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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.
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.
Global Dimming Dec 18
Hint to editors: I obtained the links by doing a Slashdot search for dimming. Also checked that a Google site:slashdot.org search also turned up results.
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
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.
depending on all the factors, more of the heat is lost to colder "space" in one situation as opposed to another. We get heat from three sources, internally from the planet itself, man made burning and normal large scale surface burning (lightning strikes to forest for example), and solar radiation. The atmosphere acts as an insulating blanket and keeps it more moderate than not, but it's not a *perfect* insulator, and tiny variables cause profound changes. In one situation with the increase in greenhouse gasses-including water vapor-the heat stays trapped longer, resulting in higher over all median temps. In another, because of a higher level of reflective particles in the upper atmosphere, we have less heat gain from solar radiation, but the heat loss is about the same, so it gets colder as a median. The point in the research is that the particulate matter tends to partially cancel the effects of "more" gasses in the atmosphere, suggesting that if we over reduce just one component in the atmosphere while the others are increasing, we could actually make it worse, not better. an interesting concept that is logical though. In this case we are getting more of the gasses and reducing the particulate matter lately due to enacted controls on how we burn things on purpose, so it would tend to then again increase the median surface temp because the envelope would be receiving more heat again.
It's a dang yo yo in other words.
The effects are profound though, about all the scientists agree that even small temp variances taken as an average over some years duration tend to then cause shifts in localised/regional climate some places much colder or drier than normal, others hotter and wetter, sea levels go up and down with how much of the water vapor is trapped as sea ice or glaciers as opposed to free flowing, etc.
We as humans get used to relatively short geological time spans and adjust and adapt our society around our surroundings obviously, so if it changes radically one way or the other it can cause any number of what to us are adverse conditions.
I think the main point is that it doesn't take extreme variables to get profound changes, and that said changes can happen rapidly, more rapidly than they used to think. We are seeing it now, there is absolutely zero doubt the poles are getting warmer and the ice is melting there. And the more that melts, the faster the remaining ice will melt because of the albedo effect. That will continue until such a time as it is "too much" for the planet to absorb in that direction, and it will start to refreeze. Back and forth, been going on for millions of years, just now they think we could be real dang close to a tipping over point in this yo yo travel.
The planet seems to have a remarkable ability to self regulate towards a median, it's the swings back and forth that are the worry and the extrmes in the travels back and forth make it "less inhabitable". We as humans tend to like it better in the middle regions there, that's how we can even handle it and thrive.
We are sort of spoiled now being in the middle of a relatively temperate time as far as the needs of humans are. With the polar caps melting, this will greatly reduce the "averaging" effects and cause some pretty dramatic temp variances in places now that are considered more moderate, and those areas are where the bulk of the humans live.
I think the real main problem that we are having in these sorts of discussions is that there is no single one noun to describe it, and various people tend to pick one or the other and try to make that data fit that noun, and it can't be done.
It is *both* a global cooling and a global warming phenomenon that occurrs,simultaneously, just that the actual perceived results are felt differently depending on where anyone "you" is standing geographically. To arctic and antarctic dwellers, they are experiencing "warming", to others in the more temperate zones, it will be getting colder. And areas that are used to x-am
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.