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Originally posted by M. Spector:
Warmth doesn't come from visible light - it comes from infra-red light. That's why Venus is so hot at the surface despite its perpetual cloud cover.

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All this will change when our temperature buffer (ice caps) finish melting... Then the temps on this globe will rise pretty sharply in just a matter of a couple years. For now, most of the extra energy on the Earths surface from the greenhouse gases isn't effecting temperature yet, it's melting ice (Ice to water and water to steam takes an incredible amount of energy to make the conversion that doesn't affect temperature). No more ice to melt means this extra energy will start warming the globe. Ever do the grade 8 highschool science of warming water over a constant heat source? It raises to 0 at a constant rate, at 0 this energy is used to melt the ice (and the temperature doesn't change). When all ice is melted, the water temperature continues to rise at the rate prior to the ice metling. Right now on Earth, we're currently in the ice melting phase.

Global dimming actually has a much greater effect than just temperatures... The molecules we are releasing into the air add additional volume to the air as well as altering the temperature. When temperature and volume increase, pressure increases as well (I've posted this before). Hurricane strength is directly linked to pressure and larger high pressure zones will create large low pressures as the air is pushed around (and much heavier winds, like what we've seen hit the west coast last week).

Funny enough, I don't think increased temperatures will be much of a threat from global warming. The extreme weather caused by larger global high pressure systems, possibilities of change to currents based on salinity as the icecaps melt, and water levels rising will result in greatest affect on humans. The globes natural cycles will kick in until we have a planet exceedingly harsh for animal life (oxyegen breathers) to one very hosipitable to plant life (CO2 breathers). Warm and tropical environments tend to fit that bill best.

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Perhaps we are headed towards a venus world here on earth?

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Global Dimming - BBC UK

From the first link:

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But perhaps the most alarming aspect of global dimming is that it may have led scientists to underestimate the true power of the greenhouse effect. They know how much extra energy is being trapped in the Earth's atmosphere by the extra carbon dioxide (CO2) we have placed there. What has been surprising is that this extra energy has so far resulted in a temperature rise of just 0.6°C.

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I would think by this statement they are neglecting the effect the icecaps have on regulating the overall temperature on the globe... Although the temperature rise may only be .6 degrees currently, the mainstay of the energy increase is melting ice and not warming temperatures.

The pattern of cooler summers/warmer winters I suggest above does occour in part to global dimming. Gaining less energy during the day creates more moderated summer/daytime temps(energy is reflected back out to space via the global dimming process) and losing less at night will create warmer winter/night time periods (global warming). The only exception to this pattern will be the larger global waves that bring exceptional temperatures in either direction.

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The worlds rain supply is an interesting subject that Global dimming really contrasts global warming. You would think that a warmer globe would mean warmer air and therefore the ability to hold much more moisture. Global dimming seems to harshly counteract this by limiting the amount of energy directly effecting surface water and limiting how much turns into vapour. Atleast it will be dry heat? This phenomenon explains the droughts much more thoroughly than Global warming was able to.

[ 18 December 2006: Message edited by: Noise ]

And added in one more time... I've got links describing the effects of a warmer ocean and what that may be like. Last time I visited these links, Global Dimming wasn't quite so well thought through... I wonder if global dimming (less energy reaching the oceans surface) will greatly conteract the extra water vapor to be in the air from the higher temps? Hehe, time to revist an older theory I guess.

[ 18 December 2006: Message edited by: Noise ]

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... the NOVA documentary “Dimming the Sun” which stirred up lively discussions among scientists and non-scientists when originally shown by BBC in the UK (under the name 'Global Dimming' – see our previous posts). The NOVA version has been thoroughly re-edited and some of the more controversial claims have apparently been excised or better put into context...

...All major climate models now have some representation of aerosol physics though they range in their complexity – e.g. from top of the atmosphere aerosol forcing to highly interactive aerosol-cloud modules. The role that aerosols play in issues like the Sahel drought (Rotstayn and Lohmann, JC, 2002) or the Asian Brown Clouds (Ramanathan et al., PNAS 2005) is starting to be understood (and both these examples are featured in the documentary), but we do not as yet have a clear picture of exactly how aerosols and the other human-related forcings have affected climate...

...Overall, in the fifteen years from the 1990 Hansen and Lacis paper to the IPCC AR4, major steps forward have been made in implementing aerosols in climate models and hence matching observations of global dimming. However, it would be misleading to claim that the new appreciation for the surface energy balance changes implied that modelers a few years back were ignorant about the role of aerosols in other aspects of climate change. It is indeed a very complex problem.

