Klimat i förändring Deliang Chen August Röhss Professur i Naturgeografi Professor i fysikaliska meteorologi Institutionen för Geovetenskaper Tack till IPCC, Erik Kjellström, Jessica Andersson, Markku.Rummukainen Miljöimpuls!, 24 november 2008
Vad ska jag prata om? Varför ändras klimat? Sammanfattning av IPCCs senaste rapporten (AR4, 2007) Vad har hänt efter 2006 (AR4)? Framtid: vad ska vi tänka på (säkerhet eller osäkerhet)?
Varför varierar jordens klimat? Variationer i solstrålningen Variationer i jordbanan Ändringar i atmosfärens sammansättning (gaser) Variationer i naturliga och antropogena aerosoler (partiklar) Ändringar i markanvändning Interna variationer i klimatsystemet
Human factors Greenhouse gases Volcanic activity Natural factors Atmospheric aerosols The earth s s climate can change because of anthropogenic or natural factors Variations of Solar radiatios Land-use change Natural variability (ENSO, NAO)
Socio-ekonomisk världsutveckling Utsläpp Hur räcknar man framtids klimat szenario/påverkan? Atmosfärens sammansättning Ofta bara det! Globalt klimat Regionala klimat Effekter
Klimat- och sårbarhetsutredningen Sverige blir varmare och blötare Risken för översvämningar, erosion, ras och skred ökar i stora delar av landet Infrastruktur hotas kostnadskrävande insatser Skogstillväxten ökar och förutsättningarna för jordbruk förbättras anpassningsåtgärder krävs för att t ex minska skadeangrepp Östersjön hotas marina arter hotas att slå ut Vattenkvaliteten försämras vattenreningen måste förbättras Fjällen förbuskas vinterturismen drabbas, markkonkurrens drabbar rennäringen Värmeböljor och smittspridning ökar nya smittbärare och ökad dödlighet Mer gynnsam energibalans ökat kylbehov, minskat uppvärmningsbehov, mer vattenkraft
Fundamental Climate Change Questions
Main aspects of IPCC AR4 (2007) Consistent and strong message. Less uncertainty, better observations, methods, models and understanding Earth is getting warmer Many aspects of warming are increasing in recent decades Most of recent warming attributable to human influences. Future changes will be larger than those experienced until now Major reductions in greenhgouse gas emissions are required to avoid large scale changes The report is a challenge to world leaders: - We are facing major climate change challenges - Decisions in the next decades will be key to the outcome
Atmospheric CO2-content is 30% higher than ever measured covering the past 650.000 years
Greenhous gas forcing over the past 10.000 years
Anthropogenic and natural forcings from 1750 to 2005
Observed change in global surface temperature Warmest 12 years: 1998,2005,2003,2002,2004,2006, 2001,1997,1995,1999,1990,2000 Period Rate 50 0.128±0.026 100 0.074±0.018 Years /decade
lobal T: 0.76 o C 1 of the 12 armest years ccurred in the ast 12 years ea level crease: 17cm ow: 3mm/år) snow cover: 0% : Sea ice area d thickness o reduced
Bergen: distribution of winter precipitation 1861-2007 1983 2005 2005 2007 1993 1992 1983 1918 2000 1989 1/500 1/30.000 Grønås og Kvamstø (2005)
Fingerprinting of the anthropogenic effects other GHGs aerosols volcanic solar natural internal Climate models
dentificaton of the anthropogenic signature on global and continental warming olid line= Observed ink = With GHG lue = Without GHG
It is very likely that the last 50 years in the NH are the warmest in the past 500 years (90% confidence based on expert judgement)... and: likely that they are the warmest in the past 1300 years (66% confidence)
It is very likely (90%) that most of the climate changes during the past 50 years originates from human activities
Future scenarios: NB: Scenarios are conservative in the sense that the main uncertainties are on the warming side, e.g. Carbon Cycle Feedbacks which most likely will exacerbate warming
SRES emission scenarios: Pathways of future greenhouse gas emissions, derived from selfconsistent sets of assumptions about energy use, population growth economic development, and other factors. A variety of possible "world-views", Explicitly exclude any global policy to reduce emissions Six illustrative SRES "marker" scenarios were selected for use in the climate projections. Scenario descriptions Economic emphasis: A1B balanced energy A2 and A1FI Fossil-fuel Intensive A1T high-tech renewable Environmental emphasis: B1, B2
CO 2 (GHG) emission scenarios A2 A1B B1
EU-target (Anomalies relative to 1980-99)
CO 2 emissions per habitant (based ontreut) Pays Inde Cuba Mexique Chili Venezuela Afrique du Sud Corée du Sud Chine Emission de CO 2 par habitant Ukraine France Italie Royaume Uni Japon Allemagne Belgique Australie Canada USA 0,00 5,00 10,00 15,00 20,00 25,00 tonne par habitant
nsemble mean from two emission scenarios: B1: major emission reductions Moderate Current trend continues 2020-29 2090-99 Some reduction in the Gulf Stream System
Precipitation 2090-2099 Consistent patterns Continuation of present trends
Extreme events: Ongoing trends will continue: Larger and more frequent heat waves More of the precipitation will come as extreme events in many places More intense tropical storms (Atlantic Ocean) AND: Continued reduction in snow and sea ice cover By the end of the 21st century it is likely that the Arctic is blue during summer
Main remaining uncertainties Regional changes and natural variability Feedbacks not accounted for interactively in model projections (e.g. C-cycle feedbacks) Ocean circulation and sea ice distribution Aerosoles-cloud albedo Dynamical changes in ice-sheets
Cryospheric vs ocean contribution? Address scientific uncertainties: sea-level rise Larger values cannot be excluded Current sealevel rise nea the upper end of the IPCC projections and accelerating why? IPCC 2001; IPCC 2007; Rahmstorf et al. 2007
Address scientific uncertainties: global carbon cycle nderstandin the role of marine and terrestrial cosystems in global arbon cycle nd climate system.
