1. What do we know about medium term climate change?
Accord de Paris : ratifié par 115 parties sur 197, représentant 79% des rejets de gaz à effet de serre
Entré en vigueur le 4 novembre dernier (1 mois après seuil de 55 pays et 55% des émissions)
Valérie Masson-Delmotte

2. The climate system External perturbations Interactions, feedbacks
Internal variability
Response to perturbations
WCRP

3. Anthropogenic CO2 emissions
Atmospheric
CO2
Concentration
(ppm)
Mettre à jour avec GCP 2016
Atmosphere
in 1870
Atmosphere
in 2015
Global Carbon Project, 2016

4. Atmospheric composition
ppb
ppm
ppb
ppt
Mettre à jour avec données les plus récentes site NOAA
NOAA, 2016

5. Radiative perturbation
Harold et al, Nature Climate Change, 2016 based on IPCC 2013

6. Components of change in radiative forcing since 1750?
Adapted from IPCC 2013 (shrinkthatfootprint.com)

7. Nos activités agissent sur le bilan d’énergie de la Terre
von Schuckmann, K. et al, Nature Climate Change, 2016

8. Change in Earth’s surface temperature
WMO 2016

9. Human influence Surface warming 1950-2010 IPCC 2013 Observed Observed
Greenhouse gas
Human influence
Anthropogenic aerosols
Solar and volcanic activity
Internal variability
IPCC 2013

10. Change in intensity and frequency
of extreme events
Hansen et al PNAS, 2012

11. State of knowledge : human influence on extreme events
Capabilities of climate models
Available observations
Physical mechanisms
NAS Report, Attribution of extreme weather events, 2016

12. Evaluation of climate models
Reto Knutti

13. Comparing projections after 2005 with observations

14. Difference between weather forecast, predictability, and projections
IPCC 2013

15. Projections explore climate response to different emission pathways
Greenhouse gas emission pathways
GIEC 2013

16. Projections explore climate response to different emission pathways
Greenhouse gas emission pathways
Radiative forcing (W/m2)

17. Projections explore climate response to different emission pathways
Greenhouse gas emission pathways
Radiative forcing (W/m2)
Climate response (°C)

18. Projections explore climate response to different emission pathways
Greenhouse gas emission pathways
Radiative forcing (W/m2)
Additional risks
Climate response (°C)

19. Cumulative emissions of carbon dioxide largely determine global mean surface warming
2°C target
Amount Used
Amount
Remaining
IPCC 2013

20. Regional aspects of surface warming
Number of very hot days
Global warming (°C)
Knutti et al, Nat. Geo., 2015

21. Regional aspects of precipitation change
Water cycle change :
for 50% of world’s population at +2°C
for 40% of land surface at +3°C
Sedlacek and Knutti, 2014; Knutti et al, Nat. Geo., 2015

22. Potential irreversible change :
marine ecosystems
Arctic sea ice extent
in September (millions of km2)
Ocean acidification (pH)
Cumulative CO2 emissions since 1850 (Gt CO2)
3 m2 loss per ton CO2 emitted
IPCC, 2013; Notz and Stroeve, Science, 2016

23. Potential irreversible consequences :
sea level
by 2100
over thousand years
Recent findings suggest risk of destabilisation of marine sectors of Antarctica
for 3°C warming or more, strongly enhancing sea level risks on time scales of 50 – 500 years
IPCC, 2013; Pollard and de Conto, Nature, 2016

24. Changing risks for 1.5 – 2°C warming
Schleussner et al, ESSD, 2016

25. Risks of abrupt change Catalogue in projections
Intensity of global warming (°C)
Drijfhout et al, PNAS, 2015

26. Mitigation pathways to reduce risks
NDC
Rogelj et al, Nature, 2016

27. Future climate assessments

28. AR6 cycle Special Reports on
Impacts of global warming of 1.5 ºC above pre-industrial levels and related global greenhouse gas emission pathways by 2018
Climate change and oceans and the cryosphere
Climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems

29. Outline of special report Global warming of 1.5 oC
Publications
Submitted by October 2017
Accepted by April 2018
Chapter 1: Framing and context Chapter 2: Mitigation pathways compatible with 1.5°C in the context of sustainable development Chapter 3: Impacts of 1.5°C global warming on natural and human systems Chapter 4: Strengthening and implementing the global response to the threat of climate change Chapter 5: Sustainable development, poverty eradication and reducing inequalities
Is it really feasible to hold global warming to 1.5°C?
In fact, the UNFCCC did not ask IPCC to answer this question. Under the Paris Agreement It asked IPCC to assess the impacts of 1.5°C warming and associated emission pathways.
But the question is frequently asked by the media and at public events.
It is a difficult question for IPCC to address because people can mean very different things by “feasibility”.
The 1.5°C report will not answer the question directly but will unpack it in ways that are useful to policymakers. Feasibility can refer to compatibility with the basic laws of chemistry and physics, to the scale and speed of change required in light of infrastructure and investment capacity, to the economic costs, to the sustainability of the necessary climate responses and to the capacity for social change. The report will touch on all these issues.

30. Notes from scoping meeting Ocean and cryosphere
Publications
Submitted by October 2018
Accepted by April 2019
Chapter 1: Framing and context Chapter 2: High mountain areas Chapter 3: Polar regions Chapter 4: Implications of sea level rise for coasts and communities Chapter 5: Changing ocean, marine ecosystems, and dependent communities Chapter 6: Extremes, abrupt change and managing risks Box : low lying islands and coasts
Is it really feasible to hold global warming to 1.5°C?
In fact, the UNFCCC did not ask IPCC to answer this question. Under the Paris Agreement It asked IPCC to assess the impacts of 1.5°C warming and associated emission pathways.
But the question is frequently asked by the media and at public events.
It is a difficult question for IPCC to address because people can mean very different things by “feasibility”.
The 1.5°C report will not answer the question directly but will unpack it in ways that are useful to policymakers. Feasibility can refer to compatibility with the basic laws of chemistry and physics, to the scale and speed of change required in light of infrastructure and investment capacity, to the economic costs, to the sustainability of the necessary climate responses and to the capacity for social change. The report will touch on all these issues.

31. In preparation AR6 Main Report Methodology Report update Cities
Expected to be released in three working group contributions in 2020/2021 and a Synthesis Report in 2022
AR6
Methodology Report update
TFI
Methodology Report on National Greenhouse Gas Inventories by 2019
Conference call januarau 18.
Cities
Attention on cities in AR6 including a conference in Jan and
special report on cities in AR7

32. Timeline Sept 2018 April 2021 October 2021 Fall 2019 April 2022
Global warming of
1.5 oC
Oceans
and cryosphere
The Physical Science Basis
Climate Change Impacts, Adaptation and Vulnerability
The Synthesis Report
Facilitative dialogue
UNFCCC
Land Use
Mitigation of Climate Change
Global Stocktake 2023
UNFCCC
We need you for this processes. Develop the scientific basis, review the daft, be Authors (CLA, LA, CA, RE). Apply. Dont be frustrated if not Selected. Many ways to contrubte.
Fall 2019
July 2021

33. IPCC assessments
Rigorous
Robust
Transparent
Comprehensive

35. World CO2emissions (Gt per year)
Chine
USA
UE-28
Inde
Global Carbon Project

36. Observed Concentrations Compared to IPCC Projections