Is global warming a threat or an opportunity?

Threat

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by Robert Williscroft

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Everybody understands how a backyard greenhouse works. Sunlight shines through the glass and gets trapped inside as heat. Even on a cold winter day, the inside of a greenhouse will be warm and cozy. In fact, if you do not block some of the incoming light, it can actually get too hot. This is why one often sees whitewash on the window panes of a greenhouse. Some of the incoming light is reflected from the painted windows, and so less energy enters the greenhouse and it doesn't get quite as hot.

The Earth is a greenhouse. Our atmosphere is quite transparent to sunlight, except for ultraviolet rays, which are absorbed in the upper atmosphere to form the ozone layer. Light reaching the surface generally is reflected or reradiated as infrared energy what you feel radiating from a warm pavement. The atmosphere is less transparent to infrared than to visible light, so it retains much of this reflected energy. Just like in the backyard greenhouse, incoming energy is trapped in the planetary greenhouse.

Two atmospheric gases are especially opaque to infrared: carbon dioxide and water vapor. Their presence in significant quantities can dramatically affect global temperature. Other gases can have an effect - methane is a good example (if you raise cows you know what I mean) - but the main ones are carbon dioxide and water vapor.

Carbon dioxide is the result of combustion. It is emitted whether you burn leaves, run an engine, or simply live and breathe. Wildfires are the largest natural source of carbon dioxide, although volcanoes and forests contribute measurably. You probably learned in school that trees absorb carbon dioxide and give off oxygen. During the day this is true, but at night many trees give off carbon dioxide. Generating electricity by burning coal, oil, or gas is the largest manmade source of this gas, with automobiles a distant second. Other sources of carbon dioxide such as fireplaces and barbecues don't count.

Water vapor in the atmosphere is always present. The amount depends upon air temperature - the higher the temperature, the more water vapor. We are not talking about clouds here. Clouds consist of specks of dust surrounded by water droplets. Water vapor is a colorless, odorless gas that makes up a measurable percentage of the atmosphere. We experience this gas as humidity.

In the backyard greenhouse, the only way to increase the internal temperature is to find a way to retain more of the sun's energy that comes through the glass in the first place. Insulate the building. Use a different glass that lets more energy in and then doesn't let it back out. In our planetary greenhouse, this happens when the amount of carbon dioxide in the atmosphere goes up.

Carbon dioxide in our atmosphere has increased due to man's activities from as far back as scientists can measure. In recent times the increase has reached multiple exponential rates. It is not difficult to figure out why. With industrialization, our output of carbon dioxide has increased dramatically. Nearly every industrial activity involves the emission of carbon dioxide, either directly, or indirectly through consumption of electricity, since most common ways of generating electric power release carbon dioxide.

Researchers have created several mathematical models of our atmosphere. Since the 1970s, they have refined these models so that they have become increasingly predictive - until recently. None of these is entirely accurate, but all allow relatively accurate predictions for specific phenomena. All clearly predict global temperature increases from increased atmospheric carbon dioxide, although each gives somewhat different results.

It is quite difficult to measure global changes in temperature. Our planetary atmosphere is a very large dynamic system. Trying to establish an average increase of a fraction of a degree is a nearly impossible task. A five-degree temperature increase would be easy to measure, but the thinking is that a change this large would have such cataclysmic effect that we really would like to know what is happening before it goes this far.

One thing is very clear. As the atmosphere warms, it will hold more water vapor, which directly contributes to the warming process. Each of the models predicts a point where global warming increases uncontrollably - like a snowball rolling downhill. Increasing water vapor causes global temperature to increase dramatically and rapidly, once the trigger point is passed. Since none of the models accurately predicts this point, we cannot know how much carbon dioxide and water vapor will trigger this effect. It is clear, nevertheless, that once the effect is triggered, once global temperature begins to spiral upwards uncontrollably, there is nothing humankind can do to stop it - at least nothing we know about today.

Oceanic models predict sufficient melting of polar ice when this happens to raise worldwide sea levels by as much as twenty feet. A glance at any globe will make it clear what kind of disaster would result from this.

But wait a minute. Remember the backyard greenhouse? Remember the whitewashed panes? Let's go back to the model; let's take another look at the predictions. There doesn't seem to be any question that an increase in greenhouse gases - primarily carbon dioxide - will cause the atmospheric temperature to increase. In fact, the reason we have relatively balmy temperatures around the world, on average anyway, is because we are currently experiencing a stabilized planetary greenhouse. Let's buy into the models that predict an increase in temperature. We won't worry about how much. This increase, no matter how large or small, will produce a corresponding increase in atmospheric water vapor more for some models and less for others, but always an increase. This additional water vapor increases the greenhouse effect, which increases the temperature, which increases the water vapor, which . . .

