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Click to edit Master title style • • • Click to edit Master text styles Climate Forcing Factors Second level Third level. Earth History Fourth level Eric J. Barron Fifth level March 14, 2009 in List of Nominations 1

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level What is the Nature of the Challenge? List of Nominations 2

An Enormous Spectrum of Click to. Change edit Master style Climate and title Variability • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations Rob Rohde; wikipedia 3

Rich Spatial Record of Climate Click to edit Master title style Change • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 4

The Concept of “Forcing Click to edit Master title style Factors” • Complex interaction of the components of • the Click to edit Master text styles ocean, climate system (atmosphere, • land, Second ice, level biota) Third level • • Separate the “interaction” from the of climate change • “causes” Fourth level External • –Fifth levelto the climate system as a “forcing” List of Nominations vs, – Internal dynamics and feedbacks 5

Distinguish between External Forcing Factors and Responses or Click to edit Master title style Feedbacks Click to. Biological edit Master text styles • • Forcing? innovation that covers the land plants and alters the energy balance (yes) • with Second level • Forcing? redistribution of plants in response to List of Nominations • climate Thirdthat level alters the surface energy balance (no) Fourth. Injection level of massive amounts of carbon • • Forcing? in the formation of flood basalts (yes) • dioxide Fifth level • Forcing? Higher water vapor content in the atmosphere in response to warming (no) 6

Organize our Thinking with a Click to. Energy edit Master title. Model style Global Balance Energy must Balance • Click to edit Master text styles 4 So/4 (1 -α) = ЄσTp • Second level So/4 – solar constant divided by 4 since the • Third level area of the Earth’s surface is 4 x the • Fourth area levelof the disk that intercepts sunlight (1 -α) – level α is the albedo of the planet • Fifth List of Nominations Є– Tp – σ- emissivity planetary temperature constant 7

First Order Climate Forcing Click to edit. Factors Master title style • Three categories • Click to edit Master text styles – Solar input • Second level Atmospheric opacity • –Third level Albedo • –Fourth level List of Nominations • Fifth level 8

Not sufficient characterization of Click to editforcing Master title style • Add a spatial element – so, for example, • the Click to edit Master text stylesmatters not distribution of solar energy • just Second levelconstant the solar Third level • • Add a temporal element – so, for example, needlevel to add heat capacity • we Fourth • • Combined Fifth level- Include forcing factors that change the structure of the circulation – heat transport List of Nominations 9

Classification of Forcing Factors Click to edit Master title style • Solar energy at the top of the Atmosphere • Click to edit Master text styles • Changes in the Composition of the • Atmosphere Second level Third level • • Changes in the solid Earth interface with • the Fourth level ocean and the atmosphere • Fifth level List of Nominations 10

First Major Class of Click to edit. Forcing Master. Factors title style Climate • The magnitude, character and distribution • of. Click edit Master solartoenergy at thetext top styles of the • atmosphere Second level Solar level evolution and variability • –Third Changes in the Earth’s orbit • –Fourth level – Change in the transmission of energy between • Fifth level List of Nominations the Sun and the Earth 11

Click to edit Master title style • Main Sequence Evolution • Hydrogen burned to Helium • Click to edit Master text styles • Number of particles per unit mass changes • Second level • Rebalance of pressure and List of Nominations temperature • Third level • T and Solar luminosity • Fourth level increases through time • 100 My ago – 0. 9% less than • Fifth level today (about 10% per billion years) 12

Click to edit Master title style • • • Othertext Timestyles Scales of Variability Click to edit Master • Mixing perturbations Second level • Decreased luminosity, slow recovery, overshoot Third level • Potential cause of glaciation? Fourth level • A few million years + • A few % changes in luminosity Fifth level • What else on dynamical, thermal List of Nominations and convection time scales? 13

• The Solar Cycle • Sunspot record • 11 year • Observed correlations • cosmic ray flux Master text styles • Potential Click to edit Master title style • • • Click to edit Second level Third level Fourth level Fifth level List of Nominations 14

Click to edit Master title style • Click to edit Master text styles • Second level • Third level Changes in the Earth’s Orbit modify the • Fourth level Distribution and Amount of Solar Energy at • the. Fifth Top level of the Atmosphere List of Nominations 15

Click to edit Master title style Differences in • • • Distance: +/- 3 % withstyles current orbit Click to edit Master text Little annual Second level difference Third level Fourth level Fifth level List of Nominations 16

Click to edit Master title style • Changes in the latitudinal distribution in solar input • • • Click to edit Master text styles • 21. 5 to 24. 5 o Second level • Few W/M 2 at high latitudes Third level Fourth level Fifth level List of Nominations 17

Amplitude of Seasonal Cycle Click to edit Master title style • • • Closest to Sun in N. Summer or Winter Click to edit Master text styles 20 W/M 2 seasonally Second level Third level Fourth level Fifth level List of Nominations 18

