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Global targets and their implications forGlobal targets and their implications for

risk andrisk and adaptationadaptation: new findings on the

feasibility of a 1.5r

C goal

Nicola Ranger

Grantham Research Institute on Climate Change and the Environment

Centre for Climate Change Economics and Policy

Research in

collaborationwith:

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Context

Ad-Hoc Working Group on Long-term CooperativeAction under the Convention: Text to facilitatenegotiations among Parties (9th July):

Agrees that Deep cuts in global emissions arerequired according to the science, and as

documented in the FourthAssessment Report of theIntergovernmental Panel on Climate Change, with aview to reducing global emissions so as to maintainthe increase in global temperature below [1][1.5][2]degrees Celsius above pre-industrial levels

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Contents

Current status: emissions and pledges

Findings on the feasibility of 2rC and 1.5rC goal

Implications for risk

If time a new result on normalisation of losses

due to extreme events

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Current Status: Emissions and Pledges

20

25

30

35

40

45

50

55

60

1990 1995 2000 2005 2010 2015 2020 2025

lo

al

H

Emissions

(Billionsoftonnes

of

arondioid

eequivalent)

Estimates fr m

ccor Pledges

Business as Usual

Sources: Pledge calculations from Rogelj et al. 2010 and Taylor & Stern 2009, and

historical emissions from the World Resources Institute CAIT database/IEA2009

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Feasibility of a 2rC goal

Previous work has shown that it is

scientifically, economically andtechnologically feasibility to limit globalmean warming to 2rC with at least a 50%probability

48GtCO2e

44GtCO2e

40GtCO2e

GlobalGreenhou

seGasEmissions

(billionsoftonnesofcarbondioxideequivalentemissions,GtCO

2e)

This will require strong and earlyglobal emissions reductions

Global emissions will need topeak within the next 5 10years and fall at a rate ofaround 3 4% per yearafterwards.

Global emissions between

40 48 GtCO2e in 2020(current = 48GtCO2e)

Evidence suggests that sucha target is challenging, butboth technically feasible andeconomically desirable

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Current Status: Emissions and Pledges

20

25

30

35

40

45

50

55

60

1990 1995 2000 2005 2010 2015 2020 2025

lo

al

H

Emissions

(Billionsoftonnes

of

arondioideequivalent)

Estimates from

ccord Pledges

Business as Usual

22rrC windowC window

(50:50 chance)(50:50 chance)

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Is a 1.5C goal feasible?

Gi en where we are now,it looks ery unlikely thatglobal meantemperatures can bemaintained below 1.5rCabo e pre-industrialle els (i.e. not

o ershooting).

To give a 50:50 chance ofremaining below 1.5rCwould require emissions topeak by 2012 and then

decline at very high rates(at least 6% per year).

0.0

10.0

20.0

30.0

40.0

50.0

60.0

1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

GlobalEm

issionsofGreenhouseGases

(billionso

ftonnesofCO2equivalent)

48Gt

40Gt

Even if emissions

were reduced to

zero in 2020, thechance of exceeding

1.5 degrees would

be roughly 55%

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Current Status: Emissions and Pledges

20

25

30

35

40

45

50

55

60

1990 1995 2000 2005 2010 2015 2020 2025

lo

al

H

Emissions

(Billionsoftonnes

of

arondioideequivalent)

Estimates from

ccord Pledges

Business as Usual

22rrC windowC window

(50:50 chance)(50:50 chance)

1.51.5rrC windowC window(50:50 chance)(50:50 chance)

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Feasibility of a 1.5rC Goal

This research does not rule out the achievement of a 1.5rC goal

in the long run.

However, it may be feasible reduce emissions strongly enough

to limit the duration of overshoot to a few decades, giving at

least a 50% chance of keeping global temperatures below 2rC

and returning below 1.5rC before 2100.

