The Paris Agreement: Are 1.5 C a reasonable limit?

Transcription

1 The Paris Agreement: Are 1.5 C a reasonable limit? INES CAMILLONI Centro de Investigaciones del Mar y la Atmósfera (CIMA/UBA-CONICET) Dpto. Ciencias de la Atmósfera y los Océanos (FCEN/UBA) Instituto Franco-Argentino sobre el Clima y sus Impactos (UMI-IFAECI) Buenos Aires, Argentina São Paulo, 14 July 2017

2 UNFCCC & the Paris Agreement T global & CO C world Conclusions

3 A global legal instrument (international agreement) on the control and management of greenhouse gases (GHG). Adopted in 1992, entered into force in Status of participation: 197 Parties (196 States + 1 regional economic integration organization).

4 What is the overall goal? to protect the climate system for the benefit of present and future generations of mankind. What is the further objective? to achieve stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

5 Conference of the Parties (CoP) The COP is the supreme decision-making body of the Convention. All States that are Parties to the Convention are represented at the COP. A key task for the COP is to review the national communications and emission inventories submitted by Parties to assesses the progress made in achieving the ultimate objective of the Convention. The COP meets every year, unless the Parties decide otherwise. The first COP meeting was held in Berlin, Germany in 1995.

6 The Paris Agreement: Long-Term Global Goals To limit warming to well below 2 C above preindustrial levels To pursue efforts to limit it to 1.5 C recognizing that this would significantly reduce the risks and impacts of climate change

7 The Paris Agreement Nationally Determined Contributions All Parties have to put forward their best efforts through nationally determined contributions (NDCs): contributions that each individual country should make in order to achieve the worldwide goal. In 2018, Parties will take stock of the collective efforts.. There will also be a global stocktake every 5 years to assess the collective progress towards achieving the purpose of the Agreement.

8 The Paris Agreement Satus of ratification The Paris Agreement entered into force on 4 November 2016, 30 days after the date on which at least 55 Parties to the Convention accounting in total for at least 55 % of the total global GHGs have deposited their instruments of ratification, acceptance, approval or accession with the Depositary.

9 Source: UNFCCC, 31 May 2017

10 28% #1 #3 16% #2

11

12 1.5 C, 2 C and 4 C worlds Knutti et al. (2016)

13 1.5 C, 2 C and 4 C worlds Knutti et al. (2016)

14 1.5 C, 2 C and 4 C worlds Knutti et al. (2016)

15 T global & CO 2 Cumulative Emissions and Carbon Budget

16 Only the RCP2.6 scenario is in line with keeping T global increase above pre-industrial levels to below 2 C with a likely chance (66% probability) and no pathway is in line with a 1.5 C limit. IPCC (2013)

17 Direct link between cumulative CO2 emissions and climate response IPCC (2013)

18 A T global target can be linked to a cumulative emissions target IPCC (2013)

19 Total Carbon Budget 65% of the carbon budget compatible with a 2 C goal already used IPCC (2014)

20 4-years of current emissions would be enough to blow what s left of the carbon budget for a good chance of keeping T global rise to 1.5C

21 1.5 C world Impacts & Avoided Risks

22 Reasons for concern (RFC) The reasons for concern framework communicates scientific understanding about risks in relation to varying levels of climate change. The framework aggregates global risks into five categories as a function of global mean temperature change.

23 Reasons for concern (RFC) RFC1: tropical glaciers, coral reefs, mangrove ecosystems, etc. RFC2: risks from heat waves, heavy rain, drought, etc. RFC3: impacts that affect particular groups due to uneven distribution of physical climate change hazards, exposure or vulnerability. RFC4: impacts that can be aggregated globally according to a single metric such as lives affected, monetary damage, number of species at risk of extinction, etc. RFC5: Large-scale abrupt and sometimes irreversible changes: i.e. disintegration of the Greenland and West Antarctic ice sheets leading to a large and rapid sea-level rise.

