Transcript 50000 widespread species

Ecosystem Impacts and
the Economic Costs of
Climate Change
Dr. Rachel Warren
Tyndall Centre, University of East Anglia
Funded by
Outline
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Quantifying the economic impacts of climate
change that are avoided by mitigation
Why we used the PAGE09 model
Issues with the cost benefit approach to
economics of climate change
Role of ecosystems and their services
Quantifying the impacts of climate change
upon biodiversity that are avoided by
mitigation
Other ecosystem impacts
Mitigation can avoid up to one half of
aggregate economic damages by 2080s
Equity-weighted
Global Impacts
(year 2000)million
US$
***Both physical modelling and economic
analysis produce same key finding***
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10.0
5.0
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A1B
2.5°C
pathway
2°C
pathway
Year
PAGE09 Economic Model
• Excel 2010 workbook with @RISK 5.7 add-in
• 8 regions
• 10 analysis years
• 4 impact sectors including discontinuity
• Look at 2 policies and their difference
• 112 uncertain inputs
• 100000 runs to calculate distributions of outputs
• Choice to include/exclude equity weighting
Mitigation benefits in economic and
physical metrics
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Early, stringent mitigation can avoid a large proportion of
the aggregate economic impacts of climate change that
would otherwise occur during the second half of the 21st
century
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If global emissions peak in 2016, around one half of the
global aggregate economic impacts can be avoided,
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if mitigation is delayed so that emissions peak in 2030,
only around one third can be avoided
Comparison with cost-benefit analysis
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Sometimes recommends ‘optimal’ pathways to eg
3°C or higher
Derives optimal tradeoffs between mitigation,
damage and sometimes, adaptation
Incomplete representation of the climate system,
climate change impacts, and adaptation.
Depends on uncertain discount rate, equity
weights, climate sensitivity, cost of adaptation
...new knowledge renders it sub optimal
No single decision maker or budget holder
Subjective valuation of impacts
Outcomes of cost-benefit analysis
is determined by input assumptions
Values increase with Aggregation method changing from
Social cost of carbon: range of values
output weighted….
Factors that decrease
SCC:
Low climate sensitivity
High adaptive capacity
Perfect foresight
Omission of abrupt change
Short-lived damages
Low value of life
Low ecosystem value
Limited impact coverage
Direct costs only
Limited geographic detail
…..to equity weighted
Factors that increase
SCC:
High climate sensitivity
Low adaptive capacity
Imperfect foresight
Coverage of abrupt change
Enduring damages
High value of life
High ecosystem value
Comprehensive impacts
Indirect & direct costs
High geographic detail
Values increase with decreasing discount rate
IPCC AR5 ‘Reasons for Concern’
‘Burning embers’ and ‘Representative Concentration
Pathways’
60% of plants and 33% of animals lose ≥50% of their
climatic range by 2080s.
50,000 widespread species
Losses reduced by 60% in 2°C pathway, 40% in 2.5°C
pathway
50,000 widespread species
Mitigation reduces the land area where climate becomes
unsuited to 75% of species now present
BIRDS
PLANTS
AMPHIBIANS
MAMMALS
Areas remaining climatically suitable for 75% of
plants currently present: 2°C plant refugia
Areas remaining climatically suitable for 75% of plants
current present: 3.5°C plant refugia
Plant areas of concern at 2°C
Wallace Initiative
Plant areas of concern at 3.5°C
Wallace Initiative
Global mean temperature rise
How mitigation ‘buys time’ for adaptation
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2010
42 years adaptation
time ‘bought’
2030
2050
Year
2070
2090
Baseline
Mitigation
Mitigation avoids significant terrestrial
carbon loss in 2080s
Caveats: other impacts on ecosystems
• Climate change also affects productivity
• Climate variability will impact biodiversity
• Changes in phenology or distribution may
result in temporal or spatial ‘mismatch’
• Dispersal ability constrained by man made
barriers
• Species extinction (not covered here)
• Loss of Arctic summer sea ice
Conclusions 1
• Avoided impacts for aggregate economic impacts,
biodiversity and ecosystem services are large and
increasing throughout the 21st century
• With 2°C target, ~50% of global aggregate economic
impacts can be avoided
• In 2.5°C target ~33% can be avoided
• 60% of plants and 33% of animals likely to lose ≥50% of
their current climatic range by the 2080s.
• With mitigation, losses reduced by 60% in 2C target, 40%
in 2.5C target
• Avoiding biodiversity loss also avoids loss of substantial
amounts of terrestrial carbon
• Avoided impacts increase with time
• Stringent mitigation buys decades for adaptation
• Delay in mitigation reduces avoided impacts