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Climate Change – is it really happening? Kathy Maskell and Maria Noguer Walker Institute for Climate System Research, University of Reading Overview • MYTH 1: Recent changes are nothing unusual • MYTH 2: People are not to blame • MYTH 3: We can’t believe forecasts of climate • MYTH 4: Maybe a bit of warming wouldn’t be so bad! • MYTH 5: We’re doomed – there’s nothing we can do MYTH 1: Recent changes are nothing unusual – climate has always varied Recent warming is unusual The northern hemisphere is probably the warmest it’s been for at least 1000 years Temperature can be inferred from tree ring width Mann et al., Science 1999 (Northern Hemisphere only) FACT 1: Something unusual is happening to our climate • The land, oceans and the air are all warming, sea ice and glaciers are melting Mountain 2004 1941 glaciers are melting Sub-Saharan Africa and Mediterranean are getting drier Northern Europe is getting wetter MYTH 2: People are not to blame Variation’s in the Sun’s output Volcanoes People are changing the atmosphere in drastic ways Carbon dioxide levels are higher than at any time in last 650,000 years! The Greenhouse Effect The natural greenhouse effect – without it temperature would be -15oC - brrr Burning fossil fuels is adding to the natural greenhouse effect enhanced a warmer world greenhouse effect ..most escapes to outer space and cools the earth... SUN More CO2 traps more IR, thus reducing the cooling further Most sunlight passes through the atmosphere.. ..and warms the earth. CO2 CO2 Infra-red radiation is given off by the earth... The Climate System Climate models must contain the atmosphere, the oceans, ice and the land surface and consider all the possible influences on climate Climate models are our laboratory. We use them to understand past changes and to predict the future. The earth is represented by a grid of squares, typically of length 250 km, and by a stack of layers. This gives us a 3-D picture of the circulation of the atmosphere and oceans FACT 2: People are warming the Earth MYTH 3: We can’t forecast climate 100 years into the future. How do we forecast climate? Future greenhouse gas/aerosol emissions depend on population, energy use, new technologies, etc Climate forcing Climate system response - clouds, ice, oceans etc Emissions of CO2 through the 21st century But why should we trust climate models? • Physically based – incorporate huge amount of research into climate processes • Models can simulate current and past climate • Even without using climate models there are sound physical reasons why increasing GHGs will cause warming Climate models have their limitations: • Less confidence in regional/local and extremes • Less confidence in rainfall than temperature FACT 3: Climate change will get worse in the 21st Century By 2100: world could be 2 to 4oC warmer – on top of the 0.7oC we’ve already seen. IPCC (2001) MYTH 4: Maybe warming wouldn’t be so bad! Climate change – bring it on! What about the UK? Remember lower confidence at regional/local scales: More hot/dry summers likely - nice on the beach, not so nice in the city More winter flooding Sea level rise More storms?? Sea level rise Sea level could rise by around 0.5m by 2100 Millions more people at risk of flooding Change from the present day to the 2080s UK Climate Impacts Programme Food Impacts on food Percentage change in average crop yields for staple crops: wheat, maize and rice. 2020’s Yellow, brown and red areas denote lower yields 2050’s But note increased yields in some northern latitudes due to more favourable climate 2080’s % change -40 +40 FACT 4: We know there is a risk of serious impacts from climate change MYTH 5: We’re all doomed – there’s nothing we can do! FACT 5: We can deal with climate change if we do something now Coping with the climate change we can’t avoid Reducing emissions to stop climate change getting too bad CLIMATE CHANGE IS HAPPENING……. …..AND ITS EFFECTS ARE LIKELY TO BE VERY PROFOUND