To glean insights into climate change, a small clan of intrepid scientists deploys to some of the most extreme places on Earth: the Greenland and Antarctic ice sheets.
From temporary camps, they drill long cores of ice that yield valuable clues into how spaceship Earth’s climatic life support system works.
Like other members of the ice-coring clan, Dorthe Dahl-Jensen hopes this knowledge can ultimately help inform decisions critical to avoiding the worst possible outcomes of human-caused climate change.
Saying the world is going under is dangerous because young people will say, ‘Why should I take an education, there is no future for me anyway.’ That has never been more wrong. Many people have shown that we can solve this problem." — Dorthe Dahl-Jensen
Dahl-Jensen is a researcher at the University of Manitoba’s Centre for Earth Observation Science, and a Professor at the Niels Bohr Institute, the University of Copenhagen. She was recently awarded the Mohn Prize, a prestigious honor for excellence in Arctic research.
I sat down to chat with her at the recent Arctic Frontiers conference in Tromsø, Norway, where she received the award. Joining me was a friend and fellow science journalist, Tomasz Ulanowski, a reporter for the Polish publication Gazeta Wyborcza. We both posed questions to her about what scientists are learning from studying ice. What follows is a mix of questions and answers interwoven with background information from my own reporting.
Make sure to read through to the end, where Dahl-Jensen moves beyond the science to address what she thinks it is saying about the urgent need to act on climate change. Unlike what we often hear, it is not actually a depressing or even scary message.
My colleague got things going with this question: What does the ice teach us?
She began by noting just how unusual water ice is: “Ice is lighter than water," she said. "There are not many other materials where the solid form is lighter than the liquid form. So it floats on the water.”
That might not sound so special, but ice floating on water rather than sinking actually has a profound impact: It helps regulate our planet’s climate.
That's because floating sea ice forms a bright shield over the Arctic Ocean and surrounding waters. That shield reflects huge amounts of solar energy back into space — energy that otherwise would warm the region. This helps maintain frigid conditions in the high north.
But human-caused warming has caused this reflective shield of floating sea ice to shrink at a rate of 12.85 percent per decade since 1979, as measured every September. (This is when the ice reaches its yearly lowest extent at the end of summer.) Studies suggest that since the late 20th century, the decline in summer Arctic sea ice has been steeper than at any time in the past 1,450 years.
As sea ice shrivels, more and more solar energy is being absorbed by the relatively dark ocean surface rather than being reflected back to space. The result: The Arctic has warmed twice as much as any other region on Earth, a phenomenon scientists call “Arctic amplification.”
The fact that ice floats on the surface of the sea also makes it “super fundamental — because it shields the life in the ocean,” Dahl-Jensen told us.
At the base of life’s food web in Arctic waters are phytoplankton. As winter turns to spring and temperatures naturally warm, sea ice thins, breaks up and finally melts, providing phytoplankton with the solar energy they need to grow. Springtime blooms of phytoplankton are grazed on by animals known as zooplankton. Arctic species are relatively big and fatty, providing the Arctic cod that feed on them a lot of energy per bite. The cod are in turn eaten by seals, which are the favorite meal of polar bears.
As the Arctic has warmed, the shield of sea ice has thinned and broken up earlier, in turn causing earlier blooms of phytoplankton. This is sending impacts rippling up the Arctic marine food web. For example, there is evidence that the Arctic zooplankton are being replaced by more southerly, less nutritious species. And more southerly fish species seem to be migrating northward.
Thinning sea ice has allowed more sunlight to reach the water right beneath the ice, triggering blooms of phytoplankton earlier than in the past.
Scientists say that a huge shift in Arctic marine ecosystems may be in the offing, but they are not yet sure what the outcome will be. As Dorothy Dankel, a fisheries scientist at Norway’s University of Bergen, put it to me for a feature story I wrote not long ago, “It’s a fascinating, complex, perfect storm. It can either come out really great, or everything could go down the shithole.”
Shifting to a different aspect of Arctic ice during our interview with Dahl-Jensen, my colleague asked this: What can it teach us about Earth’s history?
Dahl-Jensen has long studied the chemical and other clues trapped within cores of ice drilled from the Greenland ice cap in order to gain insights into past climates. The hope is that those insights can help us see better what the future holds as we continue to pump carbon dioxide and other heat-trapping greenhouse gases into the atmosphere.
Dahl-Jensen noted that every year’s snowfall on the ice cap “creates a layered record. It is very much like tree rings,” she said. “You get a layer from each year.” And each annual layer of snow eventually compresses into ice, trapping climatic clues within it.
“On the Greenland Ice Sheet we get climate information going 200,000 years back in time,” she said. “At the bottom, we also find material that is 1 million years old.”
In Antarctica, Dahl-Jensen noted that the layered ice record goes back more than 800,000 years. “We are hoping for 1.5 million years, and we even believe that it must be at least 5 million years in places,” she said.
“We use ice as a history book,” she said. “That’s what fascinates me.”
That history book contains information about the makeup of the atmosphere in millennia past. When snow falls to the surface and is then covered by yet more, it eventually turns to ice under the overlying pressure. Air that was trapped between the snowflakes is then preserved, first in bubbles and then within the matrix of ice crystals. Going back layer-by-layer, and thus year-by-year, scientists can recover that air and determine how much carbon dioxide, methane and other gases were present.
