Listen up, guys. This is important. In fact, it may be the most important news story you hear this year. It’s about the relationship between “Global Warming” and “Global Dimming” — which I’d never heard of until last night.
NOVA broadcast a TV show about it that everyone – repeat, EVERYONE — needs to see. Since you probably won’t see it, I took notes, which I’ll present herewith.
You may already know that the earth's temperature has increased by .6 to .8 degrees Celsius. Well, that’s only part of the story, which NOVA recounted by beginning with September 12, 2001, when a climate scientist named David Travis noticed that the Wisconsin sky was unusually clear. This meant something special to him, since he had been studying airplane “contrails“ for several years. After 9/11, almost all airplanes in the US were grounded, so there were no contrails, though the atmospheric conditions were ideal for creating them.
Next we go to Israel, where 40 years ago another scientist, Gerry Stanhill, had begun measuring the intensity of the sun in various parts of Israel so as to determine how much water was needed for plants. In the 1980s, Stanhill had updated his measurements and was astonished to find a reduction in the sunlight by about 22 percent. Though he published these findings, other scientists ignored them.
But in Germany, Beate Liepert was studying the solar levels in the Bavarian Alps, and she too found remarkable reductions. Both Liepert and Stanhill independently began searching records around the world and found declines everywhere – in some places as little as 9 percent, in other places as much as 30%. Overall, the worldwide amount of sunshine had declined by 2-4 percent. This was puzzling. If there is less sunshine, the world should be cooling, but in fact it is heating up.
Next NOVA took us to Australia, where climatologists Roderick and Farquhar had been recording the “pan evaporation rate.” This term refers to the process of measurement that had been followed worldwide for about 100 years. Scientists pour sufficient water into an outdoor pan each day to bring the level up to that of the previous day. The difference is the amount that had evaporated. The Australian researchers found that evaporation is decreasing. Why, when the earth’s temperature is increasing? Because heat is not the main determining factor; sunlight is. It’s the impact of photons hitting the surface of the water. By accident they discovered an article in Nature magazine titled “Evaporation is Losing its Strength.” Measurements in Russia, Eastern Europe, and the United States matched the findings of Liepert and Stanhill; sunshine is declining everywhere.
Onward, to the Maldive Islands in the Indian Ocean. These islands run from north to south, with the northern ones receiving polluted air blown from India, and the southern islands receiving pristine air blown from Antarctica. The climatologist Veerabhadren Ramanathan undertook a major international study to document and explain these differences. The difference between the amount of sunshine reaching land in the northern and southern Maldives indicates the extent of the “global dimming.” It turned out to be more than ten percent. Ramanathan had expected it to be between half a degree and one degree Celsius, so these results were ten times the predicted amount.
What is “global dimming”? It is the amount of sunlight filtered out or reflected back into space by the visible pollution in the air—soot, or sea salt, say, or the clouds produced from contrails.
What causes it? Particles of pollution. Water droplets collect on particles, then often bump into and merge with other particles that hold water, getting larger and larger until they may fall as rain. There were up to ten times as many man-made particles in the northern Maldives as in the south. Numerous small droplets reflect more light than fewer big ones, so the polluted clouds were reflecting more light back into space, preventing the heat of the sun from getting through. This is the same thing that goes on all around the world – especially today in India and China.
These more reflective clouds can alter the world’s rainfall, with tragic consequences. For 20 years in the 1970s and 1980s, the belt of clouds around the equator failed to move northward, as they do ordinarily. As a result, the Sahel in Africa received no monsoon rains – the source of water on which they depend. Drought followed, causing suffering and death of 50 million people, notably in Ethiopia.
But why had the rainbelt failed to move upward? According to Leon Rothstein, pollution from North America and Europe had been blown across the ocean as usual. But when Rothstein took account of the Maldives findings, he could recognize that the polluted clouds had stopped the heat that would have drawn the raincloud belt northward. Others had supposed until then that the explanation must have had something to do with global warming, but in this case, it was the cooling effect instead – global dimming.
As Ramanathan points out, there are billions of people in Asia whose lives are at stake. We have to cut down on air pollution, if not indeed eliminate it altogether. In the rich countries this is happening because of such inventions as catalytic converters on cars, smokestack scrubbers, and the like. That is probably why the monsoons have returned to the Sahel. But the growing economies in Asia also are suffering from pollution, with huge numbers of respiratory diseases. Those countries will probably reduce their pollution too, since it is much easier to achieve than the reduction of CO2. But now we see that pollution, for all its horrible qualities, has been protecting us from an even greater threat: accelerated global warming.
