Complexities of climate change
There's more to the issue than a warming world and rising sea level
Posted May 30, 2008
A chunk of the Wilkins Ice Shelf along the Antarctic Peninsula breaks off, leaving the rest of the floating ice slab, roughly the size of Connecticut, hanging by the proverbial thread. Next summer, maybe in three, the Wilkins will become the latest in a series of West Antarctic ice shelves to slough away from the continent.
The disintegration, which started in February, caught scientists by surprise by its timing and rapidity. Many thought the ice shelf would be safe for several more decades.
Elsewhere in the world, glaciers are retreating and ice caps shrinking quicker than anyone could have predicted even five years ago. Book your trip to Mount Kilimanjaro today, because the glaciers on Africa’s highest mountain probably won’t survive past 2020 if predictions prove true.
Tourists will have to visit Lonnie Thompson’s cold storage facility at Byrd Polar Research Center (BPRC) at The Ohio State University to see ice from Kilimanjaro. Thompson and colleagues have made several trips to the 5,895-meter peak to collect ice cores in an effort to save the unique climate record stored in the ice before it disappears.
His estimate of 2020, recently revised to as early as 2015, illustrates that the climate prediction game remains an inexact science. In Antarctica, where temperatures have soared along the peninsula in the last several decades but have changed little over East Antarctica, projecting the future has proven even more difficult, but vital, considering the amount of water stored in the continent’s ice sheets.
“Can we ever know enough fast enough in order to actually predict? And if we did predict, would there be any response by human beings to adapt to these things?” Thompson muses during an interview at BPRC, following a planning session with his team about an upcoming trip to the Peruvian Andes.
“How fast can these glaciers actually flow into the ocean and change sea level? How fast can sea level rise?” he continues in the rhetorical vein, noting the scientific questions serve pragmatic purposes: “People want to know how high they need to build bridges.
“What we’ve learned is how much we don’t know,” he says. “Ten years ago people wouldn’t believe a glacier could increase its speed twofold in one year.” Those glaciers, he notes, can actually flow eight times faster.
“I think [the Intergovernmental Panel on Climate Change] was very conservative,” he adds. “It didn’t take into account any of this rapid response.”
The Intergovernmental Panel on Climate Change (IPCC) is a scientific body under the auspices of the United Nations. Its mission is to assess peer-reviewed scientific literature related to climate change, its impacts and strategies to mitigate possible effects. Its most recent report, released last year, bluntly warned, “Warming of the climate system is unequivocal.”
The IPCC concluded, “Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (human) greenhouse gas concentrations.”
World temperatures, the IPCC said, could rise by between 1.1 and 6.4 degrees Celsius during the 21st century and that sea level will probably rise 18 to 59 centimeters. It’s the sea level rise number that Thompson and others have criticized.
Hot and cold
In particular, Antarctica remains an enigma. A recent NASA-led study said that the rate of Antarctic ice loss increased by 75 percent in the last 10 years as glacier flow accelerated. That study’s lead investigator, Eric Rignot of NASA’s Jet Propulsion Laboratory, noted that last year’s report by the IPCC did not properly account for Antarctica’s role in sea level rise estimates. His team estimated Antarctic ice loss is now nearly as great as that observed in Greenland.
On the flip side, a recent paper by researchers at OSU and the National Center for Atmospheric Research in Boulder, Colo., found current climate models of Antarctica consistently overstate warming.
The study, published in Geophysical Research Letters and funded by the National Science Foundation and the Department of Energy, compared recently constructed temperature data sets from Antarctica, based on information from ice cores and ground weather stations, to 20th century simulations from computer models used by scientists to simulate global climate.
While the observed Antarctic temperatures rose by about 0.2 degrees Celsius over the past century, the climate models simulated increases in Antarctic temperatures during the same period of 0.75 degrees Celsius, nearly matching the observed increase of global temperatures that the models reproduce accurately.
“They’re not doing great,” says David Bromwich of the computer models. A professor of atmospheric sciences in OSU’s Department of Geography and a researcher at BPRC, Bromwich explains that the Antarctic climate has not warmed like the rest of the globe due, in part, to the strengthening of winds around the continent. That strengthening is driven by a combination of the Antarctic ozone hole in the stratosphere, increased greenhouse gases and internal climate variability across the continent.
