Why earth is still getting warmer
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Why Earth is (Still) Getting Warmer. Northern Virginia Community College Annandale Science Seminar March 21, 2014. Basic Principles. Temperature measures kinetic energy of system’s molecules or atoms: thermal energy Energy gain ≠ energy loss: temperature change

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Why earth is still getting warmer

Why Earth is (Still) Getting Warmer

Northern Virginia Community College

Annandale Science Seminar

March 21, 2014


Basic principles

Basic Principles

  • Temperature measures kinetic energy of system’s molecules or atoms: thermal energy

  • Energy gain ≠ energy loss: temperature change

  • Gain = loss: equilibrium temperature

Why Earth is still warming


Applying the principles to earth

Applying the Principles to Earth

Why Earth is still warming


The beginning of an explanation

The Beginning of an Explanation

  • Earth gains/loses energy only through radiation

    • Incoming solar radiation

    • Outgoing reflected solar and Earth’s thermal radiation

  • It is warming because incoming radiation exceeds outgoing (positive radiative forcing)

  • WHY?

Why Earth is still warming


The saga of planet keeling

The saga of planet keeling

Why Earth is still warming


Long ago in a galaxy far away

Long ago in a galaxy far away

  • Planet Keeling ejected from home system

  • No atmosphere or internal heat source

  • Dull black – reflects nothing

  • No atmosphere

  • Cools to ~absolute zero during journey

Why Earth is still warming


Keeling arrives

Keeling Arrives

  • Captured by Sun-like star in near-circular orbit of 150 million km radius

  • Incoming solar radiation:

    • Cross-section: 1366 watts/meter2

    • Average for Keeling’s surface: 342 watts/meter2

  • Initial outgoing radiation: ~none

  • Radiative forcing: 342 watts/meter2

Why Earth is still warming


Now what the path to equilibrium

Now What?The Path to Equilibrium

  • Radiative forcing adds energy  temperature rises

  • Higher temperature  outgoing thermal radiation  less radiative forcing

  • Equilibrium temperature: equal incoming and outgoing radiation (no radiative forcing)

Why Earth is still warming


The path to equilibrium

The Path to Equilibrium

6o C

Why Earth is still warming


For the curious

For the Curious

  • Stefan-Boltzmann (1870s): radiation = σT4

    • Radiation is in w/m2

    • Temperature is in degrees Kelvin (centigrade + 273)

    • σ = 5.67 x 10-8 watts

  • Task: Solve for T for σT4 = 342

  • Some algebra: T4 = 342/(5.67 x 10-8)

  • And more : T = (342/5.67)1/4 x (108)1/4 = 279o K = 6o C

  • Why Earth is still warming


    Equilibrium for planet keeling i

    Equilibrium for Planet Keeling I

    Incoming

    Solar

    Outgoing

    Thermal

    =

    Why Earth is still warming


    Why earth is still getting warmer

    Good (19th century) Physics

    But Wrong Answer for Earth:

    Not Warm Enough

    Why Earth is still warming


    Planet keeling mark ii add albedo

    Planet Keeling Mark II: Add Albedo

    • Reflects 30% of solar radiation (0.3 albedo)

    • Solar radiation now balanced by:

      • Keeling’s own thermal radiation plus

      • Reflected solar radiation

    • Equilibrium requires less thermal radiation  reached at lower temperature

    Why Earth is still warming


    The new path to equilibrium

    The New Path to Equilibrium

    -18 C

    Why Earth is still warming


    Why earth is still getting warmer

    The Model is More Realistic

    But the Answer is More Wrong:

    Earth Isn’t a Snowball

    Why Earth is still warming


    The greenhouse effect

    The Greenhouse Effect

    Why Earth is still warming


    The missing piece

    The Missing Piece

    • Fourier (1824): Atmosphere must trap heat

    • But what part of atmosphere does this

    • And how does it do it?

    Why Earth is still warming


    John tyndall answers the first question

    John Tyndall Answers the First Question

    Why Earth is still warming


    Tyndall s 1859 experiment

    Tyndall’s 1859 Experiment

    • Determines what part of atmosphere traps heat

    • Oxygen and nitrogen (99% of atmosphere) are transparent to infrared radiation

    • Water, CO2 and methane (CH4) are not

    Why Earth is still warming


    Tyndall s experiment modern version

    Tyndall’s Experiment:Modern Version

    CO2

    Infrared Camera

    Glass tube

    Person

    Full-spectrum radiation

    Reduced infrared component

    Why Earth is still warming


    Infrared image of face with normal atmosphere

    Infrared Image of Face with Normal Atmosphere

    Why Earth is still warming


    Add co 2 to tube and more and more

    Add CO2 to Tube– And More and More

    Why Earth is still warming


    The second question how do these gases do it

    The Second Question:How do these gases do it?

