Showing posts with label Jared Diamond. Show all posts
Showing posts with label Jared Diamond. Show all posts

Wednesday 27 September 2017

Cow farts and climate fiddling: has agriculture prevented a new glaciation?

Call me an old grouch, but I have to say that one of my bugbears is the use of the term 'ice age' when what is usually meant is a glacial period. We currently live in an interglacial (i.e. warmer) era, the last glaciation having ended about 11,700 years ago. These periods are part of the Quaternary glaciation that has existed for almost 2.6 million years and deserving of the name 'Ice Age', with alternating but irregular cycles of warm and cold. There, that wasn't too difficult now, was it?

What is rather more interesting is that certain geology textbooks published from the 1940s to 1970s hypothesised that the Earth is overdue for the next glaciation. Since the evidence suggests the last glacial era ended in a matter of decades, the proposed future growth of the ice sheets could be equally rapid. Subsequent research has shown this notion to be flawed, with reliance on extremely limited data leading to over-confident conclusions. In fact, current estimates put interglacial periods as lasting anywhere from ten thousand to fifty thousand years, so even without human intervention in global climate, there would presumably be little to panic about just yet.

Over the past three decades or so this cooling hypothesis has given way to the opposing notion of a rapid increase in global temperatures. You only have to read such recent news items as the breakaway of a six thousand square kilometre piece of the Antarctic ice shelf to realise something is going on, regardless of whether you believe it is manmade, natural or a combination of both. But there is a minority of scientists who claim there is evidence for global warming - and an associated postponement of the next glaciation - having begun thousands of years prior to the Industrial Revolution. This then generates two key questions:

  1. Has there been a genuine steady increase in global temperature or is the data flawed?
  2. Assuming the increase to be accurate, is it due to natural changes (e.g. orbital variations or fluctuations in solar output) or is it anthropogenic, that is caused by human activity?

As anyone with even a vague interest in or knowledge of climate understands, the study of temperature variation over long timescales is fraught with issues, with computer modelling often seen as the only way to fill in the gaps. Therefore, like weather forecasting, it is far from being an exact science (insert as many smileys here as deemed appropriate). Although there are climate-recording techniques involving dendrochronology (tree rings) and coral growth that cover the past few thousand years, and ice cores that go back hundreds of thousands, there are still gaps and assumptions that mean the reconstructions involve variable margins of error. One cross-discipline assumption is that species found in the fossil record thrived in environments - and crucially at temperatures - similar to their descendants today. All in all this indicates that none of the numerous charts and diagrams displaying global temperatures over the past twelve thousand years are completely accurate, being more along the lines of a reconstruction via extrapolation.

Having looked at some of these charts I have to say that to my untrained eye there is extremely limited correlation for the majority of the post-glacial epoch. There have been several short-term fluctuations in both directions in the past two thousand years alone, from the so-called Mediaeval Warm Period to the Little Ice Age of the Thirteenth to Nineteenth centuries. One issue of great importance is just how wide a region did these two anomalous periods cover outside of Europe and western Asia? Assuming however that the gradual warming hypothesis is correct, what are the pertinent details?

Developed in the 1920s, the Milankovitch cycles provide a reasonable fit for the evidence of regular, long-term variations in the global climate. The theory states that changes in the Earth's orbit and axial tilt are the primary causes of these variations, although the timelines do not provide indisputable correlation. This margin of error has helped to lead other researchers towards an anthropogenic cause for a gradual increase in planet-wide warming since the last glaciation.

The first I heard of this was via Professor Iain Stewart's 2010 BBC series How Earth Made Us, in which he summarised the ideas of American palaeoclimatologist Professor William Ruddiman, author of Plows, Plagues and Petroleum: How Humans Took Control of Climate. Although many authors, Jared Diamond amongst them, have noted the effects of regional climate on local agriculture and indeed the society engaged in farming, Professor Ruddiman is a key exponent of the reverse: that pre-industrial global warming has resulted from human activities. Specifically, he argues that the development of agriculture has led to increases in atmospheric methane and carbon dioxide, creating an artificial greenhouse effect long before burning fossil fuels became ubiquitous. It is this form of climate change that has been cited as postponing the next glaciation, assuming that the current interglacial is at the shorter end of such timescales. Ruddiman's research defines two major causes for an increase in these greenhouse gases:

  1. Increased carbon dioxide emissions from burning vegetation, especially trees, as a form of land clearance, i.e. slash and burn agriculture.
  2. Increased methane from certain crops, especially rice, and from ruminant species, mostly cattle and sheep/goat.

