AN OVERVIEW OF THE HISTORY OF CLIMATE SCIENCE

Today we know that the Earth’s atmosphere functions same way as the glass ceiling of a greenhouse: it allows solar radiation to enter the surface of the Earth, while preventing the Earth’s thermal radiation from escaping directly into space.

Atmospheric greenhouse gases, the most important of which are water vapour and carbon dioxide, perform the functions of the greenhouse’s glass ceiling. They create

a natural greenhouse effect without which the earth’s average temperature would be around 15°C colder than it is at present.

At the beginning of the 19^th century, Joseph Fourier (1768–1830) studied the greenhouse effect at a theoretical level. In the middle of the same century, British chemist John Tyndall (1820–1893) carried out the first empirical experiments on greenhouse gases, calling them “hot house gases”. Tyndall discovered that they let solar radiation, especially visible light, almost completely through, while at the same time absorbing a considerable portion of the longer-wave thermal radiation (infrared radiation) emitted from the surface of the planet, thus preventing it from escaping into space. Thirty years later, in their much more detailed experiments and calculations, the pioneers of atmospheric science, Swedish chemist Svante Arrhenius and American geologist Thomas Chamberlin – each without knowledge of the other – came to corresponding conclusions about the essence and influence of the greenhouse effect. Arrhenius (1896) even presented the first estimates of the earth’s climate sensitivity to greenhouse gases. According to him, halving or doubling the carbon dioxide content in the atmosphere would lead to earth surface temperature changes of 4–5 °C – a calculation which is surprisingly close to the current estimates (2–4.5 °C, IPCC 2007). (Kellogg 1987; Hart & Victor 1993; Weart 2003; Hulme 2009a)

The first extensive, modern climate report can be attributed to the Austrian geographer Eduard Brückner. In his dissertation, which was completed in 1890, he offered mathematical-statistical analyses suggesting that the climate warmed in large areas of Central Europe and Russia towards the end of the 19^th century. He made a connection between this change and industrial clearing of forests (von Storch

& Stehr 2006). Brückner assessed the consequences of the change for agriculture and natural environments, and listed countries that benefited or suffered as a result.

He also proposed an international parliamentary agreement, a kind of primitive

“climate law,” to remedy the matter.

Ever since the beginning of the industrial revolution, the world’s fossil resources – coal, oil and natural gas – have nourished the development of the world economy, at the same time causing excess release of greenhouse gases into the atmosphere.

The first attempt to link the increase in greenhouse gas emissions caused by human activities with the extensive warming of the climate was made by the English mechanical engineer Guy Stewart Callendar in his lecture at the Royal Meteorological Society in London in 1938 (Callendar 1938 as cited in Hulme 2009a: 50).

The early observation of the greenhouse effect by Arrhenius and Chamberlin can be considered incidental to some extent, for the actual purpose of their research was to find a theory that would explain the climatic variations of great ice ages (Corfee-Morlot et al. 2007, Victor 2011:33). The by-product of this research, therefore, the observed greenhouse effect, lay dormant for decades until Callendar, using meteorological data, proved that warming was indeed taking place, demonstrating

its connection with CO₂ emissions and the use of fossil fuels (Bolin et al. 1986; Hart

& Victor 1993, Weart 2003). On the basis of calculations performed by Arrhenius, Callendar concluded that the rise in temperatures and the fact that winters were becoming milder, as he observed over large areas at the beginning of the 20^th century, were a consequence of the simultaneous increase of greenhouse gas emissions in the atmosphere caused by industrial production. He stated, on the basis of his measurements, that the Earth’s temperature had already risen by approximately 0.5

°C during the 50 years preceding the 1930s, and he estimated that the temperature would rise at the rate of 0.3 degrees per one hundred years in the future.

In the opinion of Callendar, and of other early greenhouse-gas theorists, the warming was a positive development, because it would permit humankind to better overcome shortages, poverty and disease. However, Callendar’s conclusions did not garner wider support. The Director of the UK Meteorological Office (now the

“Met Office”), Sir George Simpson, for example, regarded the observed connection between greenhouse gas concentrations and the temperature rise as completely coincidental (Hulme 2009a:50).

Around the same time, several considerations diverted interest away from the question of anthropogenic climate change. First, discoveries of significant natural factors affecting the climate, including sunspots and ocean currents, were made, and compared with these, the factor of human influence seemed minor. Second, World War II attracted everyone’s attention and diverted interest towards the more immediate concerns of nuclear physics and armament. Third, there was widespread belief that the means offered by technology were able to solve most of the world’s problems caused by human beings (Hart & Victor 1993).

