: what happens at temperature extremes?
Tick-borne (viral) Encephalitis, Sweden: 1990s v 1980s (winter warming)Changing Distribution of the Tick Vector
Early 1980s
Mid-1990s
Lindgren et al., 2000, 2001
White dots indicate locations where ticks were reported. Black line indicates study region.
Baima lake Hongze lake
Freezing zone 1960-1990
Freezing zone 1970-2000
Schistosomiasis: Potential transmission of S japonicum in Jiangsu province due to raised avg January temperature. [Red lines = part of planned Sth-Nth water canal.]
Recent studies in China indicate that the increase in recorded incidence of schistosomiasis over the past decade may in part reflect recent warming. The “freeze line” limits survival of the intermediate host (Oncomelania water snails) and hence limits transmission of Schistosomiasis japonica. This parasite has moved northwards, putting 20.7 million extra people at risk (Yang, Vounatsou, et al. 2005).
Temperature change in China from 1960s to1990s
0.6-1.2 oC
1.2-1.8 oC
Yangtze River
Shanghai
Hurricane Katrina crossing Gulf of Mexico
Yellow/orange/red areas at or above 82°F (27.8°C) – the temperature needed for hurricanes to strengthen.
(NASA, 2005)
DroughtCSIRO estimates:• By 2030, drought frequency
increases by up to 20% over most of Australia
• By 2070, drought frequency increases by 20-80% in south, 20-40% in Qld, 0-20% elsewhere (except central WA)
CSIRO Mk2 model: 2030 (high)
% change in drought frequency
+80
+60
+40
+20
0
-20
-40
+80
+60
+40
+20
0
-20
-40
Mpelasoka et al. (in preparation)
Evidence of El Niño: 1997, 2006Sept 15 2006 Sept 20 1997
Sept 20 1997
Note: Warm surface equatorial waters are flowing east across the Pacific, brining rain to Central and South America coasts,
and leaving drought in Australia (and beyond)
TRANSMISSION POTENTIAL
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0.2
0.4
0.6
0.8
1
14 17 20 23 26 29 32 35 38 41
Temperature (°C)
Plasmodium Incubation period
0
10
20
30
40
50
15 20 25 30 35 40
(day
s)
Biting frequency
0
0.1
0.2
0.3
10 15 20 25 30 35 40
Temp (°C)(p
er d
ay)
Survival probability
0
0.2
0.4
0.6
0.8
1
10 15 20 25 30 35 40
(per
day
)
Temp (°C) Temp (°C)
Malaria Transmissibility: Temperature and Biology
P.vivaxP.falciparum
Also: Pascual et al 2006
Baseline 2000 2025 2050
Ebi et al., 2005
Climate Change & Malaria (potential transmission) in Zimbabwe
Harare
Baseline 2000 2025 2050
Ebi et al., 2005
Climate Change & Malaria (potential transmission) in Zimbabwe
Baseline 2000 2025 2050
Ebi et al., 2005
Climate Change & Malaria (potential transmission) in Zimbabwe
Dengue Fever: Modelling of receptive geographic region for Ae. Aegyptii mosquito, under alternative
climate-change scenarios for 2050
Risk region for mediumemissions scenario, 2050
Darwin
Katherine
Cairns
Mackay
Rockhampton
Townsville
Port Hedland
Broome ..
....
..Carnarvon.
Darwin
Katherine
Cairns
Mackay
Rockhampton
Townsville
Port Hedland
Broome..
.
...
..
Brisbane.Current risk region for dengue transmission Darwin
Katherine
Cairns
Mackay
Rockhampton
Townsville
Port Hedland
Broome..
..
..
..
Carnarvon. Risk region for high emissions scenario, 2050
NCEPH/CSIRO/BoM, 2003
Environmental Refugees UN projection (2006)
• By 2020: up to 50 million people escaping effects of environmental deterioration. – order-of-magnitude increase vs. 2005
• Inevitable spectrum of health risks – physical, nutritional, infectious, mental, and conflict situations
CO2 Stabilisation & Global Warming
0
1
2
3
4
5
6
1980 2000 2020 2040 2060 2080 2100
Year
Tem
pera
ture
ch
ang
e (o C
) SRES highSRES lowIPCC 450 ppm lowIPCC 450 ppm highIPCC 550 ppm lowIPCC 550 ppm high
1.21.41.5
2.3
2.9
5.8
Stabilising CO2 at:
550 ppm by 2150 could limit warming to 1.5-2.9°C by 2100.
450 ppm by 2090 could limit warming to 1.2-2.3°C by 2100.Note: Current level = 380 ppm (vs 275 pre-industrial)
Major Domains of Adaptation• Strengthening natural and infrastructural defences
against physical disasters– Institutional disaster preparedness
• Advance warning of epidemic outbreaks (Colombia, Indonesia, etc.)
• Managing water resources– Safety/quality and access– Mosquito breeding
• Reducing urban vulnerability– Protecting energy systems (decentralisation?)– Minimising heat islands
• Protecting food-producing systems and food access• Data systems: Monitoring, surveillance, analysis,
dissemination• Health-care system: structure, staffing, connectedness
Tasks for formal health sector1. Disease prevention
2. Public education
3. Disaster Preparedness
4. Early warning systems
5. Surveillance of disease occurrence and risk factors
6. Forecasting of likely future health risks
7. Engage in inter-sectoral discussions & policy devt
8. Minimise greenhouse gas emissions by health system infrastructure
- Resource-intensive hospitals: ~60% of public consumption
- Vic DHS: “HERO”; green hospitals