The Fifth Assessment: A Discussion of the IPCC Working Group 1 AR5 Report

The Fifth Assessment: A Discussion of the IPCC Working Group 1 AR5 Report Prof. Chris E. Forest The Pennsylvania State University (ceforest@psu.edu) Lead Author - Chapter 9 - Evaluation of Climate Models! 19th Annual Energy and Climate Change Research Seminar May 13, 2014 Washington Marriott at Metro Center

IPCC WG1 Summary! The human influence on Earth s climate is clear It s still warming... but with more observables. More warming to come. New lines of evidence New concepts www.climatechange2013.org

The Timeline 2010 MAY - IPCC WG1 Authors and Reviewers Selected 2010 NOVEMBER - First Lead Author Meeting - Kunming, China 2011 MARCH 18 - Zeroth Order Draft 2011 JULY - Second Lead Author Meeting - Brest, France 2011 NOVEMBER 18 - First Order Draft 2012 APRIL - Third Lead Author Meeting - Marrakech, Morocco 2012 AUGUST 10 - Second Order Draft 2013 JANUARY - Fourth Lead Author Meeting - Hobart, Australia 2013 MAY 13 - Final Draft 2013 SEPTEMBER 27 - IPCC Plenary Approval of SPM - Stockholm, Sweden

(b) Observed change in surface temperature 1901 2012 Observed Surface Temperature Changes Figure SPM.1a (a) Observed globally averaged combined land and ocean surface temperature anomaly 1850 2012 0.6 Annual average 0.4 Temperature anomaly ( C) relative to 1961 1990 0.2 0.0 0.2 0.4 0.6 0.6 0.4 0.2 0.0 0.2 Decadal average (b) Observed change in surface temperature 1901 2012 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1.0 1.25 1.5 1.75 2.5 ( C) 0.4 0.6 1850 1900 1950 2000 Year

Increased focus on observed precipitation changes Observed change in annual precipitation over land 1901 2010 1951 2010 100 50 25 10 5 2.5 0 2.5 5 10 25 50 100 (mm yr -1 per decade) (IPCC WG1 AR5 Figure SPM.2)

Many additional observations are now used to assess historical climate change Year (a) 45 Northern Hemisphere spring snow cover (c) 20 Change in global average upper ocean heat content (million km 2 ) 40 35 (10 22 J) 10 0 10 (b) 30 1900 1920 1940 1960 1980 2000 Year 14 Arctic summer sea ice extent (d) 20 1900 1920 1940 1960 1980 2000 Year 200 Global average sea level change 12 150 (million km 2 ) 10 8 6 (mm) 100 50 0 (c) 4 1900 1920 1940 1960 1980 2000 Year 50 1900 1920 1940 1960 1980 2000 Year (IPCC WG1 AR5 Figure SPM.3)

Including key Carbon Cycle observations (a) CO2 (ppm) 400 380 360 340 320 Atmospheric CO 2 300 1950 1960 1970 1980 1990 2000 2010 Year (b) pco2 (μatm) 400 380 360 340 320 Surface ocean CO 2 and ph 1950 1960 1970 1980 1990 2000 2010 Year 8.12 8.09 8.06 in situ ph unit (IPCC WG1 AR5 Figure SPM.4)

Anthropogenic warming has mainly occurred in the ocean.! Evidence in the Global Energy Budget Accumulated Energy Increase since 1970 >90% of energy increase in ocean heat content ZJ = 10 21 Joules IPCC WG1 AR5 Box 3.1, Figure 1

The Drivers of Climate Change Radiative Forcing: Figure SPM.5 Emitted compound Resulting atmospheric drivers Radiative forcing by emissions and drivers Level of confidence Well-mixed greenhouse gases CO 2 CH 4 Halocarbons N 2 O CO 2 CO 2 H 2 O str O 3 CH 4 O 3 N 2 O CFCs HCFCs 1.68 [1.33 to 2.03] 0.97 [0.74 to 1.20] 0.18 [0.01 to 0.35] 0.17 [0.13 to 0.21] VH H H VH Anthropogenic Short lived gases and aerosols CO NMVOC NO x Aerosols and precursors (Mineral dust, SO 2, NH 3, Organic carbon and Black carbon) CO 2 CH 4 O 3 CO 2 CH 4 O 3 Nitrate CH 4 O 3 Mineral dust Organic carbon Sulphate Black carbon Cloud adjustments due to aerosols Nitrate 0.23 [0.16 to 0.30] 0.10 [0.05 to 0.15] -0.15 [-0.34 to 0.03] -0.27 [-0.77 to 0.23] -0.55 [-1.33 to -0.06] M M M H L Albedo change due to land use -0.15 [-0.25 to -0.05] M Natural Changes in solar irradiance 0.05 [0.00 to 0.10] M Total anthropogenic RF relative to 1750 2011 1980 1950 2.29 [1.13 to 3.33] 1.25 [0.64 to 1.86] 0.57 [0.29 to 0.85] 1 0 1 2 3 Radiative forcing relative to 1750 (W m 2 ) H H 2.6 M Wm -2

