Factors and processes controlling climate variations at different time scales: supporting documents Camille Risi LMD/IPSL/CNRS 3 july 2012
Outline Goals understand factors and processes controlling climate variations at different time scales place present-day climate change in the context of past variations and to identify its specificities. 1. The Earth radiative budget 2. Climate variations at geological time scales (>million years) 3. Climate variations at orbital time scales(tens of thousands years) 4. Anthropogenic climate change 2/27
1) The Earth radiative budget Ö Ø ÙÒÐ Ø α S 0 Ò Ö ¹Ö Ö Ø ÓÒ (1 G) σ T 4 incident sunlight S 0 Ö Ò ÓÙ σ T 4 ÖØ ØÑÓ Ô Ö (1 α) S 0 = (1 G) σ T 4 3/27
1) The Earth radiative budget Ö Ø ÙÒÐ Ø α S 0 Ò Ö ¹Ö Ö Ø ÓÒ (1 G) σ T 4 incident sunlight S 0 Ö Ò ÓÙ σ T 4 ÖØ ØÑÓ Ô Ö (1 α) S 0 = (1 G) σ T 4 Exercise 1: vary S 0, α, G 3/27
1) The Earth radiative budget Ö Ø ÙÒÐ Ø α S 0 Ò Ö ¹Ö Ö Ø ÓÒ (1 G) σ T 4 incident sunlight S 0 Ö Ò ÓÙ σ T 4 ÖØ ØÑÓ Ô Ö (1 α) S 0 = (1 G) σ T 4 Exercise 1: vary S 0, α, G Exercise 2.1: equilibria 3/27
Equilibrium states Fin Fout ¼¼ ¼ ¼¼ ¼ ¼¼ ¾ ¼ ¾¼¼ ½ ¼ ½¼¼ ¼ F in F out CO 2 = 100ppm F out CO 2 = 500ppm F out CO 2 = 12500ppm F out CO 2 = 62500ppm F out CO 2 = 30% ÒÓÛ ÐÐ ÖØ ÒÓ ¹ Ø ¼ ½¼¼ ½ ¼ ¾¼¼ ¾ ¼ ¼¼ ¼ Ì ÑÔ Ö ØÙÖ Ãµ 4/27
2) Variations at geological time scales Snow ball evidence Sediments in Namibia 1m cap dolostone ice rafted debris 5/27
Snow ball earths in Earth s history snow balls snow balls 6/27
Geological evolution of temperature 7/27
Geological evolution of CO2 8/27
Carbon cycle sources ans sinks? 9/27
Carbon cycle sources ans sinks? photosynthesis respiration decomposition land alteration 0.083 Gt/yr volcanism 0.083 Gt/yr 110 Gt/yr 110 Gt/yr 90 Gt/yr 90 Gt/yr ocean carbonates vegetation 9/27
Carbon cycle sources ans sinks? photosynthesis respiration decomposition land alteration 0.083 Gt/yr volcanism 0.083 Gt/yr 110 Gt/yr 110 Gt/yr 90 Gt/yr 90 Gt/yr ocean carbonates vegetation exercise 2.2 9/27
Partial summary (1/2) tertiary glaciation (alpine orogenesis, Antarctica at S pole) permo carboniferous glaciation (coal storage, Gondwana at S pole) late ordivician glaciation (volcanism decreases, Gondwana at S pole) snow balls (Rhodinia fragmentation) snow balls (ozone layer) 10/27
Partial summary (2/2) There has been extreme variations in Earth climate in the past Climate variations are due to perturbations of the radiative balance Natural CO2 variations have played a key role in the past Some climate variations are not reversible beyond some thresholds 11/27
3) Climate variations at orbital time scales Glacial-interglacial cycles present last glacial maximum Vostok ice_core records température PD CO2 CO2 (ppm) 12/27
Spectral analysis power frequency (/yr) 13/27
Obliquity 14/27
Excentricity 15/27
Precession 16/27
Role of orbital parameters Exercise 3 17/27
Exercise 3 Role of orbital parameters Clonclusion: ice sheet feedback at orbital scale orbital parameters increased insolation in summer in high latitudes ice melts more ice sheet retreat temperature increase reflected sunlight increases 17/27
Carbon cycle feedback orbital parameters temperature increase atmospheric CO2 increases ocean CO2 solubility decreases ocean CO2 degasing increases 18/27
Impact on sea level Causes? 19/27
Impact on sea level Causes? thermal dillatation ice-sheet melt 19/27
Partial summary Climate varies naturally at the scale of tens of thousands years We are in an interglacial period, but CO2 concentration is anomalously high Past variations allow us to test our conceptual understanding of climate feedbacks and to test the realism of climate models used for projections. 20/27
4) Anthropogenic climate change exercise 4.1 21/27
4) Anthropogenic climate change exercise 4.1 IPCC projections: global surface warming ( C) multi model mean precipitation change (%) 21/27
Carbone cycle feedbacks exercise 4.2 22/27
Carbone cycle feedbacks exercise 4.2 800 Gt +4 Gt/yr 8Gt/yr 1.5 Gt/yr CO2 fertilizing effect 2.5 Gt/yr T dependent degasing water stress, pollution 500Gt 13 000 000 Gt fossil fuel 36 000 Gt ocean vegetation 22/27
Are we sure CO2 increase is anthropogenic? Ǿ Ø»ÝÖ Ö Ó 13 C ÔÖÓÔÓÖØ ÓÒ Ö Ó 14 C ÔÖÓÔÓÖØ ÓÒ Ô ÓØÓ ÝÒØ ÔÐ Ø Ò 13 C Ø»ÝÖ ¼º¼ Ø»ÝÖ Ó Ò Ó Ð ÙÑ Ò Ñ ÓÒ Ô Ð Ø Ò 13 C Ò 14 C ÚÓÐ ÒÓ 23/27
Climate feedbacks exercise 4.3 24/27
Climate feedbacks exercise 4.3 albedo decreases albedo feedback snow/ice melts temperature increases greenhouse effect increases water vapor feedback air can bear more water vapor water vapor increases 24/27
Climate feedbacks: quantitative rchauffement quand 2x CO2 ( C) écart type entre les modèles ( C) aérosols océan effet de serre direct vapeur d eau neige et banquise nuages 25/27
Reversibility of changes exercise 4.4 26/27
Reversibility of changes exercise 4.4 26/27
Summary Recent CO2 increase is anthropogenic This leads to an increase in temperature, which is doubled by climate feedbacks Still some uncertainties on some feedbacks (especially clouds) and on hydrological impacts of climate change work on evaluating/improving models still needed. Changes are not immediately reversible consequences for mitigation and adaptation strategies 27/27