The Atmosphere : Climate , climate change and ozone depletion

1. TheAtmosphere: Climate, climatechange and ozone depletion Chapter 20

2. El niño and la niña

3. Atmosphere and weather

4. The atmosphere and weather atmospheric structure

5. The atmosphere and weather atmospheric structure

6. Weather • Solar radiation

7. Weather • Flowing air and convection currents • West to east • Jet streams, Earth’s rotations and air pressure gradients • Polar jet stream • Fronts • Regions of rapid weather change

8. Climate

9. Climate • Average temperature and precipitation expected throughout a typical year in a given region • Major changes in climate are a major threat to the structure and function of ecosystems

10. Climates in the past • Annual mean global surface atmospheric temperature • Periods of cooling and warming • General increase in temperature

11. Climates in the past • Proxies • Tree rings • Pollen deposits • Changes in landscapes • Marine sediments • Corals • Ice cores • Thickness • Gas content (CO2, CH4) • Isotopes • Milankovitch cycles • Rapid changes • Younger Dryas

12. Oceans and Atmosphere • Oceans have an innate heat capacity • Thermohaline circulation • Conveyor system • Affect the density of seawater • One cycle is competed in 1000 years • Heinrich events • Fresh water in the oceans can change climate

13. Global climatechange

14. Global climate change • Factors that influence the climate include: • Internal components • Oceans, the atmosphere, snow cover, sea ice • External factors • Solar radiation, Earth’s rotation, slow changes in our planet’s orbit, and the gaseous makeup of our atmosphere

15. Radiative forcing: the influence a particular factor has on the energy balance of the atmosphere – ocean – land system. • Factors can either be positive (warming) or negative (cooling)

16. Warming processes • Infrared radiation and the greenhouse effect

17. Warming processes • Greenhouse gases (GHGs) • Water vapor • Carbon dioxide • Methane • Nitrous oxides • Ozone • CFCs

18. Cooling processes • The planetary albedo • Clouds • Snow and ice • Volcanoes • Sulphate aerosols • Ozone depletion • Solar variability (11 year cycle)

19. So… • Global atmospheric temperatures are a balance between positive and negative forcing from natural causes (volcanoes, clouds, natural GHGs, solar radiation) and anthropogenic causes (sulfate aerosols, soot, ozone depletion, increases in GHGs)

20. The greenhouse gases • Carbon dioxide • Svante Arrhenius: “differences in CO2 levels in the atmosphere could greatly affect Earth’s energy budget”; he believed this change would be beneficial. • Charles Keeling, 1958, first measures of CO2 levels in Hawaii.

21. The greenhouse gases Sources of CO2 emissions from fossil fuel burning • Carbon dioxide • Sources: • Fossil fuels • Burning of forest trees • Industrial processes • Sinks • Oceans • Terrestrial ecosystems

22. Global carbon cycle Atmosphere – ocean exchange 92 (+/-0,6) Atmospheric CO2 750 6,6 Combustion 90 Oceanic dissolved inorganic carbon Surface – 1020 Depths - 38100 Fossil fuel carbon 4130 62,4 (+/-0,8) Photosynthesis 61 Respiration Terrestrial biosphere Living – 600 – 1000 Dead - 1200

23. The greenhouse gases • Water vapor • Absorbs infrared energy • Most abundant GHG • Increases the sensitivity of climate to increased anthropogenic GHG

24. The greenhouse gases • Methane • Sources • Microbial fermentation (wetlands, landfills, cattle, manure) • Coal and oil deposits • Natural gas pipelines

25. The greenhouse gases • Nitrous oxide • Sources • Agriculture • Burning of biomass • Fossil fuels • It has a long resistance time (114 years) • Also contributes to the destruction of stratospheric ozone

26. The greenhouse gases • Ozone • Short lived • Source • Reactions of sunlight with pollutants from automobiles, burning forests and agricultural wastes

27. The greenhouse gases • CFCs and other halocarbons • Long lived (50 – 100 years) • Used as refrigerants, solvents and fire retardants • Montreal Accord (1987) prohibited the use of CFCs

28. Evidence of Climate Change • 1988, the UN Environmental Program and the World Meteorologial Society established the Intergovernmental Panel on Climate Change (IPCC) • 3 working groups were established • Working group I: to asses scientific issues • Working group II: to evaluate the impact on global climate change and prospects for adapting to it • Working group III: to investigate ways of mitiating the effects

29. Evidence of Climate Change • The work of the IPCC has been guided on two basic questions: • Risk assessment: is the climate system changing, and what is the impact on society and ecosystems? • Risk management: how can we manage the systems through adaptation and mitigation?