    • For Tyndall: an empirical result

    • Explanation requires 20th century physics

      • Electromagnetic radiation

      • Interaction of radiation and gas molecules

    Why Earth is still warming


    1 electromagnetic radiation

    1. Electromagnetic Radiation

    • Includes X-rays, visible light, thermal radiation, radio waves

    • Behaves as particles (photons) and waves

    • High/low-energy photons = short/long wavelength

    Why Earth is still warming


    Sun and earth

    Sun and Earth

    • Source temperature determines photon energy/ wavelength

    • Incoming solar radiation: high energy photons/short wavelength

    • Outgoing radiation:

      • Reflected solar radiation: unchanged

      • Earth’s thermal radiation: low energy photons/long wavelength

    Why Earth is still warming


    2 molecules and greenhouse gases

    2. Molecules and Greenhouse Gases

    • Molecules can only occupy certain energy states

    • Absorb photons if energy matches interval between available states

    • Greenhouse gases: Gases with intervals matching energy of Earth’s thermal radiation

    Why Earth is still warming


    Then what

    Then What?

    • Molecule drops back to original energy level

    • Emits photon in random direction

    • Further collisions repeat process

    • Molecular bumper cars ends when photon escapes into space OR strikes Earth’s surface

    Why Earth is still warming


    Planet keeling mark iii preliminary edition

    Planet Keeling Mark III(preliminary edition)

    • Add CO2

    • Surface warmed by

      • Unreflected solar radiation plus

      • Part of reemitted thermal radiation

    • Surface warmingcontinues until escaping thermal plus reflected solar equals incoming solar

    Why Earth is still warming


    Planet keeling iii preliminary

    Planet Keeling III (preliminary)

    Incoming

    Solar

    Escaping

    Thermal

    Outgoing

    Reflected

    =

    +

    Atmospheric

    CO2

    Why Earth is still warming


    Why earth is still getting warmer

    With Earth’s CO2concentration

    Keeling temperature still is lower than actual Earth temperature

    Why Earth is still warming


    Just add water

    Just Add Water

    • Water vapor is a greenhouse gas: roughly doubles warming effect of CO2

    • But a feedback: atmospheric water vapor determined by temperature

    • CO2 is the control knob: without it, planet’s water vapor would be surface ice

    Why Earth is still warming


    Planet keeling iii final

    Planet Keeling III (final)

    Incoming

    Solar

    Outgoing

    Thermal

    Outgoing

    Reflected

    =

    +

    Atmospheric

    CO2 and H2O

    Why Earth is still warming


    Equilibrium

    Equilibrium

    • Equilibrium reached in all cases: Keeling I, II, III (preliminary and final)

    • Difference: temperature needed to reach it

    • Lower if part of incoming solar is reflected

    • Higher if only part of surface thermal radiation escapes into space

    Why Earth is still warming


    The discovery of global warming

    The discovery of global warming

    Why Earth is still warming


    1890s setting

    1890s Setting

    • Basic science in place for explaining Earth’s temperature

    • Implicitly also an explanation of how temperature could change

    • But someone had to ask the question

    Why Earth is still warming


    Arrhenius asks the question

    Arrhenius asks the question

    Why Earth is still warming


    Arrhenius 1896 analysis

    Arrhenius 1896Analysis

    • His interest: What caused global glaciation?

    • Perhaps fewer volcanic eruptions: Less CO2  cooler  less water vapor  still cooler

    • To be complete, looks at reverse: more eruptions  more CO2  more water vapor  warmer world

    Why Earth is still warming


    Quantifies impact of doubling co 2

    Quantifies Impact of Doubling CO2

    • Science: CO2 and water vapor feedback

    • Data: atmospheric absorption of thermal radiation from Langley experiments

    • Tools: pen and paper

    • Result: 5o-6o C warming

    • Moral: Plausible result with 19th century science and no computer model

    Why Earth is still warming


    Two reasons not to worry

    Two Reasons not to Worry

    • Most emissions would be absorbed by oceans

    • In any event, large emissions far in the future

    Why Earth is still warming


    Roger revelle eliminates one reason

    Roger Revelle Eliminates One Reason

    Why Earth is still warming


    Revelle s 1957 experiment

    Revelle’s 1957 Experiment

    • Grant to study ocean chemistry

      • Expects to find that ocean absorbs CO2

      • It does but (surprise) most pops back out again

    • But still expects slow growth in emissions – no need for dramatic actions

    Why Earth is still warming


    Now we need measurements

    Now We Need Measurements

    • Is atmospheric concentration of CO2 rising?

