The Decibel - You’re not wrong, snowy winters aren’t like they used to be

Episode Date: January 15, 2024

Snowy season in many parts of Canada is off to a slow start. At the end of December, fewer than half of Whistler Blackcomb’s trails in British Columbia were open due to the lack of snow. And the Prairie provinces are expected to have a milder winter, with below-normal snowfall. While the amount of snow varies from year to year, a new study says snowpack – the volume of snow that is present on the landscape – in the Northern Hemisphere is on the decline because of climate change.Ivan Semeniuk is The Globe’s science reporter. He’s on the show to explain how this loss will impact not only ski season but also water supplies and agriculture.Questions? Comments? Ideas? E-mail us at [e-mail]

Across much of Canada, so far this winter's been feeling a bit different. There's been a lot less snow. And while the amount of snow does vary from year to year, less snow has become a trend. A new study says that across the Northern Hemisphere, snowpack is shrinking because of climate change. And that doesn't just affect things like ski hills. It can change our water supply and agriculture. Ivan Semenik is the Globe science reporter. He's here to tell us about the loss of snowpack and why winter is starting to look different than it used to.

I'm Maina Karaman-Wilms, and this is The Deci look different than it used to. I'm Maina Karaman-Wilms, and this is The Decibel from The Globe and Mail. Ivan, thank you so much for being here. My pleasure. I think we should just start by defining, really, what exactly is snowpack? You know, often when we're thinking of snow, we're thinking of snow cover, you know, the fact that there's snow kind of persistent on the landscape. And that's something that's fairly easy to measure, even from space. You know, you can look down and see, is there snow in this place or isn't there? Snowpack is trickier. This is really the volume of snow

that's sitting on the landscape as opposed to just the area that's covered by snow. Measuring the thickness of snow is tricky because it's highly variable from place to place. And it's not a point measurement, you know, like temperature or pressure. Snow falls, snow might start to melt, and then more might be falling at the same time. And, you know, you can have layers of snow coming from different precipitation events. So measuring how thick the snow is or how much snow, you know, what the density and volume of snow is in different places at different times can be tricky. Okay, so snowpack is essentially, as you say, like the volume or the

depth of snow as opposed to just snow cover, which is it could be a sprinkling on the surface if it's what we can see essentially then. Exactly. So that's what snowpack is. Why does snowpack matter? It matters because it's essentially a natural storage system for water. ecosystems are set up in the northern hemisphere at the mid-latitudes to receive kind of a pulse of water in the springtime when the snow melts and all the nutrients that that water carries. And so, you know, forests and fields and so on, and the growing season in the northern hemisphere is built around that melting snowpack. And in a sense, the large population centers of the Northern Hemisphere that draw on that water as well are also kind of structured around that annual cycle.

You might think, well, if we're switching from, say, snow to rain in some parts of the world, what does it really matter? We're still getting water, whether it's snow or rain. But what you end up with is the timing of the water becomes quite different if you're having rain falling sort of in the middle of the winter as opposed to water being stored as snow. Okay. Okay. So this is good context. So let's now turn to this new study that was recently published in the journal Nature. And this study set out to measure snowpack loss. So what did it find, Ivan? It's interesting. And I should preface this by saying we don't always pay attention to single studies when we do our reporting.

You know, we're more interested in kind of the larger trends. But I think this was an interesting one to highlight because here the authors really tackled that challenging problem of how you address or measure something as highly variable as snowpack and try to see if there's a climate change signal there. And it's done that in a few different ways. It's trying to create a consistent measure of snowpack all across the Northern Hemisphere, bringing together different strands of data to really make it consistent to see, you know, to the best of our ability, what can we say about how much snowpack there is in different places and how that changes over time. They've used a way, you know, they've grouped that snow by watershed. That's kind of how like how the water flows into big bodies of water, right?

That's what we're saying there? Exactly. So, for example, all the snow that might end up melting into the Great Lakes or into the Mississippi Basin or into the Danube River if you're in Central Europe, you know, that kind of thing. And then on top of that, they've done some pretty serious modeling, which means that they've taken computer programs and tried to recreate the snowpack that we see in reality, you know, using the equations that kind of chunk through in a big giant computer simulation of the planet. Try to recreate the snowfall as we see it, but also look at how that would be different if we didn't have the same rise in greenhouse gas emissions that we know we are producing. So they've basically been able to compare over a 40-year period from about 1980 to 2020. What would the snow be doing if we weren't increasing our emissions compared to what the snow is doing when we do have the current state of our emissions? And how do those two scenarios compare?

