Action for a quick stop of global warming and dimming:
REDUCE THE FORMATION OF BLACK CARBON

Logical analysis of climate events and facts

Jože Podboj
2 June 2008

Abstract:

A series of highly adverse climate events that have been occurring in recent years has eventually made us realize that global warming is taking place on our planet along with gradual global reduction in the amount of direct irradiance reaching the surface of the Earth. Logical analysis of these phenomena and physical facts indicates that the substance which can be the cause of such effects can only be an aerosol, consisting of black-coloured particles, apt to suspend for a long time – thus black carbon or soot. Because there are probably enough such black particles in the atmosphere to generate climate changes of such proportions the formula for stopping the climate crisis is to REDUCE THE FORMATION OF BLACK CARBON. The pollutants of highest concern are the aircraft engines operating at high altitudes, where due to the high expansion very tiny particles are formed, which are capable of remaining suspended for very long periods of time. Formation of black carbon can be reduced by mileage reduction strategies or by engine quality improvement and alike. The effect of such actions will very soon prove to be efficient.

In the present article, I present strong arguments for the hypothesis, that it is soot which is the main culprit.

Introduction – the observed climatic changes

In recent years the adverse climate changes have been giving us more and more troubles. Disastrous extreme weather events, such as storms and hurricanes, floods as well as droughts, have been reported more and more frequently, deserts are growing larger and ice sheets smaller. Such disasters have been taking toll of more and more lives and entailing substantial economic fallout.

It is generally believed that this is due to the global warming. The Intergovernmental Panel on Climate Change (IPCC) is reporting that the average global surface air temperature has increased by 0.74 degrees C° over the last 100 years and assuming that this has been most likely caused by the increasing anthropogenic emission of greenhouse gases in the atmosphere (1). What is meant here is mainly CO₂. CO₂ concentrations, measured at Mauna Loa, Hawaii (altitude: about 4000 m; geographical position: in the middle of the Pacific) from 1958 till this day are the following (2):

In 1958: 315 ppm; in 1980: 337 ppm; in 1990: 354 ppm; in 2000:369 ppm; in 2007:383 ppm.

The property of greenhouse gases is to absorb the upgoing thermal radiation from the Earth’s surface (whereas they can not absorb the direct solar radiation, neither can they the reflected solar radiation) and so, as a sort of covering prevent cooling and cause warming respectively. However, in spite of the many years’ international endeavours to reduce CO₂ emissions and meet the Kyoto Protocol targets, it is more and more obvious that this provision is not enough. Although it has been more or less successfully implemented for several years, there are no results. In my opinion the main problem is not CO₂ at all. I think that it is the air pollution which plays decisive role. Also, it has to be emphasized that CO₂ is not a pollutant at all. We must not forget that this is the gas, indispensable as primary material to carry out the process of photosynthesis, converting light energy to potential chemical energy, which enables life on Earth. Therefore I find somehow unnatural to reduce emissions of CO₂ by brute force. It seems unlikely that a gas, whose concentration amounts to only 383 ppm or approximately 0.04 volume percentage, could be the cause of such significant additional greenhouse effect, just on the account of its increased share in total emissions. In my opinion the global warming is caused by rapid industrial growth and even more rapid growth of vehicle and air traffic, polluting our atmosphere.

Along with global warming another alarming phenomenon has been appearing: global dimming, i.e. gradual reduction in the amount of global direct irradiance at the Earth’s surface. This phenomenon has been observed since 1950, as systematic measurements were started. Such measurements being very intricate, these extreme results should be taken with certain reservations. In view of a large number of measurements it is difficult to assess which value is the right one (3), (4), (5), (6), (7), (8), (9), (10). According to prevailing opinion, the amount of direct irradiance has been decreasing with the average rate of 2-3 % per decade. This means a total of 10-15 % in 50 years, which should be the reason for serious concern.

It must be borne in mind that the solar irradiation is of utmost importance for all species of life on Earth, since considering globally, it means the only source of energy. The Alpha and Omega of our existence. Reduced irradiance at the surface or dimming means that by lack of light photosynthesis is impeded on Earth, that less water is evaporating from the oceans and other surface water bodies. Moreover, the aggregate global temperature should decrease and not increase, as it has been established.

