The development of our ideas of climate and climate change, and the concept of ‘greenhouse gases’, go back at least 200 years, and are not the ‘invention’ of modern-day scientists.
These are some of the scientists who made important contributions.
Jean Baptiste Joseph Fourier
The role that the atmosphere plays in controlling the Earth’s temperature was first suggested nearly 200 years ago by the mathematician and philosopher Jean Baptiste Joseph Fourier (1768-1830). He asked the question – what regulates the Earth’s temperature?
He was aware that heated surfaces emit radiation in the form of thermal energy. Why then, does not the Earth emit the energy from the sun back into space, resulting in an icy planet? Equally, why does the Earth not continue to absorb the energy in sunlight and keep warming up? He concluded that there must be some mechanism in the atmosphere to regulate the temperature of the Earth.
In 1862 John Tyndall (1820 – 1893) determined the key to the mechanism by which the atmosphere could regulate the Earth’s temperature. He found that some gases, including carbon dioxide and water vapor, are ‘opaque’ to heat rays and that in the atmosphere they played the role of preventing heat from escaping.
The effect of human activity on the climate has been well recognised for over a century.
The Swedish scientist Svante Arrhenius (1859-1927) asked the question – is there a link between variations in carbon dioxide levels in the atmosphere and the onset and passing of ice ages?
n 1896, he calculated that if the carbon dioxide level in the atmosphere was reduced by 50% the temperature of the Earth’s surface would drop by 4 -5ºC. The corollary was that if the carbon dioxide levels doubled, the Earth’s temperature would rise by 5-6ºC.
Arrhenius recognised that the large-scale burning of coal was warming the planet by releasing great quantities of carbon dioxide into the atmosphere. He calculated that coal burning alone would result in a 50% rise in carbon dioxide levels in 3,000 years. He saw this as a ‘good thing’ in that the warming of currently cold areas of the Earth could result in an expansion of agriculture.
Arrhenius should be credited for producing the first quantitative effect of global warming through increased levels of carbon dioxide in the atmosphere.
However, his calculations were somewhat off, in that current calculations show that there has been a 30% rise in carbon dioxide levels in the 20th century alone. It is now thought that a doubling of carbon dioxide levels would result in a temperature rise of 2 – 3ºC.
Just as now, Arrhenius’ work on the effect of industry-derived increased carbon dioxide levels was both supported and criticised. For example, it was argued that the oceans and plant life would absorb any extra carbon dioxide produced.
Guy Callendar (1898-1964), a steam engineer and amateur meteorologist, published a seminal paper in 1938. This linked the effect of carbon dioxide produced by the burning of fossil fuels on the temperature of the Earth’s surface. Callendar calculated that in the previous 50 years, industry had emitted 150,000 million tons (c. 136,000 million tonnes) of carbon dioxide and that about 75% of this had remained in the atmosphere. He further estimated that this had resulted in an increase in the Earth’s temperature of 0.005ºC a year. This conclusion was hotly disputed at the time.
Callendar’s view of the situation was fairly optimistic, as a quote from his paper shows:
It may be said that the combustion of fossil fuel, whether it be peat from the surface or oil from 10,000 feet below, is likely to prove beneficial to mankind in several ways, besides the provision of heat and power. For instance, the above mentioned small increases of mean temperature would be important at the northern margin of cultivation, and the growth of favourably situated plants is directly proportional to the carbon dioxide pressure. In any case, the return of the deadly glaciers should be delayed indefinitely.
In 1956, the physicist Gilbert Plass (1922-2004) confirmed much of Callendar’s conclusions by showing that increasing the levels of carbon dioxide in the atmosphere would increase the amount of infrared energy absorbed. He also stated that the continued production of carbon dioxide by industry would result in an increase in the Earth’s temperature of just over 1ºC per century. Plass and others began to warn governments that this might prove to be a serious problem in the future.
In the late 1950s and the early 1960s, Charles Keeling (1928-2005), working at the Scripps Institution of Oceanography in San Diego, recorded measurements of carbon dioxide in Antarctica and the Mauna Loa volcano in Hawaii. He noted increases in the level of carbon dioxide in the atmosphere, and concluded that the theory that the oceans would absorb any additional carbon dioxide produced by fossil fuel burning was not correct. Instead, atmospheric levels of carbon dioxide would continue to increase.
Ed Hawkins and Phil Jones
In 2013 (the 75th anniversary of the publication of Callendar’s paper) two climatologists – Ed Hawkins and Phil Jones – published a review of Callendar’s classic paper.
This review included a graph that contained some of Callendar’s data on increasing temperatures along with the more recent data from CRUTEM4 (a global gridded dataset of global near-surface air temperatures).
Two quotes by Ed Hawkins are well worth repeating:
In hindsight, Callendar’s contribution was fundamental. He is still relatively unknown, but in terms of the history of climate science, his paper is a classic. He was the first scientist to discover that the planet had warmed by collating temperature measurements from around the globe, and suggested that this warming was partly related to man-made carbon dioxide emissions…People were sceptical about some of Callendar’s results, partly because the build-up of CO2 in the atmosphere was not very well known and because his estimates for the warming caused by CO2 were quite simplistic by modern standards. It was only in the 1950s, when improved instruments showed more precisely how water and CO2 absorbed radiation, that we reached a better understanding of its importance. Scientists at the time also couldn’t really believe that humans could impact such a large system as the climate – a problem that climate science still encounters from some people today, despite the compelling evidence to the contrary.
Doubts in the role of CO2 remained, partly because the world did not warm further – in fact land temperatures fell slightly until around 1975, before the warming resumed. This temperature plateau is very likely due to increased levels of particulates (or ‘aerosols’) in the atmosphere reflecting solar radiation back into space. Ironically, these aerosols are also the product of fossil fuel burning and strict regulations were imposed in the developed world on their emissions in the 1960s and 1970s which allowed the warming from carbon dioxide to emerge again. Aerosol emissions from the developing world may also have played a role in the temperature plateau since around 2000.
Since the 1980s, the study of climate change and its effect on the world in general and the human population in particular, has been recognised as one of the great scientific endeavors of our time.
An important aspect of the current climate – perhaps the most important – is how the world generates its power. Some energy producing technologies have little or no significant effect on the climate while others have a major negative effect through the production of greenhouse gases.
Let’s take a look at the various sources of energy available.