Global Dimming

wiredog writes "The Guardian reports on research which shows that the amount of sunlight reaching the Earth's surface has decreased by 10% in 30 years. This has implications for global warming models and, especially, agricultural output."

So instead

[flafish]

of Global Warming, we have to worry about Global Cooling. Is that why it is 45F out in S. Florida? :-)

How will H usage affect this?

[Malc]

This makes me wonder about the drive towards a hydrogen-powered economy. All that water vapour coming out of car exhaust pipes, etc. Probably a better form of pollution from a health perspective, but will it also result in limiting sun light or producing clouds that trap heat?

tomorrows weather, 20 and sunny.

[fuck_this_shit]

We can thus conclude that we know nothing. Weather patterns haven't been recorded for a long enough time to make any valid long time prediction of such things as global warming or freezing. Once they manage to consistently predict tomorrows weather successfully they may go onwards and claim they have a clue how the weather will be 100 years from now. For those screaming "Kyoto!" etc: yes, reducing pollution is good and should be something to strive for for every somewhat intelligent human being, but I wouldn't draw a conclusion about global warming from what was presented yet.

weird

[ikoleverhate]

Quite weird - there was an elderly farmer saying much the same thing this morning on my bus to work.

I'm pretty sure he wasn't a guardian reader, it's just something he'd noticed over the years.

At the time, I thought he was talking crazy talk...

The unintended benefits of pollution

[G4from128k]

I suspect that some of this global dimming is due to pollution from sulfates (coal), jet contrails, and dust from wind-borne erosion. Sulfate and particulate pollution provides nice nucleation sites for cloud formation. These pollution-created artificial clouds probably reduce global warming (the article mentions this effect and a correlated decrease in cloudiness and increase in temperatures in the 1990s).

The scary part comes if we reduce these forms of pollution, reduce cloudiness, and thus accelerate global warming. Whether we like it or not, humanity is changing the climate -- as attractive as it seems, preservation is impossible. At this point, it might be better to think about climate engineering -- deciding how we want to change the climate rather than holding on to the false hope that we can avoid changing the climate.

Crude (correct or incorrect?) Analogy

[chia_monkey]

I wonder if this is similar to a greenhouse. This would explain both the dimming AND the global warming. The glass from a greenhouse (comparable to the atmospheric gasses) undoubtably blocks some of the sunlight getting to the plants/surface. Yet we all know it's a bit warmer in the greenhouse than in the surrounding area outside.

If this analogy is correct, we really do have a lot to fear. Not only will we continue to have global warming but it seems as if the humidity level of the planet may rise too. Of course, at some point (if we're losing 10% a decade) you would think there is a break-even point and we'll start experiencing global cooling because it'll be like putting the shades down on the windows.

Re:So instead

[Urkki]

So it also means you'd better not forget your 100% UV blocking sunglasses unless you want to get too much UV radiation into your eyes (as eyes adjust to the visible light, while it is UV light that can cause eye damage).

Re:weird

[arivanov]

I have noticed that as well. In the early eighties I needed to use suncream in the summer and had a few cases of vicious sunburns when I did not. Nowdays I no longer need it unless I go as far south as the tropics. Another thing I have noticed is that unfortunately all these studies do not give you a distribution across the visible, near UV and near IR spectrum. They are a sum of all. If there was distribution data the actual reason would have been much easier to pinpoint. For example a flat decrease/increase will point to particles. A decrease in near IR will point to water and CO2. A decrease in UV will point to excessive ozone in the low atmosphere (which is something that has happened as a result of polution in Europe). So on, so forth. So met offices need to start putting some filters in front of these black disks. In btw, when I have observed 2 petrol strikes/blocades in the last 10 years around Europe. During both the traffic nearly stopped and there were less then 5% of the usual vehicles on the roads. During both it was fairly obvious that the sun shined much stronger then usual (not pointing any fingers here...).

Increased solar radiation - less light?

[SysKoll]

I challenge their result, a 10% dimming is a lot. They should redo the measurements with the same instruments instead of comparing modern instrumnets with what they used 10 years ago. We don't even know if the two sets of instruments have the same sensitivity in the measured wavelenght range. Also, there is a known cyclic effect linking to the 11-year solar cycle. We need a measurement over a full cycle before crying wolf.

That said, there has been an increase in the solar output. The number of sun spots at solar peak is increasing steadily. And the Mars polar cap is melting, which is consistent with the solar output increase observation.

Note that currently, the sun is close to its radiation peak. Which means that since the high atmosphere is acting like a bubble chamber, we will see more ice crystals and water droplets at high altitude (and more precipitations). Which raises the Earth's albedo (reflectivity) and could decrease the amount of solar light reaching the ground. So at least, the findings don't contradict atmospheric physics.

But I still want to see these measurements done over an 11-year solar cycle, otherwise it's gimme-a-grant voodoo, not science.

-- SysKoll

Interesting Statistic

[swordboy]

Every day, we get enough sunlight to power 27 years worth of the world's energy needs [nrel.gov]. Now, I thought about the implications of that. Obviously, we couldn't absorb/store the entire amount, but if we could put a dent in it, we'd have some global cooling. That is what this article is about.

