Climate Change: The Scientific Basis for Concern

1. Climate Change:The Scientific Basis for Concern Physics Seminar September 27, 2007 Lecture by G.A. McBean, Ph.D., FRSC

2. The global climate system • Interacting components: atmosphere, ocean, land surface, sea ice, glaciers… • Processes are complicated and all components are interconnected

3. Climate System and its Science The system is complex and our understanding is based on decades of scientific study • Archimedes, Newton, … • 1824 – Fourier – first paper on greenhouse effect • 1896 – Arrhenius- theoretical model of Greenhouse

4. Atmospheric RadiativeTransfer O3 Sun – 6000oK Solar radiation Earth – 288oK Earth radiation

5. GREENHOUSE EFFECT – gases in atmosphere trap energy and warm the surface and lower atmosphere Warming: Venus +500C >90% CO2 90 atmos. Earth +30C 0.04% CO2 1% H2O 1 atmos. Mars +10C >80% CO2 0.007 atmos. 5700 C ~25% ~10% ~65% 15 C

6. Climate System and its Science The system is complex and our understanding is based on decades of scientific study • Archimedes, Newton, … • 1824 – Fourier – first paper on greenhouse effect • 1896 – Arrhenius- theoretical model of Greenhouse • 1950’s • International Geophysical Year - 1957 • Revelle – carbon cycle and oceans • Phillips – atmospheric circulation models • 1960’s • Manabe – climate models • 1967 – start of Global Atmospheric Research Program • First weather satellites • 1980 – start of World Climate Research Program • 1986 – start of International Geosphere-Biosphere Program • 1980’s – Vostok and other cores

7. 4 2 0 -2 -4 -6 -8 -10 400,000 300,000 200,000 100,000 0 The Earth’s climate has always been variable Variation with Time of the Vostok Isotope Temperature Record Warm Periods Variations in the Earth’s orbit around the Sun and in the tilt of the Earth explain most of these temperature variations Temperature Variation (°C) “… global warming rates as large as 2C per millennium… during retreat of glaciers …” US NAS report 2001 Ice Ages 400K years ago NOW Years Before Present Source: Petit, et.al. (PAGES / IGBP)

8. Carbon Dioxide from bubbles trapped in Antarctic Ice CO2 Concentration in the Vostok Ice Core 300 ppm CO2 Concentration (ppmv) 180 ppm NOW 400K years ago Source: Barnola, et.al. (PAGES / IGBP)

9. Temperature and CO2 together. Temperature led but a reduced greenhouse effect amplified the cooling Vostok Ice Core CO2Concentrationand Temperature Variation Record CO2 Concentration (ppmv) - carbon dioxide 180 to 310 ppm - temperature (polar) -9 to +2 C - temperature (global) -5 to +1 C Ice age to Present-like NOW 400K years ago Source: Barnola, et.al.; Petit et.al. (PAGES / IGBP)

10. Earth’s climate has varied considerably over its billions of years history. Factors include: • Sun and its changing intensity • 11 year solar cycle – 0.1% variation • millions of years for larger, more gradual change • Variations in the Earth’s orbit around the Sun and the tilt of the Earth’s axis of rotation • 20,000 yrs to 400,000 yrs • - Collisions with outside bodies - asteroids • Changes in composition of the Earth’s atmosphere • Volcanic eruptions – cool the planet • Greenhouse effect – the topic of concern today

11. Climate System and its Science The system is complex and our understanding is based on decades of scientific study • Archimedes, Newton, … • 1824 – Fourier – first paper on greenhouse effect • 1896 – Arrhenius- theoretical model of Greenhouse • 1980 – start of World Climate Research Program • 1986 – start of International Geosphere-Biosphere Program • 1980’s – Vostok and other cores • 1988 – creation of Intergovernmental Panel for Climate Change

12. Climate Science Assessment • The Intergovernmental Panel on Climate Change • Established in 1988 by the World Meteorological Organization and the United Nations Environmental Programme • Three Working Groups • I. Science • II. Impacts, Adaptation and Vulnerability • III. Mitigation (Emission Reductions) • Science Assessments – 1990, 1995, 2001, 2007 • Summaries for Policy Makers – www.ipcc.ch

