Human-caused global warming already has doomed a large fraction of Earth's glaciers

ImaGeo iconImaGeoBy Tom YulsmanJan 30, 2019 6:02 AM


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But thereʼs a silver lining to this dark cloud: You can still make a personal difference in preserving glacial ice.

A large chunk of ice (known as a ‘bergy bit’) about one-story high floats in the waters of Kongsfjorden in Svalbard on Tuesday, Sept. 6, 2016. This was two days after what was likely the largest calving event ever monitored from the Kongsbreen glacier front up until that point. (Photo: © Tom Yulsman) Even if we somehow stopped climate change dead in its tracks right now, recent research shows that more than a third of the world's 200,000 glaciers would melt anyway. That's because glacial ice takes decades to fully respond to the human-caused global warming that has already occurred. And as the inevitable thawing continues, meltwater flowing into the oceans will contribute to sea level rise, posing challenges for low-lying coastal cities already struggling to cope with flooding. “Whatever we do, we have little wiggle room left because we have already committed to melting a large fraction of the ice,” says University of Bremen climate scientist Ben Marzeion, lead author on the study, which was published in the journal Nature Climate Change. I spoke with him at the Arctic Frontiers conference in Tromsø, Norway last week. Findings like these can make us feel helpless, because they suggest we have little influence on the course of climate change. But there’s also a flip side to Marzeion’s research, one that offers an antidote to helplessness: In addition to documenting the inevitability of glacier melting, his findings also show just how much of a difference each one of us can make in saving glacial ice. For his research, Marzeion used climate models to feed information on temperature and other climatic factors into other models that predict how glaciers will respond. In particular, he and his colleagues focused on the kind of glaciers found in mountainous regions like the Alps, or in Norway’s Svalbard archipelago, leaving Greenland and Antarctica’s giant ice sheets out of the analysis.

Hikers descend Longyearbreen, a glacier in Svalbard. The Arctic archipelago's glaciers, which cover 60 percent of the land surface, have been thinning as the climate has warmed. Research shows that over the past 40 years, Svalbard has lost a volume of glacial ice equal to about 388 cubic kilometers. That works out to a cube nearly 100 miles on a side. [Photo: ©Tom Yulsman. Glacier data: Christopher Nuth et al, Svalbard glacier elevation changes and contribution to sea level rise, Journal of Geophysical Research: Earth Surface, Journal of Geophysical Research , 115 (f1) ] It’s not that melting of ice in Greenland and Antarctica are unimportant. In fact, research published last week shows that Greenland’s ice is melting faster than previously thought and will likely trigger faster sea level rise in coming decades. But big ice sheets and the smaller glaciers of the kind included in Marzeion’s study are different beasts. And better understanding of how the latter are responding to human-caused warming is vital. That’s because their melting is already contributing about half of the 3 millimeters per year of global sea level rise currently being observed. That works out to about 0.05 inches annually. By comparison, Greenland has lately been contributing about 0.03 inches to sea level each year. In one of a number of modeling scenarios Marzeion and his colleagues undertook, they examined what would happen if we somehow kept the climate as it is now — a little less than 1 degree C warmer than it was in preindustrial times. In this scenario, “you keep exposing the glaciers to our current climate,” Marzeion said. And the question is, “How are they going to respond in the long term?” In our conversation at the Arctic Frontiers conference, he summarized the results this way: “On a global scale, with the present day climate, roughly one third of the glacier mass will be lost. So there is a disequilibrium between what the glaciers are looking like at the moment, and what the climate is looking like at the moment.” In other words, the glaciers take time to respond — they haven’t yet caught up to the climate warming we’ve caused so far. Turning off climate change overnight is obviously a physical impossibility. But we can work to limit future temperature increases by reducing how much heat-trapping carbon dioxide we’re pouring into the atmosphere. The Paris Agreement on climate change was intended to do just that. So, how much of a difference could the agreement make for the glaciers? Signatory nations committed to restraining global warming to well below 2 degrees C above preindustrial levels — and preferably to no more than 1.5 degrees C. Achieving that goal would reduce risks of a number of other climate change impacts, such as heat waves and droughts. “But with 1.5 degrees of warming, or four or five, we see only a little difference in glacier melting,” Marzeion said. If we kept global warming to just 1.5 degrees C, the modeling shows that about 52 percent of the glaciers would still melt in the long run. If we limited it to 2 degrees C of warming, 62 percent would melt anyway.

