Historical background on climate change

This historical background was prepared by the late Barry Allen (PhD, DSc, AO). It shows that the basic science of global warming has been known for about two centuries, and that early predictions of the extent of temperature rise were reasonably accurate.

It is readily shown that, without any atmosphere at all, the surface temperature of the Earth (averaged over the entire Earth and over all seasons) would be about -15 degrees C compared with its actual surface temperature of about +15 degrees C (i.e. about 30 degrees C lower than the actual surface temperature)! This difference is attributable to the heating effect of the so-called green-house gases which absorb some of the outgoing infra-red radiation from the Earth and re-radiates some of this energy back to Earth (in effect reducing the efficiency of heat-loss from the Earth), thus causing the surface temperature to rise above its “no-atmosphere” value.

This was first recognised by the great French mathematician Jean Baptiste Fourier in the 1820s. Unable to find any alternate explanation for the additional heating required, he concluded that the atmosphere was acting as some form of blanket and drew parallels with the measured temperature rise observed in a closed vessel with a glass top exposed to sunlight. However, he did not know which component of the atmosphere was responsible for this effect and did not use the term “greenhouse effect”. [“Remarques Generales sur les Temperatures du Globe Terrestre et des Espace Planetaires”, Annales de Chimie et de Physique, Vol 27, pp 136-167, 1824]

In 1859, Irish scientist James Tyndall determined experimentally the atmospheric gases responsible for this heat-trapping effect. He found that the main components (nitrogen and oxygen) had little effect. He concluded that only water vapour, carbon dioxide (CO2), methane (CH4) and a few other trace gases were the principal contributors (even though they constitute less than 1% of the atmosphere).

Scientists in the 19th Century were chiefly interested in the possibility that a lower level of atmospheric carbon dioxide might explain ice ages, though they were unable to find a credible explanation for the required natural decrease in CO2. In 1896, Svante Arrhenius in Stockholm investigated this effect. He also made a calculation for doubling the CO2 in the atmosphere, estimating it would raise the Earth’s temperature by a few degrees, though he believed that it would take millenia of human activity to reach such a level.

Nobody took much interest in the hypothetical future warming caused by human industry.

In the 1930s, during a period of particularly hot summers in Europe, Guy Stewart Callendar (a British engineer specializing in steam technology) using records from 147 weather stations around the world, concluded that the world was gradually getting warmer. He also showed that CO2 concentrations had increased over the same period. He published his results in 1938. Shortly afterwards, Europe underwent a prolonged cold spell, so nobody took any notice.

After World War II, US scientists enjoyed massively increased government funding, notably from military agencies and aimed at pressing military needs. Almost anything that happened in the atmosphere and oceans could be important for national security (including infra-red absorption). In 1955, using improved equipment, US researcher Gilbert Plass performed a detailed analysis of infra-red absorption of various gases. He concluded that doubling CO2 concentrations would increase temperatures by 3 – 4 degrees C.

In 1957, US oceanographer Roger Revelle and chemist Hans Suess (Scripps Institution of Oceanography in La Jolla, California) showed that seawater will not absorb all of the additional CO2 entering the atmosphere, as many had assumed.

In 1958, Charles David Keeling began systematic measurements of atmospheric CO2 concentrations at Mauna Loa in Hawaii and in Antarctica. The Mauna Loa measurements continue to the present day and prove unequivocally that CO2 levels are rising.

From the 1960s onwards, climate change has received ever-increasing attention with more and more measurements of both the current and past historical climates and the development of increasingly sophisticated climate models.

In 1988, the Intergovernmental Panel on Climate Change (IPCC) was established to collate and assess evidence on climate change.

In 1989, the UK Prime Minister Margaret Thatcher (who had a chemistry degree) warned in a speech to the UN that “We are seeing a vast increase in the amount of carbon dioxide reaching the atmosphere….The result is that change in future is likely to be more fundamental and more widespread than anything we have known hitherto”. She called for a global treaty on climate change.

Today there is no argument about the reality of the Greenhouse Gas effect or its importance. The controversy revolves around the degree to which human activity is contributing to the atmospheric concentration of greenhouse gases and its consequence.