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2nd one to consider... What happens to weather patterns when the majority of energy coming into the system is at the cloud level (and not warming the surface). I wonder what a hurricane heated from the top looks like?

and a final 3rd... 40% less sunlight hitting the ocean could mean 40% less plankton and other plantlife. Not just oceanic of course... All plant life is receiving less light. What does that do to plant life, and future plant life (hey, me might get to see low light plants evolve right infront of our eyes ^^)?

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Suppose the average rain cloud is a klick higher than 40 years ago, do you think the scientists know one way or another?

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Yes, they would know. Clouds form in various types, usually dictated by wind patterns and altitude. Weather predicition includes knowing your cloud types

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Clouds are essentially watervapour, water droplets and dust.

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Include all the other crap we've spewed into our atmosphere as well that comes back to us in the form of rain. Whats interesting about global dimming comparitively is the cycle seems to destroy itself if we don't continually inject particulate into the atmosphere (it comes back down in rain) and it doesn't seem to snowball. Reversely, Global warming has several 'snowballing' characteristics and the cyce continues to feed itself (for example, ice reflects better than water... less ice/more water means more light is absorbed and less reflected increasing the rate of warming).

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Anyone like to hunt down the latent heats for ice to water and water to steam?

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Brian... from wiki (it's called the 'Heat of Fusion' btw):

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To heat one kilogram (about 1 liter) of water 20 °C from 10 °C to 30 °C requires 20 kcal.
However, to melt ice and raise the resulting water temperature 20 °C requires extra energy. To heat ice from 0 °C to water at 20 °C requires:

(1) 80 cal/g (heat of fusion of ice) = 80 kcal for 1 kg
PLUS
(2) 1 cal/(g·°C) = 20 kcal for 1 kg to go up 20 °C
= 100 kcal

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As to your other question... Soil is rated around 0.8 while water is 4.18 (pends the soil composition of course). Something like wood is 0.4 and most metals are in the 0.9 to 1.0 area. Our atmospher however, rates closer to 0.01 instead. It's important to understand how insignificant our atmosphere is when we speak on this level. The amount of energy required to raise our entire ocean system 1 degree would be enough to raise our atmosphere by a few thousand degrees.

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How much global warming heat has snuck down into the earth?

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- The Earth is a water based planet... More surface is covered in water than is in land. Had any land warming occoured, it'd leech off into waters. Also might want to note, theres alot of subsurface waters and ice that would be effected before much happens with slightly warmer soil
- Earth is composed of tectonic plates on it's surface... There is plenty of room for subsurface heat to escape (Venus is interesting though as it has no plates and just a solid shell).
- Approx 90% of what goes down under the surface we walk on... we have no clue how it works hehe, and the 10% we do know is directly related to mining and oil.

I have problems seeing any of 'soil warming' as significant simply because the level we're working on here. 500 ft down is a tiny amount really. Then again, many chemical reactions occour and balances reached occour because of temperatures.

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I question the presumption that global dimming will stop if polution stops or slows down.

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People should be a bit open minded about global dimming. I think so anyways.

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There was another article in there that brought evidence that once upon a time, the oceans were likely 15 to 18 degrees warmer than they are today.

[ 20 December 2006: Message edited by: Noise ]

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Originally posted by Brian White:
The main point I argue is about the amount of extra light reflected back into space by the clouds.
Perhaps it is being absorbed and converted to heat by the clouds and the watervapour and dust and all the other chemicals up there.
This is too complicated to model (according to the modelers).

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I think the problem is that infra-red light is increasingly trapped in the earth's atmosphere by CO2 buildup and not being reflected back into space, if I'm not mistaken?. Infra-red light is being absorbed by the oceans and melting the arctic ice cap. The northern ice cap is a large reflector of the sun's rays back into space. But as it melts, less of the sun's rays are reflected back into space. Greenland has lost so much ice that geographers are saying that maps of the world are in need of re-drawing.

According to this site, global dimming is a daytime effect.

I remember the Al Gore video describing how the earth's vegatation, wich is mainly/largely in the Northern Hemisphere, inhales CO2 in the months when trees and plants are foliated, but then "exhales" CO2 in autumn when leaves turn brown and fall.

[ 29 December 2006: Message edited by: Fidel ]

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Originally posted by Fidel:

co.uk/sn/tvradio/programmes/horizon/dimming_qa.shtml]this site[/URL], global dimming is a daytime effect.
[ 29 December 2006: Message edited by: Fidel ]

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