major fluctuations in the cryosphere, one property of snow in particular is vital: its whiteness. This gives it a thoroughly unusual capacity to reflect sunlight, up to 90 percent of sunlight in the case of new snow. If we take into account the fact that snow can cover up to half the land surface of the northern hemisphere in winter, as well as large expanses of sea ice and glaciers, it goes without saying that the climate effects can be considerable. Indeed, this albedo effect (see “A Closer Look: Albedo”) can trigger self-reinforcing climate processes in both directions: when the albedo diminishes because the sea ice and snow cover are vanishing, the temperature rises because land and sea absorb more of the sun’s heat, which leads to even more melting, and hence more heat absorbed, and so on. The opposite also applies: when more snow comes, the albedo increases, more of the sun’s heat is reflected, and it grows even colder, and so on, in a self-reinforcing feedback mechanism that has triggered an ice age on several occasions.
SNOW AND ICE also affect the climate in other ways, albeit at a more local level. When water freezes in the autumn, it releases large amounts of energy, which has a warming effect on the surrounding area: it feels warmer than it actually “ought” to be. In spring, when snow and ice melt, the opposite occurs. Melting takes a lot of energy, which makes the air grow colder than it would otherwise be. So in both autumn and spring, snow works as a kind of buffer, making the temperature changes happen a bit more slowly than they otherwise would. And snow has even more unusual qualities owing to the special structure of the snow crystals. One of them is that snow, though cold in itself, is one of the best insulators of heat in existence. This is what makes it possible for reindeer to find unfrozen lichen beneath the snow—and what makes snow-free winters a nightmare for reindeer herders, my neighbors during childhood.
A CLOSER LOOK
Albedo—the Effect of Whiteness
One reason why the cryosphere is so important for the climate is its whiteness, albedo in Latin.9 The Latin word is used to describe how much of the sun’s radiation a surface reflects. The reflection depends on the wavelength of the radiation, the angle at which it strikes the surface, and the nature of the surface. How much of the sun’s energy the surface of the Earth reflects has major implications for the temperature.
When snow settles on the ground, the albedo increases. New, dry snow reflects between 80 and 90 percent of the radiation. We say that new snow has an albedo of 0.8 to 0.9, where 1 indicates full (100 percent) reflection. When snow has been on the ground for some time and has become compacted and dirty, the effect diminishes but will still be considerable.
Sea ice has an albedo of 0.5 to 0.7, while open sea has an extremely low albedo of around 0.06. This means that when ice forms on the sea, the albedo increases dramatically, even more so if it is then covered in snow. While open sea absorbs almost all the energy from the sun and is warmed up, snow-covered sea ice reflects almost all the energy. With less ice and more open sea, the ocean will absorb more solar energy, which will cause even more ice to vanish, leading to more heat absorption, and so on.
Vegetation also influences albedo. Coniferous forests have almost no albedo, between 0.08 and 0.15. Deciduous trees have between 0.15 and 0.18, while green grass has an albedo of around 0.25. Generally speaking, the more forest and shrubs there are, the weaker the albedo effect; the more grass, the higher the albedo.
How important is the albedo effect? Today, Earth’s mean temperature is 59 degrees Fahrenheit. Calculations have shown that if Earth were entirely covered in sea, which has a pretty low albedo (0.06), the mean temperature would be just below 80 degrees, which would make large swaths of the planet uninhabitable. On the other hand, if Earth were totally white, with an albedo of close to 1, the mean temperature would fall to around −40 degrees.
— 4 —
IN THE REALM OF THE SNOW QUEEN
SNOW IS QUIET. Not just when it falls, but also when it has settled and covers the landscape as far as the eye can see. Like on Finnmarksvidda on a winter’s day, far away from all the houses, roads, and traffic—the way it could be on the plateau when I grew up there in the sixties. There was a silence that was more than the mere absence of sound. Because there was sound: the sound of silence, but most of all the sound of endless space. And of endless time, as if the snow had always lain there peacefully. Which, of course, it hadn’t. Because snow also has another face.
At dawn, as we reached Bæskades, a storm came blowing up. A flaying rush of driving snow whined on the mountaintop. Heavily leaned we into the storm, forced to rest a while, Our reindeer too were weary after many a long mile.10
It isn’t so long since people traveling in northern Norway in midwinter had to go by reindeer over the Bæskades plateau, just like Nordahl Grieg. As depicted in his poem, idyllically entitled “Morning on Finnmarksvidda,” it could be a grueling experience if the weather gods didn’t smile upon you. A journey that takes two hours by car today in summer conditions could well take one or two days, so it was a good thing there were plenty of mountain lodges en route.
When I traveled over Bæskades in winter as a lad, it wasn’t by reindeer but by a peculiar weasel-like vehicle known as a snowmobil (not to be confused with modern snowmobiles). It was a sort of tracked vehicle in which around ten passengers sat huddled together in a circle, barely catching a glimpse of the white landscape speeding past on the other side of a few tiny round windows, like the portholes on a boat. The snowmobil traveled faster than the reindeer and didn’t tire as easily; it was usually the passengers who had to stop for a break and a drop of coffee. I don’t remember how long the trip took, but it was the better part of a day. And why did I spend two days—there and back—on a trip like that? To stand shivering for hours on end watching somebody go around and around on a skating rink, that’s why.
I was ten years old and lived in Kautokeino, Norway’s most isolated municipal center, especially in winter. It was also the coldest—in competition with Karasjok—with winter temperatures sometimes falling toward −58 degrees Fahrenheit. That was fine by me: when it fell below minus 40, we were given the day off school. We moved to Kautokeino at the end of the 1950s, before the coastal town of Alta could be reached by a road that was open all year round, and when our community could still be isolated for weeks in spring. Then it was impossible to drive either car or snowmobil owing to the spring thaw. The snow grew wet and impassable, rivers and lakes could no longer be crossed, and even the reindeer had to throw in the towel. Today, a situation like that would merit helicopter airdrops and a news feature on TV, and the parliamentary public safety committee would be hauled in for a hearing to find out who was to blame. In those days, it was just the way the world was. The seasons had their rhythm: the snow came in autumn, the water froze, and later, in spring, everything started to thaw again and you just had to stay where you were, hoping you had enough of the bare necessities. It was what we were used to.
Young as I was, I knew no better and thought this was quite normal. As a child, I also got out of doing the most unpleasant chores, like going outside to fetch water from the ice-covered tarns or brooks when the water pipes froze. This was the kind of thing my father often had to do, and once he lost his footing and fell into the water. He ended up under the ice and spent a good while lying there flailing about before hauling himself out, soaking wet in the bitter cold. That he got home without freezing to death and didn’t fall ill tells you something about how hardy his generation was up there in the north. The same must be said of the young woman who set off to give birth at the clinic in Kautokeino one cold winter’s day—alone, on foot, in the snow. She didn’t make it in time and had to deliver the child herself by the side of the road, before carrying it onward to the clinic. Mother and child were doing fine, we were told.
I escaped any such
