THE GREENHOUSE EFFECT THERE IS A NATURAL LIMIT TO ANTHROPOGENIC GLOBAL WARMING

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THE GREENHOUSE EFFECTTHERE IS A NATURAL LIMIT
TOANTHROPOGENIC GLOBAL WARMING

• William Kininmonth
• Melbourne, Australia
• Recognising
• H. Riehl and J.S. Malkus, 1958. On the heat
  balance of the equatorial trough zone.
  Geophysica, vol 6, Nos 2-3 pp503-538
• C.H.B. Priestley, 1966. The limitation of
  temperature by evaporation in hot climates. Agr.
  Meteor., 3241-246

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What is the Greenhouse Effect?

• The earths radiation temperature, as seen from
  space, is -19oC
• The earths surface temperature is 14oC-15oC
• The Greenhouse Effect increases the surface
  temperature by 33oC, thus making earth habitable
  
• How?

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• Greenhouse gases emit infrared radiation
  independently of absorption

From IPCC
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Longwave radiation cools the atmosphere and the
earths surface Atmosphere emission 195
324 519 absorption 350 Surface emission
390 absorption 324
Loss 169 Loss 66
IPCC from Kiehl and Trenberth, 1997
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Energy is exchanged between the surface and the
Atmospheric boundary layer as heat and latent
energy of evaporation
Radiation Cools the Atmosphere -102 W/m2
Radiation Warms the Surface 102 W/m2
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THE HYDROLOGICAL CYCLEExpansion of ice sheets
lower the Earths energy state
LATENT ENERGY GAIN BY THE ATMOSPHERE
ATMOSPHERIC TRANSPORT OF WATER VAPOUR - ASCENT
AND COOLING
CONDENSATION, AND CLOUDS
PRECIPITATION RAIN OR SNOW
ICE ACCUMULATION
WATER RUNOFF
LATENT ENERGY TAKEN UP IN ICE MELT
EVAPORATION
LATENT ENERGY LOSS FROM THE SURFACE
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The Greenhouse Effect.

• Deep convection towers distribute heat and
  latent energy from the surface through the
  atmosphere.
• Riehl and Malkus (Geophysica, 1958)
• Buoyant convection requires temperature in
  the atmosphere to decrease with altitude at
  6.5oC/km.

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Magnitude of Greenhouse Effect

• Infrared radiation to space
• Emission temperature -19oC
• Emission altitude 5 km
• Temperature lapse rate -6.5oC/km
• Surface temperature 33oC warmer than emission
  temperature 14oC

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Representing Convection in Climate Models- A
Gap between Simulation and Understanding
Despite several major observational campaigns
designed to guide us toward appropriate closures
for deep, moist convection, little consensus
exists as to the best formulations for climate
models. Isaac Held (GFDL), BAMS November 2005
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Assumptions of the AGW Hypothesis

• Prior to industrialisation there was global
  average radiation
• balance at the Top of the Atmosphere (TOA)
• Radiation Forcing by anthropogenic
  greenhouse gases is the
• global average reduction in upward directed
  infrared
• radiation at the tropopause
• There is a direct relationship between
  Radiation Forcing, ?Fu
• and surface temperature increase, ?Ts
• ?Fu ? ?Ts
• Seemingly plausible but not verified

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• Anthropogenic emissions of carbon dioxide to the
  atmosphere change the infrared (IR) radiation
  magnitudes
• Reduced IR radiation to space in CO2 band
• Increased IR back radiation at the surface

(Kiehl and Trenberth 1997)
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• There is very little change in Infrared Radiation
  Loss
• from the Atmosphere as CO2 concentration changes
• IR to space decreases
• IR back radiation to surface increases

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There is no local radiation balance at the top of
the atmosphere
Excess Solar Radiation
Excess IR to Space
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Climatology of Radiation to Space- dominated by
cloud and moisture distribution
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Carbon dioxide increases surface back radiation

• The surface temperature rises, and

• Surface radiation emission increases

• Latent energy exchange increases
• (Earths surface 70 percent ocean)

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Back IR radiation forcing, ?FCO2 causes a surface
temperature response, ?Ts
?FCO2 dFu/dT dLH/dT - dFd/dT
?Ts where ?Ts the change in surface
temperature due to an increase in back infrared
radiation ?FCO2 from increased CO2
concentration dFu/dT the rate of increase in
surface emission of infrared radiation with
temperature dFd/dT the rate of increase in
back infrared radiation with temperature at the
surface dLH/dT the rate of increase of latent
energy exchange between the surface and
atmosphere with temperature.
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• The Radiation Forcing equation can be re-arranged
  to give
• ?Ts ?TCO2 / (1 r)
• ?TCO2 the direct surface temperature change
• without feedbacks due to CO2 forcing
• ?TCO2 ?FCO2/ dFu/dT dLH/dT
• 1 / (1 r) the feedback amplification of surface
  
• temperature
• r dFd/dT/dFu/dT dLH/dT
• Note
• The rate of increase of surface energy loss with
  temperature
• dFu/dT dLH/dT constrains both the direct
  surface temperature response to Radiation Forcing
  and the feedback amplification
• Latent heat exchange is an important component of
  the constraint

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Variation of surface energy exchange
components with temperature (constant CO2
concentration)
Surface IR emission (Fu)
Back IR at the Surface (Fd)
Net surface IR Loss (Fu Fd)
Surface Latent energy exchange (LH) dLH/dT
7C-1
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The Earths Global Mean Surface Temperature is
stable (constant CO2)
Surface Energy Loss
Solar and Reservoir Exchange
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Surface Temperature Change with Double Carbon
Dioxide
Surface Energy Loss dLH/dT 6C-1
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Computer Models underestimate the rate of global
evaporation increase with temperature
Computer Models exaggerate surface temperature
increase with anthropogenic emissions of CO2
Enhanced Surface Temperature Rise 1.5oC
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Sensitivity of Surface Temperature to Evaporation
?Ts ?TCO2 / (1 r) ?TCO2 ?FCO2/ dFu/dT
dLH/dT 1 / (1 r) 1/(1 dFd/dT/dFu/dT
dLH/dT) dFu/dT 5.4 Wm-2C-1 (Stefan
Boltzman) dFd/dT 4.8 Wm-2C-1 (MODTRANS)
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Summary (1)

• The greenhouse effect is real
• The magnitude is regulated by the infrared
  emission properties of the atmosphere and
  convective overturning
• Anthropogenic Global Warming is real
• CO2 concentration affects global temperature
  through its increase in back radiation at the
  surface
• Water vapour amplifies the CO2 forcing
• Surface energy loss constrains the temperature
  rise

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Summary (2)

• The rate of increase in surface latent energy
  exchange with temperature constrains the surface
  temperature response from CO2 forcing
• GCM used in the IPCC Fourth Assessment
  underestimate the rate of increase in latent
  energy exchange with temperature and grossly
  exaggerate the surface temperature response to
  CO2 forcing
• AGW is real but at 0.6oC for 2xCO2 is not
  dangerous (much less than the amplitude of
  natural variability)