13. IPCC Process • Preparation of draft Assessments • lead and contributing authors - chosen on basis of their publications within peer-reviewed scientific literature • Double peer-review process • international community of experts (including those identified by governments) • experts and government representatives • 2001 and 2007 assessments - more than 1000 scientific experts involved. • Focusing the science towards policy • Working Group I - The Science of Climate Change (800+ pages) • responsibility of lead authors • Technical Summary of Working Group I Report (75 pages) • accepted by the IPCC • Summary for Policy Makers (18 pages) • Approved by Working Group I and accepted by IPCC • Similar process for WGs II and III • IPCC 2nd Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UNFCCC (17 pages) • Approved by IPCC

14. Governments address climate (and ozone) issues • 1972 – Stockholm Conference on Environment • 1972 - Study of Man’s Impact on Climate • 1979 – First World Climate Conference - Geneva • 1980 – World Climate Research Program • 1985 & 1987 – Villach, Austria Conferences • 1985 – Vienna Ozone Convention • 1985-6 – International ozone assessment • 1985 – Antarctic ozone hole • 1987 – Montreal Protocol of Ozone Convention • 1988 - Toronto, Canada Conference [The Changing Atmosphere: Implications for Global Security] • 1990 – London Protocol of ozone convention • 1988: Formation of the IPCC (by WMO & UNEP) • 1990: 2nd World Climate Conference, Geneva • 1990: Intergovernmental Negotiating Committee for a Framework Convention on Climate Change

15. Governments address climate (and ozone) issues • 1990 – First IPCC scientific assessment • 1992 – Rio – Earth Summit • UN Framework Convention on Climate Change • Conventions on biodiversity, desertification, … • 1994 – UNFCCC – ratified and in effect • 1995 – First Conference of Parties (Berlin) • 1995 – Second IPCC assessment • 1996 – Second Conference of Parties (Geneva) • Science “good enough” • 1997 – Third Conference of Parties (Kyoto) • Kyoto Protocol • 1998-2004 – CoP’s • 2001 – Third IPCC Assessment • 2004 – Kyoto ratified and in effect • 2005 – CoP11 – Montreal • 2006 – onward CoP’s • 2007 – 4th IPCC Assessment

16. Time scales of the greenhouse - climate system • Recycle water in atmosphere 10 days • Mixing of greenhouse gases 2-4 y • 50% of methane pulse to disappear 8-12y • 50% of CO2 pulse to disappear 50-200y • Air temperature - response CO2 pulse 120-150 y • Sea level – response CO2 pulse 100’s y

17. Water is an important greenhouse gas, but • it re-adjusts quickly • not observed to be changing very much • its changes are a response Feedbacks in Climate System Water CO2 T=15 Water More CO2 warming More water More CO2 More warming CO2 emissions evaporation Water vapour feedback enhances warming – positive feedback High clouds warming wetter More CO2 warm Clouds More CO2 warm Low clouds cooling Clouds can warm or cool – positive or negative feedback evaporation

18. Feedbacks in Climate System Water CO2 T=15 Water More CO2 warming Less refection of sunlight More warming CO2 emissions Melt surface snow Snow-albedo feedback enhances warming – positive feedback A reason for more warming in higher latitudes Climate sensitivity 40% of warming due to direct greenhouse effect 60% due to feedbacks Amplification - Water vapour = 1.6, Total = 2.5

19. Climate Change:The Scientific Basis for Concern Is the climate changing?

20. Changing Greenhouse Gas Concentrationsfrom ice cores and modern data Now 1957 Carbon dioxide Methane Last 10,000 y Nitrous oxide

21. WGI The Physical Science Basis Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850).

22. The Last 50 Years The Arctic is warming most. And winters are warming more than summers.

23. Climate Change:The Scientific Basis for Concern Why is the climate changing?

24. Detection and attribution

25. How do we know the cause of change? • Construct climate models - based on our best understanding • of climate system • Physics – motion, mass, energy, radiation • Mathematics and computer science • Chemistry • Biology And solve on powerful computers.

26. Compare observations with model simulations Observations Climate simulated by model with volcanoes, solar variations and other natural factors included.

27. Compare observations with model simulations Climate simulated by model with greenhouse gases, aerosols, “anthropogenic factors” included. Observations

28. Compare observations with model simulations Observations Climate simulated by model with natural and anthropogenic all factors included.