Photosynthesis is a chemical reaction using energy of light to produce glucose and oxygen from water and CO₂:

6 CO₂ + 12 H₂O + light energy → C₆H₁₂O₆ + 6 O₂ + 6 H₂O

and is fundamental to life on Earth, to flora and as a result, to fauna ashore and in the water. Without this reaction there would not be any oxygen in Earth’s atmosphere at all. The reduced irradiance at the surface means slower growth of overall vegetation, agricultural crops as well as forests and other vegetated areas ashore and phitoplancton in the sea, supplying sea animals with food. Photosynthesis can be simply defined as conversion of light energy into chemical energy by living organisms. Its intensity depends on the amount of irradiance, concentration of CO₂ and temperature. This means that at certain temperature and certain amount of irradiance a limit concentration of CO₂ occurs in the atmosphere, which represents the threshold at which the reaction is initiated. In our case the reaction space is the Earth’s surface and the whole atmosphere. This reaction space is constantly supplied with new amounts of the gas CO2, generated by exhalation of humans and animals, by putrefaction of wood and combustion of wood, coal, oil derivatives etc. However, as soon as the limit concentration is exceeded, all these amounts of gas are converted by photosynthesis into plants and phytoplankton. Since the amount of irradiance, as it has been established, is now lower than in past decades, as a result the limit concentration of CO₂ is increased and can not be reduced by restriction on CO₂ emissions! With the same temperature levels it could only be reduced by increasing the amount of irradiance!

For the time being we have not yet been badly affected by slower growth of plants as a result of reduced irradiance at the surface, since all the inflow of CO2 can still be processed by photosynthesis in due course. We are much more directly affected by reduced evaporation from the oceans and other surface water bodies, seeing that meteorologists have by means of special measurements established that decrease in the amount of irradiance at water surface proportionally reduces the evaporation of water. Based on this, inferences can be made that in fact, nowadays 10-15 % less water is evaporating from the oceans than 50 years ago and hence, accordingly less precipitations. This results in unusually long spells of draught, which have impact on agriculture. There is a lack of potable water. Desert areas are growing on the account of green areas.

Soot as the main culprit

Contrary to expectation that in view of the established global dimming the global temperature should be on the decrease, its trend is just the opposite. There is no more genuine winter weather. Meteorologists keep on reporting new high temperature records. Glaciers everywhere in the world have been shrinking rapidly. There is no doubt that global temperature has actually been increasing, and relatively rapidly. The point is that global dimming and warming are taking place simultaneously. The substance being able to cause such effects can only be aerosol of black colour, with the capacity of lasting floating. This is of course, black carbon or soot.

Black carbon (BC) is by-product of incomplete combustion of oil derivatives and other organic substances: coal, wood, leaves and also cigarettes, etc. Mainly it is the black constituent of engine exhausts. BC is amorphous form of carbon, having extremely large surface in proportion to its volume. Therefore it is easily floating aloft and intercepting large amounts of direct and reflected solar radiation as well as upgoing thermal radiation from the Earth. Owing to its exceptional property to be completely black, in accordance with the definition of black bodies, it absorbs all this radiation, it does not let anything through and does not reflect anything! It converts it into thermal energy, and mainly give it away to adjacent air molecules through conduction and convection. Thus black carbon particles function very much like greenhouse gases, but much more effectively, since they do not absorb only thermal energy but also direct solar radiation and the one reflected by the Earth. Included is the total amount of BC: BC from air traffic, terrestrial traffic consisting of various engine exhausts as well as soot from fires and heating. It seems that we are particularly threatened by growing amount of BC pollution, generated by the aircraft engines aloft at the altitude of 10 km. I suppose that in the presence of these circumstances, due to great expansion even smaller particles are generated as usually, which consequently have different properties – still greater proportion between their surface and volume. These black particles create such unnatural situation that part of light energy, supplied to the Earth by the Sun does not reach the Earth’s surface, but instead directly warms the atmosphere. Instead of usual surface warming there is some ceiling variant, where warmed high-altitude air is carried about by the winds and storms respectively, and bring the part of thermal energy, caught by the BC down to the Earth’s surface. And this obviously causes the atmosphere to be very instable in summer – occurrence of thunderstorms and hurricanes – and the Earth’s surface to be unable to cool down sufficiently – and therefore occurrence of less severe winters with less snowfall and less cold spells. On the other hand, weakened irradiation of water surfaces causes decrease in evaporation and consequent lack of rainfall and potable water.

I am convinced that global warming is influenced by the increased presence of greenhouse gases only to a minor extent. This phenomenon is largely due to the exceptional property of aerosol black carbon, practically not to reflect light at all, but fully absorb it. Their presence is therefore changing the planetary albedo in the direction of decrease of incoming light energy reflection. In other words: viewed from space, due to large quantity of floating black carbon, our planet has become a trifle darker (more black), so that the reflection of light back into space is therefore reduced. Thus the Earth as a whole with the same rate of incoming light actually retains a slightly larger amount of light energy per time unit. And that means global warming.

