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Monday 28 January 2019

Peak snow

The northern hemisphere is close to the point of maximum snow cover for the season, which makes this a good time to think about saving it for the future

By Giles Whittell

For 94 years the record for the biggest one-day snow event ever measured was held by Silver Lake, Colorado, high in the Rockies and three miles east of the continental divide. There, between April 14 and 15, 1921, a storm that gathered over the prairies and rolled up the eastern slopes of the mountains, dropped three inches an hour for 27 and a half hours straight. The 24-hour total was 76 inches – enough to bury a six-foot-four cowboy standing up.

I would give a lot to have been there, with measuring stick and fur-lined moccasins. And hip flask. And paraffin lamp flickering in the window of a log cabin stocked with enough food to last until the great spring thaw.

Will we ever see such snow again? It would be easy to look on in despair as glaciers recede above the tree line and white Christmases recede into memory, but it would be unnecessary. For many humans the experience of being in snow is so rare that it’s easy to assume the same is true of snow itself. In fact, even now, we get a staggering amount of it.

Professor Kenneth Libbrecht, former head of physics at the California Institute of Technology, has come up with a mind-bending illustration of how much snow still falls on the planet as a whole. In numerical terms he puts it at a million billion snowflakes per second, on average, every second of the year. To reach an estimate for a whole year from this starting point you would simply multiply a million billion by 60 to reach a number for each minute, then by 60 again for each hour, then by 24 for each day and finally by 365. That works out at 315,000,000, 000,000,000,000,000, or 315 billion trillion snowflakes a year. Which is a big number, and impossible to visualise. So, taking 100 million snowflakes as a reasonable estimate for a modestly proportioned snowman, Libbrecht offers this thought: enough snow falls on our planet to build one snowman for every man, woman and child living on it, every ten minutes throughout the year. That’s enough for seven billion snowmen every ten minutes, even in July.

Can this be true?

From any ordinary point of view it’s hard to visualise enough snow falling in ten minutes to create this many snowmen, especially if you are one of the majority of humans who have never seen snow or only seen it sporadically. What’s needed is an extraordinary point of view, and this is what the Global Snow Lab at Rutgers University in New Jersey has found.

In 2006, Nasa launched a three-tonne satellite from Cape Canaveral aboard a Boeing Delta rocket. It’s called the Geostationary Operational Environmental Satellite 13, or GOES 13, and it soars 30,000 kilometres above the North Atlantic with an unobstructed view of half the northern hemisphere. The other half is monitored and photographed by the GOES 15, parked in a similar orbit over the Pacific. Among other data streams, they provide continuously updated information on which parts of the globe are covered in snow, and the snow lab at Rutgers University turns this information into maps.

We don’t know much from the Global Snow Report about the depth of this snow cover. Some of it will be thin or short-lived like the snow that came and went before Christmas in the Alps in 2016. Some of it will be deep and crisp and even, and immovable until the spring sun gets to it. What we do know is that GOES 13 mapped 50 million square kilometres of snow cover in the northern hemisphere alone in 2016-17, from the high Arctic to Anatolia. Professor Libbrecht didn’t pluck his figure of a million billion flakes per second from thin air. He knew all about snow’s planetary scale, and he bases his numbers on a sensible, middling estimate for the number of flakes per cubic unit of snow. Such estimates range from a few tens of millions to a billion per cubic foot, depending on the size of flake.

So he was not exaggerating about the snowmen. If all snow fell as snowmen there would indeed be a gigantic army of them, replenishing itself every few minutes. Even so, we have taken snow for granted for too long. It teases us with sporadic reminders of how deep and crisp and even it could be, but on the whole it’s making itself scarce. It’s skulking in the high country like the yeti it has occasionally betrayed.

getty images

Grande Chartreuse monastery

At the monastery of La Grande Chartreuse north of Grenoble, the monks do not talk to outsiders (as I discovered after driving there one spring hoping to persuade them to) but they do measure snowfall in their mountain fastness. There was 30 per cent less of it in the three decades after 1980 than in the three before. The snowpack has thinned by half and the snow lies on the ground for 30 fewer days per year.

