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BBC on Global Dimming
linoleo writes "The BBC reports that the amount of solar energy reaching the Earth's surface has declined significantly between the 1950s and the 1990s, apparently due to particulate air pollution. Scientists are worried that this global dimming may be disrupting the pattern of the world's rainfall. Most alarmingly, it may have led us to greatly underestimate the greenhouse effect: with particulate pollution being brought under control, a global temperature rise of 10 degrees Celsius by 2100 could be on the cards, rendering many parts of the world uninhabitable." The lengthy transcript of the show is available.
Great - the UK might be a nice place to live by then! You can keep your Med coasts in France, and Spain - arrid deserts, they'll be in 100 years. Invest in Dorset, I say :)
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Really, this article jumps to far too many conclusions with far too little data.
And with exactly the same certainty as this statement expresses, if I dance around in a circle every Thursday night, an average rainfall increase of 17 inches could be in the cards!
Global temperature has risen, fallen, and risen since 1880, even though carbon dioxide levels have steadily risen. In fact, for 30 years between 1940 and 1970 the temperature dropped all that it had gained in the past 50 years. Overall in the past 120 years global temperature has risen 1 degree celsius.
One brings into question the level of accuracy from third world countries in the early 1900's. When one looks at the average temperature in America it tells a different story. From 1880 to 1920 temperatures dropped 0.5 degrees celsius. From 1920 to 1934 temperatures rose 0.9 degree celsius. From 1934 to 1976 temperatures dropped 0.8 degrees celsius. From 1976 to present temperatures have risen 0.7 degrees celsius, for a net total of 0.3 degrees celsius in 124 years.
And at the same time the amount of energy put out by the Sun is increasing.y /sun_output_0 30320.html
http://www.space.com/scienceastronom
http://www.hypography.com/article.cfm?id=32945
Yes, essentially the program says that we are getting less sunlight and the world is getting hotter.
They say we are getting less sunlight thanks the visible pollution in the atmosphere which encourages cloud formation in a fashion which reflects more sunlight than clouds formed around natural pollutants such as pollen.
We are making big steps to clean up the visible pollution and therefore bringing the amount of sunlight back to normal levels.
However given that the world is still warming up despite the cooling effect of this reduction of sunlight they are supposing this must mean that global warming is in fact a lot more powerful than they first thought since we can still detect noticable warming despite a reduction in sunlight.
As we clean up more and more of our visible pollution without cleaning up our CO2 pollution we may face a much bigger temperature increase than we were expecting.
The program was fairly sensastionalist and towards the end went through some highly speculative "we are all going to die" scenarios. I would have liked them to concetrate more on the evidence they have for global dimming and maybe some contrary evidence or any doubts the scientific community may have about the results of the scientists they did show.
To suggest that little or no climate changed is being "caused" by something man made without backing it up goes beyond the bounds of irresponsible ...
Excuse me, he's suggesting that both are causing a massive affect, the most noticeable part of both canceling each other out. Let's say we have an egg on a roof. We push it one way, it falls off. We push it the other way, it falls off. He's saying we're pushing it both ways. It's not going to fall off right now because it's balances but if we drop the force on one side, it'll fall off. Incidentally, not suggested by him but by me: It can crack where it stands.
"Waking up" to something simply means to take notice of it. Rejecting the obvious truth has nothing to do with it. It's impossible for scientists to keep track of all the minutiae that comprise the universe.
Secondly, I don't think the journalist came up with that conclusion. Scientists did, and the journalist is just reporting it, which incidentally is his job.
The media can be irresponsible at times, and does make mistakes. But reporting the findings of scientists, like this, is not one of them, even if the conclusions they have reached do not agree with yours. After all, if they didn't report it, and thus did not feed the "pop-sci crap" to the public, others would feel they're not doing their job. So relax.
I saw the actual programme, and it was far from Pop Science. In paticular the 9/11 data was fairly stark in underlining the impact of removal of aeroplanes from the skys for just two days over the US.
But of course, we could all just bury our heads in the sand and claim it is pop science.
The programme went into a "light" amount of detail, but mainly said this was something that required more research but was on the scary side of its implications. They certainly didn't say it was cancelling out the greenhouse effect, they claimed it was MASKING its impact, a very different claim.
The real trouble is that anything that claims there is a global warming problem caused by pollution comes up against one basic problem:
The US Energy Policy.
To my mind these elements equate to the old "the odds of this thing going critical if I drop it are pretty low" school of porting nuclear materials. The odds may be low, but the cost is huge, hence the reason you don't just lob the stuff about.
So it was a lightweight programme, well yes it wasn't the Open University, but "Pop Science", not really. It definately played for some dramatic effect, but there was evidence for those who were watching.