Okay. So it sounds like they've been looking at a lot of numbers over a 40-year period. And so what did they find, Ivan, about snowpack loss over that time? So what they're showing is unequivocally there is a climate change signal. So this is the thing that was hard to detect because of the variability, but they are definitely showing in many places that there is an overall decrease in snowpack, even though, you know, from year to year, month to month, there might be, you know, big dumps of snow and then periods where there isn't snow, you know, so in small bursts,

it might be hard to see. But over that 40-year period, there's a definite trend. The trend is not the same everywhere, though. So it's highly variable to region. There are even some places where they're getting more snow than ever. Some of those places include kind of along the northern part of Siberia or up in the northwest of the Canadian Arctic. And the cause of that might actually also be related to climate change because the Arctic Ocean has less and less ice, especially in the summer months.

And so that means more open water and more ability, more evaporation from the ocean, more ability for water to be transported onto land where it might fall as snow. So those are areas that are actually seeing an increase in snowpack. Where are we actually seeing a loss then in snowpack? So in many places, there is a parallel loss of snowpack. So it means more rain, less snow. And the areas where it's particularly predominant are central and eastern Europe, northeastern U.S., where the change has been almost 10% per decade.

So, you know, over a 40-year period, you can imagine that's quite a big decrease in snow. The Great Lakes region has definitely also been influenced by this. We're seeing maybe up to a 7% or so decrease per decade. So that's another area where snowpack. And you can imagine that's, you know, the southern edge of the Great Lakes, you know, the US states that border the Great Lakes, but all across Ontario, where you have Ontario rivers and Quebec rivers feeding into the St. Lawrence, and also in the US Southwest. Now, this is a part of the continent that people might think, well, you know, I'm not really thinking about snow in Arizona. But of course, here, river systems are being fed by snow up in the mountains.

So altitude is also a factor here in addition to latitude. And so the US Southwest depends a lot on snowfall from the Rockies. And that's another place where we see a drastic decline in snowpack. Okay, so the scientists behind the study know that snowpack loss is happening. How do they know exactly, Ivan, that it's climate change related? Well, that's where you look at the simulations that compare the effect if you were not increasing greenhouse gas emissions to the effect when you include the greenhouse gas emissions that we have already produced. So that difference tells you how much of an effect human-caused climate change is having, and it also allows you to project forward. And there's an interesting effect here because what they're finding is that this is a very nonlinear relationship.

So in other words, if it gets twice as warm, that doesn't mean that you have twice as much snowpack loss. It's more of a threshold effect. In places where it's very cold, if things get a little bit warmer, it's not really going to affect the snow very much because you're still well below the melting point of snow. But places that are kind of more on the threshold of the melting point, even a slight increase in warming could cause quite a dramatic change in the snow regime of that place. And so what they're finding is there are certain places, especially kind of along the more southerly parts of the hemisphere where there's routinely, you know, kind of snow-covered

landscapes in the winter, what they're finding is that the threshold seems to be around minus 8 degrees Celsius. So in other words, if your average winter temperature is minus 8, and by average I mean daytime, nighttime, over several weeks, over the months of winter, if your average temperature is minus 8 degrees Celsius, below that, if you're below that average, your snow will more or less be stable or some additional warming isn't going to affect it too much. If you're above the minus 8 degree average, then you could see quite a dramatic change. And so as the Earth gets incrementally warmer because of continued greenhouse gas emissions, there are areas that are going to be kind of pushing over that threshold. And, you know, the scientists describe it as a snow-loss cliff. You know, suddenly there's going to be a drastic change in how those areas experience snow through the winter.

Okay, so this is a really interesting and important part of this, it sounds like. So someplace that's kind of consistently cold over the winter, you're not going to see that snowpack loss so dramatically. But someplace, I'm thinking like Toronto, like that Great Lakes region that you're talking about, where it kind of fluctuates, you know, maybe minus 10, maybe plus five, that's a place that's really going to see a big difference. Absolutely. And one way I should say that the scientists controlled for the variability that makes it really hard to tell from year to year is they focus the simulations and their data on the month of March. March is basically for any given year. March is when you're going to tend to, it's more or less going to be at its highest.

The pack will be at its highest by March. And so that's allowed them also to have kind of a more consistent picture. For example, places that would be typically used to being snow covered through the winter and to have a good, dense, deep amount of snow by March, if those places start to have thin, patchy or non-existent snow, it's basically a different world for those places, for their water regime and for their ecosystems. We'll be back in a minute. Okay, Ivan, let's talk about what we're seeing happening in those areas with less snowpack. I guess, can you walk us through maybe an example of a place that's affected by this? I think maybe places like California, we can already see the effect in a more meaningful way that water managers have to deal with. California is very dry in the summertime,

and water managers have to draw on the reservoirs to make sure that people are supplied with water. And we know that California has kind of been in drought conditions for the last little while, but that seemed to change this past year. One thing that changed was an awful lot of rain in the mountains about a year ago. And that led to swollen reservoirs in the spring of 2023, which then forced managers to have to release water from reservoirs because they were essentially, they had too much water to deal with. At a time of year where they would rather not have to release water, they were having to let water go. So if that water stayed in the form of snow for longer,

