Past, current and projected changes of global GHG emissions and concentrations

Transcription

1 Past, current and projected changes of global GHG emissions and concentrations Corinne Le Quéré, University of East Anglia lead author, WGI Chapter 6 Yann Arthus-Bertrand / Altitude

2 Change in greenhouse gas concentrations CO ppm 390. ppm (+40%) CH ppb 1803 ppb (+%) N 2 O 271 ppb ppb (+20%) The largest contribution to total radiative forcing since 170 is from CO 2 The increase in CO 2 is responsible for most of the increase in radiative forcing since AR4

3 CO 2 flux (GtC y -1 ) CO 2 emissions 0 emissions land-use change uncertainty of ± year source: Chapter 6; Houghton et al. Biogeosciences 2013

4 CO 2 emissions (GtC yr -1 ) CO 2 emissions from land-use change Houghton bookkeeping 7 Process Models Satellite data (tropics only) 3 Model average forest regrowth (1.6±0.) year Land-use change emissions have large uncertainties Land-use change emissions can be negative gross deforestation (2.9±0.) Pan et al. (2011) Net emissions (1.3±0.7) source: Chapter 6

5 CO 2 flux (GtC y -1 ) CO 2 emissions 0 emissions Cumulative emissions: 180 [0 to 260] GtC land-use change year source: Chapter 6; Houghton et al. 2013

6 CO 2 flux (GtC y -1 ) CO 2 emissions 0 Fossil fuel cumulative emissions : 37 [34 to 40] GtC emissions fossil fuel & cement uncertainty of ±8% land-use change year source: Chapter 6; CDIAC emissions

7 CO 2 emissions Period Fossil fuel Land-use change Fossil / Land-use [34 40] 180 [0 260] 70% / 30% [ ] 0.9 [ ] 90% / % source: Chapter 6; CDIAC emissions

8 Cumulative historical emissions Period Historical emissions GtC GtCO 2 Mean Range Mean Range to to to to 2 Cumulative historical emissions known to about ±8 GtC mainly due to uncertainties in land-use emissions source: IPCC AR

9 CO 2 flux (GtC y -1 ) Carbon balance in the environment fossil fuel & cement 0 emissions partitioning land-use change year source: Chapter 6; CDIAC/Houghton emissions

10 CO 2 flux (GtC y -1 ) Carbon balance in the environment fossil fuel & cement 0 emissions partitioning land-use change residual land sink uncertainty of ± year source: Chapter 6

11 CO 2 flux (GtC y -1 ) Carbon balance in the environment fossil fuel & cement 0 emissions partitioning land-use change residual land sink atmospheric growth uncertainty of ± year source: Chapter 6; NOAA/ESRL & Scripps Institute of Oceanography

12 CO 2 flux (GtC y -1 ) Carbon balance in the environment fossil fuel & cement 0 emissions partitioning land-use change residual land sink atmospheric growth year ocean sink uncertainty of ±0.7 source: Chapter 6

13 1 Earth System Models (ESMs) were used to compute emissions compatible with the RCP scenarios ESMs represent climate and carbon cycle processes and how they interact ESMs provide compatible emissions, which include the uncertainty in carbon climate feedbacks

14 ESM response to increasing atmospheric CO 2 only Land and ocean CO 2 sinks continue in response to increasing CO 2 alone decreasing sink increasing sink source: Chapter 6

15 ESM response to climate change only Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO 2 in the atmosphere (high confidence) decreasing sink increasing sink models do not include the release of permafrost C source: Chapter 6

16 GtC/yr Emissions compatible with the RCP scenarios from ESMs By 200, emissions in RCP2.6 are smaller than 1990 emissions by 0% on average (range 14-96%) By 20, about half the models have emissions below zero in RCP2.6 Uncertainties in carbon cycle feedback included in the uncertainties in emissions source: Chapter 6

17 Compatible emissions for all RCPs compared to historical Historical emissions Period GtC GtCO 2 Mean Range Mean Range to to to to 2 Historical emissions exceed emissions in RCP2.6 Range in compatible emissions for a given scenario is large Total CO 2 emissions in 2011 about GtC and growing source: IPCC AR

18 CO 2 Emissions (GtC) Historical CO 2 emissions compared to future pathways fossil fuel & cement land-use change Updated from Peters et al., Nature Climate Change 2013; CDIAC Data; Global Carbon Project 2012 Side Event here November 20, 3pm for 2012 update and 2013 projection

19 CO 2 climate feedbacks not in ESMs Frozen permafrost C stock in permafrost: 1700 GtC C released to the atmosphere from permafrost thawing: 0 20 GtC in RCP8., or 3-1 % of compatible emissions (low confidence) Other feedbacks not included in models: Wetlands CH 4 increased emissions under warmer climate (agreement in direction; amplitude less than permafrost effect in models) Large CH 4 release to the atmosphere from marine hydrates unlikely this century source: Chapters 12 & 6

20 Renewed growth in atmospheric CH 4 concentration after ppb CH 4 growth rate (ppb/yr) CH 4 concentration 1800 ppb CH 4 concentration Recent rise probably caused by rise in natural wetlands and by fossil fuel emissions, but their relative contribution is uncertain Year Kirscke et al Nature Geosciences 2013

21 Summary: The largest contribution to total radiative forcing is caused by the increase in atmospheric CO 2 CO 2 emissions from fossil fuel & cement now account for about 90% of total CO 2 emissions Climate change will affect carbon cycle processes in a way that will exacerbate the CO 2 increase in the atmosphere Cumulative emissions compatible with RCP2.6 are less than historical emissions WGIII Chapter will assess emissions by sectors and countries

22 Further Information Yann Arthus-Bertrand / Altitude