If the atmospheric aerosol particles were white coloured they would enhance reflection and through this besides equal global dimming also just the opposite effect, i.e. global cooling.

From the chemical point of view BC is a remarkably inert substance. It reacts neither to acids nor to lyes. It begins to burn only at a high temperature. But it reacts with ozone at room temperature!

Thus, there is probability that at the altitude of 10 kilometers, which is already the bottom limit of the stratosphere, BC particles, heated by the sunlight meet ozon and interaction takes place between them. As a product of this reaction oxygen and CO2 are generated. This means that to make matters worse, BC causes thinning of the ozone layer, by which we are protected from dangerous UVB radiation. Or even the opposite might be true, that BC even supports the protection from high energy radiation by absorbing it and getting heated to the extent that it reacts with oxygen. As to these occurrences we can only speculate. However, it seems likely that a large portion of BC, accumulated in the upper layers of the atmosphere burns relatively rapidly, dissolving into CO2 and thus provides for partial purification of the atmosphere. This may be inferred from the events of September 11, 2001 in New York, when all air traffic in the USA was suspended. Although the suspension lasted only three days, meteorologists established prompt and intensive climatic response - increase in diurnal temperature variation (11).

Depending on their origin, BC particles are very different as to size and voluminosity. Therefore their longevity pattern is very different, too. Those particles, which do not burn in the atmosphere, remain suspended into air for different periods of time, depending on their form. Some of them are carried by the wind and migrate long distances, to all appearances even across the oceans, before they land on water surface, mainland or glaciers. Due to its chemical inertia BC remains unchanged. In water it floats down to the bottom, on the mainland it is washed away into the ground by rainwater, deposited on glaciers it inflicts great damage. That is to say that ice surface largely reflects light radiation back to space, whereas carbon black particles deposited on it, fully absorb it and convert it to thermal energy, which is the cause of melting. BC remains continuously active until it disappears from the surface.

Another interesting property of soot is that it cannot be seen on the dark background (on clear sky), because they do not reflect light radiation! Thus in condensation trails behind aircrafts only bright aerosols and water droplets can be seen, but no BC, the amount of which is considerable. BC becomes visible only on white clouds on the background, which turn grey by its presence in the atmosphere (on the way from our eyes to a cloud). Such appearance of clouds is rather frequent.

Conclusion

I believe that it is just this “invisibility of black carbon” which is the cause of the prevailing wrong opinion that the quantity of soot in the atmosphere is too small to cause any large scale troubles.

So basing on the above reasoning the formula for stopping the global warming and dimming is to
REDUCE THE FORMATION OF BLACK CARBON! Anyway, Nature will take care of purification of the atmosphere by itself!

There are certainly several ways to reduce formation of BC. We can reduce daily or weekly aircraft flight mileage and motor vehicle traffic. We can improve the quality of engines in view of diminishing the amount of BC in the exhaust gas. Perhaps another fuel and the like. Certainly a combination of several measures would be the most effective. It is to be expected that the results of measures, even only partial ones, would be evident very soon, in the same manner as with the above mentioned events of September 11, 2001 in New York.

Anyway, success will depend on political will of large countries. I firmly believe that a general agreement will be reached for the benefit of all the inhabitants of the Earth. We would all like to have normal climate without new record temperatures again, days with cool mornings and sufficient rainfall and enough snow in winter, no hurricanes and floods, as in former times, and enough food, drinking water and unpolluted air. If we manage to reduce formation of BC to minimum we shall really have such climate as we used to have – hundred years ago or so. The CO₂ content in the atmosphere would decrease to its former levels, too!

BC, generated from oil derivatives is known to be specially cancerogenous, due to its content of aromatic compounds and therefore most likely responsible for frequent occurrence of cancerous diseases recently. I hope that we shall succeed in cutting the rate of cancer to former level as well.

It looks like humanity has, besides technical advancement, done some really bad turns with excessive consumption of oil in the past hundred years.

The proposed mechanism – soot – explains simultaneously in a satisfactory way both types of phenomena – global warming and dimming. This supports the mechanism with enough credibility that it deserves more attention than it has received so far. I am launching an appeal on the institutions which have enough experimental equipment to verify quantitatively, what is the amount of soot in the atmosphere and how abundant is the emission of soot from airplanes. Quantitative proofs would more efficiently encourage the political will to act correspondingly as soon as possible!

References

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