1. © 2011 Martin Beniston Climatic change in the light of scientific knowledge Martin Beniston Institute for Environnemental Sciences University of Geneva

2. © 2011 Martin Beniston The functionning of the climate system

3. © 2011 Martin Beniston Energy exchange around the planet Solar Reflected energy Infrared

4. © 2011 Martin Beniston Volcanic eruptions

5. © 2011 Martin Beniston Fluctuations of solar irradiance Weak activity January 2005 Stronger activity March 2001

6. © 2011 Martin Beniston ENSO (El Niño/Southern Oscillation) February 2011 La Niña

7. © 2011 Martin Beniston Human perturbations to the climate system

8. © 2011 Martin Beniston CO 2 and CH 4 concentrations 10’0005’000010’0005’0000 Years before present 250 300 350 500 1000 1500 CH 4 ppbvCO 2 ppmv Years before present

9. © 2011 Martin Beniston Attribution of recent trends to anthropogenic forcing

10. © 2011 Martin Beniston Human responsibility…? 1900 1950 2000 0.0 0.5 1.0  T with respect to 1961-1990 [°C] Observations Natural forcing Natural + Greenhouse-Gas Forcing IPCC, 2007

11. © 2011 Martin Beniston Future warming will be linked to emissions - and thus to the choices we make in terms of policy, economics and technology

12. © 2011 Martin Beniston Global warming futures IPCC, 2007 -0.4 -0.2 0 0.2 0.4 0.6 1.0 10001100120013001400150016001700180019002000  T respect to 20 th century means [°C] 0.8 2.0 3.0 4.0 5.0 6.0 20502100 A2 B2

13. © 2011 Martin Beniston Global temperature change by 2100

14. © 2011 Martin Beniston Heatwave days: Exceedance of 40°C threshold in Europe 5101520251 Days EU-FP6 « ENSEMBLES » Project, 2009 1961-1990 2021-2050 2071-2100 PrecipT CH

15. © 2011 Martin Beniston Changes in seasonal temperatures (at 2,500 m asl) Beniston, 2006: Geophysical Research Letters 15 WinterSpringSummerAutumn Temperature [°C] 10 5 0 -5 Beniston, 2004: Climatic Change and Impacts, Springer 1961-1990 2071-2100

16. © 2011 Martin Beniston Global precipitation change (IPCC AR4, 2007)

17. © 2011 Martin Beniston Changes in summer precipitation (june-july-august) (Differences in % between 2071-2100 and 1961-1990) (HIRHAM RCM; A-2 Scenario) Christensen and Christensen, Nature, 2003 Seasonal precipitation Events greater than 50 mm/day -40-30-20-100+10+20+30+40 % change Accelerated warming Impacts p CH

18. © 2011 Martin Beniston Changes in seasonal precipitation Beniston, 2006: Geophysical Research Letters -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 40.0 WinterSpringSummerAutumn Precipitation change 2071/2100 vs 1961/1990 [%] Impacts Accelerated warming

19. © 2011 Martin Beniston Since the 2007 IPCC reports, climate has shown signs of accelerated change…

20. © 2011 Martin Beniston IPCC projections with respect to observations 19901995200020052010 0 0.25 0.50 Changes in temperature [°C] Projections (IPCC 3 rd Assessment Report ) Observed Updated from Rahmstorff, 2007 in « Science »

21. © 2011 Martin Beniston Feedback mechanisms stronger than expected n Certain irreversible thresholds may be reached earlier than expected u changes in Arctic sea ice u release of methane in polar permafrost u changing patterns of land-use n Whatever we achieve in terms of policy, climate is likely to warm by at least 1.5-2°C compared to the 1990 baseline levels n This is the upper bound of the EU policy limits brought to the COP-15 negotiations in Copenhagen in December, 2009… Impacts Polar ice decline

22. © 2011 Martin Beniston One probable cause of accelerated warming: Arctic Ocean processes

23. © 2011 Martin Beniston Some reasons to address issues related to climatic change quickly…

24. © 2011 Martin Beniston Distribution of impacts Aggregate impacts Tipping points Natural systems Climatic impacts… Extremes 012345  T compated to 1980-1999 Risks to someRisks to many IncreaseLarge increase Negative for some Positive for others Negative for almost all Positive and negative market impacts Negative in all metrics Low riskHigh risk Costs Examples of impacts

25. © 2011 Martin Beniston Coastal-zone vulnerability by 2100 IPCC, 2007

26. © 2011 Martin Beniston Water availability 0 500 1000 1500 2000 2500 3000 3500 4000 4500 JapanSpainIndia 2000 2050, without climatic change 2050, with climatic change m 3 /person/year IPCC, 2001 Haiti

27. © 2011 Martin Beniston Possible future discharge by 2100 (m 3 /s, River Rhone) Beniston, 2010: Journal of Hydrology 0 50 100 150 200 250 300 350 400 JFMAMJJASOND Average monthly discharge [m 3 /s] 1961-1990 2071-2100 (B2) 2071-2100 (A2)

28. © 2011 Martin Beniston Tropical storms 0 40 80 120 160 960940920900 880 Pressure at center of system [hPa] Number of events Cat 3 Cat 4 Cat 5 1961-1990 2071-2100 K. Emmanuel, Science: 2006

29. © 2011 Martin Beniston Vector-borne and water-borne diseases (WHO, 2005) DiseasesRelation to Populations climate at risk (2050) MalariaTemp., humidity (moskitos) 2.2 billion DengueTemp., humidity 2.5 billion SchistosomiasisWater for the snails 600 million Sleeping sicknessTemp., humidity (flies) 55 million Chagas disease Temp., humidity (flies) 100 million LeishmaniasisTemp., humidity (flies) 350 million River blindessWater for the black flies 120 million

30. © 2011 Martin Beniston Even in today’s world, climate is a costly business

31. © 2011 Martin Beniston Costs related to natural hazards 4 11 14 24 47 88 160 345 103 495 0 50 100 150 200 250 300 350 400 450 500 56-6566-7576-8586-9596-05 Geologic Billions of USD/decade Decade Climatic Swiss Re, 2007 End The way forward

32. © 2011 Martin Beniston The way forward

33. © 2011 Martin Beniston Where we should be going… n In view of the long inertia of environmental and climatic change, it will not be possible to stop current trends rapidly n While addressing the long-term issues of emission abatements, adaptation strategies need to be implemented in order to ensure access to: u Health u Clean water and food u Sustained biodiversity conservation u Shelter u Education n This raises ethical questions of equal access to resources and technologies, and a genuine move towards the eradication of poverty

34. © 2011 Martin Beniston Climatic change in the light of scientific knowledge www.unige.ch/climate Martin.Beniston@unige.ch Many thanks for your attention!