Climate Change: some key points about the physical basis

Transcription

1 Climate Change: some key points about the physical basis Jean-Pascal van Ypersele Université catholique de Louvain Former IPCC Vice-Chair WMO seminar for TV weather presenters, Marrakech, COP22, 10 November 2016 Thanks to the Government of Wallonia and to my team at the Université catholique de Louvain for their support

2 Agarwal et al., 1999

3 to provide policy-makers with an objec<ve source of informa<on about causes of climate change, poten<al environmental and socio-economic impacts, possible response op<ons (adapta<on & mi<ga<on). Why the IPCC? Established by WMO and UNEP in 1988 WMO=World Meteorological Organiza<on UNEP= United Na<ons Environment Programme

4 What is happening in the climate system? What are the risks? What can be done?

5 Key messages from IPCC AR5! Human influence on the climate system is clear! Continued emissions of greenhouse gases will increase the likelihood of severe, pervasive and irreversible impacts for people and ecosystems! While climate change is a threat to sustainable development, there are many opportunities to integrate mitigation, adaptation, and the pursuit of other societal objectives! Humanity has the means to limit climate change and build a more sustainable and resilient future IPCC AR5 Synthesis Report

6 (IPCC 2013, Fig. SPM.1a) Each of the last three decades has been successively warmer at the Earth s surface than any preceding decade since In the Northern Hemisphere, was likely the warmest 30-year period of the last 1400 years (medium confidence).

7 Since 1950, extreme hot days and heavy precipitation have become more common 7 There is evidence that anthropogenic influences, including increasing atmospheric greenhouse gas concentrations, have changed these extremes

8 Plateau Glacier (1961) (Alaska) h"p://

9 Plateau Glacier (2003) (Alaska) h"p://

10 K!)/6(J1/J)2(+)6(J0()53(2(3J,!)/6(J

11 Cycle de l énergie et effet de serre Rayonnement solaire Infrarouges 20% -18 C

12 L(J+)8-//(.(/*J0-3)1+(J#)00(J3)+6(.(/*J 3M)*.-0#!N+(OJJ3ME'F'J(0*J3)+6(.(/*J)P0-+PQJ Soleil Terre absorption Source : J. Mitchell, Reviews of Geophysics,

13 Cycle de l énergie et effet de serre Rayonnement solaire Infrarouges 20% H 2 O CO 2,... Convection, etc C 95% Source des chi!res : AR4!

14 A/(+61(J#+1.)1+(J R-7+,($JS3-P)3JA/(+68JT00(00.(/*JU9:;9VJ

15 )+92&9%-5<+9$&9$)F Q $1&$T$9+.&4:-&$QRMO$ A)+=-:&$0&$U&&1/9?C$ Source: 0,+1##0'7,0W'(W7%#+-6+).0%4((31/6,7+2(%J

16 Atmospheric concentrations of CO 2! +40% 2016 CO 2 Concentrations (ppm) 1000 years before present (Lüthi et al.,2008, NOAA) The concentrations of CO 2 have increased to levels unprecedented in at least the last 800,000 years.

17 Carbon cycle: unperturbed fluxes Atmosphere pre-ind : 597 GtC 280 ppmv (1ppmv = 2.2 GtC) photosynthesis respiration 70 Physical, 70.5 Chemical, and Biological processes 2300 Ocean vanyp@climate.be Units: GtC (billions tons of carbon) or GtC/year (multiply by 3.7 to get GtCO 2 )

18 Carbon cycle: perturbed by human activities (numbers for the decade s, based on IPCC AR4) Atmosphere 280 ppmv ppmv/yr (1ppmv = 2.2 GtC) pre-ind : 597 GtC + 3.2/yr photosynthesis respiration sinks Physical, Chemical, and Biological processes déforestation (& land use changes) 6.4 Fossil fuels Ocean vanyp@climate.be Units: GtC (billions tons of carbon) or GtC/year Stocks!

