glacier Posted December 18, 2003 Share Posted December 18, 2003 No wonder my SADD is getting worse. darkness falls Quote Link to comment Share on other sites More sharing options...
RobBob Posted December 18, 2003 Share Posted December 18, 2003 I don't buy it. Meanwhile, supposedly the cattle in Patagonia are getting more sunburn and glaucoma than ever. Quote Link to comment Share on other sites More sharing options...
Dan_Harris Posted December 18, 2003 Share Posted December 18, 2003 Did I miss something in the article? I still do not know how Global Dimming and Global Warming square. Seems less sunlight, less warming. Quote Link to comment Share on other sites More sharing options...
catbirdseat Posted December 18, 2003 Share Posted December 18, 2003 Global warming is caused by carbon dioxide trapping more infrared radiation from the sun. Surfaces radiate infrared into space at night. CO2 blocks this some degree. Incoming solar radiation is also absorbed so that less reaches the ground. Can that be such a surprise? The method by which they measure insolation involves measuring the temperature of a black plate. This method does not distinguish between the various wavelenghts of light. In fact it is biased towards the infrared and longer wavelengths. So it may be that visible light is not attenuated at all- that most of the reduction is in the infrared. Quote Link to comment Share on other sites More sharing options...
glacier Posted December 18, 2003 Author Share Posted December 18, 2003 I don't think they were able to pull a connection, either. Although they did see the correlation between the dimming and pan evaporation rates, which would be counter to warming, although evaporation is not necessarily connected to temperature, rather other radiation. With respect to potential global warming - it is connected not necessarily to the amount of radiation that the earth is receiving, but the amount that is being held in the atmosphere due to the increase of CO2, etc. There could be less input, but a more 'efficient' insulation keeping the energy in (e.g. a simple balansce equation input +/- change in storage = output). I'll have to forward this to my buddy in atmospheric sciences to see if he has an opinion. Quote Link to comment Share on other sites More sharing options...
Dru Posted December 18, 2003 Share Posted December 18, 2003 dan think about it this way. in global warming, it is the atmosphere that warms. in global dimming, it is the amount of sunlight RECIEVED AT THE EARTH SURFACE that diminishes. two different things. for instance Venus has 100% cloud cover and NO sunlight reaches the surface but it is still a hot place. Quote Link to comment Share on other sites More sharing options...
catbirdseat Posted December 18, 2003 Share Posted December 18, 2003 Exactly, Dru. Now, what needs to be done is work which documents how much light at various wavelengths reaches the surface. It is blue and orange light which is used by plants, with blue being them most important. Blue is a shorter wavelength and would be expected to be less affected by CO2 in the atmosphere. If we are talking aerosols, then yes, blue light is affected more than the shorter wavelegths. Quote Link to comment Share on other sites More sharing options...
RobBob Posted December 18, 2003 Share Posted December 18, 2003 I think the key words here are Europe, Soviet Union, Japan---all heavily industrialized nations, particularly when you make comparisons from the 60s to the 80s. I have traveled to Europe regularly over the past 20 years, and a Hell of a lot of the time the sky is strikingly dark when you arrive, compared to leaving the states. I'm not sure I'll believe there's a difference in light shining on Colorado Springs, or LA, or NY or Miami until specific studies are done there. Quote Link to comment Share on other sites More sharing options...
Dru Posted December 18, 2003 Share Posted December 18, 2003 evaporation pans are a useless measure anyways. i can make water evaporate from a pan in my basement* just by turning the heater up, nothing to do with solar radiation. * except that I don't have a basement cause I live on a 2nd floor Quote Link to comment Share on other sites More sharing options...
RobBob Posted December 18, 2003 Share Posted December 18, 2003 My grandmother used to do that with pans of water, but she always claimed that the elves out of Palmer Scott books drank it. Quote Link to comment Share on other sites More sharing options...
Doctorb Posted December 18, 2003 Share Posted December 18, 2003 for instance Venus has 100% cloud cover and NO sunlight reaches the surface but it is still a hot place. So...why is it so hot? Quote Link to comment Share on other sites More sharing options...
iain Posted December 18, 2003 Share Posted December 18, 2003 she always claimed that the elves out of Palmer Scott books drank it. sounds like Bush's reasoning behind many environmental policies Quote Link to comment Share on other sites More sharing options...
iain Posted December 18, 2003 Share Posted December 18, 2003 So...why is it so hot? cause it's Venus man, she's hot! Quote Link to comment Share on other sites More sharing options...
Doctorb Posted December 18, 2003 Share Posted December 18, 2003 i can make water evaporate from a pan in my basement* just by turning the heater up, nothing to do with solar radiation. Nothing to do with SOLAR radiation. Quote Link to comment Share on other sites More sharing options...