Develop and test next generation climate models, confront them with observations and build confidence At various scales: time (seasonal to decadal prediction and attribution), space (global to regional prediction) Refine model intercomparison techniques Advance full Earth system model development
Fundamental :oupled climate mode run including the oceans. Develop and test next generation climate models: First decadal climate prediction Smith et al., Science 10.08.2007
Grid points in climate models
Why downscaling of GCM output? (3) Global climate models often do not provide what is needed in impact studies!
Temperatur och nederbörd i Sverige sedan 1860 Källa: SMHI
Medelvärde i trenden över alla stationer 2 0 8 R 2 =0.2 slope=0.11 R 2 =0.2 y=0.11*x 179.7 4.8 4.6 29 28 R 2 =0.03 0.3 d/100år (R 2 =0.03) R 2 =0.1 slope=0.04 y=0.04*x 54 y=0.003*x 2.7 27 6 4 2 0 8 6 nrain smoothed linear trend Antal nederbördsdagar 960 1965 1970 1975 1980 1985 1990 1995 2000 2005 years rain per rain day (mm) 4.4 4.2 4 3.8 3.6 Nederb./nederbördsdag pint smoothed linear trend 3.4 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 years 99th percentile (mm) 26 25 24 23 22 21 99. percentil pq99 smoothed linear trend 20 1960 1965 1970 1975 1980 1985 1990 1995 2000 years 70 65 px5d smoothed linear trend 2 =0.3 R 2 =0.3 slope=0.1 y = 0.19*x 322 16 15 pxcwd smoothed linear trend 2 =0.12 y = 0.04*x 68 R 2 =0.12 slope=0.04 14 max. 5 day amount (mm) 60 55 max. no of consecutive wet days 13 12 11 10 50 största 5-dygns nb. 45 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 years 9 max. antal sammanh. blöta dagar 8 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 years
Trender i olika årstider Röd: sig. 95%
Ändring i 2m-temperatur (A2) jämfört med 1961-1990 (SMHI) DJF 1981-2010 2011-2040 2041-2070 2071-2100 6 6 6 6 5.5 5.5 5.5 5.5 5 5 5 5 4.5 4.5 4.5 4.5 4 4 4 4 3.5 3.5 3.5 3.5 3 3 3 3 2.5 2.5 2.5 2.5 2 2 2 2 1.5 1.5 1.5 1.5 1 1 1 1 0.5 0.5 0.5 0.5 0 0 0 0 4.5 5.5 6 4 5 5.5 4.5 5 3.5 2 3 1.5 2.5 4 JJA 3.5 2 3 1 5 3.5 3.5 2.5 3 2.5 2 0.5 1 0 2 1.5 1 0.5 0 1.5 0.5 2.5 0.5 2 6 6 5.5 5.5 1.5 3.5 5 5 3 4.5 4.5 4 4 3.5 3.5 3 3 2.5 2.5 2 2 1 1.5 1.5 0.5 1 1 0.5 0.5 0 0 2.5 2 1 1 0 4 2 1.5 0 2.5 ÅR 5.5 4 3 1.5 0.5 1.5 0 0 Göteborg University 4.5 6 http://www.gvc2.gu.se/rcg 1 0.5 0 Regional Climate Group 37
Ändring i nederbörd jämfört med 1961-1990 (B2) (SMHI) 1981-2010 2011-2040 2041-2070 2071-2100 ÅR JJA DJF
Förändring i årsmedelvärden: SRES A2 (2071-2100) minus kontroll (1961-1990)
Hantering av osäkerheter i klimatfrågan Det finns naturliga variationer i klimatet. Gör många klimatsimuleringar. Emissionsscenarierna bygger på en rad antaganden. Använder flera scenarier. Förbättrar scenarierna. Klimatmodellerna innehåller svagheter. Använder flera olika modeller. Förbättrar modellerna. Det kan finnas överraskningar i klimatsystemet. Försöker förstå systemet bättre.
Summary of key messages Global warming is unequivocal Warming since the mid of the 20 century is mostly due to human activities (90-95% likelihood) Climate change projections generally in line with previous assessments and observations so far Dependent on emission scenarios Regional patterns emerging Abrupt changes are not projected to occur in the 21 st century, but they could occur at longer time scales under sustained warming