A recent (September 2023) press release from the Swiss Academy of Sciences contained a startling statistic: over the past two years, the volume of glacial ice in the Swiss Alps decreased by ten percent (see https://scnat.ch/en/id/Cpd5S). It doesn’t take advanced mathematics to conclude that at such a rate all Swiss glaciers – currently there are around 1800 – will be gone well before the end of this century.
Of course the past two years, characterized by high temperatures and low snowfall, may have been anomalies. But since 2000 there have been no years when glacial ice in Switzerland actually increased, and eight (including 2022 and 2023) when it decreased by more than two percent.
These numbers are of more than academic interest because they reflect a worldwide phenomenon with serious consequences for hundreds of millions of people. In many parts of the world glaciers are a primary source of water for agriculture, industry, and general consumption. This is particularly true in densely populated South Asia, where Himalayan glaciers insure a reliable supply of water to rivers such as the Ganges and Indus during both seasonal dry periods and prolonged droughts. If – or perhaps more accurately, when – Himalayan glaciers disappear, there will be no water source to replace them.
Shrinking mountain glaciers, just one consequence of global warming, have not received as much attention as other effects such as storms, floods, heatwaves and wildfires. But glaciologists and climate researchers have been documenting the phenomenon for decades at various sites across the globe. The Swiss have an especially long tradition of glacier study, partly because they live in close proximity to so many glaciers. Indeed, the man generally acknowledged as the originator of the idea of ice ages, times when large parts of the earth’s surface were covered in glacial ice, was a Swiss naturalist named Louis Agassiz.
Agassiz was not the first to entertain the idea that glaciers had been more extensive in the distant past than they are today. Swiss farmers, encountering huge boulders standing in their Alpine valley fields where they had no right to be, reasoned that they must have been carried there by flowing ice. Several Swiss scientists and engineers had come to similar conclusions. But none of them had proposed anything like the theory of an ice age conceived by Agassiz.
I profiled Louis Agassiz in my book Frozen Earth. He was a biologist by training whose primary interest was fossil fish. But after conversations with scientific colleagues about the possibility that Alpine glaciers had once extended to lower elevations, he began to see evidence of past glaciation everywhere. On field trips he made observations of the giant ‘erratic’ boulders noticed by the farmers, of moraines (hills of sand and gravel left behind when glaciers melt back), of glacially scratched and scoured bedrock, and of landscapes shaped by flowing ice. All existed in places far from any active glaciers, but they closely resembled features he saw when he climbed to higher elevations to examine the glaciers themselves. Furthermore, similar phenomena had been reported in other parts of Europe, and in Asia and North America. Agassiz concluded that the earth must have endured a period of intense cold with vast sheets of ice covering much of the land in the Northern Hemisphere. In 1840 he published a book outlining his ideas. Many of his contemporaries were sceptical.
But the evidence was so compelling that soon scientists everywhere began to see evidence of a past ice age. It was a classic example of a universal experience: it’s easy to miss something until it has been pointed out to you. Charles Darwin, an astute observer of nature himself, wrote in his autobiography that years before Agassiz published his ideas, he (Darwin) had been on a field trip in a part of Wales that was full of glacial features – moraines, erratic boulders, glacial scour marks – but he did not recognize them for what they were. “How easy it is to overlook phenomena, however conspicuous, before they have been observed by anyone …,” he wrote.
Agassiz thought our planet must have endured a single period of deep freeze in the distant past, but today we know that the earth has experienced many such intervals over its four and a half billion years of existence. The glacier-produced features Agassiz observed result from only the most recent episode, the cold period spanning roughly the past three million years that we know as the Pleistocene Ice Age. Even this ice age, however, is more complex than he envisioned. Instead of being a single period of constant cold, the climate alternated between frigid intervals and warm ones like today. In response the glaciers, some of them miles thick, advanced and retreated multiple times over large parts of the earth’s surface, particularly in the Northern Hemisphere.
We don’t know precisely how these swings in global temperatures came about. We do know they correlate closely with changes in the way the earth orbits the sun, which affects the amount of solar energy received by the planet. But those changes alone are not large enough to explain the extreme climate shifts, which most scientists have concluded must result because of multiple positive feedback effects. One factor, however, is crystal clear: the importance of greenhouse gasses. During the Pleistocene Ice Age, warm periods have always been characterized by high greenhouse gas levels in the atmosphere, cold periods by low levels.
Until the past few hundred years these greenhouse gas fluctuations were natural, a consequence of the earth’s climate cycles and interactions between the atmosphere, oceans, and rocks of the continental crust. But since the industrial revolution human activity has been adding greenhouse gasses to the atmosphere at increasingly rapid rates – rates that are, as far as we know, unprecedented in the earth’s history.
And in 2023 the atmospheric concentration of the primary greenhouse gas carbon dioxide reached a level our planet has not experienced in more than three million years (see https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide; and https://www.noaa.gov/news-release/broken-record-atmospheric-carbon-dioxide-levels-jump-again). Unless urgent measures are taken to drastically reduce emissions, global temperatures will continue to increase and the glaciers of Switzerland and other parts of the world will disappear. Humans will have abruptly ended the natural cycles of the Pleistocene Ice Age. And we will have condemned the hundreds of millions of people who rely on glacial meltwater to an uncertain and potentially disastrous future.