The monastery is 945 metres above sea level. At that level snow is in retreat across Switzerland as well, but even way up at 3,000 metres and higher not one Swiss weather station has recorded an increase in average snowfall over the past 70 years.

In Bariloche, the Patagonian mountain town where Nazis went to hide after the war, it used to snow prettily every winter. Not in the past five years. In Alaska, where the 1,000-mile Iditarod dog race used to pull sleds over nothing but crisp snow from Anchorage to Nome, they tend to move the start these days to Fairbanks, 300 miles further north. In Mora, where Sweden’s biggest cross-country ski race is held each year in the first week of March, they rely on artificial snow that has to be helicoptered in when the course gets too soggy for trucks.

The question is whether snow’s retreat is irreversible, and it may be. It is possible that children born in England this century will never see a white Christmas, except perhaps in the Peak District and on the Lakeland fells. Already, children born this century in Moscow are used to rain in winter even as their parents struggle to adjust to it.

But it’s too soon to declare snow doomed.

getty images

Remote cottage in the snow

The science of global warming due to greenhouse gases is not new or controversial. The principle that atmospheric gases trap heat and make life comfortable was established in the mid-19th century by the Irish physicist John Tyndall. Without them, NASA estimates that the mean global surface temperature on planet Earth would be minus 18°C rather than plus 15°C.

Water vapour is the most abundant naturally occurring greenhouse gas. Carbon dioxide is the second most abundant. Pump more of it into the atmosphere artificially and it stands to reason temperatures will rise. As they do, complex changes occur in ocean circulation and wind patterns, and simpler changes make themselves felt in people’s lives. Winters tend to start later and end sooner. Freezing points rise. More of what would have fallen as snow falls as rain. Average snowpacks thin. Come the summer, the effect is plain to see in depleted reservoirs. Farmers and householders adjust accordingly. This is not heresy or groupthink. It’s just what’s happening.

The evidence is clear to anyone who prefers not to outsource information gathering and analysis to the divine. On May 9, 2013, infrared air-sampling instruments at the Mauna Loa observatory in Hawaii, 11,000 feet up and far from anything that might distort their readings, counted more than 400 parts per million of carbon dioxide for the first time in the modern age. Polar ice cores suggest this was the highest recorded CO2 concentration at a location that can be taken to represent the atmosphere as a whole (rather than, say, in cities, where CO2 levels are much higher) in three million years.

A plaque at the entrance to the observatory shows a graph of CO2 levels recorded there rising steadily from 315 parts per million in 1958 to 380 in 2005. There was nothing special about the number 400 except that it was round and roughly double the average pre-industrial level, and many people had hoped we wouldn’t get there. But we did and we’ve gone on up. The count in 2018 is about 412, and one result is an increase in average sea surface temperatures since the 1970s of about 0.4 degrees.

The warmer the ocean, the more moisture it will release through evaporation, and the warmer the air above it, the more moisture it can hold. This was established in the early 19th century by a French railway engineer named Benoit Clapeyron, with the help of the German physicist Rudolf Clausius. They worked out that for every degree the sea’s surface temperature rises, the atmosphere’s water content should rise by 7 per cent. Several decades of measurements taken by American satellites have proved them right. Temperature increases over the past half-century suggest the mass of atmospheric water vapour should have gone up by 4 per cent, and it has.

That 4 per cent amounts to an extra 500 cubic kilometres of water in the air around us, Dr Kevin Trenberth of the US National Center for Atmospheric Research told me a few years ago. That is one Lake Erie or three Dead Seas. Such a huge amount of water would mean more storms, he went on. “As time goes on more of these storms will be rain rather than snow, but as long as the temperatures remain low enough you may actually end up getting bigger snowstorms. We’re going to have some big blizzards.”

