Teaching Climate Change EPO Special Interest Group Aileen O’Donoghue Priest Associate Professor of Physics St. Lawrence University, Canton, NY Emphases for the Public Earth Will Be FINE! it’s been much hotter and much colder the 6.8 billion people won’t be fine nor will the polar bears, pikas, and other megafauna What we know: Data & Theories Not NEW! “amplified warming” since 1850 (John Tyndall) Data carefully collected & analyzed for decades requires careful study understanding before dismissal! How we know it: Process of science peer review: trying to insure honesty, not orthodoxy What do we know Past climates how do we know of past climates? Variations in climate how does climate vary naturally? Predicting the future how do we model inputs & feedbacks? IPCC UCC Skeptics Past Climate Records Instrumental 18th – 21st centuries with increasing accuracy Best in Europe, N. America, Australia Very little data over oceans, 70% of surface Keeling Curve: 1957 - present CO2 in air over Mauna Loa, Hawaii Northern Winter: CO2 builds up from decay. Northern Summer: Plants absorb CO2 Past Climate Records Proxy (indirect natural) Records Tree rings Temperature, precipitation, fire, insects, etc. Depends on area, species level of stress best near stress limit Back to ~1000 years (bristlecone pine in CA) plus overlapping with structures Past Climates Proxy (indirect natural) Records Palynology (pollen) from sediments shrub Accumulated in peat bogs & lakes Must be independently dated (cross-matched or 12C) Local influences complicate records eg. Fire, flood, etc. Types of pollen vary in uniqueness eg. Pine pollen everywhere … even ice caps! birch sedge spruce oak Pine Past Climates Vostok, Antarctica & Greenland Ice Cores Greenland Ice Core Summers indicated by arrows. Past Climates Vostok, Antarctica & Greenland Ice Cores Show annual* variations of atmosphere Bubbles of air contain old atmosphere Variations in CO2, CH4 Give Comparisons to today, Correlations with temperature Ice crystals vary in composition Different Isotopes of Oxygen, Hydrogen, etc. Dust Volcanos, Impacts, Winds, Organic Matter *Where annual layers unclear, chronology is reconstructed from other annual variables Isotopes Number of neutrons in nuclei varies eg. Oxygen 16 (16O) & 18 (18O) 16O 8 protons 8 neutrons 18O 18O 8 protons 10 neutrons heavier than 16O On average: 1 18O for 1000 16O harder to evaporate Ice Cores High ratio of 18O/16O for warm globe Deep Sea Sediments High ratio of 18O/16O for cool globe Isotopes Variations indicate temperature Higher 18O/16O in ice warmer Lower 18O/16O in ice cooler 18O/16O Arctic & Antarctic show same variations variations are global 2H/1H Isotopes Sea Temp. Higher 18O/16O cooler Lower 18O/16O warmer Sea surface temperature 18O/16O C. R. W. Ellison et al., Science 312, 1929 -1932 (2006) Isotopes Variations track with GH gases Methane 2H/1H Carbon Dioxide now www.realclimate.org/index.php?p=221 2H/1H then Temperature & GH Gases Temperature tracks with gases … Carbon Dioxide Temp (°C) Which drives which? Methane now then Ice Core Contributions to Global Change Research: Past Successes and Future Directions National Ice Core Laboratory Ice Core Working Group, May, 1998. Global CO2 CO2 from Ice Cores & Mauna Loa Isotopes Necessary to understand ice core data! Allows reconstruction of temperature Only way to get to last curve! Respects the audience Demands they respect the science Discussion: How much should we simplify? Modeling the Climate Climate Systems Sun – source of (almost) all energy Atmosphere – changes over hours Oceans – surface changes over weeks – depths change over millennia Biosphere – changes annually to centuries Cryosphere – ice, glaciers permafrost, snow – various change scales Geosphere – volcanos, continental drif – long time scales, large changes Modeling the Climate Systems & Feedbacks Among Radiation, Surface and Atmosphere (CO2) insolation (incoming sunlight varies) reflection, absorption, re-radiation by surface, air Water cycle evaporation, precipitation, runoff Land surface soil moisture, vegetation, topography, snow & ice Ocean surface currents, deep currents, chemistry (salinity) Sea Ice strongly affected by feedbacks Carbon Dioxide Long-term sources: Volcanoes & Humans Long-term sinks: Chemical Weathering H2O + CO2 H2CO3 H+ + HCO3 Carbonic Acid CaCO3 + H+ Ca + HCO3 Bicarbonate can combine with many compounds eg. NaHCO3, Ca(HCO3)2 Variable storage: Biosphere plants absorb CO2 to grow trees make wood out of air! plants make us … we’re made of air! decay releases CO2 Feedbacks Greenhouse Effect: Warming Good … makes Earth inhabitable!! Ground absorbs sunlight Ground heats (parking lots in summer) Ground radiates heat (Infrared, IR) Atmosphere absorbs (some) IR Atmosphere heats Greenhouse Effect Concept Inventory Dr. John Keller, Cal Poly Poster C24 Feedbacks Feedback Mechanism: Evaporation Clouds shade surface, cool it, warming stops? H2O vapor absorbs more IR, more warming Runaway Greenhouse … Venus! Feedback Mechanism: Plant Growth More CO2 increases plant growth More