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 19

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Potential for changes in dust between Fourth level the Sun and thelevel Earth Fifth List of Nominations Current increases (? ) Time scale; impact ? ? 20

Second Major Class of Click to edit. Forcing Master. Factors title style Climate • Click to edit Master text styles • Changes in the Composition of the • Atmosphere Second level • –Third level Selective absorbers (greenhouse gases) • –Fourth level Aerosols • Fifth level List of Nominations 21

Click to edit Master title style • Click to edit Master text styles • Second level Wavelength specific absorption • Third level (Selective Absorbers) • Fourth level Molecule • Fifth specific level characteristics List of Nominations vibration, rotation modes Reradiates energy in all directions 22

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 23

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 24

Human Forcing on Short Time Scales Click to edit Master title style • Human source term that is measured and • larger Click than to edit textinstyles the. Master increase the atmospheric • reservoir Second level • Third level • Fourth level • Fifth level List of Nominations 25

Click to edit Master title style Barnola et al. Vostok • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 26

The Vostok core demonstrating the close link between carbon dioxide and temperature Clickthrough to edit the Master last glacialtitle cycle. style • • • Click to edit Master text styles Second level CO ppm Third level Fourth level Temperature from Deuterium isotopes Fifth level 2 List of Nominations From J. M. Barnola et al. , Nature 329 (1987): 408 -414, p. 410. 27

Intersection of the Geologic and Biologic Carbon Cycle –Not all Click to edit Master title style correlations imply the nature of the forcing • • Can temperature (ice age)text perturb (lead) the carbon Click to edit Master styles balance • –Second More ice – level lower sea level – sediment flux with nutrients changes ocean productivity and CO 2 draw down • –Third level More ice – more wind transported dust – more ocean fertilization – greater CO 2 draw down • –Fourth level More wind – more intense circulation – greater upwelling (nutrients) – greater productivity and CO 2 draw down • –Fifth level Cold temperatures of the ocean – increased gas solubility List of Nominations – deep water carbon dioxide reservoir grows – Cold temperatures and more ice – decreased plant and soil reservoir for carbon – atmospheric reservoir source declines 28

Perturbing the Geologic Carbon Cycle (very Master long time title scales) Click to edit style • • Alter theto balance of volcanism Click edit Master text (carbon styles dioxide input) and the rates of weathering (carbon dioxide removal) • - yields Second levelin atmospheric levels changes Rate of sea floor spreading and subduction • ––Third level Sea level – area of continent to weather Topography and/or silicate exposure – rates of weathering • –Fourth level • Analysis – • –Fifth level models based on weathering assessments (Sr mass balance List of Nominations isotopes), volcanism, carbonate deposition, sea level etc. , – carbonate character – stomatal density 29

Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 30

Click to edit Master title style • Click to edit Master text styles • Second level • Potential Third level for Abrupt Changes in Greenhouse • Fourth level. Gases • Fifth level Flood basalts Clathrates (forcing or feedback) List of Nominations 31

Click to edit Master title style • Click to edit Master text styles • Second level • Third level Dust loading – Stratosphere – alters reflection and absorption • Fourth level • Fifth level List of Nominations Changes in Stratospheric chemistry Tropospheric aerosols 32

Click to edit Master title style • Click to edit Master text styles • Second level • Third level Transmission effects El Chichon • Fourth level – 78% Pinatubo • Fifth level – 82% List of Nominations Period 1 -3 years Can the forcing be sustained to create a Climate forcing in the geologic record? 33

T difference Pinatubo (Robock) Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations Plate 8. Winter (December-January-February (DJF)) lower tropospheric temperature anomalies (with the nonvolcanic period of 1984– 1990 used to calculate the mean) for the 1991– 1992 Northern Hemisphere (NH) winter following the 1991 Mount Pinatubo eruption. This pattern is typical of that following all large tropical eruptions, with warming over North America, Europe, and Siberia and cooling over Alaska, Greenland, the Middle East, and China. Data are from microwave sounding unit channel 2 R [Spencer et al. , 1990], updated courtesy of J. Christy and now called channel 2 LT. 34

Multiple sources of aerosols Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations Can continental configuration yield an aerosol forcing? Light blue lowest; purple highest Source: NASA global aerosol project 35

Third Major Class of Click to edit. Forcing Master. Factors title style Climate • Click to edit Master text styles • Changes in the Earth’s Surface • Second level Distribution of land sea • –Third level • –Fourth level Orography • –Fifth level Land cover List of Nominations 36

Plate Tectonic Forcing Changes Click to Many edit Master title style Factors • Distribution of Land Sea • –Click to edit Master textheat styles Surface energy balance; capacity; potentiallevel for snow cover; mechanisms of heat • Second transport • Third level(ocean gateways); position of planetary waves; storm tracks • Fourth level • Orography • –Fifth level Potential for snow cover, position of planetary List of Nominations waves; distribution of precipitation; major circulation features such as the monsoons 37

