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Global warming - why and what happens in the future?

Erland Källén Department of Meteorology Stockholm University. Global warming - why and what happens in the future?. Temperature change. 0.5. 14.5. ( °C). 0.0. 14.0. Temperature ( °C). -0.5. 13.5. 1850. 1900. 1950. 2000. Sea level. 50. 0. -50. (mm). -100. -150. 1850. 1900.

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Global warming - why and what happens in the future?

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  1. Erland Källén Department of Meteorology Stockholm University Global warming -why and what happens in the future?

  2. Temperature change 0.5 14.5 (°C) 0.0 14.0 Temperature (°C) -0.5 13.5 1850 1900 1950 2000

  3. Sea level 50 0 -50 (mm) -100 -150 1850 1900 1950 2000

  4. Global warming indicators • Arctic sea-ice retreat • Mountain glacier melting • More heavy precipitation events • More frequent droughts and heat waves • Less cold winter nights

  5. Retreat of Arctic sea-ice 1979 2003

  6. Arctic sea-ice extent Summer ice

  7. Greenland ice cap melting zone

  8. Why? Increased greenhouse effect due to man-made emissions of carbon dioxide and other greenhouse gases

  9. Carbon dioxide change 10 000 5 000 0 Time (before 2005) 350 1 Carbon dioxide (ppm) Radiative forcing (W m-2) 300 0 250

  10. Other climate change factors • Man-made aerosols • Cooling effect, partly offsets greenhouse gas warming • Man-made changes in cloud properties • Very uncertain, some cooling • De-forestation (man-made) • Small cooling effect • Changes in solar radiation • Some warming, < 10% of net man-made climate forcing

  11. Global temperature change Red – man-made and natural forcing Blue – only natural forcing

  12. Continental temperature change Red – man-made and natural forcing Blue – only natural forcing

  13. Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.(IPCC, 2007)

  14. Future climate change • Greenhouse gas emissions - scenarios • Climate model projections • Temperature • Precipitation • Climate change effects • Vegetation • Society

  15. Future CO2 concentrations - scenarios CO2 concentration (ppm) Year

  16. Multi-model Averages and Assessed ranges for Surface Warming 6.0 5.0 4.0 Globally averaged warming (ºC) 3.0 2.0 1.0 A1FI A1B A1T A2 B2 B1 0.0 -1.0 1900 2000 2100

  17. Future warming A2: 2020-2029 A2: 2090-2099 High CO2 0 1 2 3 4 5 6 7 8 B1: 2020-2029 B1: 2090-2099 Lower CO2

  18. Future climate change year 2100 • More rain in wet areas • Less rain in dry areas • Increasing sea levels (0.2 - 0.6 meters) • Continued sea-ice melting and permafrost thawing • More intense tropical cyclones

  19. European warming perspective Annually averaged temperature 1961-1990 Observed 2071-2100 Scenario A2

  20. Changes of extreme temperatures during 21st century Warming of winter minimum Warming of summer maximum Emission scenario A2

  21. Beyond 2100? • Continued warming, especially oceans • Continued sea level rise • Continued melting of Greenland (totally 7 meters of sea level rise)

  22. Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21stcentury that would very likelybe larger than those observed during the 20th century.(IPCC, 2007)

  23. Erland Källén Department of Meteorology Stockholm University Global Climate ChangeThe Physical Science BasisIPCC 2007

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