Climate Science and IPCC Scenarios

Report
IPCC AR4 to AR5
Terminology
• Unchanged
– GCMs – General Circulation Models
• AR4
– SRES – Special Report on Emissions Scenarios
• AR5
– SSPs – Shared Socioeconomic Pathways
– RCPs – Representative Concentration Pathways
– RAPs – Representative Agricultural Pathways
How are these terms related?
SRES (A1B, •SSP
B1, etc.) •RCP
IPRs from •RAPs
IMPACT
RCPs
• RCP 2.6 is below anything from
AR4
• RCP 6 is most similar to A1B
• RCP 8.5 is higher than anything
AR4
RCP – Trends
RCP Details
Description
RCP8.5
RCP6
RCP4.5
RCP2.6
IA Model
Rising radiative forcing
pathway leading to 8.5 W/m2
in 2100.
Stabilization without
overshoot pathway to 6
W/m2 at stabilization after
2100
Stabilization without
overshoot pathway to 4.5
W/m2 at stabilization after
2100
Peak in radiative forcing at ~
3 W/m2 before 2100 and
decline
Publication – IA Model
MESSAGE
Riahi et al. (2007)
Rao & Riahi (2006)
AIM
Fujino et al. (2006)
Hijioka et al. (2008)
GCAM (MiniCAM)
Smith and Wigley (2006)
Clarke et al. (2007)
Wise et al. (2009)
IMAGE
van Vuuren et al. (2006;
2007)
Climate impacts under RCP 8.5 - GFDL
Climate impacts under RCP 8.5 - HadGem
Climate impacts under RCP 8.5 - IPSL
Climate impacts under RCP 8.5 - MIROC
SSPs
• SSP1 – Low Challenges
• SSP2 – Intermediate
Challenges, business as
usual (med-med)
• SSP3 – High Challenges
• SSP4 – Adaptation
Challenges Dominates
• SSP5 – Mitigation Challenges
Dominates
Combining SSPs with RCPs
• SSPs are separated from
emissions, but not all SSPs
are compatible with all RCPs

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