so powerful that, as a result of the large amount of wood burned in winter in Sweden, sufficient CO2 would be given off to increase the greenhouse effect and to produce a warm, productive climate all the year round. Using the Stefan–Boltzmann equation, he calculated that doubling the amount of CO2 in the atmosphere would increase the temperature on the ground by an overall 4–4.8ºC. At the time he made his observations there was no way of measuring the concentration of CO2 at the very low levels present in the atmosphere. As the actual concentration of CO2 is less than 0.038 per cent, it is easily doubled by what, in global terms, is a very small increase in CO2. It is the fear that in the next hundred years human activity will add significantly to the CO2 concentration in the atmosphere that has provoked the present global-warming panic.
Although the term ‘greenhouse-gas effect’ has come to be used to describe the total effect of all elements in the atmosphere on the temperatures we enjoy on the surface of our planet, it was only the part played by CO2, methane and sulphur dioxide, in preventing Earth from freezing when the sun sets, that was highlighted by Arrhenius.
The sun is the only major source of heat on our planet. When it shines it warms us up. Some of that energy is absorbed by the Earth’s crust, warming it up. Some of that heat diffuses from the surface into the soil and rock below. This is geothermal heat and it can be tapped into by the heat pumps that are used to supplement domestic heating. As the surface of the Earth gets hotter, it acts like a radiator, dispersing its heat back into the atmosphere. Because this radiation is in the infrared, invisible spectrum, we cannot see it happening, although we can feel its effect as it warms us up. It is the infrared radiation given off by the planet once it has been warmed that is buffered by the greenhouse gases in the atmosphere. They do it by absorbing the energy within their molecules. It was Arrhenius who pointed out that it was those gases that had the capacity to absorb energy with a wavelength in the infrared spectrum that could buffer heat energy in this way. He studied CO2, methane and sulphur dioxide, all of which share this property. However, it is water molecules that are the most potent of the greenhouse gases because they absorb energy over a very wide range of wave bands, from infrared to visible light.
Were it not for the blanket of greenhouse gases in the atmosphere the temperatures on the earth would be boiling hot during the day and freezing at night. It is the result of the presence of these gases in our atmosphere that some of the infrared energy that would otherwise reach the surface of the Earth when the sun is shining is absorbed, reducing the extreme heat that would otherwise ensue.
Because of the greenhouse gases, much of the Earth’s warmth, acquired during the day, is prevented from being dissipated into space at night. The proponents of the theory of anthropogenic global warming (i.e. global warming caused by humans) point out that, as a result of this effect, increasing the amount of greenhouse gases in the atmosphere will reduce the amount of heat dissipated into space at night and therefore, over time, it is likely to cause the earth’s temperature to rise.
Arrhenius failed to persuade the climatologists of his era of the significance of his theory. The wood burning in Sweden did not produce the warm winters he forecast. His predictions, based on the greenhouse-gas effect of CO2, turned out to be wrong. The theory did not explain the recurrent swings in temperature that have occurred since the Earth was born. It failed to answer the question of why, in the not-too-distant past, his Scandinavian ancestors had been able to live, farm and colonise Greenland and the frozen north of his country but had been forced to abandon their settlements due to the encroaching ice in the 16th and 17th centuries, without evidence to suggest there had been any reduction in the atmosphere’s CO2 concentration. It seemed more likely, to the climatologists, that the explanation lay with the small deviation that occurs in the axis of Earth as it circles the sun and the flattening of its slightly elliptical circuit, the so-called Milankovitch effects.
A new ice age?
In 1938, a British scientist, G S (Guy) Callendar, drew attention to the potential beneficial effect on the agriculture and farming of a rise in temperature as a result of an increase in CO2 in the atmosphere, but his views were largely ignored. His predictions were based on the observations of Dr Keeling’s team of scientists on the CO2 content of the atmosphere at the top of a mountain in Hawaii. They had demonstrated that the level of CO2 in the atmosphere in the Pacific was slowly rising each year. Callendar’s words went unheeded as, in spite of his prediction of a warmer world, it was followed by a 35-year period, from 1940 to 1975, of progressively colder times. Before we accept that an increase in CO2 causes warming of the planet, the fall in temperature that occurred in this period in spite of a documented incremental rise in CO2 must be explained.
It is almost certain that the levels of atmospheric CO2 would have increased rapidly during World War II and the post-war reconstruction period, and that this should have caused a rise in temperature due to the greenhouse-gas effect. But the temperatures actually fell by 0.3–0.4ºC. The effect was sufficiently worrying for climatologists, at that time, to warn of the advent of a new ice age.
STANLEY FELDMAN
DOGMA
Greenhouse gases are all the fault of human activity.
ANYONE LYING ON an English beach enjoying the summer sunshine could be excused for jumping to the conclusion that it was the occasional cloud that obscures the sun that causes their world to cool. They are probably right. Under cloudless skies the temperature drops dramatically the moment the sun sets or one moves from the sunshine into the shade, although the CO2 levels do not change.
When one listens to the weather forecast, it is clear that it is the cloud cover that determines whether the sun will shine and the weather will warm up. It is the amount of energy in the water molecules that make up the clouds that determines whether or not a particular wind will warm us up or cool us down. It would be nonsense to consider the effect of gases in the atmosphere on Earth’s temperature without accepting a major role for these clouds, especially those at the lower levels. To concentrate solely on the CO2 ignores the fact that many different processes are involved in determining the planet’s temperature.
There is one principal source of heat, and that is the sun; it far exceeds any other influence on the global temperature. Nevertheless, significant but comparatively small amounts of geothermal energy are constantly being released from the molten mass in the depths of the Earth. This energy warms areas of the oceans, through the hydrothermal vents of underwater volcanoes, and the land where the Earth’s crust is sufficiently thin to allow thermal warming, as in, for example, Arizona, Iceland, New Zealand and Antarctica. However, their global contribution of energy is tiny.
There is good evidence that the sun’s heat varies from time to time and that this is related to magnetic activity and sunspots. There is strong correlation between the number and frequency of these changes and the sun’s energy output. When there are a lot of sunspots the energy is reduced and the temperature, not only of Earth but of other planets such as Jupiter and Mars, falls slightly. Sunspots affect not only the amount of heat given off by the sun but also the amount of cosmic bombardment from outer space, due to their strong magnetic effect.
The mean temperature on Earth depends upon how much of the sun’s energy reaches the surface of our planet when the sun shines and how much of this heat is lost from the Earth when it gets dark. There is no doubt that this is affected by the atmosphere.
