Jiggy Lloyd asks whether the issue of climate change should have been recognised sooner
Slow progress on tackling the drivers of climate change since the Rio summit in 1992 has been discussed at length. But given that the greenhouse effect was first described in 1824, the difficulties of the past 24 years pale into insignificance. Why has it taken just short of 200 years to get to where we are now? And what does this tell us about the development of environmental understanding?
Early believers
Four scientists proposed very early, but largely correct, theories about the greenhouse effect. In France, Jean Baptiste Fourier identified the differential absorption effects of the Earth’s atmosphere while developing his Théorie Analytique de la Chaleur (the analytical theory of heat), which was published in 1822.
In the 1850s, Irish-born physicist John Tyndall demonstrated in laboratory experiments the validity of Fourier’s proposition that constituents of the atmosphere would influence heat absorption. He then went a step further in proposing that changes in the constituents of the atmosphere could have produced past changes in climate. Arvid Högbom was a Swedish geologist who, in 1893, demonstrated that carbon dioxide was emitted to the atmosphere from limestone and that variations in atmospheric concentration of CO2 were likely in different geological times. His colleague, Svante Arrhenius, proposed that a doubling of carbon dioxide concentration might generate a 5°C–6°C rise in temperature and then, in 1904, suggested that burning fossil fuels might increase the atmospheric concentration of CO2.
Note the time lapses between these studies and the locations of those involved. Some limited ‘networking’ did operate: Fourier addressed the Royal Society in London and Tyndall was a member of the X Club, a dining group for professional scientists, but overall there was little overlap in general.
Vegetation removal
There is another explanation for climate change with a long pedigree: the ‘vegetation-desiccation’ theory. This is the belief that climate is affected by vegetation removal. Diarist and horticulturalist John Evelyn asserted in 1664 that cutting down trees improved the climate in Ireland. Colonists in North America believed that clearing vegetation improved climate, as did Christopher Columbus in relation to the West Indies. Climatic determinism was a common belief in the Enlightenment and in 1719 Abbe Du Bos proposed that interchange between air and earth dictated climate, and that vegetation clearance in North America would change climate as well as culture.
Over the period that encompassed the work of Fourier, Tyndall, Högbom and Arrhenius, an influential, well-connected but less scientific community in Britain strengthened its belief in the vegetation-desiccation theory. Its members were the geographers, missionaries and natural historians whose observations in overseas territories suggested a past climate less arid than they personally experienced. There was a major debate at the Royal Geographical Society (RGS) in London in 1865, which brought together observations from the Americas, Russia, Greece, Asia Minor, India and North and South Africa in support of the desiccation theory.
The belief that vegetation removal changed the climate had characteristics of a ‘convenient truth’ in that deforestation could be portrayed as a threat to the economic wellbeing of the empire and its remedy advanced the interests of those involved. For most of the second half of the 19th century, the RGS was at the forefront of lobbying for afforestation in India and elsewhere, using fear of desiccation as key to its argument.
It is worth noting that vegetation and climate change was not just a British preoccupation but that others were more circumspect in their views. Prussian geographer Alexander von Humboldt cited a link during his early career, though by 1850 he used data from America to question whether climate was anything other than stable over man’s lifetime. In 1864, the US conservationist George Perkins Marsh said ‘felling of the woods... had consequences… probably also to [sic] the local climate’. This more nuanced view of the link between vegetation and climate is of course closer to that held today.
Vegetation removal was not the only factor considered in the quest to explain climate change. It was not uncommon for tectonic upheaval to be cited as the explanation for changing climate in Africa. Missionary David Livingstone was an early exponent of this theory, while botanist John Croumbie Brown cited tectonic upheaval and vegetation removal operating together in his 1877 text, Forest and Moisture.
Other scientific minds were preoccupied with volcanoes. A cold winter followed the eruption of the Icelandic volcano, Hekla, in 1783 and the 12 months after Mount Tambora in Indonesia erupted in 1815 was described as the ‘year without summer’. It is therefore not surprising that many scientists in the early 19th century were exploring the possibility that volcanic emissions reduced heat penetration to the earth. By the beginning of the 20th century, the theories of US geologist Thomas Chrowder Chamberlin about deep-sea circulation patterns were gaining ground and the sunspot explanation of climate change, first espoused by astronomer William Herschel in the 18th century, was re-emerging.
Beliefs mechanisms
Various explanations for past climate change were reinforced by religious and moral beliefs of the time. In the case of the vegetation-desiccation theory, the British missionary Robert Moffatt linked the worsening condition of the Kalahari Desert with ‘man’s first disobedience’. Racism made it easy to blame indigenous people for the tree felling, over-grazing or burning that was believed to have changed the climate.
Post-Darwin, belief in catastrophe, such as ‘The Great Flood’, gave way to uniformitarianism. This was a set of beliefs that highlighted the perpetual and circulatory working of nature. Arrhenius described his own estimates of temperature rise due to man’s actions as ‘a theoretical possibility’ and said any change might be ‘for the best’.
More widely, climate trends were interpreted in a culture that had confidence in the ‘balance of nature’ and the belief that the oceans would regulate any change in the atmosphere. Perhaps most crucially, Arrhenius and his contemporaries did not know how fast the human population was growing, even at that time, and how this would affect consumption and hence emissions. All this might help explain why 50 years went by before Roger Revelle’s hypothesis – that economic growth fuelled by oil and coal was likely to increase CO2 in the Earth’s atmosphere – led him in 1956 to establish the monitoring centreat Mauna Loa on Hawaii. From here emerged the evidence that CO2 was building up in the atmosphere. In the late 1960s and 1970s, this was matched with past climate data, and converged with the work of Swedish meteorologist Bert Bolin and others highlighting the significance of forest biomass to provide the now-familiar explanation of climate change.
This convergence coincided with the growth of an environmental movement that was beginning to persuade wider society that actions had consequences and that nature was not as perpetual or benevolent as had been believed. In other words, the knowledge that human action was causing the climate to change began to fuse with a wider acceptance that it could.
Learning the lessons
Hindsight is a wonderful thing. What should we learn from the above? Let’s not condemn the exponents of the vegetation-desiccation theory; they were early proponents of the importance of forest cover even if somewhat adrift in their appreciation of climate change.
On a practical level, the story of the past 200 years should remind the environment profession to appreciate the datasets and the computational power that underpin the work of the Intergovernmental Panel on Climate Change and others. Without them the consensus shown in Paris in December would have been unachievable. Those who thought volcanoes changed the climate erred in their tendency to scale up short-term observations to create wider explanations; modern science can handle this differently. Vested interests operated and religious or moral norms were influential. Is this any less likely in today’s world? Connections were important; it is interesting to speculate how things might have turned out if Fourier had addressed the RGS, for example.
Most of all, the story of the quest to understand climate change is one about belief. Human society is conditioned not just by knowledge but by the interplay of knowledge and belief. This interplay continues to this day – and will be key to success or otherwise in the post-Paris era.
