Global Dimming

[Turtle]

Just finished watchting a new Nova on PBS, on the topic of 'global dimming'. This is first I heard of this under that term, although I recall hearing about the findings of a higher range of daily temps measured in the US during the total flight groundings following the attack in NY.

It seems that particulates-& yes my contrails by about 2%- are reflecting a lot of sunlight. So much in fact that the cooling effect has actually been hiding just how severe the greenhouse gas warming is.

Today was sunny here by Portland Oregon, & the contrails were abundant. Using the little-finger-at-arms-length= 1 degree of arc, the one trail I watched expand for 20 minutes or so reached 6 degrees of arc in width & stretched from horizon to horizon as it slowly drifted East.

Anyway, here's a link to the PBS site & global dimming story.

http://www.pbs.org/wgbh/nova/sun/

:hihi:

[Racoon]

Cool Link to PBS Turtle. I do miss PBS. (I haven't watched TV in months now)

 

It sounds interesting, and plausible.

Britain is concerned enough to lower the altitude of their commercial flights :shrug:

 

Seeing as how much people fly, it makes sense that the Contrails (or chemtrails ;) ) could have a deletrious effect on global climate.

 

Its hard to study this and find conclusive evidence, much like Global Warming...

 

Thank you for the Awareness. Today was a Beautiful day in the Great Northwest! :pirate: :pirate:

[InfiniteNow]

I really thought this was going to be a thread in Social Sciences about global intelligence levels. Oh well, it's still really cool. :phones:

 

A similar story was featured on NPR last year:

http://www.npr.org/templates/story/story.php?storyId=4636777

 

 

And a brief mention on the same program a few weeks ago about the change recorded while planes were grounded after nine eleven.

[TheBigDog]

I think that it is plausable to calculate the cooling effect from jet contrails. At least to get a ballpark figure. Anyone want to help take a stab at coming up with the formula?

 

The effect would be dimished by other cloud cover, but for statistical purposes that could be given a constant value. It would be proportional to the number of miles flow in daylight. There would be a factor for how long the trails last. That would yeild the daily area of the trails and give a number that could be used to figure the change to albedo of the area under the trails. There is no doubt that they have some effect. With a little figuring we could estimate the extent of that effect.

 

Bill

[Turtle]

I think that it is plausable to calculate the cooling effect from jet contrails. At least to get a ballpark figure. Anyone want to help take a stab at coming up with the formula?

Bill

 

I have the feeling it's way more complex than that. Size of particles, ambient temp, wind direction/speed, & humidity to name a few. I did think I might calculate a rough estimate of the area covered by the 6 degree contrail I mentioned earlier. Mmmm...might get to that.

Its hard to study this and find conclusive evidence, much like Global Warming...

Actually it isn't hard to find conclusive evidence of either 'global warming' or 'global dimming'. The facts are in & they are hard. The problem seems to reside in getting people to understand & act on the facts.

[arkain101]

It was a good show.

 

We have a huge catch 22 disastor awaiting.

 

Reflection of light and Capture of what light/energy/heat does pass through.

 

Remove reflection, big problem with heat being captured. Too much heat = massive wildfires which adds to heat capturing problems.

 

Continue heat reflection, poor accuracy of what kind of heat capturing is happening.

 

Its like we are in an oven that is luckily in the shade. However, stuck in the shade and the oven will fail.

 

I wonder if ice ages are a cycle of this type.

 

We are in big trouble here with our air..

 

Chemists!! get your weapons, go to work!

[Zythryn]

It was a very interesting show. It actually is much larger than jet contrails though.

 

Did you see the part where they took a look at some pacific islands of which the north half was under the polution drifting in from India, while the southern section was under 'clean' air from the antartic? As I recall the polution was blocking about 10% of the suns energy from reaching the ground.

 

There were a number of indipendant studies made by different groups which seem to support each other.

 

One of the other issues is, the US and Europe are doing a good job of reducing particulate polution, however the greenhouse gases (especially in the US) is still climbing, so we risk loosing the cooling of the global dimming effect, while still accelerating the global warming effect. This raises the possibility that global warming is going to happen sooner, or more suddenly than anyone thought.

 

This also explains why the temperature at the poles seems to be getting warmer than the rest of the earth (little to no particulate pollution).

 

Mark

[Cedars]

I think this needs to be retested several times before it can be given credence. To see this much of a temp change based on a few days of commerical flight groundings in the USA leads me to be skeptical of the actual cause of this warming.

[Zythryn]

I think this needs to be retested several times before it can be given credence. To see this much of a temp change based on a few days of commerical flight groundings in the USA leads me to be skeptical of the actual cause of this warming.

 

For this particular test, I agree. Problem is, how often can you get all flights to stop for a period of days :hihi:

 

The general occurance of global dimming has been run through a number of varied tests (water evaporation measured over decades, energy from the sun in neighboring geographical areas which only have a difference of overhead polution, and a few others).

 

The main thrust seems to be that a rise in the amount of particles in the air from any source, seems to have a much larger affect on the amount of the sun's energy that reaches the surface of the earth.

 

I look forward to more tests to confirm this and allow us to better quantify the effect.

 

Mark

[arkain101]

I think this needs to be retested several times before it can be given credence. To see this much of a temp change based on a few days of commerical flight groundings in the USA leads me to be skeptical of the actual cause of this warming.

 

Look at it this way.

 

If a meteor hit earth that was big enough to send dust around the earth just enough to darken the sun by about 15%, it would very obviously be accepted that the dust, clouded, or reflected some of the suns energy and we would experience colder weather.

