Anthropocene: The closing door of climate targets Thomas Stocker Climate and Environmental Phyics, University of Bern

Grantham Lecture 2013

1. The Anthropocene: A new Epoch

2. Climate Change: The IPCC AR5

3. Climate Targets: What can we achieve?

Anthropocene: The closing door of climate targets Thomas Stocker Climate and Environmental Phyics, University of Bern

Grantham Lecture 2013

Anthropocene: Crutzen and Stoermer (2000)

(Lüthi et al.,2008, NOAA)

+30% 2013

Unprecedented: CO2 of the past 800,000 years

( mod

ified

from

Pet

ers

et a

l., 2

013)

2012

Unprecedented: CO2 Emissions by human activity

9.7±0.5 GtC/yr

+57% since Rio '92

1. The Anthropocene: A new Epoch

2. Climate Change: The IPCC AR5

3. Climate Targets: What can we achieve?

Anthropocene: The closing door of climate targets

Grantham Lecture 2013

to assess on a comprehensive, objective, open and transparent basis the scientific, [...] information

relevant to understanding the scientific basis of risk of human-induced climate change,

...

Charge of the Intergovernmental Panel on Climate Change (IPCC):

www.climatechange2013.org

Key SPM Messages

19 Headlines on less than 2 Pages

8

2009: WGI Outline Approved

14 Chapters, >106 Words Atlas of Regional Projections

54,677 Review Comments by 1089 Experts

2010: 259 Authors Selected

Summary for Policymakers ca. 14,000 Words

9

Observation

Understanding

Future

Warming of the climate system is unequivocal, [...]

Human influence on the climate system is clear.

Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

Anthropocene: A key component in the Earth system

(Sto

cker

, 201

3)

Global Mean Temperature Change

Anthropogenic CO2 Emissions

Cumulative Emissions from 1870 to 2011: 515 GtC

Warming since 1880: 0.85 °C

Transient Climate Response to

Cumulative Carbon Emissions (TCRE)

Cumulative emissions of CO2 and global mean surface temperature response are approximately linearly related.

IPC

C 2

013,

Fig

. 12.

43

Glo

bal m

ean

war

min

g (°

C)

Cumulative CO2 Emissions (GtC) Cumulative CO2 Emissions (GtC)

Transient Climate Response to Cumulative Carbon Emissions

TRCE = 0.8 to 2.5°C per 1000 GtC

CO2-induced warming < 2°C implies less than 1000 GtC

IPC

C 2

013,

Fig

. SPM

.10

Anthropogenic warming < 2°C implies less than 800 GtC

IPC

C 2

013,

Fig

. SPM

.10

Limiting climate change will require substantial and sustained reductions of

greenhouse gas emissions.

Cumulative CO2 emissions to date: about 515 GtC

IPC

C 2

013,

Fig

. SPM

.10

Limiting climate change will require substantial and sustained reductions of

greenhouse gas emissions.

∆T(1850-1900 to 2100) Likelihood Scenarios

> 1.5°C likely RCP4.5, RCP6.0, RCP8.5

> 2°C likely RCP6.0, RCP8.5

> 2°C more likely than not RCP4.5

1. The Anthropocene: A new Epoch

2. Climate Change: The IPCC AR5

3. Climate Targets: What can we achieve?

Anthropocene: The closing door of climate targets

Grantham Lecture 2013

( mod

ified

from

Pet

ers

et a

l., 2

013)

CO2 Emissions: Nearly exponential increase

~ e+1.8 %/yr ∙ t

2020

Academic scenarios to reach the climate target 2°C

2020

2030

Academic scenarios to reach the climate target 2°C

2040

2020

2030

Academic scenarios to reach the climate target 2°C

)s,t(TCRET 1f⋅=∆

∫=∞ dt)t(EC

∞⋅=∆ CTCRET

Cumulative CO2 Emissions:

Peak Warming:

Determinants of Peak Warming

Start Time of CO2 Emission Reduction

Rate of CO2 Emission Reduction

Clim

ate

Targ

et (°

C)

Starting Year of Emissions Reduction

The closing door of climate targets

(Sto

cker

, 201

3)

Rate of CO2 Emission Reduction

Clim

ate

Targ

et (°

C)

Starting Year of Emissions Reduction

The closing door of climate targets

(Sto

cker

, 201

3)

InstantaneousEmission Stop

Clim

ate

Targ

et (°

C)

Starting Year of Emissions Reduction

The closing door of climate targets

(Sto

cker

, 201

3)

Clim

ate

Targ

et (°

C)

The closing door of climate targets

(Sto

cker

, 201

3)

Clim

ate

Targ

et (°

C)

The closing door of climate targets

(Sto

cker

, 201

3)

)s,t(dtdTCRE

dtTd

111

f⋅=∆

∞⋅=∆ CTCRETPeak Warming:

Mitigation Delay Sensitivity:

Trdt

Td

1

∆⋅≈∆

Rate of CO2 Emission Increase

Mitigation delay: Peak temperature rises fast

Peak warming rises at the rate of emissions

(Alle

n an

d St

ocke

r, 20

13)

Mitigation delay: Peak temperature rises fast

Mitigation delay: Peak temperature rises fast

20th century warming: ≈ 0.08 °C per decade

1998 to 2012 warming: ≈ 0.05 °C per decade

increasing of peak warming under continued emissions:

≈ 0.4 °C per decade

Committed peak warming rises 3 to 8 times faster than observed warming

1951 to 2012 warming: ≈ 0.12 °C per decade

RCP8.5 CO2eq = 1313 ppm

IPC

C 2

013,

Fig

. SPM

.8

RCP2.6 CO2eq = 475 ppm

Warming of the climate system is unequivocal.

Human influence on the climate system is clear.

Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

Climate targets disappear rapidly as CO2 emissions continue

Committed peak warming increases at rates similar to those of the emission increase, i.e. 3 to 8 times faster than the observed warming

less-than-2°C world ─ more-than- 4°C world:

Today, we have a choice.