Can we avoid 1.5 C warming? Glen Peters (CICERO) Klima Omstilling (25/04/2018, Sogndal)

Transcription

1 Can we avoid 1.5 C warming? Glen Peters (CICERO) Klima Omstilling (25/04/2018, Sogndal)

2 The pathway ahead Temperature and cumulative emissions (carbon budgets) From carbon budgets to emission pathways Key characteristics of 1.5 C pathways Are the models leading us astray? Can we avoid 1.5 C of warming?

3 Temperature and cumulative emissions Popularized recently as the carbon budget

4 Temperature versus cumulative emissions Continued emissions lead to continued temperature increase: CO 2 emissions must go to zero! Stylized figure 1Gt CO 2 equals 1 billion tonnes CO 2

5 Cumulative emissions to emission pathways We have already emitted a lot of CO 2 and we can only emit a little more The total amount we can emit depends on The temperature level we would like Uncertainties in the climate system How much non-co 2 we emit How much overshoot we can accept For 1.5 C, CO 2 emissions from 2016 to 2100 range from 200 to +500 GtCO 2 (median: +250 GtCO 2 ) Source: Rogelj et al (2018)

6 From carbon budgets to emission pathways

7 Emission pathways We have already emitted a lot of CO 2, and thus we can only emit a little more to stay under 1.5 C or 2 C. 1Gt CO 2 equals 1 billion tonnes CO 2

8 Emission pathways We have already emitted a lot of CO 2, and thus we can only emit a little more to stay under 1.5 C or 2 C. The dark grey area is an approximate carbon budget of 250GtCO 2 from 2017 (consistent with well below 2 C ). Illustrative pathway consistent with the Paris Agreement s well below 2 C (~1.5 C) 1Gt CO 2 equals 1 billion tonnes CO 2

9 Emission pathways with overshoot If we (deliberately) allow CO 2 emissions to decline slower in the short-term, then we overshoot the carbon budget, and then must repay that carbon debt by removing carbon from the atmosphere at a planetary scale. Illustrative pathway consistent with the Paris Agreement s well below 2 C (~1.5 C) 1Gt CO 2 equals 1 billion tonnes CO 2

10 Negative emissions To reach zero emissions in 2050, we need to start planetary-scale carbon dioxide removal (negative emissions) now! It is likely that we cannot get positive emissions to zero, thus, we will always need some level of negative emissions Illustrative pathway consistent with the Paris Agreement s well below 2 C (~1.5 C) 1Gt CO 2 equals 1 billion tonnes CO 2

11 Everyone needs net-zero emissions To stabilize global average temperature (at any level) requires global net emissions to be zero. Because of equity, one would expect rich countries to be zero first and poor countries later (but still zero). Illustrative pathway consistent with the Paris Agreement s well below 2 C (~1.5 C) Zero-year for a rich country Zero-year for a poor country

12 Key characteristics of 1.5 C

13 What does the literature say about 1.5 C? Source: Rogelj et al 2018

14 1.5 C is 2 C, but more and faster Net-zero CO 2 emissions by , radical short-term reductions, large-scale CO 2 removal, high carbon prices No policy baselines Paris pledges Paris ambition Source: Rogelj et al 2018

15 Non-CO 2 is important (CH 4, N 2 O, SO 2 ) While radical mitigation on CO 2 is needed, parallel rapid mitigation on non-co 2 makes the task easier! Important contributions from agriculture, waste, meat, etc (all related to consumption) Less non-co 2, more CO 2 More non-co 2, less CO 2 Source: Rogelj et al 2018

16 Energy system in transformation Rapid growth in non-biomass renewables Rapid scale up of carbon dioxide removal Rapid decline in unabated fossil fuels Source: Rogelj et al 2018

17 Carbon capture & storage Love it or hate it, we need it at scale. CCS is most needed in industry, for CO 2 removal, but not fossil fuels. Needs policy to drive it (too expensive for a business case), risky and big investments (hard for policy). 30,000 facilities 20,000 facilities 10,000 facilities Source: Rogelj et al 2018

