Bill Ward
REMOVETHISix.netcom.com> wrote:
>On Sun, 11 May 2008 23:35:36 -0700, neutralino wrote:
>
>
>>
>> "The energy that is not reflected back to space is absorbed by the
>> Earth?s surface and atmosphere. This amount is approximately 240 Watts
>> per square metre (W m?2). To balance the incoming energy, the Earth
>> itself must radiate, on average, the same amount of energy back to space.
>> The Earth does this by emitting outgoing longwave radiation. Everything on
>> Earth emits longwave radiation continuously. That is the heat energy one
>> feels radiating out from a fire; the warmer an object, the more heat
>> energy it radiates. To emit 240 W m?2, a surface would have to have a
>> temperature of around ?19?C. This is much colder than the conditions
>> that actually exist at the Earth?s surface (the global mean surface
>> temperature is about 14?C). Instead, the necessary ?19?C is found at
>> an altitude about 5 km above the surface.
>> The reason the Earth?s surface is this warm is the presence of
>> greenhouse gases, which act as a partial blanket for the longwave
>> radiation coming from the surface. This blanketing is known as the natural
>> greenhouse effect.
>
>So far, so good, but you omit the effect of convection of the latent heat
>of water up from the surface to the radiating level you mention (cloud
>tops). My understanding is that most of the energy is carried there by
>latent and sensible heat, not radiation. What evidence is there that CO2
>plays any significant role, compared to the phase changes and absorption
>spectrum of water? Can you cite any climate models that accurately
>compute the mechanisms of convection? My understanding is that they are
>generally considered inadequate, particularly in that respect.
>
>
>> The most important greenhouse gases are water vapour
>> and carbon dioxide. The two most abundant constituents of the atmosphere
>> ? nitrogen and oxygen ? have no such effect. Clouds, on the other
>> hand, do exert a blanketing effect similar to that of the greenhouse
>> gases; however, this effect is offset by their reflectivity, such that on
>> average, clouds tend to have a cooling effect on climate (although locally
>> one can feel the warming effect: cloudy nights tend to remain warmer than
>> clear nights because the clouds radiate longwave energy back down to the
>> surface).
>
>During the day, clouds are often formed by convecting water vapor up from
>the surface to the condensation level. The resulting cloud radiates the
>transferred latent heat to space as IR and reflects incoming solar energy.
>Both mechanisms cool the surface.
His description seems to infer, accept or ignore the dynamics in
clouds, as if every water droplet was just there until it precips.
In reality, there is a very great amount of thermal transfer going
on in clouds, with sun, there is vaporization and strong convection above
the cloud, contact of that vapor with colder air, condensation and release
of the latent heat gained from the direct absorption of solar energy.
This activity is so great, it is the primary driver in thunderheads,
how could it simply be ignored, and clouds ignored as equal blocking and
reflecting?
And another factor in this is at night, the greatly increased broadband
radiation from cloud tops to space (or GHGs higher up) cools the droplets,
initiating precipitation, which falls to Earth and cools the surface, or
falls through warm air and vaporizes, moving the cloud components downward.
In heavy rain, and especially hail, there is huge amounts of thermal
energy transfer, with the raindrops and hail acting as almost a perfect
heat exchanger, causing a compounding of precip, and downward motion of
large masses of air with the downward motion accelerated by the aerodynamics
of the rain and/or hail.
This type of activity may not be too obvious if storms are not active,
but it can be going on in the cloud, too subtle to be obvious.
The big driver of storms is the reduction in volume as water vapor
condenses in large quantities, reducing pressure, with higher pressure
from all directions forcing atmosphere into the lower pressure region,
trying to equalize. With substantial activity like this, cyclones
develop and are self perpetuating as long as there is cold air aloft,
the cold air being more of a factor than the temperature of the air
or water.
Regardless of how the calculation is done, or where the problem
is started or finishes, the net effect is cooling the surface by at least
the latent heat removed from the vapor leaving the rain.
The latent heat in 10 inches or more average over possibly as much
as a million square kilometers, is a lot of latent heat, and surely a
scientist could not ignore that in any model or calculation of energy
balance.
Perhaps there should be a conference of specialists in the sciences
involved, away from the influence of the Hansen organization where a lot
of biased science appears to be originating, just as a check of the
rational thought on the science.
