Post on 18-Jan-2018
description
Ecosystem Impacts and the Economic Costs of Climate Change
Dr. Rachel WarrenTyndall Centre, University of East Anglia
Funded by
Outline
• 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
***Both physical modelling and economic analysis produce same key finding***
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
•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
•If global emissions peak in 2016, around one half of the global
aggregate economic impacts can be avoided,
•if mitigation is delayed so that emissions peak in 2030, only
around one third can be avoided
Comparison with cost-benefit analysis
• 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 analysisis determined by input assumptions
Values increase with decreasing discount rate
Factors that decrease SCC:
Low climate sensitivityHigh adaptive capacity
Perfect foresightOmission of abrupt change
Short-lived damagesLow value of life
Low ecosystem valueLimited impact coverage
Direct costs onlyLimited geographic detail
Factors that increaseSCC:
High climate sensitivityLow adaptive capacity
Imperfect foresightCoverage of abrupt change
Enduring damagesHigh value of life
High ecosystem valueComprehensive impacts
Indirect & direct costsHigh geographic detail
Soci
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output weighted…. …..to equity weighted
Values increase with Aggregation method changing from
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 AMPHIBIANS
PLANTS 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
How mitigation ‘buys time’ for adaptation
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