Plate Tectonic Forcing changes Click many to editcomponents Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations 6 to 12 o Temperature Difference Plate tectonics Direct and CO 2 38

Sea Level Change Click to edit Master title style • • • Click to edit Master text styles Second level Third level Fourth level Fifth level List of Nominations Red Hallam, Blue Exxon 39

Orography and Continental Click to Configuration edit Master title style • • • Click to edit Master text styles Second level. Single feature Ocean gateways Continental elevation Third level Low latitude snow Fourth level Indian Monsoon Fifth level List of Nominations 40

Biologic Innovation – Land Click to edit. Plants Master title style • • • Click to edit Master text. Changes stylesin surface albedo Surface Energy Fluxes Second level Third level Fourth level Fifth level List of Nominations 41

Rich Spectrum of Forcing Click to edit. Factors Master title style • Solar energy at the top of the Atmosphere • Click to edit Master text styles • Changes in the Composition of the • Atmosphere Second level Third level • • Changes in the solid Earth interface with • the Fourth level ocean and the atmosphere • Fifth level How important are these factors in governing climate? List of Nominations 42

Definition of Climate Sensitivity Click to edit Master title style Equilibrium change in global mean • Click to edit Master text styles temperature in response to a change in • Second levelmean radiative forcing global • Third level • Fourth level o • CFifth level per W/m 2 change in forcing change List of Nominations 43

Climate Sensitivity with no feedbacks Click to edit Master title style • The direct temperature effect for a change • in. Click to edit Master text styles forcing Fix the albedo • –Second level(ice doesn’t change; clouds don’t change, vegetation doesn’t change, etc) • –Third level Fix the emissivity (no change in water vapor or any other character • Fourth level of the atmosphere) -2 • • Change the solar insolation by 1 Wm Fifth level List of Nominations • Complete the calculation =. 21 o. C per 1 Wm-2 • Solar constant 1 % change = 3. 4 Wm-2 44

Ice Age Climate Click to edit Master title style • Distribution of temperature data (such as CLIMAP) yields o. C globally average surface temperature from 3 to 5 • Click to edit Master text styles difference Second level • • Driving Forcing Factor (orbit driven changes in solar -2) insolation – 1% change – 3. 4 Wm List of Nominations • Third level • Ice age record demands that climate be sensitive to • external Fourth level forcing. • • Importantly, a great deal changed in response to the orbit Fifth level – – – Atmospheric composition (CO 2 and CH 4 from ice cores) Dust levels (from ice cores) Ice cover (most significant element - CLIMAP) Water vapor and cloud cover (? ) Vegetation – CLIMAP and others 45

Mid-Cretaceous Click to edit Master title style • Data – warmer by 7 o C +/- 2 (Barron et al. , • 1995) Click to edit Master text styles • Carbon Dioxide – 2 to 6 X present day (wide • variety Second level of estimates – Berner) List of Nominations Third level • • Assume direct forcing is linear with growth in -2 carbon dioxide – 4. 2 to 12. 6 Wm • Fourth level • Use the greatest possible range • –Fifth level Translate to CO doubling yields 1. 7 to 9 o. C – (remember climate models predict 1. 5 to 4. 5 o. C) 2 • But, sun was also weaker ~1% • How important is the geography? 46

Sensitivity: Doubling of Carbon Click to edit. Dioxide Master title style • Direct forcing for a doubling would equal 4. 2 -2 edit Master text styles • Watts/m Click to • • Using energy balance with no feedbacks would Second level o. C (. 88) yield less than 1 List of Nominations • Third level • Modern Climate Models Predict ~1. 5 -4. 5 o. C • Fourth level • The key is to be able to determine the nature of • the Fifth level feedbacks – e. g. Ice-albedo feedback • The geologic record demands a high level of climate senstivity 47

Tool Set Click to edit Master title style • Characterize the forcing (not all are well • known) Click to edit Master text styles • –Second level Magnitude Time level scale • –Third Spatial level character • –Fourth • • Correlation Fifth level with geologic phenomena (not always indicative in the confusion of forcing vs feedback) List of Nominations 48

Tool Set Click to edit Master title style • Climate Model Application (increasingly • prominent Click to edit Master text styles – many examples not shown) • –Second levelwith independent geologic data Comparison becomes • Third levelcrucial • Fourth level • Fifth level List of Nominations 49

The Greatest Challenge Click to edit Master title style • The planet is not the product of a single • cause Click and to edit its Master effect text styles Second level are operating • • Many forcings • simultaneously Third level (consider only the of the ice age forcing) • complexity Fourth level • • AFifth forcing at one time scale can be a level feedback at another time scale • A geologist senses the fully integrated forcing and response of the Earth system List of Nominations 50