An Eye for an Eye will make the whole world blind - Gandhi
This would certainly explain something that has bothered me for some time. I am cursed with a memory that remembors images with clarity I wish I didn't have. I have noticed that images from my childhood, (admittedly decades old now), seem to be 'brighter' than those I have of recent times. It's not a 'hazy' difference as you would expect. It is that the images seem 'brighter' to me. If I revisit the same location, it's not the same, even on a bright sunny day.
I know it probably seems ludicrous to most people. I don't talk about things like that normally, because people just dismiss you as nuts, but it's real to me. I am curious, are there any others out there with long term photo memories that exhibit the same thing as I see?
As a student of global climate change (the warming part has long since been dropped), a few scientific facts need to be added.
#1 - Global climate change means exactly that - it will get warmer in some places, colder in others. And while idyllic thoughts of long summers around Great Bear Lake might spark a real estate boom, there will be a few downsides to the change. Disease vectors love warm weather, which means that pesky malaria (so, caused by bad air after all!) will become a feature of northern summers.
#2 - The problem of increased warming due to pollution reduction is well known. These are relatively large particles being talked about, the ones that reflect sunlight back out (like after a volcano) - this does not include the smaller particles that have a much larger "green house" effect. Thus as we reduce large particulate pollution, the speed of warming will indeed increase.
#3 - The "wait and study it so we know what is happending" arguement. This arguement has many supporters, including those who love discount rates. The fact is, once a glacier begins to melt (ahem, Greenland), there will be no way to stop it. Mind you, it might take a few hundred to a few thousand years... so maybe 2k'ers get the last laugh?
sig? what sig? i didn't see any sig...
Fortunately, the models & supercomputers are just slightly more complex than your fallacious argument. Merits of the BBC presention nonwithstanding, the theory that is advanced is not inconsisent with the observations at all. (Any of those could might be wrong, but that's a different story.)
... errr... well, greenhouses and shading/clouds. They may may have opposite effect on temperature, but they are not matter & antimatter. The theory of global shading has two major implications:
Replace the common useage of' 'Global warming' as 'greenhouse effect', and then park GW for the time being. If you don't understand this, consider that a car with windows rolled up acts a like a greenhouse. Sit in the shade and you might get a little uncomfortable, but not seriously so. Move out of the shade and... toast. In both cases there was complete Car Warming, but you can easily see the two major and independent factors. The make of the car does *not* matter...
So, greenhouse effects and shading are as different as
1 - Our models are wrong. Shading deducts X amount of energy which means that our estimate for the strength of greenhouse-effect is probably off by X.
2 - Ironically, shading helps, in the sense that we get less total increase in temperature - but it isn't all good, and it isn't that simple. Most importantly, reducing shading by without reducing the greenhouse effect would is tantamount to raising the temperature - which is a big no-no.
Incidentally, the particles are doing exactly what you suggest, but the implication is not what you understand it to be. One of many observations was that during flight-less days post 9/11, it didn't just get "warmer", energy flow & flux (both ways!) increased. Warmer days, cooler nights.
Global warming is a train-wreck towards which we're all headed, and I guess Big Bro' wants to downplay it to avoid panic.
YOU CAN (AND SHOULD) READ THE ARTICLE YOURSELF AT http://www.bbc.co.uk/sn/tvradio/programmes/horizon
Mad poster wrote: "I like when news outlets use this type of language. 'Woke up'."
The article does not try to imply scientists are closed-minded or doddards. The portion of the article "mad poster" is referring to is simply pointing out that light-meter measurements indicating the Global Dimming pattern did not receive much attention until they had been corroborated by a completely different method of measurement: water evaporation rates.
Global Dimming required corroboration by multiple methods of measurement because it was very surprising, very surprising for two reasons: (1) the effect was so large that scientists found it hard to believe nobody had mentioned it before (extraordinary claims require extraordinary evidence), and (2) it seems to contradict Global Warming.
These two kinds of measurements, light-meter, and water evaporation rates, have been made at least back to the 1950's, and both indicate that the amount of sunlight reaching the Earth's surface has declined by 10 to 30 percent, depending on location, from the 1950s to the early 1990s.
Mad poster wrote: "To suggest that little or no climate changed is being 'caused' by something man made without backing it up goes beyond the bounds of irresponsible journalism
I'm not even sure what the first sentence means. The article didn't give evidence why humans aren't causing climate change? What? He was in a hurry to be one of the first posts, I suppose -- before a TRULY informative post was submitted, which would make it harder for the slashdot disinformtion network to manipulate the modding process.
The article actually presents the following evidence that Global Dimming has been caused by pollution particles in the air:
Project INDOEX found a 10 percent reduction in sunlight reaching the Earth's surface due to pollution particles in the air. This was attributed to pollution particles making clouds more reflective. Clouds are formed by water vapor condensing on the surface of airborne particles. The presence of air pollutant particles causes these droplets to be smaller and so more reflective. The droplets are smaller because there are ten times as many particles for droplets to form about. Why smaller droplets are more reflective the article does not say.