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

al c

ost o

f car

bon:

rang

e of

val

ues

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