The research behind climate change science
The Research Behind Climate Change Science
One of the most common complaints I receive from the public is the difficulty they have in accessing research papers on climate change science. Articles are invariably published in journals, virtually all of which require payment to access the full content. Most aren’t hugely expensive in themselves but if you want to peruse more than just a handful, you’re soon looking at a credit card bill akin to a small national debt; not great for aspiring scientists who want to delve into the detail. So I’m delighted to see the publication of The Warming Papers: The Scientific Foundation for the Climate Change Forecast, edited by David Archer and Raymond Pierrehumbert, and published by Wiley-Blackwell. In this compendium, the pedigree of climate change science is beautifully laid out through a collection of papers spanning some 180 years. As a history of science, it’s a fascinating selection. Here you will find the very first articulation of the greenhouse effect, why our planet isn’t a snowball Earth, how the oceans are taking up most of the extra heat trapped by elevated greenhouse gas levels, how tropical soils and the Southern Ocean have amplified temperatures in the past (and might do so again), and why greater levels of carbon dioxide are acidifying the world’s seas. Where the language is esoteric and specialised, Archer and Pierrehumbert provide easy to understand explanations of the papers and why they are so important.
It's fascinating to read how the discoveries and insights were made. Each scientific advance marked a step closer to understanding how our planet works. Where questions remained or opinions differed, science explored, probed and tested. Sometimes, the answers came quickly; others took decades to centuries. Scientists working in what was a nascent field of research during the nineteenth and early twentieth centuries were often grasping for fundamentals without the language or knowledge base that we take for granted today. Sometimes they were just plain wrong. There are several great examples where the science moved forward two steps and then majestically jumped back one. In The Warming Papers we learn of Joseph Fourier's belief in the role of outer space in controlling the Earth’s temperature, John Tyndall's interest in ether and Knut Ångström’s misguided obsession with carbon dioxide saturation of the atmosphere.
And yet the science progressed. One of the heroes of the story is the Swede Svante Arrhenius. In 1896 he crunched the first numbers to determine the amount of warming from carbon dioxide levels in the atmosphere - though Arrhenius described this greenhouse gas by the name of the time: carbonic acid. Curiously, the Swede wasn't really interested in the future; he was trying to find out what caused ice ages. But Arrhenius did consider what might happen if humans went about 'evaporating the coal mines into the atmosphere'. Crunching the numbers he showed that a doubling of CO2 would increase the temperature of the Earth's surface by 6˚C. It was a first and not far off the most recent estimates.
Arrhenius sits over the science of climate change as a grand collosus, recognizing all manner of processes but hamstrung by the lack of computational power available in the late nineteenth century. Given the simple assumptions Arrhenius had to make, it is remarkable how accurate the Swede’s calculations were. Part of his great insight was the concept that water vapour in the atmosphere could act as a strong greenhouse gas through what we now describe as a positive feedback. Arrhenius recognized that increasing temperatures would evaporate greater quantities of water from the world’s oceans, leading to further warming. Amazingly, many of the later papers ignored this great conceptual leap forward and it was only in the 1970s that such ideas found themselves woven into climate models. Much like Arrhenius, many of the early workers couldn’t conceive that humans would flood a future atmosphere with enough carbon to change the world’s climate.
Other papers are perhaps less well known by the public but are classics in their own right. Syukuro Manabe and Richard Wetherald's contributions in the 1960s and 1970s put the science of climate change on a solid footing. The basic concepts, elegantly described in their first computer climate models formed the basis of future studies. In 1967, Manabe and Stouffer first suggested the upper atmosphere should cool alongside a warming surface. This is exactly what we see today. Part of the reason is because of ozone depletion in the stratosphere, resulting in less heat absorption by oxygen molecules. But this can’t explain the magnitude of cooling seen aloft by satellites. Instead, the ever thickening blanket of greenhouse gases near the surface prevents less heat reaching the upper confines of our atmosphere. The upshot is gases at higher altitudes continue to give off heat but receive less in return from below. The result is an inevitable cooling. Incidentally, this is one reason why changes in the sun’s activity cannot be the cause of warming seen over recent decades; if our star was the cause of the temperature increase, all of the atmosphere should be warming and not just the lower levels as predicted for an increase in greenhouse gases.
By Intrepid Science