30. Working group I third assessment (2001) • An increasing body of observations gives a collective picture of a warming world and other changes in climate system • Correlation CO2 / global atmospheric temperatures • Heat content in oceans increased dramatically • Retreat of glaciers • Thinning of polar ice • Global temperature has increased 1oF • Increase in precipitation, greater frequency of El Niñoevents • More frequent and intense droughts, heat waves, rainfall and tornadoes • Rise in sea level between 0,1 and 0,2 mts (2mm/year)

31. Working group I third assessment (2001) • Emissions of GHGs and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate. • GHGs and aerosols continue to increase in the atmosphere

32. Working group I third assessment (2001) • Confidence in the ability of models to project future climate has increased • Forecasts are more accurate • Coupled general circulation models (CGCM) are capable of simulating long-term climatic conditions • The main purpose of the models is to project the future global climate.

33. Working group I third assessment (2001) • There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities

34. Working group I third assessment (2001) • Human influences will continue to change atmospheric composition throughout the 21st century • Different scenarios project a rise in CO2 levels as a consequence of burning fossil fuels • The scenarios demonstrate the crucial importance of our energy choices.

36. Working group I third assessment (2001) • Global average temperature and sea level are projected to rise under all IPCC scenarios • The global averaged surface temperature is projected to increase by 1.4 to 5.8oC over the period 1990 to 2100. • Climate will be seriously affected • Sea level is projected to increase from 9 to 88cm

37. Working group I third assessment (2001) • Anthropogenic climate change will persist for many centuries • Once atmospheric greenhouse gas levels are stabilized, temperatures and sea levels will continue to rise for hundreds of years because of the slow response time of the oceans.

38. Working group I third assessment (2001) • Further action is required to address remaining gaps in information and understanding • More research is needed on current climate variables such as: • Occurrence and impacts of clouds • Changes in glaciers and sea ice • Functioning of the carbon cycle • Natural variability of climate • Impacts of aerosols

39. Response toclimatechange

40. Response to climate change • Mitigation: take action to reduce emissions • Adaptation: anticipate some harm and plan adaptive responses

41. Why should we take action? • Precautionary principle: “the lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation” • Polluter pays principle: polluters should pay for the damage their pollution causes • Equity principle: the rich and privileged should care about those generations which follow

42. Mitigation: taking steps towards sustainability • What has been done? • Framework convention on climate change (FCCC) • Goal to stabilize greenhouse gas levels in the atmosphere, starting by reducing greenhouse gas emissions to 1990 levels by the year 2000 • Kyoto protocol • Goal to reduce emissions of six GHGs to 5,2% below 1990 levels to be achieved by 2012

43. Mitigation • What has been done? • U.S Policy • Opposed to the Kyoto protocol • Compromised to protect the environment by reducing CO2 emissions and other GHGs • Global climate change initiative • 18% cut in emissions intensity over the next 10 years • U.S climate change science program (CCSP) • Seeks to address several issues on climate science • States and corporations • Fourteen states are adopting renewable portfolio standards to regulate CO2 emissions

44. Adaptation • Climate change is already happening? • Crop yields are likely to be reduced in tropical and subtropical regions as warming and droughts become more severe • Water is more scarce in many regions • Increased heat and moisture will lead to an increase in infectious disease • Increased intensity and frequency of storm events

45. Adaptation • What is being done? • New funds • Least Developed Countries Fund: to advice countries on adaptation strategies • Special Climate Change Fund: to provide additional financial assistance to developing countries affected by climate change

46. Adaptation • Specific adaptation strategies: • Improved governance • Vulnerability assessments • Access to accurate information on climate change • Integration of impacts into economic processes.

47. Depletion of the ozone layer

48. Radiation and importance of the shield • Shorter wavelengths are more energetic and therefore can cause more damage

49. Formation and breakdown of the shield O2 + UVB  O + O O + O2  O3 O + O3 O2 + O2 O3 + UVB  O + O2

50. Halogens in the atmosphere CFCl3 + UV  Cl + CFCl2 Cl + O3  ClO + O2 Chlorine catalytic cycle ClO + ClO  2Cl + O2