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T Q i I it

Professor H. J. Schellnhuber CBEPotsdam Institute for Climate Impact Research

Terra Quasi-Incognita:Beyond the 2°C Line

p

AuthorsJohan Rockström, Will Steffen, Kevin Noone, Åsa Persson, F. Stuart Chapin, III, Eric F. Lambin, Timothy M. Lenton, Marten Scheffer, Carl Folke Hans Joachim Schellnhuber BjörnCarl Folke, Hans Joachim Schellnhuber, Björn Nykvist, Cynthia A. de Wit, Terry Hughes, Sander van der Leeuw, Henning Rodhe, Sverker Sörlin, Peter K. Snyder, Robert Costanza, Uno Svedin, Malin Falkenmark, Louise Karlberg, Robert W. Corell, Victoria J. Fabry, James Hansen, Brian Walker, Diana Liverman, Katherine Richardson, Paul Crutzen, Jonathan A. Foley

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1995: The WBGU Tolerable Windows Approach

First justification / operationalization of the 2°C guardrail

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G8 and Emerging Economies Agree on 2°C Long-term Target

[ ]

Global mean annual temperature change relative to 1980-1999 (°C)

Source: IPCC

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Global mean annual temperature change relative to 1980-1999 (°C)

Source: IPCC

TAR (2001) Reasons For Concern Updated Reasons For Concern

Updated Reasons for Concern

EU 2°C-Guardrail

Figure 8 Synthesis Report (Smith et al. 2009 PNAS)

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MILESTONES of the Great TransformationAn effective and just global agreement on climate change

A low carbon infrastructure

Forest protection, conservation and restoration

„[…] we should confine the temperature rise to 2°C to avoid unmanageable climate„[…] we should confine the temperature rise to 2 C to avoid unmanageable climate risks. This can only be achieved

• with a peak of global emissions of all greenhouse gases by 2015

• at least a 50% emission reduction by 2050 on a 1990 baseline. […] developed countries have to aim for a 25-40% reduction by 2020.

[…] a total carbon budget […] should be accepted as the base for measuring the effectiveness of short-term (2020) and long-term (2050) targets“

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Meinshausen et al. 2009aAllen et al. 2009

Emissions Peaking After 2020:More than 1 Kyoto per Year

(Meinshausen et al. 2009b)

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Emissions Peaking After 2020: More than 1 Kyoto per Year

(Meinshausen et al. 2009b)

Emissions Peaking After 2020:More than 1 Kyoto per Year

Negative

Emissions

(Meinshausen et al. 2009b)

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∫=2

1

)()(T

Tglobglob dttEpC

“World Formula” for Climate Policy

)()()()(

2

1 Mglob

Mnatglob

T

Tnatnat TM

TMpCdttEC == ∫

Total global CO2 budget in period [T1,T2] that keeps global warming below 2°C with probability p

Integral over global profile of CO2 emissions

National CO2budget in [T1,T2]

Integral over national emission profile

Fraction of global CO2 budget as determined by ratio of national population Mnat to world population Mglob at time TM

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“World Formula“ for Climate PolicyIllustration

Russia Vietnam

Remaining Asia

Share in world populationGlobal carbon budget National carbon budget

Germany Remaining Europe

Nigeria

Remaining Africa

United States Brazil

Mexico Remaining America

China

India

Indonesia Pakistan

Bangladesh Japan

Philippines

Vietnam

Australia/OceaniaOther

Inter-Temporal FlexibilityNational emission profiles respecting national CO2 budgets

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Inter-Regional Flexibility

Scenario 2: Climate CompromiseT1 = 2010, T2 = 2050, TM = 2010, p = 2/3

Emission paths per capita for selected countries

18

20

Germany

8

10

12

14

16

CO

2 per

cap

ita

GermanyUSAChinaIndiaBurkina Faso

Global budget per capita assumingconstant annual emissions

0

2

4

6

2005 2010 2015 2020 2025 2030 2035 2040 2045 2050

t

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Examples of Per-Capita Emissions Paths of CO2 for Three Groups of Countries without Emissions TradingExamples of Per-Capita Emissions Paths of CO2 for

