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

© 2011 Martin Beniston The functionning of the climate system

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

© 2011 Martin Beniston Volcanic eruptions

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

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

© 2011 Martin Beniston Human perturbations to the climate system

© 2011 Martin Beniston CO 2 and CH 4 concentrations 10’0005’000010’0005’0000 Years before present CH 4 ppbvCO 2 ppmv Years before present

© 2011 Martin Beniston Attribution of recent trends to anthropogenic forcing

© 2011 Martin Beniston Human responsibility…?  T with respect to [°C] Observations Natural forcing Natural + Greenhouse-Gas Forcing IPCC, 2007

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

© 2011 Martin Beniston Global warming futures IPCC,  T respect to 20 th century means [°C] A2 B2

© 2011 Martin Beniston Global temperature change by 2100

© 2011 Martin Beniston Heatwave days: Exceedance of 40°C threshold in Europe Days EU-FP6 « ENSEMBLES » Project, PrecipT CH

© 2011 Martin Beniston Changes in seasonal temperatures (at 2,500 m asl) Beniston, 2006: Geophysical Research Letters 15 WinterSpringSummerAutumn Temperature [°C] Beniston, 2004: Climatic Change and Impacts, Springer

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

© 2011 Martin Beniston Changes in summer precipitation (june-july-august) (Differences in % between and ) (HIRHAM RCM; A-2 Scenario) Christensen and Christensen, Nature, 2003 Seasonal precipitation Events greater than 50 mm/day % change Accelerated warming Impacts p CH

© 2011 Martin Beniston Changes in seasonal precipitation Beniston, 2006: Geophysical Research Letters WinterSpringSummerAutumn Precipitation change 2071/2100 vs 1961/1990 [%] Impacts Accelerated warming

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

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

© 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

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

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

© 2011 Martin Beniston Distribution of impacts Aggregate impacts Tipping points Natural systems Climatic impacts… Extremes  T compated to 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

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

© 2011 Martin Beniston Water availability JapanSpainIndia , without climatic change 2050, with climatic change m 3 /person/year IPCC, 2001 Haiti

© 2011 Martin Beniston Possible future discharge by 2100 (m 3 /s, River Rhone) Beniston, 2010: Journal of Hydrology JFMAMJJASOND Average monthly discharge [m 3 /s] (B2) (A2)

© 2011 Martin Beniston Tropical storms Pressure at center of system [hPa] Number of events Cat 3 Cat 4 Cat K. Emmanuel, Science: 2006

© 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

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

© 2011 Martin Beniston Costs related to natural hazards Geologic Billions of USD/decade Decade Climatic Swiss Re, 2007 End The way forward

© 2011 Martin Beniston The way forward

© 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

© 2011 Martin Beniston Climatic change in the light of scientific knowledge Many thanks for your attention!