Climate change: the scientists who saw it coming

The Earth is warming because of humans. Today this seems like an incontrovertible fact, but despite scientific evidence dating back to 1825, it took decades for it to be accepted.

In 1938, steam engineer Guy Callendar shocked the world when he published a study showing that the Earth had warmed by 0.3°C in just 50 years. Except the world wasn’t shocked. In fact it didn’t even notice.

Whether it was because he was an amateur in the field of meteorology, or because the world just didn’t want to know, Callendar’s study was dismissed by the public and most other academics.

His idea wasn’t even a new one.

Scientists have been warning about climate change since the 19th Century

Joseph Fourier, a French mathematician and physicist, had first suggested that atmospheric gases could warm the Earth in 1825.

In an 1837 paper for The American Journal of Science and Arts, he argued that over a long period of time, the amount of heat held in by the atmosphere could change due to human activities.

By the 1860s, thanks to scientists like John Tyndall and suffragette Eunice Newton Foote, it was understood that gases like carbon dioxide, water vapour and methane could trap heat in the atmosphere.

When writing up an experiment for an 1856 issue of The American Journal of Science, Foote had warned that “An atmosphere of that gas (carbon dioxide),” she wrote, “would give to our earth a high temperature.”

In 1895, Swedish physicist Svante Arrhenius had even calculated that doubling the amount of CO2 in the atmosphere would raise the world’s temperature by 5 to 6 degrees Celsius — an analysis that holds up pretty well today.

However despite the work of these 19th century scientists, the world at large remained unconcerned. Even Arrhenius and his peers did not worry about global warming as they didn’t imagine the consumption of fossil fuels could ever become large enough to seriously impact the planet. Callendar even thought that a warming planet could be a good thing for farming in colder parts of the globe.

Arrhenius himself predicted that it would take 3,000 years for CO2 levels in the atmosphere to rise by 50%. However just 100 years later they had risen by 30%.

So why didn’t people take more notice?

“I think there was a lot of scepticism that humans could influence something as large as the planet,” says Ed Hawkins MBE, professor of climate science at the University of Reading.

“It was a brand new suggestion in many ways, so it took a long time for the implications to be understood.”

Linking global warming to fossil fuels

Despite Callendar proving that the Earth was warming in 1938, most scientists still didn’t believe that fossil fuels, and humans, could be responsible.

It wasn’t until 1953 that Charles David Keeling, a young postgraduate geochemist inspired by Callendar’s work, set up a carbon dioxide monitoring station on the top of the Mauna Loa volcano in Hawaii.

Within five years he provided the first unequivocal proof that CO2 concentrations were rising. What’s more, by analysing the CO2 in his samples, Keeling was able to attribute this rise to the use of fossil fuels.

The Keeling curve, as at October 5 2021. Image via Scripps Institution of Oceanography

Keeling’s discovery was one of the most important scientific works of the 20th century. Since then, daily readings at Mauna Loa have continued almost uninterrupted for more than 60 years. The “Keeling curve”, which documents changes in CO2 levels over time is the longest continuous record of carbon dioxide concentrations in the world.

But the world still didn’t really take climate change seriously.

Part of the problem was uncertainty within the science at that time.

“In the 1950s, 60s and 70s, global temperatures didn’t rise very much, and in fact they fell slightly during that period,” says Hawkins.

“That was a puzzle at the time, as it wasn’t clear why. We now understand that a by-product of burning coal is it adds lots of small dust particles called aerosols into the atmosphere. Those particles in the atmosphere actually stop the sunlight reaching the earth’s surface, and so they act to cool the planet.”

After the introduction of the Clean Air Acts in the UK and various other countries, temperatures started to rise again. However despite increasing certainty within the scientific community, the world was still slow to react.

World wakes up to reality of climate change

One of the first scientists to warn about the consequences of global warming was John Mercer, a glaciologist at Ohio State University in Columbus.

In 1968, Mercer was conducting fieldwork at the Reedy Glacier in West Antarctica when he discovered evidence of a former freshwater lake 1,400 meters high up in the Transantarctic Mountains.

Mercer took that as evidence that the entire West Antarctic Ice Sheet had once melted away — something that previously had been thought to be impossible.

His landmark paper found evidence that sea levels rose 6 metres in the previous interglacial period — around 120,000 years ago. Temperatures at that time were 6–7C higher than they are today.

In his study, Mercer called the West Antarctic Ice Sheet a “uniquely vulnerable and unstable body of ice.”

He warned that current atmospheric warming could once more cause the ice shelves to disintegrate, causing a sea level rise of about five metres.

But it took a while for his warnings to take hold, even when in 1995 the massive Larsen A ice shelf collapsed. The B ice shelf followed in 2002, followed by a major rift in Larsen C in 2017.

So why has it taken the world so long to take climate change seriously?

“Ultimately part of it is down to the science developing,” says Hawkins. “We were pretty confident around about 1990 that our actions were warming the planet, but it wasn’t absolutely certain at that point.”

However now that scientists are unequivocally certain, there are signs that attitudes are shifting.

“I think many people have woken up and are now understanding the risks,” says Hawkins. “From heatwaves in Canada to wildfires in California and Turkey, I think there is recognition now that this isn’t a remote problem far away in the future, we are living through the consequences here and now.”

Today’s monitoring

Monitoring the climate continues to play an important role in climate change research — paticularly in the polar regions, which are experiencing faster changes than much of the rest of the planet.

The British Antarctic Survey has been monitoring temperatures at the Rothera Research Station in Antarctica since 1997, revealing that atmospheric temperatures in the Western Antarctic Peninsula have risen by almost 0.4°C per decade during the second half of the twentieth century. The Southern Ocean in this region has also experienced rapid warming in this period, with summer surface temperatures rising by over 1°C.

BAS is also part of the International Thwaites Glacier Collaboration, which monitors the Thwaites Glacier, one of the most unstable glaciers in Antarctica.

Ice loss from the glacier, which is roughly the same size as Britain, currently contributes to around 4% of all global sea-level rise — if it was to collapse entirely, global sea levels would increase by 65 cm. The ITGC monitors and evaluates crucial data such as how the ice boundary is changing, and rates of ice melt, as well as examining the core of the glacier.

Better awareness of the processes that drive the glacier to retreat is critical to improving models of the glacier’s future behaviour and exploring conditions that could lead to a rapid increase in ice loss.

This data gives us vital insights into how climate change is affecting Antarctica, and by extension, the rest of the planet. What happens in Antarctica has implications for weather patterns, carbon cycling, sea level rise and biodiversity across the world.

Whatever our past track record of listening to climate scientists, we should certainly pay close attention now.

Want to know more?

If you’re a UK taxpayer, your contributions help fund the work of researchers monitoring climate change, via UK Research and Innovation — the UK’s largest public funder of research — and the nine research councils. Projects in this article are funded by the Natural Environment Research Council. You can read more about what we do here.

You can read more on the work to monitor Thwaites here.

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