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Posted on 3/25/14 at 12:59 pm to GumboPot
I think I see where you got confused. In your NOLA/Mandeville example, you mixed up rate of temperature change with average temperature. The lower water vapor concentrations in Mandeville allow the temperature to change at a faster rate than NOLA because the extra water vapor in the atmosphere in NOLA acts as an insulator. But, the part that really matters is the average temperature for each location. As you stated in your post, despite the higher rates of change, Mandeville still averages lower temperatures than NOLA. Higher water vapor concentrations -> higher average temperatures -> water vapor acts as a greenhouse gas.
This is all neglecting a variety of other factors that can contribute to average local temperatures, however.
This is all neglecting a variety of other factors that can contribute to average local temperatures, however.
Posted on 3/25/14 at 1:11 pm to NC_Tigah
quote:
Presumably the video differentiates between effects of water vapor (+) and clouds (-/+)?
Not that I recall. The question answered in the video is; does water vapor (measured by humidity) cause a positive feedback on atmospheric temperatures as hypothesized by the Greenhouse Effect theory?
Conclusion from the empirical and observed data: NO. Water vapor caused a NEGATIVE feedback on temperature...which is opposite of GH theory...that is contrary to GH theory.
For the same reason a swimming pool only get to 90 degrees on a 100 degree day and 80 degrees on a 70 degree night water vapor has a negative feedback on atmospheric temperature.
Posted on 3/25/14 at 1:19 pm to weedGOKU666
quote:
Higher water vapor concentrations -> higher average temperatures -> water vapor acts as a greenhouse gas.
No.
Huntsville and Las Vegas are at the same latitude. They see the same amount of sunlight per day.
They are both sufficiently inland.
Their elevations are not drastically different.
The only major difference between the two cities is humidity or water vapor concentration.
Huntsville is a cooler city because it has more water vapor. The water vapor has more of a negative feedback on temperature in Huntsville than Las Vegas.
In the video, the author makes the same comparison with other locations around the world and the results are consistent.
ETA: Mandeville/New Orleans was probably a poor example to demonstrate the effects of water vapor on temperature because there are too many other variables that make the temperatures different/same between the two cities.
This post was edited on 3/25/14 at 1:25 pm
Posted on 3/25/14 at 1:32 pm to GumboPot
quote:
The water vapor has more of a negative feedback on temperature in Huntsville than Las Vegas.
Yes, but it's because that humid air takes much more energy to heat up. It's like if you put aluminum foil and a cast iron pan in the oven and set it to 300. You can touch the foil for a few moments without getting burned, but I wouldn't advise doing the same with the cast iron. Same temperature, different result.
I'm assuming then the argument for WV being a greenhouse gas is that it traps more energy from the sun in the atmosphere, even if it has a moderating effect on temperature.
Posted on 3/25/14 at 1:36 pm to Duke
quote:
I'm assuming then the argument for WV being a greenhouse gas is that it traps more energy from the sun in the atmosphere, even if it has a moderating effect on temperature.
The problem is it does and it doesn't. In addition to trapping heat and moderating temperatures, it also REFLECTS heat when it forms clouds.
Posted on 3/25/14 at 1:49 pm to kingbob
quote:
In addition to trapping heat and moderating temperatures, it also REFLECTS heat when it forms clouds.
I know. I was just speaking to his humidity level and temperature situation. It's certainly quite a bit more complicated than that. I suspect the reflection doesn't match the energy it's captured, but I'm also just pulling that out of my arse.
Posted on 3/25/14 at 2:14 pm to Duke
quote:
Yes, but it's because that humid air takes much more energy to heat up.
Totally agree. The property we are talking about here is heat capacity measured in mass per unit mass-temperature. The heat capacity of water vapor is 1.859 kJ/kgK (275 K). The heat capacity of air (which contains water vapor) is 1.002 kJ/kgK (275 K).
quote:
It's like if you put aluminum foil and a cast iron pan in the oven and set it to 300. You can touch the foil for a few moments without getting burned, but I wouldn't advise doing the same with the cast iron. Same temperature, different result.