There are of course issues surrounding many of the details, even down to accurately pinpointing the start dates of human agriculture around the world. The earliest evidence of farming in the Near East is usually dated to a few millennia after the end of the last glaciation, with animal husbandry preceding the cultivation of crops. One key issue concerns the lack of sophistication in estimating the area of cultivated land and ruminant population size until comparatively recent times, especially outside of Western Europe. Therefore generally unsatisfactory data concerning global climate is accompanied by even less knowledge concerning the scale of agriculture across the planet for most of its existence.

The archaeological evidence in New Zealand proves without a doubt that the ancestors of today's Maori, who probably first settled the islands in the Thirteenth Century, undertook enormous land clearance schemes. Therefore even cultures remote from the primary agricultural civilisations have used similar techniques on a wide scale. The magnitude of these works challenges the assumption that until chemical fertilisers and pesticides were developed in the Twentieth Century, the area of land required per person had altered little since the first farmers. In a 2013 report Professor Ruddiman claims that the level of agriculture practiced by New Zealand Maori is just one example of wider-scale agricultural land use in pre-industrial societies.

As for the role played by domesticated livestock, Ruddiman goes on to argue that ice core data shows an anomalous increase in atmospheric methane from circa 3000BCE onwards. He hypothesises that a rising human population led to a corresponding increase in the scale of agriculture, with rice paddies and ruminants the prime suspects. As mentioned above, the number of animals and size of cultivated areas remain largely conjectural for much of the period in question.  Estimates suggest that contemporary livestock are responsible for 37% of anthropogenic methane and 9% of anthropogenic carbon dioxide whilst cultivated rice may be generating up to 20% of anthropogenic methane. Extrapolating back in time allows the hypothesis to gain credence, despite lack of access to exact data.

In addition, researchers both in support and opposition to pre-industrial anthropogenic global warming admit that the complexity of feedback loops, particularly with respect to the role of temperature variation in the oceans, further complicates matters. Indeed, such intricacy, including the potential latency between cause and effect, means that proponents of Professor Ruddiman's ideas could be using selective data for support whilst suppressing its antithesis. Needless to say, cherry-picking results is hardly model science.

There are certainly some intriguing aspects to this idea of pre-industrial anthropogenic climate change, but personally I think the jury is still out (as I believe it is for the majority of professionals in this area).  There just isn't the level of data to guarantee its validity and what data is available doesn't provide enough correlation to rule out other causes. I still think such research is useful, since it could well prove essential in the fight to mitigate industrial-era global warming. The more we know about longer term variations in climate change, the better the chance we have of understanding the causes - and potentially the solutions - to our current predicament. And who knows, the research might even persuade a few of the naysayers to move in the right direction. That can't be bad!

Thursday 28 May 2015

Presenting the universe: 3 landmark science documentary series

They say you carry tastes from your formative years with you for the rest of your life, so perhaps this explains why there are three science documentary television series that still have the power to enchant some decades after first viewing. Whilst there has been no shortage of good television science programming since - Planet Earth and the Walking with... series amongst them - there are three that remain the standard by which I judge all others:
  1. The Ascent of Man (1972) - an account of how humanity has evolved culturally and technology via biological and man-made tools. Presented by mathematician and renaissance man Jacob Bronowski.
  2. Cosmos (1980) - the history of astronomy and planetary exploration, interwoven with the origins of life. Presented by Carl Sagan (as if you didn't know).
  3. The Day the Universe Changed (1985) - a study of how scientific and technological breakthroughs in Western society generate paradigm shifts. Presented by the historian of science James Burke.

All three series have been proclaimed 'landmark' shows so it is interesting to compare their themes, viewpoints and production techniques, discovering just how similar they are in many ways. For a start, their excellent production values allowed for a wide range of international locations and historical recreations. They each have a charismatic presenter who admits to espousing a personal viewpoint, although it's quite easy to note that they get progressively more casual: if Jacob Bronowski has the appearance of a warm elder statesman then Carl Sagan is the father figure for a subsequent generation of scientists; James Burke's on-screen persona is more akin to the cheeky uncle, with a regular supply of puns, some good, some less so.