And so it has proved. In 2015 Silver Lake’s one-day snowfall record was beaten by the unassuming hill town of Capracotta in the Apennines, on the same latitude as Rome. It was buried under 100 inches (2.54 metres) of snow in 18 hours flat. In America, for the first five years after Trenberth’s prediction the Sierra Nevada mountains in California endured a dreadful drought. Then, in the winter of 2016-17, the whole range practically disappeared under snow. Squaw Valley, which claims an average of 35 feet a year, was still digging out from under 47 feet in April. That month the town announced it would stay open for skiing right through summer for the first time in its history.

Squaw had never seen anything like it. Meteorologists attributed the season’s wild falls to “atmospheric rivers” supercharged with moisture thanks to the El Niño effect – a periodic warming of the Pacific that may be intensified by more general warming. If so, that warming could mean more snow before it means less, at least in a few fortunate high places. The greatest blizzard of all time may be yet to come.

But when? And where? And what sort of snow will it bring? These are serious questions for anyone who wants to be there when it happens. The answer to the first is of course unknowable, but I once asked a slightly different question – when will the last great blizzard happen – of the splendidly named Raymond T. Pierrehumbert, now Halley Professor of Physics at Oxford. I got a surprisingly specific answer: 2040. That was the year his statistical modelling said would yield the last big Goldilocks combination of low air temperatures, high atmospheric moisture content and heavy snow.

I hope he’s wrong.

getty images

Snow covers the Yorkshire Coast

There will be a final snowflake, just as there was a first one. It may not start its earthward journey for millions of generations, closer to the time when the sun expands to evaporate the oceans and consume the planet. Or it may come sooner. Can we push it back?

Sure we can. I say this because it beats moping and because stories sometimes come along that allow a snow junkie to hope. One of these I wrote myself. It was an interview with Professor Stephen Emmott, the scientist hired by Bill Gates to run the Microsoft Research Centre in Cambridge. He was pessimistic about humans’ ability to slow their birth rate to a sustainable level, but he was puckish on climate change. He had put a team to work on artificial photosynthesis, and he had a dream of scaling it up into a forest of a trillion artificial trees. These would create energy as plants do when they photosynthesise. In the process they would absorb carbon dioxide from the air on a colossal scale.

Even I could grasp the essence of the idea. The graph at the entrance to the Mauna Loa observatory is, from a distance, a steadily rising line to represent carbon parts per million in the atmosphere. Viewed closer up it is a rising zigzag, with sharp downward zags each spring when trees come into leaf across the northern hemisphere. As they do this they take carbon from the atmosphere much faster than for the rest of the year. The holy grail of artificial photosynthesis is to have this process running full time. It could happen.

Another story to lift the spirit as autumn and spring eat away at winter came from British government carbon dioxide emissions data in March 2018. The level of emissions from fossil fuel consumption was lower than in 1890 and 38 per cent lower than in 1990, thanks largely to a steady fall in the quantity of coal consumed by power stations. To this sort of news the standard response from those willing to let snow go the way of the Lorax is that China is building coal-fired power plants rather than shutting them down, and in that context efforts made by small countries like Britain are insignificant. I disagree. All efforts matter. They can prove concepts and offer examples. And no one wants to cut air pollution and promote skiing quite as urgently as President Xi Jinping.

No one, that is, apart from a son of mine who once sat, inconsolable, on a low stone wall at the foot of a French mountain, yearning for snow that wouldn’t come. He’s ten now, and catching up with his brothers on skis, and he would be grateful if we could all get stuck into the life-affirming job of saving snow. If we don’t, we’ll miss it when it’s gone.

Extracted from Snow, by Giles Whittell (£16.99, 2018, Short Books)


Event Details:

Tuesday 12 February
Q&A with Giles Whittell
author of Snow: The Biography6.30pm-7.30pm

Drinks 6pm
Location:187 Piccadilly, London, W1J 9LE

How many snowflakes are needed to make a snowman? Where is the snowiest place on Earth? When will the last snowflake fall? Snow has a lot in common with religion. It comes from heaven. It changes everything. It creates an alternative reality and brings on irrational behaviour in humans. But unlike most religions, snow has never had a bible, until now. Giles Whittell, a passionate snow enthusiast and one of our Tortoise Editors, takes the reader on a quest through centuries and continents to reveal the wonders of snow.

Book now