18 Are the models leading us astray?

19 Kaya Identity (drivers for CO 2 ) CO 2 = GDP (Energy Intensity) (Carbon Intensity) Source: Peters et al 2017

20 Kaya Identity GDP (Energy/GDP) (CO 2 /Energy) Source: Peters et al 2017

21 Linking income and CO 2 Richest 10% responsible for 50% of global emissions, perhaps a big opportunity? Rapid reductions possible, but unclear how the economics play out as emissions may just redistribute. Source: Oxfam (2015)

22 Final energy use can triple! Scenarios don t get below 1.5C through radical energy efficiency, perhaps an opportunity? Source: Rogelj et al 2018

23 Lifestyle change can help technology Lifestyle change can put less pressure on negative emissions, particularly those that reduce non-co 2 (e.g., meat) Source: van Vuuren et al (2018)

24 Summary

25 Key characteristics of C pathways Need global, coordinated, and strong climate policy Need to grow non-fossil energy sources Need to shut down existing fossil infrastructure Need carbon capture and storage, at scale Need carbon dioxide removal, at scale Need all countries to contribute Need all sectors to contribute

26 Can we avoid 1.5 C warming? No, be realistic If you don t understand the obstacles, 1.5 C is not an option! Misjudge the challenges, then underinvest in adaptation Yes, there is hope Aggressive demand reductions relatively unexplored (not easy) Pleasant surprises may come Models may give a false impression of challenges Begin the journey and see where it takes us

27 Glen Peters Peters_Glen cicero.oslo.no cicerosenterforklimaforskning

28 Carbon budget extras

29 Remaining budget for 1.5 C (66%) Big range in estimates, from -200 to +700GtCO 2, with methods and definitions important factors Source: Carbon Brief (2018)

30 Remaining budget for 1.5 C (50%) Big range in estimates, from -200 to +700GtCO 2, with methods and definitions important factors Source: Carbon Brief (2018)

31 Definitions, methods, pathways Temperature response independent of pathway only for CO 2, not when including non-co 2. Definitions, methods, and non-co 2 pathways all critical parameters Exceeding 1.5 C Temperature exceeded Earth System Models Inertia important Non-CO 2 not as important Policy irrelevant? Avoiding 1.5 C Temperature avoided Integrated Assess Models Non-CO 2 critical factor Scenario dependent More policy irrelevant Source: Rogelj et al 2018; Peters 2018 (in review)

32 What does 1.5 C mean?

33 The Paris Agreement Holding the increase to well below 2 C pursue efforts to limit to 1.5 C global peaking as soon as possible undertake rapid reductions achieve a balance between sources and sinks in the second half of this century Source: Peters (2017)

34 A 66% chance to stay below 2 C Emission scenarios consistent with a 66% chance of staying below 2 C have a median temperature of C. The uncertainty range of the climate sensitivity is too broad for a 90% or higher chance of staying below 2 C. Only scenarios with a radiative forcing of 2.6Watts/m 2 shown in this figure, with weighting based on a Global Warming Potential (100yrs) Source: Riahi et al. 2016; IIASA SSP Database

35 A balance in sources & sinks Only about a half of emission scenarios with a 66% chance of 2 C are below zero in the second half of the century. The balance requirement is rather strict and pushes scenarios closer to 1.5 C. Only a half of scenarios below zero Only scenarios with a radiative forcing of 2.6Watts/m 2 shown in this figure, with weighting based on a Global Warming Potential (100yrs) Source: Riahi et al. 2016; IIASA SSP Database

36 Defining well below 2 C Several factors at play What scenarios were available in the literature before Paris? 66% below 2 C What does pursue efforts to limit to 1.5 C mean? Not 66% below 1.5 C (not in my opinion) Why settle for 66%, why not 99% chance? Uncertainties in the climate system are too broad for higher thresholds What is realistic? 66% below 2 C is likely infeasible in the real world Take 66% chance of 2 C & be happy if we achieve it! Source: Peters (2017)