To some extent it is easy to see that the earliest series begat the second that in turn influenced the third. In fact, there is a direct link in that Carl Sagan hired several of the producers from The Ascent of Man for his own series, clearly seeing the earlier show as a template for Cosmos. What all three have is something extremely rare in other science documentaries: a passion for the arts that promotes a holistic interpretation of humanity's development; science does not exist in isolation. As such, the programmes are supported by superbly-illustrated tie-in books that extend the broadcast material from the latter two series whilst Bronowski's book is primarily a transcript of his semi-improvised monologue.

In addition to considering some of the standard examples of key developments in Western civilisation such as Ancient Greece and Galileo, the series include the occasional examination of Eastern cultures. The programmes also contain discussions of religions, both West and East. In fact, between them the series cover a vast amount of what has made the world the way it is. So not small potatoes, then!

The series themselves:

The Ascent of Man

To some extent, Jacob Bronowski was inspired by the earlier series Civilisation, which examined the history of Western arts. Both series were commissioned by David Attenborough, himself a natural sciences graduate who went on to present ground-breaking series in his own discipline as well as commissioning these landmark programmes. (As an aside, if there are any presenters around today who appears to embody the antithesis of C.P. Snow's 'the two cultures' then Sir David is surely in the top ten).

Bronowski's presentation is an astonishingly erudite (for all its improvisation) analysis of the development of our species and its technological society. Although primarily focused on the West, there is some consideration of other regions, from the advanced steel-making technology of medieval Japan to Meso-American astronomy or the relatively static culture of Easter Island. Time and again, the narrative predates the encumbrance of political correctness: that it was the West that almost solely generated our modern technological society - the 'rage for knowledge' for once outshining dogma and inertia.

Of course, it would be interesting to see how Bronowski might have written it today, in light of Jared Diamond's ground-breaking (in my humble opinion) Guns, Germs and Steel. Although he works hard to present science, the plastic arts, literature and myth as emerging from the same basic elements of our nature, it is clear that Bronowski considers the former to be much rarer - and therefore the more precious - discipline. Having said that, Bronowski makes a large number of Biblical references, primarily from the Old Testament. In light of the current issues with fundamentalism in the USA and elsewhere, it is doubtful that any science documentary today would so easily incorporate the breadth of religious allusions.

If there is a thesis underlying the series it is that considering how natural selection has provided humanity with a unique combination of mental gifts, we should use them to exploit the opportunities thus presented. By having foresight and imagination, our species is the only one capable of great heights - and, as he makes no pretence of - terrible depths. As he considers the latter, Bronowski admits that we should remain humble as to the state of contemporary knowledge and technology, which five hundred years hence will no doubt appear childlike. In addition, he states that belief in absolute knowledge can lead to arrogance; if we aspire to be gods, it can only end in the likes of Auschwitz. But his final speeches contain the wonderful notion that the path to annihilation can be avoided if science is communicated to all of society with the same vigour and zest as given to the humanities.

Cosmos

I was already an astronomy and astronautics fan when I saw this series. Its first UK broadcast slot was somewhat later than my usual bedtime, so it seemed a treat to be allowed to stay up after the rest of the family had gone to bed. Like Star Wars a few years before, it appeared to me to be an audio-visual tour-de-force; not surprisingly, both the tie-in hardback and soundtrack album arrived on my birthday that year.

Nostalgia aside, another key reason for the series' success was the charisma of the presenter himself. Much has been written of Sagan's abilities as a self-publicist, and the programmes do suffer from rather too many staring-beatifically-into-the-distance shots (as to some extent replicated more recently by Brian Cox in his various Wonders Of... series). Of course, it must have taken considerable effort to get the series made in the first place, especially in gaining a budget of over $6 million. After all, another great science populariser, the evolutionary biologist Stephen Jay Gould, never managed to gain anything beyond the occasional one-off documentary.

What is most apparent is Sagan's deep commitment to presenting science to the widest possible audience without distorting the material through over-simplification. However, in retrospect it is also obvious that he was using ideas from several scientific disciplines, such as the Miller-Urey experiment, to bolster his opinions on the likelihood of extra-terrestrial life. To some extent his co-writers reined him in, the final episode given over not to SETI but to plea for environmental stewardship.

