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Global Warming ‘Political hype or reality?’

Global Warming ‘Political hype or reality?’. The Fernhurst Society - 5 April 2007 - John Clement. Global warming - questions. What is happening? What are the reasons? What is likely to happen from now on? What can we do?. What’s happening? Observable warming.

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Global Warming ‘Political hype or reality?’

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  1. Global Warming‘Political hype or reality?’ The Fernhurst Society - 5 April 2007 - John Clement

  2. Global warming - questions • What is happening? • What are the reasons? • What is likely to happen from now on? • What can we do?

  3. What’s happening? Observable warming Trending strongly above long-term averages since mid ‘70-s

  4. - + 5 - 0 - - 5 - - NOT the Earth’s long-term climate cycle ‘000 years before present This cycle is driven by Earth’s orbit changes

  5. What’s happening? Consistent observations Similar trending since mid ‘70-s by three independent measures

  6. What are the reasons? The climate system

  7. Energy coming into the Earth from the Sun — SOLAR radiation • Energy leaving the Earth to outer Space — INVISIBLE INFRARED radiation What are the reasons? Radiation balance

  8. Near the poles, the Sun’s rays are spread out over a wide area, so the heating is less intense Solar radiation at poles and equator SUN’S RAYS Near the equator, the Sun’s rays are spread out over a smaller area, so the heating is more intense The Earth’s climate systems in the atmosphere and oceans transport heat between the equator and the poles - and produce the ‘weather’

  9. Range of global temperatures

  10. What are the reasons? Is it solar radiation?

  11. Implied changes in global temperature (°C) What are the reasons? Solar radiation? 0.2 0.1 0 Solar radiation – has been stable for the last 50 years

  12. Energy coming into the Earth from the Sun — SOLAR radiation • Energy leaving the Earth to outer Space — INVISIBLE INFRARED radiation What is the reason?

  13. What is the reason? The ‘greenhouse’ effect?

  14. What is the reason? The ‘greenhouse’ effect?

  15. Greenhouse gas increases through Industrial Age • CO2 – roughly constant at 280 ppm until 1800 – then rising rapidly to 380+ ppm today, and further yet. • Methane – 800 ppb until 1800, now 1,750 ppb. • Nitrous oxide 270ppb until 1800 – now 310 ppb • Lower atmosphere ozone increased around 30% over the same period.

  16. Greenhouse gases Predicted warming effect over the next 100 years Methane 24% Carbon dioxide 63% Nitrous oxide 10% Others 3% CO2 is the major contributor

  17. Volcanoes also affect the atmosphere

  18. Volcanic aerosols in the atmosphere 5 4 3 2 1 0 5 4 3 2 1 0 1883 Krakatau 1991 Mt. Pinatubo 1980 Mt. St. Helens Estimated cooling effect, Wm

  19. What’s happening? Observable warming Suspected effect of atmospheric particulates Trending strongly above long-term averages since mid ‘70-s

  20. Climate models - improving

  21. Natural factors alone do not explain the pattern of global warming since industrialisation

  22. CO2 in the atmosphere – long term stability until industrialisation The Industrial Age

  23. CO2 from fossil fuels – rapid rise since 1950

  24. Addition of man-made factors to models duplicates observations

  25. Q. Global Warming? Change between 1750 and 2000 A. Man-made gases dominate

  26. Global warming - questions • What is happening? • What are the reasons? • What is likely to happen from now on? • What can we do?

  27. Global warming • What is happening? • What are the reasons? • What is likely to happen from now on? • What can we do?

  28. What is likely to happen from now on? • Depends on what we do. • Slowing down GHG emissions, particularly carbon, will mitigate future temperature rises – but there is a lot of momentum already embedded in the climate system. • Adaptation will be needed for coming changes in – rainfall patterns - glaciers and sea-ice - sea-levels - land temperatures - food crop, forest and animal ranges - human impacts – livelihoods, wealth and health

  29. RainfallGlaciers and sea-iceSea levelsLand temperatures

  30. Rainfall - changing

  31. UK precipitation by 2080s

  32. European summer rainfall outlook - 2080s

  33. RainfallGlaciers and sea-iceSea levelsLand temperatures

  34. Glaciers – melting 16,700 in the world – 13,500 are in retreat

  35. Gangotri glacier, Himalayas – a case study

  36. Himalayan glaciers - critical

  37. Himalayan glaciers - critical Himalayan glaciers feed 7 of Asia’s great rivers - The Ganges - The Indus - The Brahmaputra - The Salween - The Mekong - The Yangtze - The Yellow river 2.3 billion people

  38. RainfallGlaciers and Sea-iceSea levelsLand temperatures

  39. Sea ice – also melting 1.3 million km2 Arctic ice lost since mid-70s

  40. Arctic sea-ice, maybe disappearing by 2080s

  41. West Antarctic and Greenland ice sheets 1,000 years to melt , but…….. = 6m sea level rise = 7m sea level rise

  42. Oceans - The north Atlantic Conveyor

  43. Hypothetical collapse in ocean currents

  44. Best forecasts of Atlantic circulation – its OK!

  45. RainfallGlaciers and sea-iceSea levelsLand temperatures

  46. Components of sea level rise

  47. Long-term momentum of sea-level rises

  48. IPCC estimates of global mean sea-level rise

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