Dru Posted December 18, 2003 Share Posted December 18, 2003 for instance Venus has 100% cloud cover and NO sunlight reaches the surface but it is still a hot place. So...why is it so hot? planet of women man! Quote Link to comment Share on other sites More sharing options...
glacier Posted December 19, 2003 Author Share Posted December 19, 2003 The word from the Atmos. Sci. doc. "It's 'Legit', sources and all. I bet much of the source of this comes from negative feedbacks to global warming natural to the climate cycle. You've heard the whole double the levels of CO2 and then you get warmer temps, but you also get more evaporation as the temp warms, this causes more clouds. Question is, are they high clouds or low clouds? Because high clouds tend to cool the atmosphere and low clouds tend to warm the atmosphere. Also through in particulates / aerosol - the very small kind that volcanic eruptions, pollution etc. create. These particles can change the planetary albedo - this might be part of the 'global dimming' picture, but probably not all of it. Now go back to the clouds, the clouds have drop and ice crystal size spectra and number concentrations. There have been very very very few studies on what the natural state of affairs is here and very very little on the variation of this. They can and do vary a bit is my intuition (and probably most atmospheric scientists) - the # and size spectra of cloud droplet and ice crystal size distributions in the clouds are heavily influenced by the aerosol populations and this in turn strongly effects radiation budgets of terrestrial (IR) and solar (vis/UV) radiation. I had not heard about this drop in radiation at the earth's surface, but given what I know about clouds and water cycle it doesn't suprise me. I bet much (maybe not all) of it lies in these issues of how aerosol, cloud droplet spectra, the rate of evaporation and cloud formation with the changing climate all interrelate. This is why climate modeling is such a nightmare (and so interesting). This is also why atmospheric scientists have such a hard time saying definitively what way the climate will go - they have soooo many variables (many not well understood like the droplet spectra in clouds and how it relates to aerosol and how this effects the radiation budget for one small example) to include in their models. The ozone whole issue was so much simpler. Release flourocarbons and their like and you will destroy the ozone whole, that is easy to predict - thus policymakers are quicker to make effective changes. Burning fossil fuels and the CO2 issure and all its global warming / now dimming ramifications are much harder to pin down - thus the struggle to control or emissions is much harder to pin a specific reason and need to (though we are fucking so hard with all the strings I think that is reason enough - but policymakers are not foward thinking enough to want to fight for the system just for hard causes - whatever - keep trying). Anyway - did I make any of that clear enough?" Clear as mud. Quote Link to comment Share on other sites More sharing options...
Dan_Harris Posted December 19, 2003 Share Posted December 19, 2003 Wow, Finally get a chance to read and respond. CBS, I understand how the warming works via CO2, and other gasses, trapping IR and keeping it from radiating back to space. I understood the piece to be talkng mainly about visible light hitting the surface. Earth's surface aborbs these frequencies and radiates the IR back and the atmosphere gasses trap these, therefore warming the atmosphere. So if less visible light is reaching the surface of Earth? Now the warming and dimming could be explained in my mind if there were more of the UV and other frequencies (magnetic field weakening?) hitting Earth and radiated back as IR. Dru, The Venutian atmosphere has a surface pressure of 90 time that of Earth, is composed of mainly CO2, and is just a bit closer to the sun than Earth. Those two would help explain the extremly high temps on Venus. Also with no magnetic field to deflect some of the other radiation emitted by the Sun, it would seeem this energy would contribute to the runaway greenhouse effect on Venus. The guy using a dark plate and measuring temps on either side seemd rather simple. I have used sechi discs to measure light penetration of water, seemd to be not very accurate. The photometer made a whole lot more sense. OK, ready to be set straight. Thanks! Quote Link to comment Share on other sites More sharing options...
catbirdseat Posted December 19, 2003 Share Posted December 19, 2003 Glacier, your stream of conciousness style is reminiscent of MtnGuide- one humongous paragraph. Can you explain what you mean by "droplet spectra"? Quote Link to comment Share on other sites More sharing options...
Dru Posted December 19, 2003 Share Posted December 19, 2003 dan my point is that a runaway greenhouse effect (venus) is not incompatible with a dark surface recieving no visible light. Venus is hot because its atmosphere is hot, not because the sun heats the surface. So earth can be dimming and warming at the same time. As a matter of fact the example of Venus suggests the two effects may even be linked. Quote Link to comment Share on other sites More sharing options...
scrambler Posted December 19, 2003 Share Posted December 19, 2003 I thought this post was going to be about a drop in global IQ. Quote Link to comment Share on other sites More sharing options...
Dan_Harris Posted December 19, 2003 Share Posted December 19, 2003 I think we are agreeing Dru. My question concerned the article and, at least my interpretation, of his talking about visible light and not mentioning UV. UV, as well as other forms of radiation, pass through clouds very well (I've had some nasty sunburns to attest to this) and so heating and dimming can co-exist quite well. Quote Link to comment Share on other sites More sharing options...
glacier Posted December 20, 2003 Author Share Posted December 20, 2003 Glacier, your stream of conciousness style is reminiscent of MtnGuide- one humongous paragraph. Can you explain what you mean by "droplet spectra"? That's my buddy's stream of consciousness. Fricking enthusiastic genius always writes/talks like that. So I have no idea what 'droplet spectra' is - I'll ask. He was likely just using it as an example. Quote Link to comment Share on other sites More sharing options...
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