0.00

0.50

1.00

1.50

2.00

1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

GlobalMeanTemper

ature(medianestimate,

C)

2rC

1.5rC

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

2000 2010 2020 2030 2040 2050

Gl

lE

ss

ns

fGeenh

useG

ses

ll

ns

ftnnes

fC

2e

u

lent

2C, 40Gt n 2020 R2 010

1.5C, 40Gt n 2020 40 _4%

2C, 48Gt n 2020 R2 010

1.5C, 48Gt n 2020 48 _5%

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Feasibility of a 1.5rC Goal: with overshooting

The feasibility of bring global temperatures down to 1.5rC by 2100 is

open to debate.Achieving this will require:

1. Early and strong reductions in global emissions: global emissions

must begin to fall within 5 years and reach less than 44 GtCO2e by 2020

2. Rapid reductions in annual global emissions after 2020: global

emissions would need to fall at 4 5% pa (depending on 2020 emissions)

3. Very low global emissions in 2100 and zero emissions in the long

term: global emissions would need to fall below 2 GtCO2e by 2100.

4. Assumption that it is possible for the global a erage temperature to

exceed a goal (i.e. o ershoot) and then return within a few decades:

there are large uncertainties in the science

We do not rule out the achie ement of a 1.5rC goal in the long

term, however, we conclude that the costs are likely to be

considerably higher than for a 2rC temperature goal

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E idence for Rising Risks

Source: Smith et al. 2008

3rC

2rC

1.5rC

1990 levels

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E idence for Rising Risks

Risks from extreme weather e ents: risks rise non-linearly with warming

Marine ecosystems

Up to 1.5rC: increased coral bleaching; negative impacts on marine

ecosystems

Around 2rC:All coral reefs bleached

All ecosystems: Around 1.5rC:Approx. 9 - 31% of species committed to extinction

Around 2.2rC:Approx. 15 37% of species committed to extinction

Around 2.9rC:Approx. 21 52% of species committed to extinction

Other impacts:

Additional implications

for food and water

supplies; & risks of

extreme events

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E idence for Rising Risks

Coastal inundation of low-lyingareas due to sea le el rise:

Sea level rise (thermalexpansion): ~ 10 20cmdifference between 1.5 and2rC (potentially a doubling)

Small increases in mean sealevel can significantly increasevulnerability to storm surge

Rising global temperatureincreases the risk of

accelerated sea level rise.Around 2 - 3rC: Threshold forirreversible melting ofGreenland Ice Sheet (7m)

resent

Da

s

Sea evelise

s

Sea evelise +

Increase

Cat

s

Sea evelise +

Decrease

Cat

ercentageChangein

resentDa

AverageAnna

loss

Example: Storm Surge Risk

in Grand Cayman

Source: Lloyds of London & RMS2008

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Current Status: Temperature

Source: Rogelj et al. 2010

Two scenarios:

Red = meet current

pledges only

Blue = meet current

pledges then go on toachieve a 50% reduction

in emissions by 2050

Conclusion: an ambitious

long-term emissions

reduction goal (beyond2020) is ital to maintain

temperatures at 2rC orbelow

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Uncertainties in Future Risks

0.00

0.50

1.00

1.50

2.00

2.50

3.00

1990 2010 2030 2050 2070 2090

Glo

balMeanTemp

erature(C)

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Conclusions

It is likely that the world will see global mean temperatures riseto at least 1.5rC abo e pre-industrial le els o er the comingfew decades (by around 2050 on median projections)

With strong action, we may be able to bring temperatures backbelow 1.5rC within 50 100 years, but this overshoot period willbring increased risks.

It may not be possible to know whether or not it is feasible for adecade or more to come. Early and strong action to reduceemissions prior to 2020, will leave open the option to strengthenthe temperature goal to 1.5rC

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Detection of Trends in Extremes

Economic loss from hurricane in the Caribbean and CentralAmerica normalised to remove exposure growth

Bender et al. (2010) rates of cat45 hurricanesincreasing (on average) but no statisticallydetectable trends for another 60 years

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EXTRA SLIDES

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