24 Reasons for concern (RFC) Quantitative differences Avoided risks (IPCC,2014)

25 RFC 1 - Unique & threatened systems The vast majority of tropical coral reefs will be at risk at 1.5 C Schleussner et al. (2016)

26 RFC 2 - Extreme Weather Events: Extreme Precipitation Changes in precipitation related extremes differ substantially on the regional level Schleussner et al. (2016)

27 Dry spell length or consecutive dry days (CDD): annual maximum number of consecutive days for which the precipitation is below 1mm per day. Heavy precipitation intensity or maximum accumulated 5-day precipitation (RX5day): absolute annual maximum of consecutive 5- day precipitation.

28 Schleussner et al.( 2016) Heavy precipitation intensity or maximum accumulated 5-day precipitation (RX5day) Dry spell length or consecutive dry days (CDD)

29 RFC 2 - Extreme Weather Events: Extreme Temperature Intensity of hot extremes (TXx): annual maximum value of daily maximum temperature. Warm spell duration indicator (WSDI): annual count of the longest consecutive period in which the daily maximum temperature for each day exceeds the 90% quantile for this day over the reference period. The minimum length is 6 consecutive days.

30 Schleussner et al.( 2016) Intensity of hot extremes (TXx) Smaller impacts at 1.5 C Warm spell duration indicator (WSDI)

31 RFC 3 - Distribution of impacts: Water availability Mediterranean hot-spot of change Schleussner et al. (2016)

32 Differences in climate impacts Schleussner et al.( 2016)

33 1.5 C Target Overshooting & Negative Emissions

34 Overshooting: CO2 Concentrations The climate change impacts of the higher levels of GHGs concentrations reached in an overshoot profile are dependent on: length of time the concentrations stay above the desired target how far carbon dioxide overshoots Stabilization at low levels of CO 2 will probably require overshooting the concentration target.

35 Overshooting: T global Overshooting It will be very hard if not imposible to keep warming below 1.5 C during the entire 21st century Rogelj and Knutti (2016)

36 Negative Emissions Negative emissions Deliberate removal of CO2 from the atmosphere by human intervention Rogelj and Knutti (2016)

37 Carbon dioxide emission pathways until 2100 Fuss et al (2014)

38 Examples of Negative Emissions Afforestation (planting trees were there were previously none) and reforestation (restoring areas where the trees have been cut down or degraded)

39 Examples of Negative Emissions Production of sustainable bioenergy with carbon capture and storage (BECCS): Farming bioenergy crops, which extract CO2 from the atmosphere as they grow and then burning them for energy and sequestering the resulting emissions underground.

40 Effects of carbon sequestration vs. surface albedo change Reforestation/afforestation leads to a warming in boreal regions Betts et al (2007)

41 Major uncertainties associated to BECCS The physical constraints, including sustainability of largescale deployment relative to other land and biomass needs, such as food security and biodiversity conservation, and the presence of safe, long term storage capacity for carbon; The costs and financing of an untested technology Socio-institutional barriers, such as public acceptance of new technologies and the related deployment policies

42 Solar Radiation Management SRM or Solar Geoengineering: Deliberate reduction in the amount of solar radiation retained by the Earth

43 Geoengineering Model Intercomparison Project (GeoMIP) 12 models abrupt 4xCO2: abrupt quadrupling of CO2 from preindustrial (pi) concentrations G1: globally instantaneous uniform reduction in insolation to balance abrupt 4xCO2 model dependent (3.8 5%) Kravitz et al (2013)

44 Tropics cooler (-0.3 K) Poles warmer (+0.8 K) Kravitz et al (2013)

45 Tropics cooler (-0.3 K) Poles warmer (+0.8 K) Global rainfall reduction (4.5%) Tropical rainfall reduction Kravitz et al (2013)

46 Kravitz et al (2013)

47 Conclusions Challenges for scientists

48 We need to: Quantify local impacts of 2 C warming above the pre-industrial level Quantify differences of these impacts with a 1.5 C warming above the pre-industrial level Identify which of these impacts will require adaptation and at what cost

49 Conclusions Challenges for society

50 We need to: Agree what risks are acceptable and which are to be avoided? (local & sector-specific) Demand decision-makers to aggregate local risks to a global actionable target (1.5 C - 2 C)

51 Ethical dimensions of the discussion If the risk is high in some places and low in others, can we simply take a global average, accepting that many of us will live dangerously?