But wait. What happens when the humidity goes up in the late afternoon on a sweltering day? Remember those thunderheads you loved to watch as a child? At some point, and this is not very well understood, atmospheric water vapor changes to clouds, and clouds block incoming sunlight. We have models for this as well. These models predict that if you generate sufficient cloud cover, it doesn't really matter how warm the atmosphere gets - it will cool rapidly. Depending on circumstances, this can carry the planet right into a massive ice age. Now understand that these models are just as predictive as the models leading to runaway high temperatures.

What we do not have yet is a way to connect these models into a whole system. It is not a matter of what you believe, or what you would like to see. Both sets of models are right; they all make accurate predictions. It's just that we have no idea at all how to get from here to there. We simply do not know what will happen when a runaway atmospheric greenhouse takes over. It could get very hot. It could get very cold. The effects could cancel each other out, leaving us about where we are now. We could experience short-term wild temperature swings.

The upward spiral of atmospheric carbon dioxide has been going on for a long time. Yes, it is accelerating, but all the models agree that, whatever happens, it will not happen overnight, or in a week, or in a month. Time is on our side. We have time to figure out what is really likely to happen. We have time to come to grips with the situation. We do know that the principal source of carbon dioxide is the production of electricity by burning fossil fuel. We also know that whatever happens, the trigger will be some level of atmospheric carbon dioxide greater than what we have today. It seems prudent, therefore, that we cut back on carbon dioxide production when practical.

The point is that we simply do not know.

Now, here is a monkey wrench that was recently thrown into the works. Ice cores taken from the Greenland icecap and from Antarctica going back 600 to 900 thousand years clearly indicate that global temperature changes are followed by changes in atmospheric carbon dioxide, not preceded by these changes. This seems to indicate that carbon dioxide is not driving the global greenhouse, despite what our models tell us. Obviously, when a model system breaks down in science, coming up with a new model is pretty important. Researchers believe that the overall greenhouse model still explains why our planet is balmy instead of frozen, but apparently something else drives the millennial variations in global temperature.

One of the fascinating things about scientific research is that things often come together in unexpected ways. While the global climate models were falling apart, astrophysicists were coming up with another explanation that seems to fit the data very well, and seems to be completely predictive. Our sun is a variable star, although the variability is sufficiently small that we don't notice it when we look at the sun in the sky. The variations, however, are completely measureable using modern instruments. Since the two longest of these cycles go back to pre-instrument times, information on them has been derived from other sources.

The "Bond Cycle" takes place over 1,100 to 1,500 years, the "Suess Cycle" over 200 to 500 years, the "Gleissberg Cycle" over 75 to 90 years, and the "Schwabe" sunspot cycle over 11 years. The first three cycles are actual increases and decreases in the sun's radiative output. The Schwabe cycle is caused by increases and decreases in the total amount of sunspots on the sun's surface, which seems to be related to inner planet orbital periods.

When the Schwabe cycle is at maximum, the sun puts out much more charged particles than when it is at minimum. As these charged particles flow past Earth, they are captured by our magnetic field. This, in turn, shields the Earth from much of the cosmic radiation that constantly bombards the Earth from every point in space. Independent research from Denmark and Israel has conclusively demonstrated that incoming cosmic rays are significantly responsible for cloud formation in our atmosphere the more incoming rays, the more cloud formation. Thus, in times of great sunspot activity, the earth has a significantly lower cloud cover which means it absorbs much more solar radiation the Earth gets measurably warmer.

When all four cycles come together on the high side, the Earth gets much warmer, and when they come together on the low side, the Earth gets much cooler. Right now the three longer cycles are moving toward a minimum, but the Schwabe cycle , while past its peak, is still allowing more than normal solar heat to reach the Earth's surface. By 2020, however, all four cycles will be at a historic low, and the planet will cool significantly.

It seems, therefore, that humans are not causing global temperature change, despite many indicators that had earlier seemed to say we were. From the mid-1950s to the mid-1960s, most new power plants were nuclear. During this period, the global increase of carbon dioxide was nearly halted. With the onset of worldwide movements (except for in France and the old Soviet Union) to limit nuclear power plants, carbon dioxide production resumed dramatically. But it seems that this is not anything to worry about, at least not in the short term. Only when human carbon dioxide production overcomes the dramatic effects of the sun's cycles, will our activity have any global climate significance. This may never happen.

The sky is not falling here, folks. We will neither fry nor freeze tomorrow, and maybe nothing at all will ever happen. It does seem kind of silly, though, to burn oil, coal, and gas when they could be used as raw material for so many other things we need, especially since we really do have a very safe, efficient, renewable way to generate electricity.

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