 

Just the same we are kicking up "dust" as it were, by our human activities, which is mainly in molecular substances so it is not as easily noticeable by the eye.

 

The problem may not be as big as they make it to be, but you cant deny we assist in reflecting sunlight, Clouds do this naturally, however they fall back down to earth and dissapear in days. The pollutents us humans create do not.. We are making an invisible cloak around an efficient oven.

 

You dont even need research to understand this is true, just look at the pollution on a global scale.

 

The details may not be right, but the reasoning is.

 

What do you think?

[arkain101]

Oh and another thing.

 

How does weather get created? We all know it very well has to do with imbalence in the atmosphere.

 

If there is high pressure here, and low pressure there, the (whats that principle/law called again?) pressures will equalize, creating, weather.

 

The more intense you can create unbalance, the greater the movement and change in weather one can create.

 

So if we picture earth with a hypothetical filter around it that causes sunlight to penitrate into it with complete equalness to reduce pressure differences, the weather we can theoretcially assume will remain calm because it is more in equalibrium.

 

If we beging to tear large holes in this filter, and also put solid blocking patches on this filter. Sun light will reach some spots intensely, some spots not at all, and some spots regularly. This will cause many different pressure differences in the atmosphere. Wind, turbulance, etc.

 

Now we apply this simple logical thinking to a cristine pure atmosphere, versus a weakening ozone atmosphere with areas that are high in heat containing, and others high in heat reflection capabilities. Weather will get more motivated to react..

 

What say you?

[Turtle]

I think this needs to be retested several times before it can be given credence. To see this much of a temp change based on a few days of commerical flight groundings in the USA leads me to be skeptical of the actual cause of this warming.

 

To clarify again, contrails account for very little (about 2% they said) of reflected sunlight, the rest coming from particulate pair pollution. Evidence of the 'global dimming' effect is actually some 30 years old, coming by way of evaporation tray readings. This is a measurement I only first learned of from this show on PBS.

A circular tray of water is left exposed to the elements, and each day the keeper measures & records how much water they must add to bring the tray back to its original level. The data provide a means of measuring the rate of evaporation.

When record keepers noticed this rate falling, i.e. less evaporation, they went looking for the cause. They looked at wind & humidity levels, but in lab experiments this did not correlate to the actual decline. The answer they found lay in less sunlight, moreover experiments showed that photons striking the water account for the majority of evaporation.

So again, the existence of global dimming is well established. What remains unknown is the amount & rate of the dimming & especially the effect these values have on slowing the global warming.:phones:

[Cedars]

To clarify again, contrails account for very little (about 2% they said) of reflected sunlight, the rest coming from particulate pair pollution. Evidence of the 'global dimming' effect is actually some 30 years old, coming by way of evaporation tray readings. This is a measurement I only first learned of from this show on PBS.

A circular tray of water is left exposed to the elements, and each day the keeper measures & records how much water they must add to bring the tray back to its original level. The data provide a means of measuring the rate of evaporation.

When record keepers noticed this rate falling, i.e. less evaporation, they went looking for the cause. They looked at wind & humidity levels, but in lab experiments this did not correlate to the actual decline. The answer they found lay in less sunlight, moreover experiments showed that photons striking the water account for the majority of evaporation.

So again, the existence of global dimming is well established. What remains unknown is the amount & rate of the dimming & especially the effect these values have on slowing the global warming.:confused:

 

When I was very young, my neighbor who owned a farm (I mentioned him in the birding thread) told me the skys were not as blue as when he was younger. While I listened to him talk of seeing nearly violet skys, the blue was so deep sometimes, I wondered if it was failing vision that accounted for this observation on his part. I will say that I too think the sky is not as blue now as when I grew up and aging eyes is not the sole cause for my observations.

 

But to see that much of a temp change from the grounding of planes alone leaves me skeptical of those particular observations.

[Turtle]

I will say that I too think the sky is not as blue now as when I grew up and aging eyes is not the sole cause for my observations.

 

But to see that much of a temp change from the grounding of planes alone leaves me skeptical of those particular observations.

 

Apparently the scientists who noticed it expressed their skepticism with surprise. While no one is suggesting stopping all flights again, it has prompted a host of other means and experiments to further examine the phenomenon of global dimming in general.

I don't recall the blueness of the sky from childhood; interesting observation though.:phones:

[Michaelangelica]

Oh and another thing.

How does weather get created?

What say you?

I vaguely heard on a BBC Discovery programme that plants exude a protein.

This protein causes water vapour to condense around it and thus create clouds.

Apparently, in the Amazon, you can test the rain for particular proteins to find out where it has come from.

I only half-heard the programme anyone else know about this?

[Turtle]

I vaguely heard on a BBC Discovery programme that plants exude a protein.

This protein causes water vapour to condense around it and thus create clouds.

Apparently, in the Amazon, you can test the rain for particular proteins to find out where it has come from.

I only half-heard the programme anyone else know about this?

I haven't read this whole transcript from BBC yet to see if it has the protein reference, however I found it as the #2 Google hit when I searched "pan evaporation rate".

Thanks again Micha.:)

http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_trans.shtml

:hihi:

PS

Sea salt and natural sulphur compounds emitted by plankton are also very important for cloud formation.

[Michaelangelica]

Latest on global dimming from the BBC

http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_prog_summary.shtml

 

I wonder if all the world's black roads were painted white, would this reflect enough sunlight to make a difference either-way?

 

I wonder if every floor, of every ofiice-block, of every city, were packed with indoor plants would this effect CO2 levels or reduce the mini-particles floating in the air?