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Monday, 24 October 2016

A potted history of climate change

I was searching for a reference that I knew was in my files, and I tracked it down, so here is some surprising news: we knew that "global warming" was happening, way back in 1950!

What is different now is that most reputable atmospheric scientists believe human activity is driving the modern slow warming of our climate. All the same, now we know that global warming is a bad description, so we call it ‘climate change’. Under any name, it’s the same beast, and the same looming disaster, and it was happening 66 years ago.

Oddly, the suspicion that humans are to blame may be even older. The problem before was that there was not a lot of hard science in the arguments, which come down to logic, reason, careful modelling — and interpretation that is likely to be biased by a generous serving of self-interest. That has changed in the last ten years.

Nobody denies that the Earth is getting warmer, because the evidence is there, and it was apparent in 1950, when George Kimble reported in Scientific American that the northern limit of wheat-growing in Canada had moved northward some 2 – 300 miles (call it 400 kilometres), adding that farmers in southern Ontario were experimenting with cotton. While that industry seems not to have taken off, he reported another trend that continues to this day, the northward retreat of the permafrost:
“In parts of Siberia the southern boundary of permanently frozen ground is receding poleward several dozen yards per annum.”
The matter open to question back then was the cause. Kimble noted that the Domesday Book featured 38 vineyards in England in 1086, in addition to those of the Crown. He pointed also to the Greenland colony which was frozen out, back around the mid-1400s and other evidence that climates change. He also looked at Biblical evidence on the distribution of date palms to suggest that conditions in 1950 were much those of Biblical times, providing a picture of a climate that fluctuates around a mean. Maybe it was just one of those cycles.

That was a time before ‘global warming’ when climate change was referred to as the ‘greenhouse effect’. In cold climates, a greenhouse is a glass shed which allows sunlight to shine in, where much of it is absorbed and changed to heat. Glass is less transparent to heat, but a greenhouse does not just trap warmth that way: it also holds a body of warm air around the plants, and protects them from wind-driven evaporation. So while we still speak of ‘greenhouse gases’, it is rare to hear anybody mention the greenhouse effect these days, but even that goes way back.

In the 1820s, Joseph Fourier realised that heat-trapping might occur. Then Svante Arrhenius reminded us in 1896 that both water vapour and carbon dioxide were ‘greenhouse gases’ (escaping that bad analogy is hard) and so water and carbon dioxide would play a role in making the planet get warmer. He also considered changes that might be happening, and consulted Arvid Högbom, who just happened to know all about carbon dioxide sources and sinks.

Carbon dioxide was coming from life forms when they breathed, from volcanoes, and from humans burning fossil and other fuels. The human additions were a very small part of the total in the air already, perhaps one part in a thousand was added by the burning of coal, and there were probably checks and balances. Arrhenius estimated that it would take 3000 years to double the atmospheric levels of carbon dioxide, if it ever happened, but that such a doubling would raise world average temperatures by 5 to 6°C.

In 1896, the CO2 level was around 290 parts per million: in 2016, the value was estimated at 396 parts per million: we had travelled one third of the projected distance in just 120 years.

To Europeans back in the 1890s, the warming effect seemed nothing to worry about, because nobody had stopped to consider the cascades, the flow-ons that might be driven by that rise in temperature. Walter Nernst, even wondered if it would be feasible to set fire to uneconomical and low-grade coal seams, so as to release enough carbon dioxide to warm the Earth’s climate deliberately!

Scientists are slow to move to a new model, a new way of understanding, something called a paradigm, and just a few years before the world’s earth scientists were shown irrefutable evidence of plate tectonics, we undergraduates in geology were being told by one of our lecturers “go and watch Carey perform at the conference — he’s mad, and thinks that the continents move!”

Sam Carey wasn’t quite right, but he was closer to the truth than his denigrator. It is, however, a well-kept secret that scientists engage in robust rhetoric and vilification. Sam seized on every scrap of evidence to push his own viewpoint, most of the audience laughed dutifully — and felt rather embarrassed a few years later when palaeomagnetic evidence showed that Carey was largely on the money. In the end, the good science was recognised and accepted.

A decade back, global warming was in much the same position, with some of the scientists arguing furiously, even when they agreed on the main principles, and as in the puzzle of the wandering continents, the key evidence is probably there. Mind you, when I covered the 2002 Spring Conference of then American Geophysical Union, there were no nay-sayers there.

The problem is that so long as people can get away with saying "global warming", we are once again stuck with a bad analogy, just as the early 1960s saw us hung up on “continental drift”.

That aside, the cost of disagreement and bickering is remarkably different. It mattered not at all if people disagreed about plate tectonics (except, perhaps, that it makes tsunamis like the 2004 Indian Ocean tsunami easier to understand), but global warming is likely to be a major disaster for humanity, and any delay has the potential to cost lives. To understand this, we have to accept some puzzling propositions.

To take one example, the formation of sea ice in the Bering Strait is probably what stops Dublin and New York being iced-in each winter. This is because the sea ice is largely free of salt, and leaves a residue of cold brine that drives a current known as the Conveyor, which in turn drives the Gulf Stream. The Gulf Stream takes warm water from the Caribbean and swirls it up around the North Atlantic, contributing to fogs and breaking icebergs loose, but keeping many ports warm and open, even in winter.

Just as the prion proteins of mad cow disease have more than one stable form, so do weather patterns, and if the weather once drops into a new pattern, we may not be able to bounce it back to where it started. The good news is that as northern Europe freezes over, the glaciers which are now melting away fast will be replenished, lowering sea levels. The increased snow cover will also increase the reflectivity of the northern hemisphere, and that may cool the planet down a little. We just have to hope it does not trigger a new stable pattern that happens to be an ice age.

The actual changes that might follow the breaking point are hard to predict. They are unlikely to be spectacular and major, and probably they will do their harm stealthily, when infrastructure, port facilities and cities are flooded, or when agricultural land is lost, either by being covered by the sea or as a result of drastically changed rainfall patterns. If rock is exposed in Antarctica, this could lead to a low pressure zone over the icy continent that could change weather patterns around the world.

It hasn’t happened yet, but we need to learn from history. Ten years ago, no politician would take a long-term view and force the changes needed in the next thirty to forty years, when most of them are elected for a mere three to four years, and then face the voters again. It is easier to bleat plaintively that there is no real agreement among the scientists yet (there is), or that some eminent scientists (they aren’t: just look at where their funding comes from) believe that there are other explanations.

That load of bollocks saves the politicians from having to act — and the honesty of scientists in saying that they cannot be sure just how things will go wrong allows devious short-term opportunists to prate that “the scientists aren’t sure…”.

Politics is a marvellous human discovery. It is a pity that politicians still have to discover humanity and consider its prospects. It is likely that politics, dithering, duck-shoving and shilly-shallying will make this disaster happen.

1 comment:

  1. Join a conservation group and keep taking the bastards to court :-)