On a similar note, the US could obtain all energy from the sun if it were to install a 200 mile square solar installation (assuming 15 percent efficiency... easily doable today). I say, put a dime of tax on each gallon of gas and use this money to subsidize solar generation - one of the only energy producers out there with net positive energy (more energy produced in the cell's lifetime than it takes to produce the cell itself). Hydro, wind and solar... I can't wait for the day.

On yet another related note, I'm in the process of building a solar/NiMH PC. I'm simply going to use store-bought NiMH rechargables to store excess daytime solar input. It certainly won't be cost effective but it'll be pretty high on the geek factor.

Re:So now...

[pe1rxq]

Dimming != Cooling

The article is about less sunlight reaching the earth's surface. Nothing about the earth cooling down....

Lets have an experiment:
1 Take a black (or very dark) plastic bag.
2 Go stand in the sun.
3 Pull the bag over your head (not to tight you are not going for a Darwin Award)
4 Stand for a while

You will notice the following:
1 You don't see much since the sunlight does not reach your eyes. (Lets call this 'dimming')
2 It gets hot in the bag. (Lets call this 'warming')

Conclusion:
You can have dimming and warming at the same time.

Jeroen

Re:weird

[Thavius]

Crazy talk nothing, I miss the very blue skies of even 15 years ago. Makes you kinda wonder what the effects of the combustion engine is really doing. After all there's more cases of cancer today, the whole global warming issue, and now this.

I'm sure we can use big scary reports like this to scare up alternative fuel research funds. Here's to hope.

This made me think of...

[mengel]

... this [confex.com] article which pointed out that in 2001 from Sept 11-14 when all the airplanes were grounded, there was a measurable increase in Diurnal Temperature Range (i.e. how much the temperature changes day to night).

So I blame jet airplane contrails.

Re:The unintended benefits of pollution

[Damek]

I'm no climate scientist, or climate engineer, but it seems to me that dark |= cold. A greenhouse can be dark but hot. The gasses keep in the heat, yet keep out the light. Venus springs to mind.

So I wouldn't see this as a benefit. I would think reducing pollution would increase light reaching the ground, but also help decrease how much heat is retained in the atmosphere.

I'm probably wrong, I suppose.

Re:Driving a Truck Through This One

[PhuCknuT]

Some counterpoints:

2) Astronomers tools have been improving and changing alot over the time period in question, and as a result their measurements may not be consistant enough going back for them to compare and notice the trend, especially if they aren't looking for it.

3) It's not necessarily just absorbed by the atmosphere, it could be reflected back into space by increased cloud cover.

4) In the long run it could be consistant with either warming or cooling, depending on the mechanism that is reducing the light levels (absorbtion vs reflection). There are other factors that could have a bigger impact on short term warming/cooling that could easily overpower the temp change from dimming in the 80s.

Re:weird

[lobsterGun]

You're probably just spending less time in the sun and not remembering it. One of the lines in the article mentioned that the sunny times are just as bright and warm as before; It 's the cloudy times that are darker. ...or I could be remembering it wrong.

Not enough data

[jason0000042]

The scientists making these observations are trying to make conclusions based on about four decades worth of research. It seems probable to me that global atmospheric trends take millennia to unfold. From the 60's till now probably accounts for a couple of data points out of the hundred or more needed to actually spot a trend.

Also, it seems that the assumption has been made that the sun produces constant output. I don't think we can make this assumption. The sun, as a system, is way bigger than our atmosphere. Until we have thousands of years worth of data, observed from outside the atmosphere, we can't prove that solar radiation is a constant. In fact, since solar flares temporarily increase solar output, you could postulate that thousand year trends in flare frequency and magnitude could affect the overall output of the sun.

So, while global dimming may or may not affect us in the short term (on the scale of centuries) and pollution is still bad (again very long term effects are unrecorded, but it's obviously very bad in the short term (again measured in centuries) and it is ugly), I'm still not all that concerned that the world is going to ice over or boil away any time soon.

Re:So instead

[tkg]

From the article: "The missing radiation is in the region of visible light and infrared..."

The three biggest IR absorbers in our atmosphere are CO2, water vapor, and ozone. Not necessarily in that order. Two are reportedly increasing with one decreasing. Draw your own conclusions.

Re:Interesting Statistic

[FJ]

There is no such thing as a free lunch.

Where do you want to dump the highly toxic chemicals that would be the result of the 200 square mile solar installation? Where are you going to put it that wouldn't make environmentalists, homeowners, or farmers go crazy and is still safe from natural disasters?

Wind is nice and clean, but it takes a lot of windmills to generate enough power to replace a power plant. Windmill farms are regarded as many to be ugly so people don't want them around their houses.

Hydro sounds like a great idea, but many people have a bias against hydrogen because of past mistakes with it. We can handle it much safer now, but it is still more dangerous than gasoline.

Also remember that the bigger you make something, the more difficult is to maintain. Snow, ice, earthquakes, tornados, and hurricanes can cause havoc on large equipment.

Everyone knows the nasty side effects of using oil & coal energy.

