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Climate Change: The Scientific Basis for Concern Physics Seminar September 27, 2007 Lecture by G.A. McBean, Ph.D., FRSC The global climate system • Interacting components: atmosphere, ocean, land surface, sea ice, glaciers… • Processes are complicated and all components are interconnected 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 O3 Atmospheric RadiativeTransfer Sun – 6000oK Solar radiation Earth – 288oK Earth radiation GREENHOUSE EFFECT – gases in atmosphere trap energy and warm the surface and lower atmosphere Warming: Venus +500C >90% CO2 90 atmos. Earth +30C 5700 C 0.04% CO2 1% H2O 1 atmos. Mars +10C >80% CO2 0.007 atmos. Carbon Dioxide ~25% 15 C ~10% Other ~65% Water Vapour 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 The Earth’s climate has always been variable Variation with Time of the Vostok Isotope Temperature Record 4 Warm Periods 0 Variations in the Earth’s orbit around the Sun and in the tilt of the Earth explain most of these temperature variations -2 -4 Temperature Variation (°C) 2 -6 -8 Ice Ages 400,000 400K years ago 300,000 “… global warming rates as large as 2C per millennium… -10 200,000 100,000 0 during retreat of glaciers Years Before Present NOW…” US NAS report 2001 Source: Petit, et.al. (PAGES / IGBP) in the Vostok Ice 2 Concentration Carbon DioxideCOfrom bubbles trapped inCore Antarctic Ice 325 300 ppm 275 250 225 200 180 ppm CO2 concentration (ppmv) CO2 Concentration (ppmv) 300 175 150 400,000 400K years ago 300,000 200,000 Years Before Present 100,000 0 NOW Source: Barnola, et.al. (PAGES / IGBP) Temperature led but a reduced greenhouse effect amplified the cooling 4 Vostok Ice Core CO2 Concentration and Temperature Variation Record 300 2 275 0 250 -2 225 -4 200 -6 175 -8 150 - carbon dioxide - temperature (polar) 180 to 310 ppm -9 to +2 C -10 300,000 0 - temperature (global) 200,000 -5 to +1 100,000 C NOW Years Before Present 400K years ago Ice age to Present-like 400,000 Source: Barnola, et.al.; Petit et.al. (PAGES / IGBP) Temperature Variation (°C) CO2 Concentration (ppmv) CO2 concentration (ppmv) Temperature and CO 3252 together. 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 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 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 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 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 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 Time scales of the greenhouse climate system • • • • • • Recycle water in atmosphere Mixing of greenhouse gases 50% of methane pulse to disappear 50% of CO2 pulse to disappear Air temperature - response CO2 pulse Sea level – response CO2 pulse 10 days 2-4 y 8-12y 50-200y 120-150 y 100’s y Feedbacks in Climate System Water is an important greenhouse gas, but -it re-adjusts quickly Water Water More water -not observed to be changing very much CO2 More CO2 2 -itsCO changes areMore a response T=15 warming CO2 emissions More warming evaporation Water vapour feedback enhances warming – positive feedback High clouds wetter More CO2 warm Clouds More CO2 warm warming Low clouds cooling evaporation Clouds can warm or cool – positive or negative feedback Feedbacks in Climate System Water CO2 T=15 Water More CO2 warming CO2 emissions Less refection of sunlight More warming 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 Climate Change: The Scientific Basis for Concern Is the climate changing? Changing Greenhouse Gas Concentrations from ice cores and modern data Now 1957 Carbon dioxide Last 10,000 y Nitrous oxide Methane 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). The Last 50 Years The Arctic is warming most. And winters are warming more than summers. Climate Change: The Scientific Basis for Concern Why is the climate changing? Detection and attribution 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. Compare observations with model simulations Observations Climate simulated by model with volcanoes, solar variations and other natural factors included. Compare observations with model simulations Observations Climate simulated by model with greenhouse gases, aerosols, “anthropogenic factors” included. Compare observations with model simulations Observations Climate simulated by model with natural and anthropogenic all factors included. Attribution of Climate Changein–global average temperatures Most of the observed increase there a human cause?is very likely due to the observed sinceisthe mid-20th century increase in anthropogenic greenhouse gas concentrations. Greenhouse gases CO2, Methane,… Comparison of drivers of change Ozone Land-use change Aerosols Jet contrails Solar radiation Solar forcing vs Total Human forcing Climate Change: The Scientific Basis for Concern How will the climate change in the future? 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 Future climate change “Our” impact 0.8? 3.4 2.8 warming °C per decade 1.8 0.18 0.13 0.2 Difference is 1 to 6oC – Ice Age 0.15? Science Uncertainty And the warming will continue for centuries to follow No one lives at the global average Medium (A1B) scenario (2090-2099): Global mean warming 2.8oC; Much of land area warms by ~3.5oC Arctic warms by ~6oC. Calculus of extremes The distribution of weather events around the climatic average follows a ‘bell-shaped’ curve. A shift of 1 standard deviation makes a 1 in 40 yr event into a 1 in 6 yr event Climate change can involve change in the average, or the spread around the average (standard deviation), or both. A shift in the distribution of temperatures has a much larger relative effect Standard deviation at the than near Most of ourextremes infrastructure the mean. 1 in 40 yr high range is designed for the extremes of the past. Need to look to future and re-evaluate risk. Projected changes with respect to standard deviation of the parameter--sense of extremes Heat Waves More frequent hot days – virtually certain Warm spells – very likely Changing Precipitation and Water Supplies Reduced wintertime precipitation Reduced summertime precipitation Projected changes with respect to standard deviation of the parameter--sense of extremes Heavy Precipitation Events More heavy precipitation events – very likely More drought areas – likely 85 The number of intense cyclones is increasing 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 tragedy of The apparent increase in the proportion of very intense storms since 1970 Hurricane Katrina in some regions is much larger than simulated by current models for that period. 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) Warming ofThe between 1.7 and 2.7Cofleads to Probability Large, irreversible melting of the Greenland Irreversible Change is Growing ice sheet. Global average sea level will increase by 7m – few thousand years, Double the rate of sea level rise in next century. 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. 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 Climate Change: The Scientific Basis for Concern Responding to climate change 3 4 2. Adaptation to reduce impacts and gain benefits all the discussion by governments has been ToAlmost reduce on how to reduce emissions. Adaptation seems almost ignored as a public policy Issue. 1 5 2 This is now changing in some provinces and institutions 1. Emission reductions Climate change A simple framework Changing 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.” What is “dangerous”? 3oC 2o C 1oC 3.4 2.8 1.8 In this discussion – relative to pre-industrial T prevent dangerous anthropogenic interference What is dangerous for Canada? Canada’s Projected GHG Emissions 900 Business as Usual Projections Mt CO2 equivalent 850 800 +23% 750 700 2010 Emissions 809 Mt ? Mt (1999) 699 Mt 1990 Emissions 607 Mt 240 Mt 650 600 550 36 Mt Kyoto Target 571 Mt 6% below 1990 US +13% 500 1990 1995 23.5 G 2000 2005 26.4 2010 2015 2.5% of global emissions 2020 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. The End