In December 2015, at the Mauna Loa Observatory in Hawaii, the measured concentration of atmospheric carbon dioxide exceeded 400 parts per million. The last time the Earth’s atmosphere contained that much CO2 was some 4 million years ago, when average global surface temperatures were around 3 degrees C higher than now.
From samples of air bubbles in ancient ice cores, we know that for the past 800,000 years, CO2 concentration has cycled within the range 170 to 300 ppm. The breakout above 300 ppm started in the 1920s, driven by a huge increase in CO2 emissions due to human activity – mainly the consumption of fossil fuels, whose burning releases CO2 trapped underground since the aptly-named Carboniferous Period 300 million years ago. In less than 100 years, our annual CO2 emissions have jumped from 4 billion to nearly 40 billion tons. Those who doubt the cause of sudden global climate change should study those numbers.
The global greenhouse
The action of atmospheric CO2, water vapour and methane in warming the planet is well understood, as the ‘greenhouse effect’. Shorter solar radiation wavelengths pass through the atmosphere easily, warm the ground, which reflects longer infrared wavelengths that are absorbed and trapped by the blanket of greenhouse gases in the lower atmosphere. The effects of a 3C rise in average surface temperature on climate are unpredictable, and such a temperature increase may sound small. But by 2017 we already had an approximate 1C rise from average pre-industrial temperatures, and are now seeing unexpectedly fast melting of polar ice, combined with droughts in tropical and sub-tropical areas and increased incidence of wildfires around the world.
There is a risk that melting permafrost in the tundra of Canada and Siberia will release large quantities of methane – four times more potent than CO2 as a greenhouse gas – and create a dangerous runaway effect.
Long years of watching
In Scotland, the effects of a warming climate were observed continuously for decades by one remarkable scientist, long before climate science became fashionable and imperative. As a young boy, Adam Watson developed a fascination for snow. He remembered how:
I could see these pale veils coming out of the sky, and as it got near the ground I saw they were actually snowflakes.”
Prodigiously bright at school, he was inspired by the writings and friendship of the naturalist, photographer, folklorist and piper, Seton Gordon. By the age of 14, Adam was keeping a ‘snow diary’, monitoring weather events around his home in Turriff, Aberdeenshire. Despite a teenage attack of emphysema that kept him in hospital for several months, he was soon walking the hills again, confounding his doctor’s predictions. Watson’s interest in ornithology led to local surveys of rooks and herons, and he made increasingly adventurous trips, climbing and skiing into the Scottish mountain ranges.
Places of ice and snow
He graduated with first-class honours in zoology from the University of Aberdeen in 1952, and used his PhD research to study the annual cycle of the rock ptarmigan, the archetypical grouse of the high Cairngorms. A year later, he won a Carnegie Arctic Scholarship to McGill University in Montreal, and then worked as a zoologist in the Baird Expedition to Baffin Island for the Arctic Institute of North America. Back home again, he joined the Institute for Terrestrial Ecology in Banchory, edited The Scottish Naturalist for eight years, and in 1967 he was awarded a second doctorate for his published research on the populations and behaviour of northern animals. His intimate knowledge of the terrain of the mountains led to his appointment as Chief Expert Witness in a fatal accident enquiry into the deaths, in a blizzard, of five children and one of their instructors in the ‘Cairngorm Plateau disaster’ of December 1971.
From Seton Gordon, Watson inherited many interests, including the monitoring of the deep snow patches which lie in the northeast-facing corries of the high Scottish mountains, the nearest things to glaciers in present-day Scotland, and persistent all through the summer – in the past. The observatory on the summit of Ben Nevis reported persistent snow on the mountain’s northeast cliffs for most years from 1883 to 1904. Adam Watson’s own detailed field observations from 1938 to 2011 were summarised in A snow book, northern Scotland. For 64 years, he recorded the proportion of snow cover at the start of June on the Ben Macdui plateau of the Cairngorms, excluding ephemeral summer snowfalls that can briefly give 100% cover.
The waning of the snow
As residents and visitors know all too well, Scotland’s weather is highly variable, and over the decades Watson found summer snow cover extremes of 2% and 98%, with no particular trend in the cover until 1986. Since then, he recorded a clear trend of diminishing summer snow cover on the plateau.