Three Groups of Countries with Emissions Trading

Source: WBGU Special Report 2009

Sea Level, m Oligocene30 Myr ago

100

Sea Level and Temperature

Today

50Pliocene3 Myr ago

1510

-50

205

Global Mean T, °C

-100

Equilibrium2x CO2

Last GlacialMaximum30 kyr ago

-150David Archer

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Acidification and Anoxia

Oxygen concentrationin mMol/L

Phosphate concentrationin mMol/L

present day

h l

year 3000global warming

only

(Hofmann & Schellnhuber 2009 PNAS)

oxygen hole

year 3000global warming

+ reduced ballast

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Dangerous Warming Commitment

(Ramanathan & Feng 2008 PNAS)

„Mass loss on Himalayan glacier endangers water resources“ (Kehrwald et al. 2008 Geophys Res Lett)

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Nature, 24 Sep 2009

Carbon Stored in Permafrost SoilsEstimates Corrected Upwards

(Tarnocai et al. 2009 Global Biogeochemical Cycles)

The new estimate of frozen carbon stored in permafrost soils of the circumpolar region is over 1.5 trillion tons, about twice as much carbon as contained in the atmosphere.

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Source: PNAS 2009

Interdependency between tipping points

Kriegler et al., 2009, PNAS

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1. Washington R et al. Dust as a tipping element: The Bodélé Depression2. Malhi Y et al. Exploring the likelihood and mechanism of a climate-change

induced dieback of the Amazon rainforest3. Levermann A et al. Basic mechanism for abrupt monsoon transitions4. Latif M et al. El Niño/Southern Oscillation response to global warming

PNAS Special Feature on Tipping Elements, December 2009

Editor Hans Joachim Schellnhuber

p g g5. Notz D The big melt: Is the loss of ice sheets and Arctic sea ice unstoppable? 6. Riebesell U et al. Sensitivity of marine carbon fluxes to ocean change7. Archer D et al. Ocean methane hydrates as a slow tipping point in the global

carbon cycle8. Hofmann M et al. On the stability of the Atlantic Meridional Overturning Circulation9. Molina M et al. Reducing abrupt climate change risk using Montreal Protocal

and other regulatory actions to complement cuts in CO2 emissions

“Runaway Greenhouse Effect”

Conceptual approach

Energy gain per additional degree of warming [W/m2/K]vs.

Energy export through thermal radiation

Venus

“Limited runaway effect”

RadiativeRadiative damping

(Levermann & Schneider v. Deimling, pers. comm., 2009)

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“Runaway Greenhouse Effect”

Past Climate on EarthNo Venus-like effect has been observed in Earth’s history

Recent study on Paleocene-Eocene Thermal MaximumThermal Maximum

showed that presently considered physical feedbacks (water vapor, lapse rate, ice-albedo and

clouds) are not sufficient to

understand amplitude of temperature

It is not clear whether ‘limited runaway feedback’ has occurred.(Possible candidate: transition to Snow-ball Earth)

(Hansen et al. 2008)

increase.

“Runaway Greenhouse Effect”

Where do we stand at present ?

Present estimate of physical feedbacksphysical feedbacks1.5 – 2.5 W/m2/K

Distance to Runaway LimitDistance to Runaway Limit0.7 – 1.7 W/m2/K

(Soden & Held, J. Clim, 2006)

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Missing Feedbacks:• Oceanic CO2 uptake

• Vegetation’s CO2 uptake

“Runaway Greenhouse Effect”

What is missing ?

Venus

“Limited runaway effect”

pos.

±

• Albedo from Greenland melting

• Albedo from Antarctic melting

• Thawing permafrost & peat land

• Oceanic methane hydrates

• Enhanced aerosol ‘wash-out’

• Vegetation albedo effect

O i Di th l lfid (DMS)

VenusRadiativedamping

pos.

pos.

pos.

pos.

±

±

• Oceanic Dimethylsulfide (DMS)

• …

(Levermann & Schneider v. Deimling, pers. comm., 2009)

neg.

Recent studies with Atmospheric-Oceanic GCMs suggest that radiative damping might

not increase with temperature, due to elevated effective radiation height.

(Colman, 2009)

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Key Message 2 - Social and Environmental Disruption

„Temperature rises above 2°C […] are likely to cause major societal and environmental

disruptions through the rest of the century and beyond.“