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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.
I'm not sure where you live but in the UK the expression is definitely "on 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.
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.
There are ominous signs that the Earth's weather patterns have begun to change dramatically and that these changes may portend a drastic decline in food production- with serious political implications for just about every nation on Earth. The drop in food output could begin quite soon, perhaps only 10 years from now. The regions destined to feel its impact are the great wheat-producing lands of Canada and the U.S.S.R. in the North, along with a number of marginally self-sufficient tropical areas - parts of India, Pakistan, Bangladesh, Indochina and Indonesia - where the growing season is dependent upon the rains brought by the monsoon.
The evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it. In England, farmers have seen their growing season decline by about two weeks since 1950, with a resultant overall loss in grain production estimated at up to 100,000 tons annually. During the same time, the average temperature around the equator has risen by a fraction of a degree - a fraction that in some areas can mean drought and desolation. Last April, in the most devastating outbreak of tornadoes ever recorded, 148 twisters killed more than 300 people and caused half a billion dollars' worth of damage in 13 U.S. states.
To scientists, these seemingly disparate incidents represent the advance signs of fundamental changes in the world's weather. Meteorologists disagree about the cause and extent of the trend, as well as over its specific impact on local weather conditions. But they are almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century. If the climatic change is as profound as some of the pessimists fear, the resulting famines could be catastrophic. "A major climatic change would force economic and social adjustments on a worldwide scale," warns a recent report by the National Academy of Sciences, "because the global patterns of food production and population that have evolved are implicitly dependent on the climate of the present century."
A survey completed last year by Dr. Murray Mitchell of the National Oceanic and Atmospheric Administration reveals a drop of half a degree in average ground temperatures in the Northern Hemisphere between 1945 and 1968. According to George Kukla of Columbia University, satellite photos indicated a sudden, large increase in Northern Hemisphere snow cover in the winter of 1971-72. And a study released last month by two NOAA scientists notes that the amount of sunshine reaching the ground in the continental U.S. diminished by 1.3% between 1964 and 1972.
To the layman, the relatively small changes in temperature and sunshine can be highly misleading. Reid Bryson of the University of Wisconsin points out that the Earth's average temperature during the great Ice Ages was only about seven degrees lower than during its warmest eras - and that the present decline has taken the planet about a sixth of the way toward the Ice Age average. Others regard the cooling as a reversion to the "little ice age" conditions that brought bitter winters to much of Europe and northern America between 1600 and 1900 - years when the Thames used to freeze so solidly that Londoners roasted oxen on the ice and when iceboats sailed the Hudson River almost as far south as New York City.
Just what causes the onset of major and minor ice ages remains a mystery. "Our knowledge of the mechanisms of climatic change is at least as fragmentary as our data," concedes the National Academy of Sciences report. "Not only are the basic scientific questions largely unanswered, but in many cases we do not yet know enough to pose the key questions."
Meteorologists think that they can forecast the short-term results of the return to the norm of the last century. They begin by noting the slight drop in overall temperature that produces large numbers of pressure centers in the upper atmosphere. These break up the smooth flow of wes
The premise is this:
We have global dimming, caused by particulate pollution, the world is getting less light than it used to.
Despite this, we have global warming, caused by greenhouse gases, the world is getting hotter.
Therefore, if we clean up the particulate pollution without tackling the greenhouse gas problem, then the global warming could become more pronounced because of the increased sunlight reaching us.
I didn't RTFA but I did WTFP (Watch the program).
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
"The evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it. In England, farmers have seen their growing season decline by about two weeks since 1950,"
r _1 6.shtml
No, it has increased by about 2 weeks in that period.
http://www.tyndall.ac.uk/media/press_releases/p
It's true that popular media accounts of the holocaust tend to include some apocryphal material -- the soap story, the lampshades, sometimes lumping all the camps together as if they were run the same way. It's also true that the weight of the evidence has convinced every credible historian on the planet of the fact that the holocaust occurred. No one smoking gun is going to demonstrate conclusively that it did, and it's possible that any given fact might be questioned -- but the big story is there and cannot be wished away.
I think there's a danger, when we start laying into vague targets like "the media," that we'll confuse the quality of the messenger with the truth of the message. And that ain't always inadvertent; holocaust deniers consciously manipulate the slightly-off pop news stories to question the whole history.
I'd agree completely with your basic mutterings about, oh, newspapers, and the 10:00 local news, and to some extent magazines like Discover. But behind Discover's "Top 100 Science Stories of 2004" article, which chose global warming as its number 1 story by the way, there is a truth: the overwhelming majority of scientists today are convinced beyond any reasonable doubt that global warming is now occurring. Get just a nudge away from the low pop sources -- to Scientific American, which is a little more highbrow among the pop stuff, or then to Nature -- and you'll see that, loud and clear, with less boneheaded news manner to the narrative. The evidence is so overwhelming that even the Bush administration, laden with energy industry biases as it clearly is, has conceded that the warming's happening.
For anyone to wish the actual phenomenon away with a "this is a big complicated phenomenon, and the pop media's suggesting it has simple explanations" would be an exercise in wishful thinking. It'd be on that level of silliness we're bemoaning in "the media," wouldn't it? At that point we're talking tortuous self-deception at the level of creationism -- speaking (indirectly) of another overwhelming truth that people try to dispel by "debating" at a pop-cultural level...
"Fundamentalism" isn't about divine morality. It's about human authority.
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.
Apparently this has been seen in Holland among people who use greenhouses to grow vegetables, that for some reason the greenhouses weren't staying as warm as they used to. This effect is one of the strongest confirmations of dimming. Thad Beier
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