An irregular decline in the persistence of snow patches in the high corries was observed too, in Watson’s surveys of northeast Scottish mountains from 1974 to 1989. Over those years, the number of snow-beds surviving till October fluctuated widely, between 2 and 79. Only 2 snow patches endured every year over the whole period.
The study, published in the journal Artic and Alpine Research, concluded that:
we aimed to compare changes in snow patches between years with changes in regional climate in the same years. This is a considerable improvement on the use of glaciers as indicators of climate change…where a big drawback is the long, variable time-lag between climate change and glacier response. The more rapid response and easier measurement of snow patches is particularly important when climate is very variable over short periods. Moreover, snow patches can themselves provide a good index of increasing variability in climate (as in our data). Summer snow patches, therefore, are a useful single index, integrating the effects of many aspects of short- and medium-term climate change.”
The Sphinx and the Pinnacles
In the summer of 1996, no snow patches persisted anywhere in Scotland, the first year without surviving patches since 1959. The most durable snow patches in the Cairngorms are those in Garbh Choire Mòr on Braeriach, the third highest mountain in the British Isles. The two snow-beds in this corrie, probably the most-studied in the world, are nicknamed the Sphinx and the Pinnacles. They have melted completely in only six summers over the last two centuries, but with increasing frequency, in 1933, 1959, 1996, 2003, 2006 and 2017. In 2018, the Sphinx succumbed to full melting for an unprecedented second year in a row. In 2019, as reported by the part-time researchers Iain Cameron and Blair Fyffe, the Pinnacles snow patch had expired by mid-October, and although the Sphinx patch survived through to winter, it was the smallest it had ever been without entirely disappearing.
Continuing the study
Iain Cameron is foremost among the researchers who follow the life-cycles of Scottish snow patches, in the footsteps of Adam Watson – who died at the age of 88 in 2019, a much-honoured Fellow of the Royal Meteorological Society (RMetS), the Institute of Biology, and the Royal Society of Edinburgh. Cameron has inherited Watson’s interest since becoming intrigued by the spring snow on Ben Lomond, visible from his childhood vantage point in his parent’s house in Port Glasgow. Though self-trained and employed as an environmental compliance officer for a building company, Cameron makes fortnightly summer trips into the mountains in his own leisure time, to monitor and report on snow patches. With colleagues, he writes the twice-yearly reports in the RMetS journal Weather on the continuing diminution of the number and extent of summer snow patches in the Scottish hills.
The steady drips of the thawing summer snow patches in Scotland’s mountain corries mark time on the unabating advance of global warming. The former weather forecaster turned forester, Matthew Hay, has written,:
As The Sphinx thaws, it does so alongside our planet’s sea ice, and the permafrost of the Arctic tundra. These frozen worlds are more than just habitats: they are our safeguards. If they disappear, they will likely send the planet spiralling inexorably towards its next stable-state, a world that is 4 or 5°C warmer than present. The suffering this would cause, to both human and non-human life on Earth, would be unimaginable.
So it is incumbent on all of us to take an interest in The Sphinx, and its frozen allies around the globe. These far-flung pieces of snow and ice may feel more distant and removed from our daily lives than ever, but what they tell us about the world we are living in, and the way we live our lives, has never been more relevant.”
420 high and rising
The poignant disappearance of Scotland’s summer snow may be the least of our problems. Concerted, decisive international action is required to ameliorate and manage the effects of climate change. There is widening recognition of the seriousness of our situation, and the 2015 Paris Agreement on climate change has targeted reductions in CO2 emissions of 40% by 2030, compared to 1990, and carbon neutrality by the end of the 21st century.
As of 2021, annual average atmospheric CO2 levels are nearly 420 ppm, rising at 2.5 ppm per year. It is not obvious that the world has the collective foresight, will or the political unity to implement meaningful countermeasures. The United Nations Climate Change Conference (COP26) took place in Glasgow in November 2021, bringing together more than 30,000 experts, delegates and heads of state to agree coordinated actions. The climate change clock is ticking.
This is the final chapter in John Mellis’s new book Scotland’s Science Next: Stories of pioneering science, technology and medicine (1850-2021).