The icy history book also contains information about the temperatures that prevailed when the snow first fell. This information comes in the form of chemical fingerprints corresponding to warmer or cooler conditions in the clouds from which the snow fell.
“We can also measure dust particles in the ice, wind-blown dust,” which mainly comes from China, Dahl-Jensen said. How much is present "is a function of how dry it was in China, and also a function of how strong the storms were that moved the dust to Greenland.”
All told, scientists can measure about 10 different parameters with annual resolution in ice cores. "This gives just a gold mine of climate information."
One of the most important insights gained from ice cores, as well as from geological records that go further back, is the tight connection between carbon dioxide and global temperatures. "Every time we’ve had high values of CO2, we’ve had warm temperatures,” Dahl-Jensen said. Given that, "it is surprising that people can doubt whether the high values of greenhouse gases now will result in warmer temperatures once our system adjusts to the vastly changing values.”
Dahl-Jensen is getting at an aspect of climate change that's not widely appreciated. Yes, global average temperature has already risen by about 1 degree C thanks to emissions of greenhouse gases so far. But if we were to shut off emissions tomorrow, we would not forestall further warming completely. We’d still see much more warming.
That’s because the oceans, which have been absorbing more than 90 percent of the heat that has built up, produce a lot of inertia in the climate system. This stems from two physical facts: It takes a long time for heat to fully warm the oceans, and also a long time for that heat to come out and warm air temperatures.
Here’s how Dahl-Jensen explained it:
“We have a system that is totally out of balance now," she said. While waters relatively close to the surface of the world's oceans have heated up significantly, "warming the deep ocean takes place on the scale of a thousand years. So we have a system that takes a thousand years to get into balance. And that means we have a strongly imbalanced system now. As a result we haven’t seen the warming you’d expect from the CO2 we have already put in the atmosphere.”
How much additional warming can we expect?
“I would say two degrees,” Dahl-Jensen said. “But I wouldn’t listen to that if I were you, because there are so many things we do not know.”
Among them: details about what happens to carbon that gets absorbed into the ocean.
“The carbon cycle is probably one of the most difficult balances to make,” Dahl-Jensen said. “How does the ocean do this uptake?” Thanks to absorption of carbon dioxide into ocean waters, “we see that the ocean is becoming more acid. This reduces its ability to take up more CO2.”
In other words, the ocean has been doing us a favor by absorbing CO2 that otherwise would have warmed the globe. (But we haven't been doing the oceans and marine organisms a favor because that CO2 is causing acidification — see the graphic above.)
How much more can we depend on the ocean to absorb lots of CO2? Scientists aren’t sure.
I then turned our conversation toward the idea of climatic tipping points. Many scientists say we have about 10 years left to avoid crossing a catastrophic threshold. But how do we reconcile that idea with the fact that we may have hundreds of years of further warming in the pipeline no matter what we do?
“I don’t really like this,” Dahl-Jenssen said. “I’m not fond of these dramatic ways of presenting things . . . I think the word tipping point is very often misused, because in my opinion, tipping point means if you reverse the process you won’t get back to the same point again. I think if we reduce the CO2 we would actually get back to the same point again.”
She also says the tipping point argument prevents people from taking action. “I think it scares people more than it tells them that we are in a world of opportunities, and [climate change] is something we can solve. We just have to take it seriously and get cracking. We should tell all our young people that this is the most important thing in the world, that we need a super-skilled set of people who can help us solve it in the future. I think that would be a much, much more valuable point of view than telling people that the world will go under in 10 years.”
Young people, like the Swedish climate activist, Greta Thunberg, are already stepping up, Dahl-Jensen observed. "They are saying, ‘Hey, come on, leave a world for us, we don’t have a Planet B.’ That is just amazing," Dahl-Jensen said.
“But I think saying the world is going under is dangerous because young people will say, ‘Why should I take an education, there is no future for me anyway.’ That has never been more wrong. Many people have shown that we can solve this problem — we can stop the emissions of greenhouse gases, we can easily go to green energy, and we can also live with a world that becomes warmer.”
Even so, there will be big challenges, Dahl-Jensen acknowledged. One is that many people will have to migrate from parts of the globe that will become impossible to live in thanks to sea level rise, soaring temperatures, drought, and other impacts.
“We have to be more tolerant of movement of populations,” she said. “We can’t allow people to go into war every time some people have to move . . . We have to say, ‘Yes, you’re right, you can’t live there, it’s underwater, or too dry.' We have to allow for movement.”
Dahl-Jensen pointed out that water shortages helped ignite the conflict in Syria that sent many refugees streaming into Europe. “Syria was the first climate change war we’ve had,” she said.
Unless we begin to plan for the inevitable increases in sea level and severe heat and drought that are coming, more wars fomented by climate change will be in the offing, she argued.
At the end of our conversation, Dahle-Jensen reflected on how difficult it is for scientists to help prompt positive action like that.
She related an incident in which a foreign minister once accused her and other scientists of hampering action by not providing definitive answers. "‘How can you expect us to respond when you say something different every day?'" she recalls him saying. In her view, that reflected a fundamental misunderstanding of how science actually works.
"We are not saying something different every day, but we are always upgrading our knowledge," Dahl-Jensen told us. "So I answered him back: ‘Why didn’t you predict the financial crisis? Because you know, it’s kind of a similar complex system that people can’t predict. ‘He got so furious he said, ‘Dorthe, I’ll never give you a grant again.’”
It didn’t actually pan out that way. “He did calm down,” she says.