Climate Uncertainty and Feedbacks

Transcription

1 Climate Uncertainty and Feedbacks Exploring the impact on climate policy scenarios IAMC 214 Maarten van den Berg, Andries Hof, Chris Jones, Detlef van Vuuren 1

2 Typical use of integrated assessment models Mitigation Action + Costs climate model Climate objective Energy/land use Climate representation important In IAMs simple climate representation E.g., MAGICC - medium representation of AOGCMs/ESMs (CMIP3/C4MIP) But uncertainty can influence mitigation strategy and costs! 2

3 Climate sensitivity uncertain but there are more feedbacks Feedbacks included in MAGICC, how does their uncertainty influence costs estimates? Feedbacks not included in MAGICC, how does these influence costs estimates? Arneth et al., 21: Semi-quantitative literature analysis, use Gregory et al metrics 3

4 Uncertainty in mitigation scenarios Mitigation Action + Costs climate model Climate objective, 2 C Energy/land use Uncertainty in feedback Uncertainty ranges within MAGICC Climate sensitivity, carbon cycle Additional uncertainties Feedback Process implementa/on Reference Permafrost CO 2 and CH 4 emissions, T dependent Burke et al. (212) Wetlands CH 4 emissions, T and [CO 2 ] dependent Melton et al. (213) Biomass Fire Added radia/ve forcing, T dependent Arneth et al. (21) Chris 4 Jones, Detlef van Vuuren Ozone (nega/ve) CO emissions, [O ] dependent Sitch et al. (27)

5 Climate Sensitivity Already included in MAGICC (CMIP3) Also historically constrained: 6 different climate setting combinations Use MAGICC6 to calculate temperatures Emulate historic temperature trend Intervals around 2, 3 and 4 C CS (also including bounded uncertainty in other parameters) frequency Climate sensitivity pdf climate sensitivity selection ranges climate sensitivity ( C) (Meinshausen et al., 211) 5

6 Climate Sensitivity CO 2 /CH 4 emissions CO2 emissions (GtCeq) CH4 emissions (MtCH4) CS4 CS3 CS CS4 CS3 CS2 Figure 1 Emission pathways for 2 C climate policy scenarios, under different climate sensitivity assumptions of 2, 3 and 4 C. 6

7 Carbon Cycle Already included in MAGICC We selected three different carbon cycle emulations in MAGICC Resulting in different levels of carbon uptake IPSL (high uptake) Bern (medium uptake) Hadley (low uptake) Meinshausen et al. (211) 7

8 Carbon Cycle CO 2 emissions and concentration CO2 emissions (GtCeq) CO2 concentrations (in ppm) Bern IPSL Hadley Bern IPSL Hadley Figure 2 CO 2 emission pathways and concentrations for 2 C climate policy scenarios, under different carbon cycle model emulations, with high (IPSL), medium (Bern) and low (Hadley) carbon uptake. 8

9 Permafrost Feedback Optimize climate policy scenario under climate constraints Incorporate permafrost CO 2 and CH 4 feedback Feedback transient temperature dependent 1 9 percentiles emission feedback parameters GtC K -1 cumulative CO2 emissions MtCH4 K -1 cumulative methane emissions (Burke et al., 212) 9

10 Permafrost Feedback - CO 2 /CH 4 emissions CO 2 emissions (GtC) CH 4 emissions (MtCH4) 4 PF 9p 2 PF 5p PF 1p CS PF 9p 26 PF 5p 24 PF 1p 22 CS Figure 3 CO 2 and CH 4 emission pathways for 2 C climate policy scenarios, under different permafrost model assumptions. Pathways are shown for 1, 5 and 9 percentile feedback factors. The default climate policy scenario, with a 3 C climate sensitivity using the Bern carbon cycle model (CS3), is also shown. 1

11 Wetlands feedback WETCHIMP wetlands intercomparison project CH 4 dependent on T and CO 2 concentration Positive feedback from increasing CO 2 Negative feedback from increasing T Ignore precipitation and interaction effects Rerun MAGICC Melton et al., 213 Addi8onal Methane Emissions (MtCH4/yr) Addi8onal Methane Emissions (MtCH4/yr) Wetlands CH4 emissions [CO2] CH4 due to deltaco change in CO2 concentra8on (ppm) Wetlands CH4 emissions - T CH4 due to deltat.5 1 change in temperature ( C) Chris 11 Jones, Detlef van Vuuren

12 Wetlands feedback - CO 2 /CH 4 emissions CO2 emissions (GtC) CH4 emissions (MtCH4) WL CS WL 22 CS Figure 4 CO 2 and CH 4 emission pathways for 2 C climate policy scenarios, for wetlands emissions driven by changes in CO2 concentration and surface temperature. The default climate policy scenario, with a 3 C climate sensitivity using the Bern carbon cycle model (CS3), is also shown. 12

13 Biomass fires Cooling or warming feedback effect Influence of emissions and aerosol precursors SOx (cooling) CH 4 /O 3 /BC (warming) Feedback parameter -.3 to +.6 W m -2 K -1 13

14 Biomass fires - CO 2 /CH 4 emissions CO2 emissions (GtCeq) CH4 emissions (MtCH4) CS3 Bbmax CS3 Bbmax Bbmin 5 Bbmin - 2 Figure 5 CO 2 and CH 4 emission pathways for 2 C climate policy scenarios, under the upper and lower estimate of the biomass burning feedback estimate. The default climate policy scenario, with a 3 C climate sensitivity using the Bern carbon cycle model, is also shown. 14

15 Ozone feedback Tropospheric ozone forcing and CO2 concentration from MAGICC (global) Next relate ozone forcing and CO2 concentration on potential impact on carbon uptake by the biosphere Sitch et al., 27 15

16 Ozone feedback CO 2 emissions/concentration CO2 emissions (GtC) CO2 concentrations (in ppm) 4 2 O3 low sens. O3 high sens. CS O3 low sens. 34 O3 high sens. 32 CS Figure 6 CO 2 emission pathways and concentrations for 2 C climate policy scenarios, under a high and low plant sensitivity to O 3. The default climate policy scenario, with a 3 C climate sensitivity using the Bern carbon cycle model (CS3), is also shown. 16

17 Climate feedback parameters Compare runs with and without feedback Ozone [.8.17] Biomass Fire [-.3.6] Wetlands [.2.1] Permafrost [.1.24] Feedback parameter (W m - 2 K - 1 ) 17

18 Change in costs of reaching 2 o C Default Ozone Wetlands Biomass Fire Permafrost Carbon Cycle Climate Sensitivity Cheaper More expensive Relative Discounted Costs 18

19 Conclusions Feedbacks relevant for costs several of the feedbacks looked at would make 2 C more difficult Climate sensitivity and carbon cycle have large impacts on required mitigation effort Climate feedbacks are very uncertain Simplified representation Permafrost and fires feedback parameters in agreement with Arneth et al. Ozone and wetlands feedback parameters are different from Arneth et al. 19