Don't get me wrong, I (like you) am looking forward to the day when I can throw away all gasoline powered devices, but we are not quite there yet. Hopefully it will be very soon.

Re:Rock On!!!

[pavon]

Good: We'll all have great skin for starts.

Actually, the article mentioned that it was visable and infrared light that was being blocked by an excess of clouds, not ultraviolet. Add to this the fact that our magnetic feild is becoming less polarized, in the process of flipping. As it does so there will be a bunch of little poles (places where the magnetic feild points into the earth not parrallel to it), guiding in additional radiation (and aroras, yay!). So if anything we will have more problems with bad skin not less.

Also, as the earth has warmed we have seen an the wet places getting more precipitation and the dry places getting less. And the article said the dimming was not constant, just that we have had more clouds and the clouds obviously block light, but the deserts, with no precipitation will have fewer clouds and thus less dimming.

My prediction: the world will be divided into radsuit wearing deserts desert dwellers, and mutant frog men, who live in swamps.

Re:Well of course

[rrkap]

Although you probably meant this as a joke, it might be. The amount of light people recieve affects lots of physical things. Chronically light deprived people (such as those who work night shifts) are heavier on average than those who don't. Lack of sufficient light also affects alertness and mood, and not only in those who have seasonal affective disorder.

That being said, I don't think a 10% reduction in light would cause a significant increase in obesity, but it might be an interesting experiment.

Re:So instead

[rrkap]

What I'm trying to get at is that if some factor (say cloud seeding from aircraft exhaust, a known phenomenon) is causing more cloud cover, it could well be that the total solar energy absorbed by the ground+atmosphere is substantially less than it used to be. The article wasn't clear on this point.

I agree with you. One thing that was hinted at (the mention that evaporation rates had decreased), but not discussed in the article is the possiblity of increased average humidity and the resultant cloud formation due to global warming. Higher humidity levels would tend to increase both reflection and absorption of solar radiation.

This is, of course, just a guess. I'd like to see more research into this.

Can you imagine the infrastructure cost for that??

[holy_smoke]

initial planning, design, materials and implementation, maintenance and repair...good idea but I doubt it would come close to paying for itself.

Re:So instead

[Becquerel]

cloud seeding from aircraft exhaust

This is the exact thought that i had. I remember reading some analysis that said there was a significantly larger temperature range recorded due to the reduction in cloud cover over the US in the days following Sept 11th, as all the planes were grounded.Link [findarticles.com]

It makes sense that on average the increase in cloud would also reduce the solar radiation.Has anyone plotted, global flight hours of jet aircraft against year on year dimming effect? Sounds like a likely answer to me, especially as roughly speaking jet travel started in the early 50's and has grown steadily since.

Some interesting details

[chrysrobyn]

The few experts who have studied the effect believe it's down to air pollution. Tiny particles of soot or chemical compounds like sulphates reflect sunlight and they also promote the formation of bigger, longer lasting clouds. "The cloudy times are getting darker," says Cohen, at the Volcani Centre. "If it's cloudy then it's darker, but when it's sunny things haven't changed much."

Please note here, much of this 10% is being reflected. There are people in this thread pointing out how untrue the observations must be because if 10% of the sun's energy was being absorbed by the atmosphere, the Earth would be getting a heck of a lot warmer than it is. Instead, the Earth should be getting 10% brigher from the moon or anywhere else in space. Particulates are reflecting and clouds are forming (which look very bright to me when I fly over them).

I've been wondering about this. Would global warming end up creating enough clouds to reflect enough energy from the sun that it balances itself out after a few decades? Or will global warming cause an imbalance in the sun's reflected energy after a few decades that causes a swing on the cold side? How much does the CO2 green house effect compare to the particulate / cloud reflector effect?

Mining H

[Anonymous Coward]

Actually you can mine H, it is a waste by product of most natural gas production. It currently gets wasted, but it can be mined

Seasonal addective Disorder

[MacGod]

I wonder if this will have any sort of noticeable effect on Seasonal Affective Disorder [discovery.com]. It has been shown that people feel more depressed with less exposure to the sun (this disorder is especially common in winter).

It's funny, everyone talks about how people seem sadder and grumpier "these days". I wonder if there could be an actual link to this "global dimming".

wind is quickly on its way to dominance

[js7a]

Wind is nice and clean, but it takes a lot of windmills to generate enough power to replace a power plant. Windmill farms are regarded as many to be ugly so people don't want them around their houses.

Actually, the entire electricity requirements of the United States could be served by wind turbines with a combined land-use footprint of only 14,000 acres, including enough grid redundancy to provide 99.5% uptime through long grid transmission to areas experiencing calm winds. (The remaining 0.5% backup could be hydro or whatever.) That area is only twice the size of the Stanford campus, and as large as the amount of Oak forest that California loses each year.

Some people consider turbines ugly at first glance, but more people want wind turbines in their neighborhood than want mercury-spewing coal smokestacks in their state.

Wind power is the fastest growning renewable industry [awea.org] and is expected to be the dominant form of power production in less than 30 years [google.com].

Please see the Windpower FAQ [windpower.org] for more information.