x Abu Dhabi, UAEThursday 27 July 2017

Warning science

Wallace Broecker was among the first scientists to perceive the threat of global warming. He gives an account of how we discovered our vulnerability.

Unfrozen: Ice boulders left behind after a flood caused by the overflowing of a lake in Greenland.
Unfrozen: Ice boulders left behind after a flood caused by the overflowing of a lake in Greenland.

Wallace Broecker made his name in science by showing that modest fluctuations in weather patterns could induce sudden and profound alterations in climate. Far from being a slow and gradual business, meteorological change can often be dramatic, suddenly plunging the world into periods of intense cold or warmth — sometimes within a century. As Broecker says: "Climate is a tetchy beast, subject to large and abrupt mood swings."

Understanding this point has been crucial as our planet has begun to spin inexorably towards a climatic catastrophe induced by rising greenhouse gas emissions. In revealing rapid climate changes of the past, Broecker has helped demonstrate our vulnerability today. And yet it could all have been different. When he was a young researcher, Broecker's promise was recognised by several senior scientists, and he was groomed for success. An august - and boringly conventional - academic career beckoned. Then one day in the 1950s, Broecker was taken aside by Hans Suess, the distinguished Austrian nuclear physicist, and warned that he should on no account spend his energy trying to climb the academic ladder. "Be a dynamic incompetent," thundered Suess. "Do at least three outrageous acts a year. Then no one will want you to be an administrator."

And so Broecker embarked on a lifetime of idiosyncratic work - taking part in ocean current surveys, coral reef studies, and glacier research - which he mixed with "outrageous acts", usually practical jokes inflicted on colleagues. One found his car raised on concrete blocks so that its wheels revolved hopelessly no matter how hard he pressed the accelerator. Strangely, the victim was not amused. Neither were university authorities.

Thus Broecker, "a fresh-faced, clean-cut young man with the devil in his eye", found himself shunned by administrators and free to indulge his scientific curiosity, to his - and our own - good fortune. These were golden days for climate research, as Broecker and Kunzig make clear. Former Manhattan Project physicist William Libby had just won a Nobel Prize for inventing radio-carbon dating. Now scientists were using the technique to find the ages of virtually anything they could get their hands on. As Broecker and Kunzig put it: "To be a radiocarbon dater in the 1950s was to be like Galileo with his new telescope in the 1610s."

Broecker was particularly interested in ancient tree trunks, pollen, leaves and vegetation that had been left behind by glaciers and ice caps as they had spread and receded over Earth's remote past. This icy ebb and flow was then thought to be slow and gradual. Broecker - after he had dated debris at a range of different sites - found this was often not the case. When change came, it did so rapidly and with considerable intensity. In particular, his studies of fluctuating American lake levels showed the last Ice Age had ended "in a geological instant" and that the Earth had turned from an ice ball to a relatively balmy blue planet in a few hundred years.

Broecker had made a first, crucial step in helping to create the modern science of climatology. In what would follow, the world learnt it was heading into a future in which sea levels could rise catastrophically, droughts could spread and temperatures could surge. Many other key players have been involved in this work, of course, and each gets his or her moment of glory in Fixing Climate - for this is a not a simple biography of a single scientist written in collaboration with a professional writer. Broecker and Kunzig, a distinguished US science journalist, have taken considerable pains to reveal the involvement of all the other geographers, physicists, meteorologists, oceanographers and chemists who have shown the world's vulnerability to abrupt climate change.

These climate heroes include Milutin Milankovic, "a nerd in a stuffed shirt" but a genius nevertheless, who calculated in 1917 that Earth's complex orbital mechanics played a key role in triggering ice ages; the British engineer Guy Callendar, who established in 1938 that humans had started to interfere with this process by pumping billion of tonnes of warming carbon dioxide into the atmosphere; and Dave Keeling, who first demonstrated that it was possible to measure carbon dioxide levels in the atmosphere.

Keeling, whose work was considered irrelevant in the 1950s and '60s, was particularly obsessive and determined. In 1958, he began measuring carbon dioxide on Mauna Loa in Hawaii, a site remote and relatively free from industrial pollution. His first results showed that global carbon dioxide levels rise and drop throughout the world as seasons change. Plants draw in carbon dioxide as they grow in spring and summer, and exhale it winter as they die off. Keeling realised he was watching the planet breathing in and out. What's more, when he continued with his measurements, he found each year's carbon dioxide reading was greater than the previous year's. When he started his work, there were around 310 parts per million of carbon dioxide in the atmosphere. Today there are about 390 and the rate of increase is rising. The cause has become more and more abundantly clear: our increasingly industrialised world is belching out more and more carbon dioxide, causing the planet to warm alarmingly. Soon our climate may undergo another abrupt and devastating change.

"If Keeling had not been so devoted to measuring carbon dioxide, the debate on global warming would be even more mired in polemics than it is now," Broecker and Kunzig write. "Instead, the 'Keeling curve' of carbon dioxide at Mauna Loa has become one of the debate's few universally acknowledged truths." Much of the work carried out by Keeling and the rest is intricate and arcane. To Kunzig and Broecker's great credit, they have distilled its key aspects and made them accessible and entertaining. The end result is a thoroughly enjoyable, adroitly written investigation of a phenomenon that will soon change all our lives.

Robin McKie is science editor of The Observer.