ESA-7. Climate Change A Brief Primer. The IPCC. Keywan Riahi

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1 ESA-7 Climate Change A Brief Primer Keywan Riahi riahi@iiasa.ac.at The IPCC Scientific body set up by WMO and UNEP Periodic Assessment Reports (AR5 in 2014) Hundreds of Scientists involved as Authors and Reviewers Does not conduct own research, but assesses the latest scientific, technical and socio-economic literature Elaborate Expert and Government Review Main findings summarized in Summary for Policy Makers Nobel Peace Price 2007 together with A. Gore 1

2 The Greenhouse Effect Solar radiation Long-wave radiation Infrared JTH COP6bis/SBSTA 4 5 Sun and Earth Radiation 2

3 Source: NASA Source: Earth s Energy Balance Source: IPCC,

4 Change of Radiative Forcing Source: Source: 4

5 Source: 14 Source: 5

6 ~10 GtC Global Carbon Cycle 1990s Atmospheric increase = industrial emissions + net land-use emissions ocean uptake residual (missing sink) 3.3 ( 0.2) = 5.5 ( 0.5) + 1.1(0 2.8) 2.0( 0.8) 1.3(0 3.3) Atmospheric CO 2 Concentration Source: Steffen,

7 Source: Global Climate Change 700 The last 160,000 years (from ice cores) and the next 100 years Business as Usual, in CO in 2100 (with business as usual) Double pre-industrial CO Lowest possible CO 2 stabilisation level by 2100 CO 2 today CO 2 now CO 2 concentration (ppmv) Temperature difference from now C Now Time (thousands of years) 100 JTH COP6bis/SBSTA 7

8 GHG Concentrations over the last years Source: IPCC-AR4, 2007 Variations of the Earth s Surface Temperature for the past 1000 years Reconstructions of climate data for the last 1000 years also indicate that this warming was unusual and unlikely to be entirely natural in origin IPCC TAR SPM 00/XXXX 12 8

9 Concentration of Carbon Dioxide and Methane Have Risen Greatly Since Pre-Industrial Times Atmospheric CO 2 from 1850 to present Analysis of gas bubbles trapped in the Antarctic ice sheet has provided a record of atmospheric carbon dioxide concentration prior to the beginning of direct measuremens of the gas at the Mauna Loa Observatory in Hawaii in These latter measurements show the seasonal cycle of CO 2 concentrations that results from growth and decay of vegetation. The atmospheric CO 2 concentration in 1750 was about 280 parts per million. Source: OSTP,

10 Carbon Emissions and Atmospheric Increase Global Carbon Budget Source: LE QUÉRÉ, 2006 Carbon emissions and uptakes since 1800 (GtC) 140 Land use change 265 Fossil emissions 115 Oceans 110 Terrestrial 180 Atmosphere Source: Watson,

11 Svante Arrhenius: Climate change as attention management problem Variations of the Earth s Surface Temperature for the past 140 years 11

12 Potential Impacts of Climate Change Source: 37 12

13 EU Regional Climate Variability: Observations (b) modeled for present (c) and future (d) conditions. Note 2003 heat wave being far outside both observational and model range. IPCC uncertainty terminology (adopted from Schneider and Moss) : <1% probability = exceptionally unlikely (but 2003 happened) Source: IPCC-AR4 Source: 40 13

14 Reasons for Concern Red Amber Source: Smith IPCC TAR, et al PNAS, 2009 Reasons for Concern Red Amber 4 o C 3 o C 2 o C Source: IPCC TAR, 2001 Source: Smith et al. PNAS, 2009 Some Impacts Appear Unavoidable (even under most stringent mitigation) Coral bleaching Species range shift Drought risk and water scarcity (Mediterranean, and particularly in the dry tropics and subtropics) Risk of wildfire Coastal damage from floods combined with sea level rise 14

15 Source: Source: Global mean temperature from an ensemble of 4 simulations using natural and anthropogenic forcing Stott et al, Science /XXXX 5 15

16 Mitigation Integrated Assessment Framework IPCC 2001 Climate Change Impacts Adaptation Emissions Socio-Economic Development Paths 16