plant growth is good!! www.co2science.org Plants absorb CO2 (Keeling curve annual cycles) CO2 is Reduced BUT … why isn’t it working yet? Feedbacks Feedback Mechanism: Ice-Albedo Effect Warming melts glaciers, sea ice Ground warms more than snow/ice Ground warms, radiates more IR Atmosphere warms More ice melts Feedback Mechanism: Evaporation More clouds & cooling, snow comes back Warming halted H2O vapor absorbs more IR, more warming “Hot House Earth” Climate Variations Due to Atmospheric variations Pacific Cycles El Niño Soutern Oscillation (ENSO) Pacific Decadal Oscillation Atlantic Cycles North Atlantic Oscillation Atlantic Multidecadal Oscillation Variations in the Atmosphere NAO Negative Phase mid 1950’s - 1970 It WAS colder when we were kids! Variations in the Atmosphere NAO Mostly positive since mid-70’s Skeptics use cooling of eastern Canada to dispute global warming Variations in the Atmosphere Atlantic Multidecadal Oscillation (AMO) Sea Surface Temperature in North Atlantic Variations in the Atmosphere AMO Correlates with numbers of major hurricanes … and southwestern droughts! Not perfect correlation … what else is going on? Variations in the Atmosphere Drought Correlation with PDO and AMO Current Conditions Droughts more severe & widespread when AMO is positive oceanword.tamu. edu Variations in the Atmosphere Insolation Variations Solar brightness variations sunspots & other stellar variations Earth orbital variations (Milankovitch) other planets’ gravity vary Earth’s orbit Solar system environmental variation Sun moves through galactic environment Insolation Varies with Milankovitch Cycles Last million years for 65 N (Berger (1991)) 9,000 years ago, ice age ended! Some argue this is the cause of ALL climate change … so we can ignore our CO2 Milankovitch and Temperatures Vostok Core Data Temperature from 18O/16O Milankovitch Insolation Connection apparent … but can it explain current warming? IPCC Intergovernmental Panel on Climate Change Established in 1988 World Meteorological Org. (WMO) UN Environment Programme (UNEP) Mandate “The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socioeconomic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation.” http://www.ipcc.ch/about/about.htm IPCC Intergovernmental Panel on Climate Change “The IPCC does not carry out research nor does it monitor climate related data or other relevant parameters. It bases its assessment mainly on peer reviewed and published scientific/technical literature. Its role, organisation, participation and general procedures are laid down in the ‘Principles Governing IPCC Work’“ http://www.ipcc.ch/about/about.htm IPCC Working Groups I: Science knowns, unknowns & projections II: Impact and Adaption vulnerability: natural and human consequences: + and – III: Mitigation options for changing human behavior and impact Task Force on National Greenhouse Gas Inventories IPCC 4th Assessment Released 2007 WGI = 701 pages! available on line ipcc-wg1.ucar.edu/wg1 available in print Cambridge U. Press IPCC 4th Assessment Released 2007 WGI = 701 pages! available on line ipcc-wg1.ucar.edu/wg1 available in print Cambridge U. Press IPCC ARF WGI Components of Climate Change Accounts for natural processes eg. Changes in evaporation eg. Melting permafrost releasing methane IPCC Climate Drivers Greenhouse Gases: CO2, CH4, H2O, NOx Grey Bars = Natural Variability Radiative forcing is a change in the radiation balance at the top of the atmosphere. Positive increases warming. Combined rate of change IPCC ARF WGI Radiative Forcing 1750 - 2005 Carbon Dioxide Methane “Ozone Layer” absorbs UV, reduces RF at tropopause Buildings increase surface albedo relative to forests Aerosols (particles) reflect sunlight AND increase cloud cover (eg. Contrails) Solar radiation has increased since 1750 (Little Ice Age end) A1B IPCC Scenarios Very rapid economic growth Global population peaks mid-century then declines rapid introduction of new, more efficient technologies. A2 Very heterogeneous world Continuously increasing global population Regionally oriented economic growth more fragmented and slower than in other storylines. B2 Same global population as in the A1 rapid changes toward a service and information economy reductions in material intensity introduction of clean, green technologies. IPCC ARF Continued Warming What we’re committed to by past behavior! Union of Concerned Scientitsts Confronting Climate Change in the U.S. Northeast: Science, Impacts and Solutions http://www.ucsusa.org/global_warming/ UCC Northeast US Climate of New York State IPCC ARF Effects of Changing Mean Does not mean it never gets cold! The Skeptics Important voices! Skeptics keep science honest Agreements CO2 in atmosphere is increasing rapidly CO2 levels correlate with temperature Arguments Climate is driven exclusively by insolation Milankovitch Cycles Sunspot Cycles Too expensive to reduce CO2: Adapt Global warming is good! Discussion What should we include & leave out? How much complexity to include? Should we confront politics directly? How do we handle hostility?