It was Travis who showed us a world without global dimming. He had been studying contrails for fifteen years. Water droplets produce clouds that can blanket the sky. In the southwest US, there are photos showing them covering half the sky. But to determine how large their effect was, Travis needed to find a period when the conditions were right for contrails to form but when there were no flights. There had been no such period until the three days following September 11, 2001. And suddenly Travis could collect data from all over the US, comparing it to other measurements taken over the past thirty years. His particular interest was in the temperature range – the differential between the highest and lowest temperature within a 24-hour period. This turned out to be much greater than expected. However, Travis knew that contrails are only a minor contributor to global dimming. If they could have this much effect, then the total amount of global dimming caused by all factors together must be huge.
Now NOVA shifts to a British climatologist, Peter Cox, who is formulating models to depict these phenomena. He explains that there has been a tug of war between two factors influencing global temperature: greenhouse gases, which produce warming effects, and pollution, which produces cooling effects. Which is stronger?
We are pumping out greenhouse gases now with enough energy to light a 100 watt bulb ever six square meters over the entire globe. That means, we’re producing 2.6 – 3 watts per square meter.
How much effect is global dimming having? In 2002 NASA launched the aqua satellite with instruments capable of measuring pollution. It seems that there’s a minus 1.5 watt effect per square mater – i.e. a cooling effect of one degree Celsius. So while greenhouse gases have been adding 2.6 watts per square meter, global dimming has subtracted 1.5 watts – more than half the effect of the greenhouse gas emissions, thus masking the gases’ emissions. Without this masking, we would have noticed the warming earlier and would have had more time to respond.
If we keep bringing particle pollution down, this will greatly benefit human health, but if we keep on pumping out greenhouse gases, we could worsen the effect on global temperature. This would soon cause a heating by more than 1 degree Celsius – which is more than we have seen already. And by continuing, the temperature could rise by 2-3 degrees Celsius or 5 degrees by mid-century. An increase of two degrees guarantees disaster.
We have already seen the Greenland ice shield melting. (Today’s Globe and Mail, page A3, has this heading: “Dramatic collapse of ice cap stuns experts: Area almost twice as big as Britain disappears in the last week alone as levels of sea ice in Arctic reach record low.” Once this starts, it is out of our control
Earth was three degrees warmer some three million years ago when there was a natural increase in gases in the atmosphere. This raised sea levels 25 METERS higher than today. At the rate we are going, most of New York City, Washington, DC, Florida, and Louisiana will be under water. The Amazon rainforest will dry and burn, releasing more CO2 and accelerating global warming.
Most current models do not take account of global dimming. Even the scientists have been misled by it. Cox says we may be underestimating the heating effect of future global warming , and that by 2100, the temperature could rise by 10 degrees Celsius. Many plant species would die. In the far north, methane hydrates would melt. Some or all of the 10,000 billion tonnes of methane would be released. That is a greenhouse gas eight times stronger than carbon dioxide. When this last happened 50 million years ago, the temperature was increased by 13 degrees Fahrenheit.
Within less than a decade we will pass the point of no return. To achieve less than 1 degrees Celsius, we’d have to make greenhouse gases decline by mid-century. As it is, we are experiencing increases of over 2 percent per year.
In other words, what we are facing is probably the greatest emergency in human history. NOVA does not tell us exactly what we should be doing about it. Nobody knows. However, I have an opinion. I believe it is too late to turn this around by any conservation measures that have any chance of political acceptance in a free society. I’m not saying that we shouldn’t take radical steps ourselves, beginning by holding meetings with our friends, co-workers, and neighbors. But I think that high-tech inventions MAY make a essential difference, if we support them quickly and with big money.
I’ll only mention three approaches, though there are several important high-tech projects being explored. First, there’s the possibility of creating “artificial trees” to remove carbon from the ambient atmosphere, then hide it underground. This approach is being developed by Professor Klaus Lackner at Columbia University. He says that to make it economically viable, we’d have to introduce a carbon tax or ration carbon emissions. I personally would like to work on promoting a carbon tax. It wouldn’t add to our total tax burden, for it would reduce income taxes while making us pay more for anything that emits greenhouse gases. If you Google Lackner you will find several sources explaining what he is doing. Or you can listen to his Q and A on NPR at: http://www.npr.org/templates/story/story.php?storyId=10621219
Lackner himself says that only solar can suffice in the long term as an alternative to fossil fuels, which are emitting greenhouse gases. There are some solar innovations that will shortly multiply by four or five the efficiency of solar panels. I cannot describe them to you now but you will have more this fall.
Finally, there is a lot of interest in hydrogen as fuel. There’s one fellow in Florida who can burn salt water in radio frequency fields, but it is controversial whether there’s any net energy payoff. (See the preceding blog about that.) And there are inventions that would possibly make hydrogen more accessible. See: http://www.npr.org/templates/story/story.php?storyId=10621219
All I intend to say here is that we cannot go on living as we have done before. We are stewards of this planet and must protect it with all the force of our intellect and physical capacities. I hereby sign up for the task. Do you?