19 Oceans are Acidifying Fast!!!. Changes in ph over the last 25 million years Today is a rare event in the history of the World! It is happening now, at a speed and to a level not experienced by marine organisms for about 60 million years!mass extinctions linked to previous ocean acidification events! Takes 10,000 s of years to recover Turley et al Slide courtesy of Carol Turley, PML

20 The carbon cycle is policy-relevant CO 2 accumulates in the atmosphere as long as human emissions are larger than the natural absorp<on capacity Historical emissions from developed countries therefore maxer for a long <me As warming is func<on of cumulated emissions, the carbon «space» is narrowing fast (to stay under 1.5 or 2 C warming)

21 Climatic Change: Are We on the Brink of a Pronounced Global Warming? (Broecker,1975)J J

22 A Progression of Understanding: Greater and Greater Certainty in Attribution AR1 (1990): unequivocal detection not likely for a decade AR2 (1995): balance of evidence suggests discernible human influence AR3 (2001): most of the warming of the past 50 years is likely (odds 2 out of 3) due to human activities AR4 (2007): most of the warming is very likely (odds 9 out of 10) due to greenhouse gases Blue: natural factors only Red: natural + human factors TF=JU9:;<VJXE*J10J&]%-&4&1#$1/6&1#$ JU-WW0JY=J-7*J-ZJ;::VJ*!)*J!7.)/J1/[7(/,(J J!)0JP((/J*!(JW-.1/)/*J,)70(\J]J AR1 AR2 AR3 AR4 IPCC

23 RCP Scenarios: Atmospheric CO2 concentration Three stabilisation scenarios: RCP 2.6 to 6 One Business-as-usual scenario: RCP 8.5 AR5, chapter 12. WGI- Adopted version / subject to final copyedit

24 Only the lowest (RCP2.6) scenario maintains the global surface temperature increase above the pre-industrial level to less than 2 C with at least 66% probability (IPCC 2013, Fig. SPM.7a)

25 years ago (Last Glacial Maximum) With permission from Dr. S. Joussaume, in «Climat d hier à demain», CNRS éditions.

26 Today, with +4-5 C globally With permission from Dr. S. Joussaume, in «Climat d hier à demain», CNRS éditions.

27 J+-%"$K=-+,&$3$E5,$+>$%&4,&-5%=-&$ 2"59?&7^$QR_M`QMRR$8/%"$-&7,&2%$%+$$ MN_O`QRR[$/9$%"&$a)(_D[$72&95-/+$A599=51C$ E^KKJ_S;J`1a!JT00(00.(/*JF(#-+*JU`1/)3Jb+)aVJ

28 !"#$%&'%()*#)+"(,+)%-."/0)$%1/%23456% 2533%71(.%+)$#)-(%(&% :%1/%(.)%% ;<=4>:%$-)/"+1&%% %% IPCC, WGI, Annex I: Atlas of Global and Regional Climate Projections Supplementary Material RCP8.5

29 Precipitation projections Annual rainfall projections

30 J+-%"$K=-+,&$3$E5,$+>$,-&2/,/%5<+9$ 2"59?&7$/9$QR_M`QMRR$8/%"$-&7,&2%$%+$$ MN_O`QRR[$/9$%"&$a)(_D[$72&95-/+$A599=51C$ E^KKJ_S;J`1a!JT00(00.(/*JF(#-+*JU`1/)3Jb+)aVJ

31 (Ref: ) (IPCC 2013, Fig. SPM.9) Sea level due to continue to increase

32

33 IPCC 2013 Fig. SPM.10 Cumulative emissions of CO 2 largely determine global mean surface warming by the late 21st century and beyond.

34 IPCC 2013 Fig. SPM.10 Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

35 The window for action is rapidly closing 65% of the carbon budget compatible with a 2 C goal is already used NB: this is with a probability greater than 66% to stay below 2 C Total Carbon Budget: 2900 GtCO 2 Amount Used : 1900 GtCO 2 Amount Remaining: 1000 GtCO 2 NB: Emissions in 2011: 38 GtCO2/yr AR5 WGI SPM IPCC AR5 Synthesis Report

36 b%5:/1/h5<+9$+>$5%4+7,"&-/2$2+92&9%-5<+97$-&c=/-&7$4+./9?$585#$>-+4$%"&$ :57&1/9&$`$-&?5-01&77$+>$%"&$4/<?5<+9$?+51D$ c<dkj e)0(wj-/j`167+(jf'gj AR5 WGIII SPM IPCC AR5 Synthesis Report

37 Intended Nationally Determined Contributions! (INDCs) h! icj(.1001-/0j6)#j+(#-+*j Baseline Unconditional INDCs ca Median estimate of level constant with 2 C 37

38 Humanity still has the choice With substantial mitigation Without additional mitigation Change in average surface temperature ( to ) AR5 WGI SPM IPCC AR5 Synthesis Report

39 Useful links:!! : IPCC (reports and videos)!! : e.g., most of my slides!! excellent responses to contrarians arguments!! On Jean-Pascal van Ypersele (vanyp@climate.be)