Try that with an aluminum pan. I bet you get burned.
The difference between the two in your example is mass. Since aluminum foil is a very good conductor and the mass is very small, it cools quickly. Quickly enough to not get burned.
Don't try this with an aluminum pan though unless you like getting burned.
Posted on 3/25/14 at 2:20 pm to GumboPot
quote:
The difference between the two in your example is mass. Since aluminum foil is a very good conductor and the mass is very small, it cools quickly. Quickly enough to not get burned.
Fair enough, not the best example to explain what I meant. I was just going back to heat capacity, but I didn't know how familiar you were with the concept.
So we're on the same page, carry on.
quote:
Don't try this with an aluminum pan though unless you like getting burned.
I was just about to try it too...
Posted on 3/25/14 at 2:26 pm to Duke
quote:
Fair enough, not the best example to explain what I meant. I was just going back to heat capacity, but I didn't know how familiar you were with the concept.
Conductance and capacity can be easily confused. I just like to think of it in simple terms...capacity is how much heat a substance can hold and conductance is how fast that substance can take on heat or get rid of heat.
If you ever welded copper or aluminum you'd have a good feel for these properties.
Posted on 3/25/14 at 2:27 pm to Duke
quote:
I know. I was just speaking to his humidity level and temperature situation. It's certainly quite a bit more complicated than that. I suspect the reflection doesn't match the energy it's captured, but I'm also just pulling that out of my arse.
Not even remotely close, it reflects orders of magnitude more than it traps. The AGW idiots would be better suited harping on declining sea ice resulting in increased heat absorption by the ocean since sea ice reflects 90%+ of the sunlight that hits it and water absorbs somewhere in the neighborhood of 70-80%.
In the end, the biggest drivers of climate are solar activity, ocean currents, mountain ranges, and the concentration of plant life in the tropics.
The vast majority of people do not realize that the ice ages were caused by the linking of North and South America, which disrupted the oceanic currents that circulated heat around the globe, regulating its temperature. Since those continents have been joined, the world's climate has been highly unstable and prone to violent shifts from warm to cold and wet to dry.
Posted on 3/25/14 at 2:32 pm to kingbob
quote:
In the end, the biggest drivers of climate are solar activity, ocean currents, mountain ranges, and the concentration of plant life in the tropics.
Wait, all this is way beyond the scope of this thread.
quote:
The vast majority of people do not realize that the ice ages were caused by the linking of North and South America, which disrupted the oceanic currents that circulated heat around the globe, regulating its temperature. Since those continents have been joined, the world's climate has been highly unstable and prone to violent shifts from warm to cold and wet to dry.
Now this interest me. I'll have to google it. Are not North America and South America linked (minus the Panama Canal)?
Posted on 3/25/14 at 2:38 pm to GumboPot
Don't forget the specific heat of water plays a role. Areas with more water are less likely to see wide temp fluctuations. Slow to heat and slow to cool.
Posted on 3/25/14 at 2:52 pm to smoked hog
quote:
Don't forget the specific heat of water plays a role. Areas with more water are less likely to see wide temp fluctuations. Slow to heat and slow to cool.
I made a minor mistake using heat capacity in place of specific heat in my previous post. Heat capacity defines a specific amount of mass of substance. The quantities I listed above for water vapor and air are technically specific heat.
For example the specific heat of water is 4.179 J/g. The heat capacity of 100 g of water is 417.9 J/100g.
Posted on 3/25/14 at 2:59 pm to GumboPot
It is
Posted on 3/25/14 at 3:03 pm to jimbeam
quote:
It is
But a greenhouse gas is supposed to have a positive feedback effect. Water vapor doesn't. It has a negative feedback effect.
ETA: I thought it was a greenhouse gas too. But after digging a little deeper, if we go by ICPP standards then water vapor is not a greenhouse gas.
This post was edited on 3/25/14 at 3:21 pm
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