Whilst the series is primarily concerned with a global history of astronomy and astrophysics, supplemented with first-hand accounts of planetary exploration, Sagan like Bronowski is equally at home with other scientific disciplines. He discusses the evolution of intelligence and incorporates elements of the humanities with equal aplomb. Another key element is the discussion of the role superstition and dead ends have played in the hindrance or even advancement of scientific progress, from Pythagorean mysticism, via Kepler's conflation of planetary orbits with the five Platonic solids, to Percival Lowell's imaginary Martian canals. Although Sagan repeats his earlier debunking of astrology, UFO sightings and the like, he doesn't rule out the role of emotions in the advancement of science and technology, citing for example the rocket pioneer Robert Goddard's Mars-centred epiphany.

Perhaps the primary reason that the series - despite the obvious dating of some of the knowledge - is still so engaging and why Sagan's narration is so widely quoted, is that he was a prose poet par excellence. Even when discussing purely scientific issues, his tone was such that the information could be effortlessly absorbed whilst allowing the viewer to retain a sense of wonder. Of course, Sagan had ample assistance from his two co-writers Ann Druyan and Steven Soter, as clearly proven by their scripts for the Neil deGrasse Tyson-hosted remake Cosmos: A Spacetime Odyssey. Nonetheless, it is hard to think of another presenter who could have made the original series the success it was on so many levels.

The Day the Universe Changed

Although James Burke had already made a large-scale history of science and technology series called Connections in 1978, it contained a rather different take on some of the same material. By focussing on interactive webs, the earlier series was somewhat glib, in that some of the connections could probably be replaced by equally valid alternatives.

In contrast, The Day the Universe Changed uses a more conventional approach that clearly shares some of the same perspectives as the earlier programmes. Like The Ascent of Man and the Cosmos remake, mediaeval Islamic science is praised for its inquisitiveness as well as the preservation of Classical knowledge. Burke was clearly influenced by his predecessors, even subtitling the series 'A Personal View by James Burke'. Perhaps inevitably he covers some of the same material too, although it would be difficult to create a brief history without reference to Newton or Ancient Greece.

As with Bronowski, Burke integrates scientific advances within wider society, a notable example being the rediscovery of perspective and its profound effect on contemporary art. He also supports the notion that rather than a gradual series of changes, paradigm shifts are fundamental to major scientific breakthroughs. In effect, he claims that new versions of the truth - as understood by a scientific consensus - may rely on abandonment of previous theories due to their irreconcilable differences. Having recently read Rachel Carson's 1950 The Sea Around Us I can offer some agreement: although Carson's geophysical analysis quietly screams in favour of plate tectonics, the contemporary lack of evidence lead her to state the no doubt establishment mantra of the period concerning static land masses.

What Burke constantly emphasises even more than his predecessors is that time and place has a fundamental influence on the scientific enquiry of each period. Being immersed in the preconceived notions of their culture, scientists can find it as difficult as anyone else to gain an objective attitude. In actuality, it is all but impossible, leading to such farcical dead-ends as Piltdown Man, a hoax that lasted for decades because it fulfilled the jingoistic expectations of British scientists. Burke's definition of genius is someone who can escape the givens of their background and thus achieve mental insights that no amount of methodical plodding can equal. Well, perhaps, on occasion.

The series also goes further than its predecessors in defining religion as anti-scientific on two grounds: its demand for absolute obedience in the face of logic and evidence, with reference to Galileo; or the lack of interest in progress, as with the cyclical yet static Buddhist view, content for the universe to endlessly repeat itself. Burke also shows how scientific ideas can be perverted for political ends, as with social Darwinism. But then he goes on to note that as the world gets ever more complex, and changes at an ever faster rate, non-specialists are unable to test new theories in any degree and so are having to rely on authority just as much as before the Enlightenment. How ironic!

All in all, these common threads are to my mind among the most important elements of the three series:
  1. Science and the humanities rely on the same basic processes of the human brain and so are not all that different;
  2. Scientific thinking can be as creative an endeavour as the arts;
  3. Scientists don't live in a cultural vacuum but are part and parcel of their world and time;
  4. Religion is the most change-resistant of human activities and therefore rarely appears sympathetic to science's aims and goals.

As Carl Sagan put it, "we make our world significant by the courage of our questions and the depth of our answers." For me, these three series are significant for their appraisal of some of those courageous explorers who have given us the knowledge and tools we call science.