Effects of global warming on global water and food

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Transcript Effects of global warming on global water and food

Effects of global warming on global
water and food supply
Nigel Arnell and Martin Parry
Working Group II (Impacts and Adaptation)
UN Intergovernmental Panel on Climate Change
Royal Society of Medicine, 12th November 2007
Climate change and health
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*
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IPCC AR4 WG2
Climate change is happening
IPCC AR4
2007
Future climate
• Change in climate
depends on:
- future emissions
- sensitivity of climate
to change
Future climate
IPCC AR4 WG1: Change in rainfall
white areas: lack of agreement between models
Implications for food and water
• How will climate change affect food
production and hunger?
• How will climate change affect the
availability of water resources?
How might climate change affect food
production?
• change in weather, affecting crop growth
• change in occurrence of pests
• change in productivity due to the direct
effects of increase in CO2 concentrations
• change in availability of irrigation water
• change in frequency of damaging events
• change in global food markets
Weather and crop growth
IPCC
AR4
Change in Multiple Cropping Production
Potential of Rain-fed Cereals
Decrease
Increase
Grain yields
Global production
Cereal production
% difference from reference case
0
-2
-4
-6
-8
-10
-12
A1
A2
B1
world
Parry et al. (2005)
Percentage change in average crop
yields. Effects of CO2 are taken into
account. Crops modelled are:
wheat, maize and rice.
B2
Pests
Range of expansion of soybean sudden death
syndrome (Fusarium solani f.sp. glycines) in
North America. (X.B. Yang).
1998
1993
1985
1971
Overwintering range of potato leafhopper under two
doubled CO2 climate change scenarios. (Stinner et al.,
1989)
GISS
GFDL
Present
CO2 enrichment effect
Crop productivity tends to increase as CO2
concentrations increase
- C3 crops (e.g.wheat) 10-20%
- C4 crops (e.g.maize) 0-10%
BUT…
effects may be offset by effects of higher
temperatures, nutrient availability, water
stress etc
Availability of irrigation water
Scholze et al. (2006)
Blue
tendency to increase
Red
tendency to decrease
Number of grains per ear
Extreme events: heat stress
40
After a single
hot day >30oC,
there is a large
reduction in
wheat grain
yield
wheat
30
20
10
0
20
25
30
35
40
Maximum air temperature (°C)
Wheeler et al. cited in the Stern Review, 2006
45
Extreme events: lost production
Reuters
Tabasco State, Mexico, November 2007: “100% of crops lost”
How might this affect risk of hunger?
• change in the price of food
• change in incomes
• change in access to resources
Change in the price of food
IPCC AR4
Impacts depend on how markets are
assumed to operate
Food prices and risk of hunger
Cereal prices
Cereal prices
% difference from reference case
160
140
120
100
80
60
40
20
Additional risk of hunger
0
A1
A2
B1
700
B2
Risk of hunger
difference from reference case
(millions)
world
600
500
400
300
200
100
0
A1
A2
B1
world
Parry et al. (2004)
B2
Climate change and water resources
Scholze et al. (2006)
Blue
tendency to increase
Red
tendency to decrease
Water scarcity
2055
Change in global water resources
Millions of people with increase in water stress
HadCM3 scenarios:
increase in stress
Millions of people
3500
3000
0.8-1.0oC
1.5-2.3oC
2.1-4.0oC
2500
2000
1500
1000
500
0
2025
2055
A1/B1
A2
2085
B1
B2
Impacts
depend on
change in
climate and
the state of
the world
Consequences
• Reduced access to safe water
Now: 1 billion people lack access to safe drinking water
2.4 billion people lack adequate sanitation
Access is not just a problem of availability
- property rights / power relations
Consequences
• Increased conflict over resources
• Increased exposure to floods
• Increased need for investment in water
management
So what can we do?
Mitigation: slow the rate of climate change
No climate policy
commitment
Van Vuuren (2007)
With policy targets
So what can we do?
change crops
Adaptation is essential
reservoirs
more irrigation
Alter resource base
Reduce
processing waste
Increase irrigation
efficiency
etc
Alter exposure
etc
Diversify
IMPACT
Raise incomes
Emergency
support
etc
Reduce vulnerability
Conclusions
• Climate change is happening, and will affect
food and water supplies
• The consequences will vary with the
amount of change, and with the vulnerability
of the community
• Mitigation will not prevent impacts in the
short-term – we need to start adapting now
Thank you
www.walker-institute.ac.uk