Cuddles and Rainbows, or Extra-Crispy? The implications of Climate Change through Geological Time

Marking lab reports for an Environmental Science course I started teaching this year, I found it interesting that several students, after examining evidence of changing sea level and ice volume in the geological record, expressed a view that ice sheet collapse and rapid resulting sea level rise in the coming century are not causes for concern because they are natural phenomena. The logical mis-step here seems to be an equation of ‘natural’ with ‘good’ or ‘harmless’. Cyanide is a naturally occurring compound, but I think we would all be concerned if it was found in our drinking water. Salt water crocodiles are natural phenomena, but I sincerely doubt that a reasonable person could fail to be thoroughly exercised if they found one in their swimming pool.

My students are not alone though in taking climatic comfort from the geological record.

The idea does have some logical basis to it – but like all scientific concepts, the key is to look at the pragmatic implications of the arguments. Climate does change naturally over timescales of thousands to millions of years, for reasons well understood by scientists – subtle variations in our planet’s orbit, variations in the output energy from the sun, and variation in the intensity of global volcanism, amongst others.

Indeed, records of climatic conditions locked within geological strata show that the current climate is not the warmest in our Earth’s history – with global temperatures estimated to have been 6°C warmer 50 million years ago during the Eocene period, and as much as 8°C warmer 510 or so million years ago in the Cambrian. Nor are levels of CO2 – probably the most widely discussed of the ‘greenhouse gases’ contributing to recent anthropogenic warming of the planet – the highest they have ever been, with levels 2-4 times as high as at present for much of the past 500 million years.

More to the point, as we see here in this widely re-published figure from a study by paleoclimatologists Lorraine Lisiecki and Maureen Raymo, if we assume (possibly somewhat charitably – the figures are pretty loose on this) that anatomically modern humans have been around for the order of 200 thousand years, the temperatures recorded over that period indicate that we must have responded to, and survived, major climatic swings and attendant consequences in sea level several times in the past.

A record of climatic change over the past 5 million years, compiled from analysis of sedimentary cores. Reproduced from Lisiecki & Raymo (2005). “A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records”, Paleoceanography 20.

So is climate change all just cuddles and rainbows? Probably not, unfortunately. The fact that we as a species have lived through significant swings in climate does not mean it was necessarily a pretty period in our history. Nor that the same approach would necessarily be effective today.

The dinosaurs, after all, lived through a lot of change in their 160 million-odd years of planetary dominance, but that didn’t buy them any extra credit at the end of the Cretaceous.

Yes, our unparalleled abilities to reason and invent give us advantages over species pushed to the edge during previous periods of global change. But only – and this is a critical point – only if we use them.

To quote human induced global warming skeptic par excellence Ian Plimer on the subject of climate change in the geological record:

“Climate change has been with us for the 4,500 million year history of planet Earth. This is what climate does. It always changes. Changes in our lifetime may be natural”.

Again I sense here the implication that natural is synonymous with harmless – nothing we should worry about. Leaving that aside though, whether or not climate changes naturally is actually a distraction from the real question here – which is whether human activity is producing climate change of a magnitude too great and on a timescale too short to allow effective adaptation. If I might return to the opening paragraph of this essay to construct a somewhat fatalistic analogy, the fact that my taking cyanide would probably prove a lethal mistake does not make me bullet-proof. Just because natural processes produce changes in climate that may be deleterious to human societies on a local to global scale does not mean we shouldn’t be deeply concerned about the fact that human activities appear on the balance of evidence to be producing the same sort of effect, but on an even faster time scale.

To return to the inimitable Professor Plimer, writing here in his recent guide to refuting climate change ‘How to Get Expelled From School’ – a gift that keeps on giving to those in search of a quotable line:

“…a clever teacher would put you in your place and may suggest that the ideal temperature for an Eskimo is not the ideal temperature for someone living in the jungles of Borneo. You could then come back and suggest that this shows that humans can adapt to a great range of temperature so why worry about a warmer world”.

Leaving aside Plimer’s choice of the derogatory term Eskimo, the Inuit people of Arctic Greenland and Canada actually do offer a nice little case study of how to respond to climate change…albeit not conforming to the ‘business as usual’ agenda Plimer seems to be pushing.

Greenland’s arctic landscape was settled by Norse colonists from Iceland in the 10th century, at the height of an interval of unusually warm temperatures known as the Medieval Warm Period. For a time, the settlers prospered and built a flourishing community, but as temperatures fell at the end of that warm interval, the Norse stuck rigidly to their European diet and farming methods. In the face of the deteriorating climate, the Norse colonists’ lifestyle became progressively more marginal and eventually untenable, with both of their settlements dying out some time around the mid 1500’s. At the same time however, Inuit people, with a lifestyle and technology adapted to the cooler conditions continued to live successfully in the same landscape. So yes, humans were quite capable of adapting to changed conditions in climate – but those that tried to resist change and pursue traditional lifestyles in the face of climatic variations were eventually overwhelmed by the changes.

William Nierenberg – American physicist and co-founder of right wing think tank the George C. Marshall Institute seriously proposed in the 1980s that the effects of climate change could be dealt with by migration.

Now, although records of prehistoric movements are imperfect and fragmentary, it does seem likely that this is indeed how people responded to the previous episodes of climate change we see in the geological record. Take this one through to its logical conclusion though – a successful strategy for a nomadic species of a few hundred thousand souls ten thousand years ago may not be the first plan to reach for when you have an urbanised population pushing 7 billion divided into geographically based nation states all looking to find a climate refuge. Let’s be honest here, mass immigration of a coherent social group into a region already settled by a long established population hasn’t turned out to be such a great recipe for convivial relationships and lasting happiness in the Middle East.

This idea is elevated from Alan Jones mouthing-off-without-concern-for-the-facts territory to dangerously loopy by the fact that Nierenberg was speaking not as an individual, but as Chair of the US National Academy of Sciences Carbon Dioxide Assessment Committee, and a key science adviser to the Reagan administration.

Fundamentally, migration as a response to climate change in the modern world is all very well if you have a summer home on Lake Michigan, but I have a sneaking suspicion Nierenberg wasn’t talking about opening his doors to Mexicans and Brazillians whose countries had gone from regular to extra crispy. As public information campaigns go, Nierenberg’s suggestion ultimately falls into the same tragicomic category as the 1950s ‘duck and cover’ ads in the USA suggesting school children should shelter under their desks in the event of Nuclear attack.

Yes, climate change has occurred through geological time – and even through human history and pre-history. There is also, however, a long record of buses driving down Stirling Highway just outside my office – so regularly, believe it or not, that you could almost think they operate to a timetable. And yet, despite that routine nature and predictability, I would still counsel you against standing in front of one as it hurtles down the road.


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