On the New Continent geophysicist Roger Revelle presented, together with Hans Suess, a revolutionary claim at the end of the 1950s: the residents of planet earth were conducting a gigantic geophysical experiment on the globe they inhabit by manipulating the atmospheric gas composition, which could have fatal consequences (Revelle & Suess 1957). The big contribution of Revelle was to show that most of the CO₂ would not go into the oceans – because the chemistry was buffered. That, in turn, led to the need for long-term measurements: Revelle therefore suggested that systematic measurement of the atmospheric gas composition should be undertaken.

This suggestion was realised in connection with the International Geophysical Year (IGY) in 1957–58, when an observatory specialising in atmospheric measurement was established in Mauna Loa. Systematic measurements over only a few years showed that the atmospheric greenhouse gas concentrations were on the increase, thus validating the earlier claims made in theoretical and experimental studies (Victor 2011:34–35).

However, it took a long time until the human-induced acceleration of the greenhouse effect was accepted as the prevailing scientific theory. The slowness with which the theory was embraced can be attributed above all to the decrease

in temperatures between the 1940s and the beginning of 1970s, which was observed in large areas all over the world. As a result of the temperature drop, the scientific community still debated intensely whether the earth was cooling or warming and whether there was actually a new ice age threatening it in the 1970s and 80s (Hecht & Tirpak 1995). For example, in the United States in the 1970s, typical headlines in daily newspapers included the following: “The Cooling World”

(Newsweek 1975), “Scientists Ask Why World Climate Is Changing: Major Cooling May Be Ahead” (The New York Times 1975) and “Earth Seems to be Cooling Off Again” (The Christian Science Monitor 1974). As late as 1978, an international meeting of climate researchers came, after lengthy disputation about details, to the unanimous conclusion that even though there was still much confusion concerning the magnitude, speed and regional occurrence of climate change, at least one thing is certain: the earth’s climate was cooling down (Mazur & Lee 1993).

When did the worry over cooling down become a worry over warming? Victor (2011: 39) regards the study published in 1981 by Hansen et al. (1981) as the turning point: Hansen constructed his first climate models on the basis of research on the planet Venus.

But how did a geophysical phenomenon, carbon dioxide, become an environmental or pollutant problem? In Victor’s opinion, one reason is that people became aware of environmental risks from the 1960s onwards: nuclear tests and radiation, its effect on breast milk, DDT, and, finally, supersonic aircraft. It was these factors, if not others, that solidified the research on the global climate as an environmental concern, especially when the destructive effect of nitrous oxides and CFC compounds on the ozone layer was discovered. The concern about climate change was naturally linked to the same issue (Victor 2011:35–39).

For the development of climate science and, in particular, for the research on the causes and effects of climate change, the year 1988 was significant in many ways. The previously mentioned establishment of the Intergovernmental Panel on Climate Change (IPCC) took place that year. A hearing of experts in the US Senate brought up climate change as a media topic. That same year, the researchers at the Climate Research Unit (CRU) of the University of East Anglia, in the UK, suggested that 1987 was the warmest year in the history of temperature measurement, and the summer was named a special “greenhouse summer”.

The growing research interest was also affected by the establishment of new international research programs and increased research funding allocated to the field. These included, for example, extensive research programs related to global environmental change coordinated by the International Council for Science (ICSU), of which the best-known ones are the World Climate Research Programme (WCRP) and the International Geosphere-Biosphere Programme (IGBP) and their numerous sub-programs. As illustrated in graph 9, scientific research dealing with climate change increased exponentially from 1988 onwards. The surge in research and

publishing activities was particularly prominent in the field of natural science. In social science, publications dealing with climate change increased significantly only after the first decade of the 21^st century. Nevertheless, it should be noted that research on climate change and, more generally, awareness of the problem, were a primarily western phenomenon until the 21^st century, whereas a larger-scale awakening to the problem in, for instance, India, China and Africa took place only during the first decade of this century (Hulme 2009a: 66).