Two peaks loom over the Kronebreen glacier and Kongsfjorden, as seen from Ny-Ålesund in the Arctic archipelago of Svalbard. (Photo: ©Tom Yulsman) To help me understand why glaciers respond this way, Marzeion asked me to imagine taking a large ice cube out of the freezer and placing it on the kitchen counter. In the much warmer room, the ice would begin to melt. But it would take a little while for the melting to become obvious. With global warming, “this is essentially what we’re doing with the glaciers,” Marzeion said. We’ve already taken them out of the freezer. And while we’ve seen melting because of it, they have not yet fully responded to the warmer temperatures. Now, let’s take the analogy a little farther. If you want to stop the large ice cube from melting any further, you’d have to put it back in the freezer. For the glaciers, that would mean going back to the temperatures of the pre-industrial era. That’s extremely unlikely. But what if we put the ice cube in the refrigerator next to, say, the milk carton? While temperatures in there are cold, they’re not below freezing. So the ice cube would still experience melting. But it would do so much more slowly than if we left it on the kitchen counter subjected to room temperature. Similarly, by limiting future temperature increases through reductions in greenhouse gas emissions, we can slow down glacial melting. That’s important because a slower pace of melting means that it would take longer for sea level to come up, giving societies more time to adapt by, say, building dykes and shifting development to higher ground. “One of the important points that society at large needs to understand is that even if we are very good at dealing with emissions, we will still have to adapt,” Marzeion said. “Some things are already inevitable, so we need to be prepared.” At the individual level, it may seem that having an impact on something as big and complex as climate change is futile. But Marzeion’s study shows otherwise. Each of us actually can make a difference. He and his colleagues used their modeling results to look at the impact driving a car has on glacial melting. For an average non-electric European automobile, they found that driving 300 meters — about the length of a football field — spews enough CO2 out of the tailpipe to eventually melt one kilogram of glacial ice. Especially given the immensity of the world’s glacial ice, at first blush that didn’t sound like very much to me. But then I considered how much I drive: in some years, as many as 15,000 miles. And that adds up to at least 90 tons of melted glacial ice — 50 times the weight of my Subaru Outback. All that melted ice contributes to sea level rise, each and every year. And actually, these numbers are conservative because an Outback almost certainly gets worse gas mileage than the kind of car Marzeion and his colleagues used to make their calculations. “So now, when you are in your car, you can imagine that for every 300 meters that you drive, you are dooming about one kilogram of glacier ice,” Marzeion said. And more if you drive an SUV.

Your's truly (Tom Yulsman), holding a chunk of ice that had calved from a glacier in Svalbard in 2016. It turns out that switching from a car to a bike over just a short distance — less than the distance to my local grocery store — I can save from melting much more ice than that. To get a sense of the positive impact I personally can have, I flipped it around: With every length of a football field I cover on my feet or my bicycle as opposed to my car, I can conjure a distinct image of putting a 2.2 pound block of ice in a freezer. Scale that up to driving, say, 5,000 fewer miles annually, multiply that by tens of millions of people taking similar steps — and now we’re talking about saving a whole lot of ice. True, as Marzeion’s research shows, a large fraction of the world’s glacial ice is already committed to melting no matter what we do, and that will contribute to sea level rise. But we can slow things down, making adaptation easier. And if we really work at it, we can even preserve some ice. Moreover, Marzeion’s results show that we would get a bigger response by getting started right now. Given today’s climate, for every kilogram of CO2 that you or I can keep out of the atmosphere by, say, driving less, we’d save about 15 kilograms of glacial ice in the long run. But if we wait to start biking more, or maybe replace the gas guzzler with a hybrid car, we’ll experience diminishing returns. According to Marzeion, once the world warms in coming decades by 3 degrees C, then every 1 kilogram of CO2 kept out of the atmosphere will save just five kilograms of glacial ice — three times less than if we got started now. That’s because the extra warming between now and then would would commit much more ice to melting. Unfortunately, global emissions of CO2 continue to rise, and over the long term, the greenhouse gas continues to accumulate in the atmosphere at ever higher concentrations. As a result, on our current path we’ll have less time to adapt. How much less time is “very hard to specify,” Marzeion said. In part that’s because the world’s glaciers aren’t the only variable. Greenland and Antarctica’s giant ice sheets have the potential to raise sea level much more. But predictions of their behavior in a warming world come with greater levels of uncertainty, he told me. Moving forward, Marzeion confided that his research findings have provided him with a new and personal way to gauge his own impact on the world. He notes that he and other glacier experts all tend to have their own favorite glaciers. “So now we can imagine how our personal actions are affecting that glacier,” he says. “It is an emotional argument, but I guess we need it to understand the impact of our actions.” With that understanding, perhaps we can step onto a different path — figuratively and literally.

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