IPCC WG1 AR5, Figure SPM.6

Can Climate Models capture the observed changes? Land surface Global averages Land and ocean surface Ocean heat content Observations Models using only natural forcings Models using both natural and anthropogenic forcings IPCC WG1 AR5 Figure SPM.6

Can Climate Models capture the observed changes? IPCC WG1 AR5 Figure SPM.6

Can Climate Models capture the observed changes? Sea Ice IPCC WG1 AR5 Figure SPM.6

Can Climate Models capture the observed changes? Sea Ice Ocean Heat Content IPCC WG1 AR5 Figure SPM.6

What are the causes of warming? Based on attributable warming using local detection of temperature trends Observed = HadCRUT4 IPCC WG1 AR5 Figure 10.5

RCP Scenarios have replaced SRES Scenarios (which replaced IS92 Scenarios RCP := Representative Concentration Pathways 2.6, 4.5, 6.0, & 8.5 := Radiative Forcing at 2100

RCP Scenarios have replaced SRES Scenarios (which replaced IS92 Scenarios RCP := Representative Concentration Pathways 2.6, 4.5, 6.0, & 8.5 := Radiative Forcing at 2100

Climate Projections using RCP Scenarios Temperature, NH Sea Ice, Ocean ph IPCC WG1 AR5 Figure SPM.7

Climate Projections using RCP Scenarios Temperature, NH Sea Ice, Ocean ph (a) ( o C) 6.0 4.0 2.0 0.0 Global average surface temperature change historical RCP2.6 RCP8.5 42 2.0 1950 2000 2050 2100 39 32 Mean over 2081 2100 RCP2.6 RCP4.5 RCP6.0 RCP8.5 (c) (ph unit) Global ocean surface ph 8.2 12 9 8.0 7.8 10 7.6 1950 2000 Year 2050 2100 RCP2.6 RCP4.5 RCP6.0 RCP8.5 (b) 10.0 Northern Hemisphere September sea ice extent 8.0 39 (5) (10 6 km 2 ) 6.0 4.0 29 (3) 2.0 37 (5) 0.0 1950 2000 2050 2100 RCP2.6 RCP4.5 RCP6.0 RCP8.5 (c) Global ocean surface ph IPCC WG1 AR5 Figure SPM.7

Chapter 9 Summary Figure

Climate Projections using RCP Scenarios Low (RCP2.6) High (RCP8.5) (a) RCP 2.6 RCP 8.5 Change in average surface temperature (1986 2005 to 2081 2100) 32 39 ( C) 2 (b) 1.5 1 0.5 0 0.5 1 1.5 2 3 4 5 7 9 11 Change in average precipitation (1986 2005 to 2081 2100) 32 50 (c) 40 30 20 10 39 0 10 20 30 40 50 (%) IPCC WG1 AR5 Figure SPM.8 Northern Hemisphere September sea ice extent (average 2081 2100)

2ºC Target 4ºC Target

Conclusions: The human influence on Earth s climate is clear

Conclusions: The human influence on Earth s climate is clear Past: It s still warming... but with more observables.

Conclusions: The human influence on Earth s climate is clear Past: It s still warming... but with more observables. Future: More warming. More sea level rise.

Conclusions: The human influence on Earth s climate is clear Past: It s still warming... but with more observables. Future: More warming. More sea level rise. New lines of evidence Deep Ocean, Carbon-cycle, sea-ice, ocean ph

Conclusions: The human influence on Earth s climate is clear Past: It s still warming... but with more observables. Future: More warming. More sea level rise. New lines of evidence Deep Ocean, Carbon-cycle, sea-ice, ocean ph New concepts Aerosol-Cloud effective forcing Earth System Models (emissions to response) Cumulative Carbon Emissions Temperature Target