Figure 9: The increase in scientific publications concerning climate change, source Hulme 2009a

Awareness of the human contribution to the detected warming of the climate has increased gradually from the 1990s. In the First IPCC Assessment Report in 1990, the Earth’s surface temperatures were estimated to have risen by 0.3–0.6 ˚C during the preceding century. It was noted that the temperature rise was in harmony with climate models but also “of the same magnitude as natural climate variability”

(IPCC 1990). The Second Assessment Report published in 1996 proposed that “the balance of evidence suggests a discernible human influence on global climate” (IPCC 1996). The conclusions in the Third Assessment Report published in 2001, were already more clearly worded with respect to the human contribution to climate

change. According to this report, the majority of the warming during the preceding 50 years can probably (probability of 66–90%) be attributed to greenhouse gas emissions caused by human activities.

The consensus among the scientists was considered vast. In 2004, Naomi Oreskes (2004) performed a survey of 928 peer-reviewed climate papers of ISI Web of Science database published between 1993 and 2003, finding none that rejected the human cause of global warming. After the analysis, she concluded that 75 percent of the examined abstracts either explicitly or implicitly backed the consensus view, while none directly dissented from it. This result⁸⁴ became soon one of the most cited studies on unanimity among the scientists and was often repeated in debates about climate policy.

According to the IPCC’s Fourth Assessment Report (IPCC 2007), the warming of the climate is indisputable. The observations show that the earth’s surface temperature has risen on average by 0.74 °C [variation range 0.56 – 0.92 °C] in 1906–2005. The temperature has risen in large areas throughout the globe, however, in high northern latitudes more than elsewhere. Satellite observations show that the average volume of Arctic ice cap has decreased by 2.7% [2.1–3.3%] per decade after 1978. In summer, the shrinking of the ice surface area has been even more rapid, 7.4% [5.0–9.8%] per decade. Furthermore, oceans have warmed, the melting of snow and ice has accelerated and the sea level has risen.

According to the IPCC, the rise of the earth’s average temperature observed during the second half of the past century is “very likely” to be due to an increase in greenhouse gas concentrations caused by emissions mostly generated by humankind. The report regards it as probable that during the past 50 years human-induced warming has been significant on all continents except Antarctica.

Human-induced global greenhouse gas emissions have increased since pre-industrial times. The augmentation was 70% between 1970 and 2004. Carbon dioxide (CO₂) is the most significant greenhouse gas generated by human activity (Lacis et al. 2010). Annual CO₂ emissions increased by about 80% during 1970–

2004. The increase of the carbon dioxide concentration is primarily caused by the use of fossil fuels. The effect of land use changes is also significant but to a lesser extent. The current CO₂ (400 ppm) and methane (CH₄) (1789 ppb) concentrations of the atmosphere clearly exceed the natural range of variation for the period of the past 650,000 years.

According to the IPCC, it is very likely that also the observed increase in CH₄ concentrations is human-induced – above all generated by agriculture and the use

84 The debate on the alleged consensus has continued since then. A similar result was published by Cook et al. (2013), on a larger database, consisting of 11944 climate abstracts. According to it, 97% of the scientific literature endorses anthropogenic climate change. This study has been criticized by Richard Tol (2014), a professor of the economics of climate change. Tol’s main argument is that a trend in composition is mistaken for a trend in endorsement.

of fossil fuels. The increase in nitrous oxide (N2O) concentrations is mainly due to agriculture. In 2007, the atmospheric carbon dioxide content was 37% higher than during the pre-industrial period, while the corresponding figures for methane and nitrous oxide were 156% and 19% respectively (Nature 2008: 558–559).

Under the current measures to curb climate change and related sustainable development practicesglobal greenhouse gas emissions will continue to increase during the following decades. The SRES scenarios⁸⁵ used by the IPCC predict that the global greenhouse gas emissions will increase by 25–90% (CO₂eq.) during 2000–

2030. These scenarios forecast that fossil fuels will maintain their dominant position in global energy production until 2030 and even further. The results of more recent scenarios, which do not take into account additional emission restrictions, follow the same lines. The SRES scenarios predict a warming of the climate of about 0.2

°C during each of the next two decades. Even if the concentrations of all greenhouse gases and aerosols were stabilised to the level of the year 2000, the climate would warm by about 0.1 °C per decade. The forecast warming after 2030 will depend more and more clearly on the selection of the emission scenario.

The conclusion of the IPCC’s Fourth Assessment Report is that if greenhouse gas emissions continue at or above the current level, warming will accelerate. This will lead to many changes in the climate system, which in this century will very likely be larger than the changes observed during the past century.