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Climate Change Bullshit or Not? How is such change reliable detected? How can the agents of change be identified in a scientifically rigorous manner? Limiting Factors Climate Data is very noisy – hard to discern “natural” timescales Past climate data has low time resolution Climate models do not know all the input physics Grid models have too coarse of resolution to adequately account for the presence of clouds in the grid cell. System Lag time! Assumptions about our Atmosphere Its thin Its in hydrostatic equilibrium Its isothermal (where most of its mass is) Equation of state is that of an ideal gas These assumptions allow us to treat the atmosphere as a thin, uniform slab of material at constant density and temperature. Equilibrium Temperature Planet radiates as a blackbody in TE with incoming solar radiation: A = Albedo; L = 1370 watts per sq meter T = 278(1-A)4 T = 255K for A=0.32 This is not the right answer compared to observations The Role of the Atmosphere Fo = incident flux Ts = transmission percentage of short wavelength incoming radiation Tt = transmission percentage of outgoing long wavelength radiation Fg = Flux from ground Fa = Flux from the atmosphere. Fo = Fa + TtFg ; Fg = Fa + TsFo Let Fa = Fo –TtFg Ultimately get that Fg = Fo The transmission factors are set by atmospheric chemical composition which human activities are modifying Our Atmosphere TS = 0.9 (Highly transparent) Tt = 0.2 (fairly opaque) Fg = 1.58Fo Tg = 255*(1.58)1/4 = 287K (limiting case Tt =0; T=300K ) Fa = 0.68Fo Ta = 255*(0.68)1/4 = 245K Net Effect: Surface is warmed above equilibrium temperature due to flux radiated by our atmosphere. Atmosphere is therefore below the equilibrium temperature. Why is Tt Relatively Low? Methane: Broad absorption from 1.5 to 2.5 and 8-10 Microns Climate Forcing Terms Changes in atmospheric composition or properties that are equivalent to flux changes (in Watts/m2) Changes in Greenhouse gas mixture Changes in scattering properties Changes in cloud cover, thickness, and altitude. Average Global Energy Balance (340 Watts/M2 incoming) • 14 absorbed by clouds • 54 absorbed by atmosphere • 20 reflected back by atmospheric molecules • 68 reflected back by mostly high clouds • 14 reflected by the service (170 reaches surface) • 20 emitted by ground • 102 emitted by oceans • 88 emitted from clouds • 130 emitted from greenhouse gases in the atmosphere • 340 in = 340 out Estimates of Climate Forcing Aerosols are Important but a very difficult mixed scattering problem Pick a Model: 2100 CO2 Doubling Source of Uncertainties Roles of clouds and aerosols in radiative transfer models? (e.g. scattering!) Role of tropical convection and the water vapor feedback loop? How well do observations constrain the input climate parameters? How to weight the inputs for best fit statistical model? Water Vapor Feedback Understanding large scale convection in the tropics may be crucial this determines high cumulonimbus clouds Effects could be significant Complete Feedback Models too Difficult to reliably construct Those Pesky Swiss GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L19809, 2005 Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe Rolf Philipona Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Davos Dorf, Switzerland Bruno Dürr MeteoSwiss, Zürich, Switzerland Atsumu Ohmura Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland Christian Ruckstuhl Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technolog Is Water Vapor Increasing? Very difficult to accurately measure even with satellites calibration issues and strong seasonal variations plus El Nino fluctuations But Tropics are everything: The Potential Role of Methane Global Warming Potential TH = Time Horizon (20 or 100 years) Ax = increased forcing from X (Watts m^2 kg) x(t) = decay following some hypothetical instantaneous release of X Denominator is relevant quantities for CO2 Methane GWP A Methane molecule has an atmospheric lifetime of 12 +/- 3 years before its broken down through chemical reactions involving OH- (Leaving some CO2 as a by product) On 100 year timescale GWP = 23 But, on 20 year timescale GWP = 62 Note that CO2 has atmospheric lifetime of 50200 years depending on SST. Sources of Methane Emission Rice Cows Sewage Oil and Gas Production Methane Tracks Population A PUZZLE So There is a Scientifically Plausible Case to be made for Potential Global Warming Based on Changing Atmospheric Composition Can extant Data support this is actually happening now? Poorest Evidence for Warming Problems with Mean Annual Temperature as and Indicator ►How is it defined or measured? ►Role of Urbanization? ►Are measurements equally reliable in time? ►Does this just reveal small natural cycles that would be lost in more distant climate record? Its not as simple as this This is not the best chi^2 fit to noisy data Those Crazy Swiss Again Better Evidence for Climate Change Latest Data It May Even be Getting Wetter Local Measurements May be the real smoking guns Statistics of Extremes Other Indicators • Rapid Loss of Arctic Ice; Larson Ice Shelf • Rapid retreat/loss of glaciers • Increase vector borne diseases (insects) • Worldwide coral bleaching • Marine life migrations • Heat Waves • Earlier Spring/Snowmelt • Increase droughts/wildfires • Well documented rise of sea level (from thermal expansion) Ice Core Data Note: Time Resolution is Not Sufficient to reveal if CO2 Increases Cause Warming or Follow Warming Using the Past as a Guide Do Tipping Points Exist in Climate? Does the system have critical phenomena? Or do the various and somewhat unknown feedback mechanisms serve to counter this? Possible Tipping Points Permafrost Melt In Western Siberia and the release of vast amounts of stored methane As the southern summer limit of Arctic sea ice cover diminishes, the reflectivity of the earth decreases and more heat is absorbed The strength of the current in the Atlantic Ocean between Africa and the east coast of America has slowed by 30 percent from 1993-2005 due to the sinking of cold, salty, dense waters in the North Atlantic Ocean. Reverse the Thermohaline? Methane Burps Source of Bermuda Triangle Disappearances Norwegian Coast landslide 8150 years ago More tipping CO2 reaches 400 ppm (in 10 years) important to remember that CO2 mixes out very slowly CO2 equivalency = 480 ppm (in 10 years) nominal 2 deg C response Does this put us in an irrecoverable (on the 50 – 200 year timescale) position? Methane is most serious potential feedback What About Hurricanes Frequency Intensity Wind Radius Tracks No connection Length of time over 83+ degree water Some measure of total power but no adequate temporal baseline Currently under analysis