29. Attribution of Climate Change – is there a human cause? Most of the observed increase in global average temperatures since the mid-20th century is very likelydue to the observed increase in anthropogenic greenhouse gas concentrations. Comparison of drivers of change Greenhouse gases CO2, Methane,… Ozone Land-use change Aerosols Solar forcing vs Jet contrails Solar radiation Total Human forcing

30. Climate Change:The Scientific Basis for Concern How will the climate change in the future?

31. Emissions scenarios – the global human choices ΔCO2 = Δ (pop)*(Δ(GDP/pop)*Δ (energy/GDP)*Δ (CO2/energy) (population)*(per capita wealth)*(energy intensity)*(carbon intensity) CO2 CH4 N2O SO2

32. Future climate change “Our” impact 3.4 0.8? 2.8 warming °C per decade 1.8 0.15? 0.2 0.18 Science Uncertainty 0.13 And the warming will continue for centuries to follow Difference is 1 to 6oC – Ice Age

33. No one lives at the global average Medium (A1B) scenario (2090-2099): Global mean warming 2.8oC;Much of land area warms by ~3.5oCArctic warms by ~6oC.

34. A shift of 1 standard deviation makes a1 in 40 yr event intoa 1 in 6 yr event A shift in the distribution of temperatures has a much larger relative effect at the extremes than near the mean. Standard deviation 1 in 40 yr high range Calculus of extremes Climate change can involve change in the average, or the spread around the average (standard deviation), or both. The distribution of weather events around the climatic average follows a ‘bell-shaped’ curve. Most of our infrastructure is designed for the extremes of the past. Need to look to future and re-evaluate risk.

35. Projected changes with respect to standard deviation of the parameter--sense of extremesHeat Waves More frequent hot days – virtually certain Warm spells – very likely

36. Changing Precipitation and Water Supplies Reduced wintertime precipitation Reduced summertime precipitation

37. Projected changes with respect to standard deviation of the parameter--sense of extremesHeavy Precipitation Events More heavy precipitation events – very likely More drought areas – likely

38. The number of intense cyclones is increasing 85 116 It is likely that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical sea surface temperatures. The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period. The tragedy of Hurricane Katrina

39. Thermohaline Circulations - Conveyor belt • Deep circulations are due to density variations arising from differences in temperature and/or salinity (thermohaline) • Move large amounts of heat poleward Will this turn off In the future? Ahrens (1999)

40. Warming of between 1.7 and 2.7C leads to irreversible melting of the Greenland ice sheet. Global average sea level will increase by 7m – few thousand years, Double the rate of sea level rise in next century. The Probability of Large, Irreversible Change is Growing

41. Joint science academies’ statement Signed by the Presidents of academies of science of all G8 countries plus those of China, India and Brazil, • “climate change is real” • There must be actions to • “reduce the causes of climate change” • “prepare for the consequences of climate change”. Nations must work together: • to reduce emissions - mitigation • to adapt to a changing climate - adaptation.

42. An Open Letter to the Prime Minister of Canada on Climate Change Science • There is increasingly unambiguous evidence of changing climate in Canada and around the world. • There will be increasing impacts of climate change on Canada’s natural ecosystems and on our socio-economic activities. • Advances in climate science since the 2001 IPCC Assessment have provided more evidence supporting the need for action and development of a strategy for adaptation to projected changes. • Canada needs a national climate change strategy with continued investments in research to track the rate and nature of changes, understand what is happening, to refine projections of changes induced by anthropogenic release of greenhouse gases and to analyse opportunities and threats presented by these changes. • Signed by 90 Canadian climate science leaders from the academic, public and private sectors across the country • 18 April 2006

43. Climate Change:The Scientific Basis for Concern Responding to climate change

44. 3 4 2. Adaptation to reduce impacts and gain benefits Almost all the discussion by governments has been on how to reduce emissions. Adaptation seems almost ignored as a public policy Issue. This is now changing in some provinces and institutions To reduce 1 5 2 Changing 1. Emission reductions Climate change A simple framework

45. UN Framework Convention on Climate Change • signed by 155 nations in 1992 – came into force in 1994 • developed countries aim to reduce emissions to 1990 levels by year 2000 Article 2 • “ … stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure food production is not threatened and to enable economic development to proceed in a sustainable manner.”

46. What is “dangerous”? 3.4 2.8 3oC 1.8 2oC 1oC In this discussion – relative to pre-industrial T

47. preventdangerousanthropogenic interference What is dangerous for Canada?

48. Canada’s Projected GHG Emissions Business as Usual Projections 2010 Emissions 809 Mt ? Mt (1999) 699 Mt +23% Mt CO2 equivalent 1990 Emissions 607 Mt 240 Mt 36 Mt US +13% Kyoto Target 571 Mt 6% below 1990 23.5 G 26.4 2.5% of global emissions

49. The Bottom Line • The climate is changing – • It will change more in the next 100 years • Due to the long lifetime of greenhouse gases, change is inevitable • There is some challenging and exciting science still to be done.

50. The End