© Yann Arthus-Bertrand / Altitude

Thomas Stocker Co-Chair IPCC Working Group I

University of Bern, Switzerland

IA Models and WGI: Lessons from AR5

IPCC 5th Assessment Cycle (2008-2014):

IPCC 5th Assessment Cycle (2008-2014):

Human influence on the climate system is clear.

Continued GHG emissions will cause further warming and

amplify existing risks.

Changes in climate have caused impacts in natural

and human systems.

Multiple pathways exist to likely limit warming to below 2°C.

IPCC Synthesis Report Climate Change 2014

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IPCC Synthesis Report Climate Change 2014

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IPCC Synthesis Report Climate Change 2014

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IPCC Synthesis Report Climate Change 2014

−25 to −55% by 2050

2°C

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IPCC 2007, WGI Fig. 10.1

IPCC Working Group I Modelling Approach:

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IPCC Working Group I Modelling Approach:

IPCC 2013, WGI Fig. 12.2

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v  IAM are rather remote from WGI daily business, but they are the recognized basis of scenarios.

v  CMIP6 will be largely independent of specific new emission scenarios.

v  Scenario building is one module of a more comprehensive CMIP6 effort: ScenarioMIP.

v  Closer and more continuous exchange between the IAM and the Earth System modelling communities.

v  Enhanced scientific understanding of emulators used in AR6 is needed.

Conclusions and Thoughts for post AR5 (1/2):

v  Timing: A detailed schedule for scenario development should be developed and communicated.

v  Ensuring self-consistency of emission and concentration scenarios should be a priority.

v  Scenarios are needed that permit investigation and quantification of climate-BGC feedbacks.

v  Regionalisation of emission scenarios and their use in comprehensive global models should be a topic of enhanced activity.

Conclusions and Thoughts for post AR5 (2/2):