    • Are global temperatures rising?

    Why Earth is still warming


    Co 2 concentration

    CO2Concentration

    • Changed by difference between flows into/out of atmosphere

    • Early 1950s: no consensus on size (or even sign) of difference

    • The problems

      • Lack of continuous measurements

      • Existing measurements affected by local sources and sinks

    Why Earth is still warming


    David keeling solves the problems

    David Keeling Solves the Problems

    Why Earth is still warming


    His solution

    His Solution

    • Monitor at isolated location: Mauna Loa

      • Observatory at 3,397 meters

      • No nearby industry or motorized vehicle traffic

      • In barren lava field

    • Monitor continuously

    Why Earth is still warming


    The keeling curve

    The Keeling Curve

    2013: 396 ppm CO2 and 478 ppm CO2eq

    2005: Keeling dies

    NSF stops supporting “routine” research – Revelle to the rescue

    Why Earth is still warming


    The keeling carbon cycles

    The Keeling Carbon Cycles

    • Biological:

      • Dominates intra-annual cycle

      • Little interannual impact

    • Fossil fuels dominate interannual changes

    Why Earth is still warming


    Co 2 emissions man vs volcanoes

    CO2 Emissions: Man vs. Volcanoes

    Why Earth is still warming


    Temperature milestones 1980 2012

    Temperature Milestones: 1980-2012

    • ~1980: NASA, NOAA and Hadley Center develop estimates of global temperature from 1880

    • 1998-99: Mann and co-authors estimate temperatures from 1000 AD primarily from tree rings

    • 2011-2012: Berkeley Earth Project reanalysis largely confirms NOAA/NASA/Hadley estimates

    Why Earth is still warming


    Berkeley earth project reanalysis

    Berkeley Earth Project Reanalysis

    Why Earth is still warming


    The current issue global warming has has not stopped paused slowed

    The current issue:Global warming has/has not stopped/paused/slowed

    Why Earth is still warming


    Why earth is still getting warmer

    2010: 0.66o

    1998: 0.63o

    Why Earth is still warming


    The deductive path

    The Deductive Path

    • Assume:

      • CO2 is a greenhouse gas

      • Its atmospheric concentration continues to rise

      • NOAA/NASA/Hadley/Berkeley properly integrate temperature readings

    • Then, CO2’s effect is being offset, or

    • An increased share of thermal energy is outside temperature readings’ spatial coverage

    Why Earth is still warming


    Potential offsets

    Potential Offsets

    • Reduced solar radiation

    • Increased aerosols from small volcanoes and/or Asian factories

    • Contribution likely but probably modest

    Why Earth is still warming


    Distribution of earth s thermal energy

    Distribution of Earth’s Thermal Energy

    • Vertical: surface and upper atmosphere

      • Measurement issue but little effect

    • Horizontal: distribution over surface

      • The no-Mauna Loa problem

    • Vertical: surface and deep ocean

    Why Earth is still warming


    Horizontal distribution the arctic hole

    Horizontal Distribution:The Arctic Hole

    • The Arctic weather station gap

      • Hadley: assumes Arctic temperature changes at global rate

      • NASA: fills gaps by interpolation

      • NOAA: like Hadley?

    • Cowtan and Way (2013)

      • Begin with satellite data

      • Develop algorithm for relating satellite data to surface temperature

      • Test algorithm for known surface temperatures

    Why Earth is still warming


    Why earth is still getting warmer

    Why Earth is still warming


    The oceans role distribution of additional thermal energy

    The Oceans’ Role:Distribution of Additional Thermal Energy

    Why Earth is still warming


    Why earth is still getting warmer

    Why Earth is still warming


    Why earth is still getting warmer

    Why Earth is still warming


    The current state of play a tentative assessment

    The Current State of Play:A Tentative Assessment

    • Slowdown is less pronounced than standard data series indicate

    • Part of slowdown is due to quieter sun and increased aerosols

    • Increased warming of deep ocean is largest contributor

    Why Earth is still warming


    Why earth is still getting warmer

    Robert C. Means

    [email protected]

    Why Earth is still warming


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