that would be more gradually released instead of all rushing at once as water. Exactly. So you could sort of say that the infrastructure, the water infrastructure of California is essentially designed to have, you know, it's got its own human-made storage system in the form of reservoirs, but that's on top of a natural storage system, which is the snow in the mountains. And if that natural storage system is changing, you know, that means they have to rethink their water plans. Wow. What about the impact on agriculture, Ivan? Like, I'm thinking

about farming, plant life. Can you talk about how that would be related? You know, when you have a snow-covered landscape, you know, think of the forests of Ontario and Quebec or, you know, other parts of Canada. You know, those northern forests are meant to be under deep snow. has an impact not only on the growth cycle, when nutrients get delivered to that landscape and when plants start to grow in the spring and so on. Just think of insects that can survive better when there's no snow cover on the ground and how that might be bringing new diseases

or impacting the health of, say, deer and moose and that kind of thing. It's a change that is not how those animals are. It's not the environment those animals are used to. Wow. Yeah. I mean, once we start dissecting this, there's so many things that could be affected by this loss of snowpack. So, Ivan, the study says that even could be affected by this loss of snowpack. So Ivan,

the study says that even a modest further increase in warming of the planet could result in major snowpack reduction. What are we talking about when we say modest in this case? What is a modest increase? So it's a good question. And it depends, again, on where you are. but what they're really trying to say there is, you know, we've now gone over a degree of warming since pre-industrial times. In fact, you know, we're getting some news this past week that in some senses, you know, 2023, not only the hottest year on record, but really pushing the 1.5 degree threshold, which the Paris Agreement was intended to try to set as a limit. That's quite significant. That's quite significant. Exactly. So modest might mean a few more fractions of degrees on average

may amount to much, much more than just a fractional snowpack loss. Ivan, we've talked on the show before about El Nino and how it's affecting this winter. I wonder, though, how is El Nino impacting this year's snowpack? Like, did the researchers account for El Nino years? So El Nino would be a part of those models. And so that's, you know, kind of a back and forth oscillation. You know, that's a back and forth cycle along with the annual cycle and other things that we see affecting the weather and the climate from year to year. And certainly during strong El Nino years, there can be a change in, warm or wet different parts of North America are. Absolutely. So this is really on top of that. You would have that El Nino change. And in some ways, El Nino, because it brings warmer temperatures in some parts of the globe, it almost is a bit of a harbinger of the future because when you're at the top of an El Nino cycle, you're sort of getting a warmer than average temperature.

And that maybe since our overall temperature is getting warmer, it might kind of give us a sense of what the future is going to look like permanently. But then that'll change a little bit when the El Nino cycle swings the other way. But what they're talking about here is really a longer term trend that would be layered on top of all of these other effects, including El Nino. Honestly, I mean, this sounds pretty concerning and dire to hear the reality of this. I don't mean to sound dramatic, but like, is this the beginning of the end of snow in some places? If you're anywhere where the temperature can be below freezing, it can snow. So it's not the end of snow, but it's a different kind of snow. You know, and I'm sure that, for example, people that run ski resorts that depend on a certain amount of snow falling on average over a certain period of time in the winter, you know, those are real, you know, there are very real economic consequences for people in places that depend on a certain amount of snow. So in that sense,

yeah, I would absolutely not minimize that. But I would say that it's another effect of climate change that we have to plan for and get used to and make sure that our systems are set up for, you know, where and when the water is going to be and the fact that in some places there's going to be less water stored on the landscape, which then becomes available later in the season. And I think, you know, again, the Southwestern United States is a prime example of this, but there will be other places that may be affected as well. I think that for some of us, the idea of a lot of snow persisting on the landscape for most of the winter may become a memory for certain parts of the planet.

So winters from 40, 50 years ago are going to be different than what we have now as a reality. You'll have to go further north. You'll have to go above that threshold to experience that. So just lastly, Ivan, I mean, there's a lot of really serious stuff we're talking about here. Is there any glimmer of optimism

in how we can approach this and maybe tackle this problem? I mean, for me, the optimism is always that science can offer these insights. We have all of these tools and all of this data that can tell us about what the climate, which is a very complicated system, is doing and what it's likely to do in the future as we kind of force it in different directions. So we just have to use those tools as best we can and try not to ignore what the planet is trying to tell us. So, I mean, to me, I'm optimistic that we have access to information and I think it's just important for people to make the best use of it.

Ivan, thank you so much for being here and walking us through all this today. Always a pleasure, Manika. That's it for today. I'm Manika Raman-Wilms. Our producers are Madeline White, Cheryl Sutherland, and Rachel Levy-McLaughlin. David Crosby edits the show. Adrienne Chung is our senior producer, and Angela Pachenza is our executive editor. Thanks so much for listening, and I'll talk to you tomorrow.