A history of climate change.

Jens Galschiot's installation, Unbearable, in Copenhagen

In the savage illustration on the right, the J-curve that is skewering the polar bear reflects the graph of the unstoppable rise of atmospheric carbon dioxide, and the curve is made from lengths of oil pipe. Sometimes, art and politics go together very well. 

We have known about what we used to call ‘global warming’ for quite a while, since the 1950s, though it was predicted (as a theory) in the 1820s and explained in the 1850s. Now reputable atmospheric scientists all believe human activity is driving the modern warming of our climate. All the same, they agree 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. The problem used to be 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 among the nay-sayers.

In 1856 at the AAAS Annual Meeting, the work of Eunice Foote was presented, showing that carbon dioxide is a heat-blanketing greenhouse gas that in the atmosphere could warm the Earth. This was years before the work of the men usually credited with the finding (Tyndall in England and Arrhenius in Sweden, and we will come to them in a bit). Her work was in a short piece in The American Journal of Science and Arts for 1856 begins on p. 382, and says: “An atmosphere of that gas [carbonic acid, CO2] would give our earth a high temperature …”

Even before that, in the 1820s, Joseph Fourier had realised that heat-trapping by what we now call greenhouse gases might occur. Then in 1856, Foote identified carbon dioxide as the most likely threat, before John Tyndall said much the same thing in 1861. Back then, nobody thought much about it, 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 that changes might be happening, and consulted Arvid Högbom, who just happened to know all about carbon dioxide sources and sinks. Carbon dioxide was coming from animals when they breathed, from volcanoes, and from humans burning fossil and other fuels. Arrhenius thought 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 in 3000 years, the atmospheric levels of carbon dioxide would double, 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 distance in 120 years. In 2018, it was 407.4 ppm, and in May 2023, it reached a seasonal peak of 424 ppm. My back-of-the-envelope scribblings suggest we will double the 1896 value by the 2070s, after about 180 years, rather than 3000 years.

To Europeans back then, 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. A thermodynamics expert, 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!

In December 2019, Australia recorded its six hottest days ever, and 2023 now looks to be set to be the hottest ever, around the globe, but the trend was apparent even in 1950, when George Kimble reported in Scientific American that the northern limit of wheat-growing in Canada had moved northward some 200 or 300 miles (call it 400 kilometres), adding that farmers in southern Ontario were experimenting with growing cotton. While the Canadian cotton industry seems not to have taken off yet, 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 in 1950 was the cause. Kimble noted that the Domesday Book listed 38 vineyards in England in 1086, in addition to those of the Crown. He pointed to the Greenland colony which was frozen out, back around the mid-1400s and other evidence that climates change. He looked also at Biblical evidence on the distribution of date palms to suggest that conditions in 1950 were much like those of Biblical times, providing a picture of a climate that fluctuates around a mean. Nothing to see here…

In the 1990s, global warming was in much the same position that “continental drift” had been in, a generation earlier, 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 was all there. The problem is that once again we were stuck with a bad analogy, just as the early 1960s saw us hung up on “continental drift”.

Mind you, when I covered the 2002 Spring Conference of the American Geophysical Union, there were no nay-sayers there on plate tectonics or climate change. The problem is that so long as people can get away with saying “global warming”, we are once again stuck with a bad label, just as the early 1960s saw us hung up on “continental drift”.

Scientists are always slow to move to a new model, a new way of understanding, something called a paradigm, and I lived through the plate tectonics paradigm shift, and saw some of the brawling. There was fuss and bother along the way, but in the end, the good science was recognised and accepted.

Now about the ‘greenhouse effect’: in cold climates, a greenhouse is a glass shed which allows sunlight to shine in, where much of the energy is absorbed and changed to heat. Glass is less transparent to heat than it is to light, 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.

In the last ten years we have seen how the climate spin-doctors were using the same crooked tactics that were used to hide the harm that tobacco does. Nowadays, nobody denies that the Earth is getting warmer, because the evidence is there, but we stay with the less-easy-to-lie about climate change.

