1. Climate Change Andrew Levan – Department of Physics

2. Outline  Setting the temperature of the planet  Out of balance  Projections of the future  Weighing the impacts  A need for action?

3. The Earth is heated from above Outward heat from molten core (~0.2 W/m 2 ) Incoming solar radiation (1370 W/m 2 at equator, 342 W/m 2 on average) Reflected (107 W/m 2 ) Absorbed (235W/m 2 ) Re-radiated (235.2 W/m 2 )

4. Equilibrium Temperature  In general Energy in = Energy out

5. Equilibrium Temperature  In general Energy in = Energy out  Earth is approximated as a perfect absorber and emitter of radiation, a so called black-body, accounting for reflection

6. Equilibrium Temperature  I n general Energy in = Energy out  Earth is approximated as a perfect absorber and emitter of radiation, a so called black-body, accounting for reflection  E in = 1370 W m 2 x Area of disc of Earth x (1-Albedo)  E out = Surface area of Earth x constant x Temperature 4

7. Equilibrium Temperature  In general Energy in = Energy out  Earth is approximated as a perfect absorber and emitter of radiation, a so called black-body, accounting for reflection  E in = 1370 W m 2 x Area of disc of Earth x (1-Albedo)  E out = Surface area of Earth x constant x Temperature 4

8. Equilibrium Temperature  In general Energy in = Energy out  Earth is approximated as a perfect absorber and emitter of radiation, a so called black-body, accounting for reflection  E in = 1370 W m 2 x Area of disc of Earth x (1-Albedo)  E out = Surface area of Earth x constant x Temperature 4  Re-arranging can give an expression for the expected temperature of the Earth (or any other planet).  The Earth should have an average temperature of -18 degrees

9. Equilibrium Temperature  In general Energy in = Energy out  Earth is approximated as a perfect absorber and emitter of radiation, a so called black-body, accounting for reflection  E in = 1370 W m 2 x Area of disc of Earth x (1-Albedo)  E out = Surface area of Earth x constant x Temperature 4  Re-arranging can give an expression for the expected temperature of the Earth (or any other planet).  The Earth should have an average temperature of -18 degrees

10. Energy balance  Incoming energy from the sun has a “temperature” of 6000 degrees. Mostly optical light  Outgoing energy from the Earth has a temperature of -18 degrees. Infrared light  The atmosphere has a profound impact. Wavelength Intensity Incoming Outgoing Optical Infrared Transparent Opaque

11. http://www.giss.nasa.gov/research/briefs/schmidt_05/

12. A greenhouse Earth Surface in-coming Re-radiated Greenhouse gas E E E E ½ E Energy in = Energy out

14. Anthropogenic greenhouse gases

15. Energy is trapped here, it warms up Energy doesn’t reach here, it cools down Eventually both troposphere and stratosphere will warm more to restore equilibrium

16. Radiative forcing  Imbalance in incoming and outgoing radiation Earth surface Top of troposphere 240 x2 CO 2 240 236 240 T=15 o C T=15+1.5 o C (2.5 o C including feedbacks) Pre-industrial CO 2 = 280 ppm, now = 400 ppm Radiative forcing arises from all greenhouse gases, and can be assessed via global warming potential (W/m 2 )

17. “Real” Climate Sensitivity No feedback With feedback (e.g. ice melt, water vapour etc)

18. Risks  Health  Increased deaths from heat stress  Spread of vector borne diseases (e.g. Malaria)  Food security  Changes in crop production/locations  Lack of fish breeding grounds  Freshwater availability  Migration/Immigration  Flooding of low-lying coastal regions (e.g. Ganges/Nile Delta) – loss of living space  Infrastructure  Flooding  Energy

19. Weather is not climate Daily Express 2013 Daily Express (yesterday)

20. Projections to the future Business as usual

21. Ocean Atmosphere General Circulation Models (OAGCM) AIM: To enable projections of future climate

22. IPCC 2013

23. Setting a target  Avoid the risks of irreversible damage to the climate system – permafrost metling, gulf stream shut-off etc  Allow unavoidable climate changes to happen at rate at which ecosystems can adapt  Food production should not be threatened  Economic development (particularly in the developing world) must be sustainable.  Possible at Kyoto? Possible now?

25. Solutions Mitigation vs Adaptation  Mitigation is probably cheaper than adaptation, but the money must be spent now (few % of GDP now and forever – Stern)  Renewables  Changing lifestyle  Etc  Adaptation is more expensive, but can be done downstream (Discounting rate? Technological solutions?)

26. www.withouthotair.com

27. The big problems….  Poverty  Ebola  Terrorism  Health  Population  Resource exhaustion  Economic growth (too much and too little)  Climate  ……………………….