Why? Mainly, the cost of disagreement and bickering is higher in this fight. 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 will 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 cold salty water in the Norwegian Sea is probably what stops Dublin and New York being iced-in each winter. This is because of the 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. A golf ball in a wok lies at the bottom, and if you move it and let it go, it will roll back down. That is a stable system. A golf ball, sitting on a long cardboard tube doesn’t fall, so we might say it is stable, but if you knocked it over, it wouldn’t come back to this position. We say it is metastable.

The golf ball on the tube is stable to small nudges, but only within limits. Humpty Dumpty had two positions, one on the wall and one off it, and according to the nursery rhyme, the second was a position of no return. On the wall, Humpty Dumpty was metastable, but beside the wall, he was stable, and broken.

Climate patterns are either stable or metastable. If they are pushed too hard, they may ‘flip’ into a new metastable pattern (or even break), and only then, too late, do we discover that they were metastable (or even breakable). The best example of a probably metastable pattern is the monsoon system that waters much of Asia and the north of Australia, but El Niño and Indian Ocean Dipole are other possibles.

Climate scientists worry that severe changes may deliver a push that will take a metastable pattern away from what we know, and there might be no way of returning to the original pattern. 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 any breaking point are hard to predict. They are unlikely to be spectacular and major, and probably they will do their harm stealthily, when roads, bridges, 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, before they face the voters again.

It is easier to bleat plaintively that there is no real agreement among the scientists yet (there is, actually), or that some eminent scientists (they aren’t eminent: just look at where their funding comes from) believe there are other explanations. That 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 prattle 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, and many of the effects will seem to be unrelated to the climate.

Take dengue (pronounced den-GAY) fever, which is caused by the dengue fever virus, which is transmitted by the Aedes aegypti mosquito. The geographic range of Aedes aegypti is limited by freezing temperatures that kill overwintering larvae and eggs, so dengue virus transmission is limited to tropical and subtropical regions.

Aedes albopictus is also capable of spreading dengue fever. As a rule, the Aedes mosquitoes are recognizable by their striped legs (which give Aedes albopictus its nickname of ‘tiger mosquito’), and the fact that they bite by day.

Dengue fever involves an internal haemorrhage that sometimes leads to shock—a drop in blood pressure and failure of blood cells to meet the metabolic demands of the body. It is a leading cause of death among children in Southeast Asia, killing about 1% of all cases. It includes four distinct viruses or serotypes, dengue 1 through dengue 4. As in the case of malaria, mosquitoes become infected with dengue after taking a blood meal from a dengue-infected person.

People infected with dengue virus develop dengue fever or dengue haemorrhagic fever. Dengue fever is also known as ‘breakbone disease’ because of severe headache and joint pain associated with it. Dengue haemorrhagic fever is far more serious than the rarely fatal dengue fever.

After a short incubation period of 1 or 2 weeks, the mosquito can transmit the infection to a susceptible person. An infection with any of the four serotypes confers protective lifelong immunity, but only to that serotype. The risk of developing haemorrhagic dengue appears to be increased among people later infected with a different serotype. In recent years, haemorrhagic dengue has become increasingly common in tropical America.

Climate change is expected not only to increase the range of the mosquito but would also reduce the size of the mosquito’s larval size and, ultimately, its adult size. Since smaller adults must feed more frequently to develop their eggs, warmer temperatures would boost the frequency of double feeding and increase the chance of transmission, which will happen when the first person bitten is carrying the virus.

Warmer temperatures reduce the incubation time for the virus. The incubation period of the dengue type-2 virus is 12 days at 30°C, but seven days at 32 to 35°C. Half the world’s population is currently at risk from the disease, and it has recently become a serious problem in Latin America. Brazil alone had a quarter of a million cases in 1997.

Dengue is hard to eradicate once it is established. In Australia, it reappeared in north Queensland in 1981 after being absent for some 25 years, and it spreads each year through the areas of northern Australia where the Aedes aegypti mosquito is found, though cases are reported from across Australia each year, as a result of people being infected in either the north of the continent or overseas.

There have been suggestions in the past that global warming could lead to a spread of the Aedes aegypti mosquito, and thus the disease, but at the moment, Australian cases seem to be limited to about 200 a year. There is, however, a massive increase in cases across the whole of the western Pacific. Our turn will come…