“Stratospheric ozone depletion has extended the winter season by about a month. It is having an effect on the troposphere,” he says. “There is a big contrast between the peninsula and the mainland, and that’s where all the water is sitting in frozen form.”
The troposphere is the part of the atmosphere where weather occurs. Sitting above that is the stratosphere, where ozone concentrations have diminished because of human activity.
“We don’t know how any of these factors will evolve during the coming century, and therefore there is still considerable uncertainty as to how much warming will occur in Antarctica,” he says.
So, on the one hand, climatic changes around the Antarctic Peninsula and elsewhere across the globe are occurring more rapidly than the models can predict. But the main body of the continent, bigger than the United States, has not kept pace with the models. Yet another recent paper, published in the journal Nature, contends that as the ozone hole recovers, the immunity from the greenhouse effect enjoyed by much of Antarctica may disappear.
“Antarctica is a pretty complicated place,” Bromwich concedes.
The models are lacking details. “Fundamentally, from a science point of view, it shows that we don’t have a good handle on the processes,” says Terry Wilson, a professor in OSU’s School of Earth Sciences and another researcher at BPRC whose research often relates to climate change. She adds the caveat: “Yet.”
“All of the research, and certainly this focused research during [the International Polar Year], is really going to make a significant difference in our understanding of the processes in these complex systems,” she adds.
Nature versus nurture
In a way, some scientists note, the loss of something like the Wilkins Ice Shelf is really just a chip of paint flaking off a wall in terms of its size compared to the whole of Antarctica. East Antarctica, which holds more ice than Greenland and West Antarctica combined, still seems relatively invulnerable.
Ken Jezek, a geophysicist with BPRC whose work involves satellite mapping of the polar regions, notes that our ability to track modern changes in polar ice caps has been largely possible thanks to remote sensing. The satellite observations only date back a few decades.
The question becomes, he says, “Is this a recent phenomenon or a phenomenon that’s been going on for a while but we’re just now able to observe it. … That seems to me to be a bit of an open issue.”
In fact, we are in what scientists call the interglacial period, an interval of warmer global temperatures that separates glacial periods. About 20,000 years ago, the world’s ice sheets and glaciers had reached their largest extent, referred to as the last glacial maximum. On the whole, glaciers and ice sheets have been shrinking for several thousand years.
The debate today is no longer whether or not the world is heating up like a car with a busted radiator. The global engine is overheating, but are we behind the wheel or just sitting in the back seat, along for the ride? The latest IPCC report, and many scientists, say the evidence indicates the former.
“I think the anthropogenic input is real,” Jezek says, but adds that he doesn’t know if human activity is entirely to blame. He notes, for example, that geothermal heat below the bedrock on top of which ice sheets sit may be partly responsible for speeding some glaciers — like holding a lighter under a bowl of ice cream.
Scientists who disagree with the IPCC assessment for rising temperatures say global warming and its associated climatic changes may be part of a natural cycle, increased solar activity or cosmic rays.
Ellen Mosley-Thompson, a professor in OSU’s Department of Geography and a member of BPRC’s ice core paleoclimatology group, says that opposition to human-induced climate change often simplifies the equation, leaving out complexities such as feedbacks in the system. For example, sea ice reflects sunlight, but as it disappears, the exposed ocean surface is darker so it absorbs more solar energy (heat), melting more sea ice, which allows the ocean to absorb more heat, and so forth.
The message from the contrarians, as Mosley-Thompson refers to climate skeptics, is that the problem of global warming and climate change is not much of a problem at all.
“Everyone wants that message,” Mosley-Thompson says. “I’d love for that message to be true. My daughter comes over to our house and says, ‘Please don’t start talking about climate change because I always leave here so depressed.’”
The dust storm
For Thompson, the questions of prediction and blame seem secondary to the one about how the world will respond to the climate changes that few deny are taking place. He tells the story of Hugh Bennett, a pioneer in soil conservation from the early 20th century, to illustrate his point.
The story goes something like this: Drought coupled with decades of intensive farming caused severe soil erosion, which led to the Dust Bowl period of the 1930s, when dust storms caused extensive damage to prairie lands. Bennett was in Washington, D.C. on a fine April day in 1935, urging the U.S. Congress to pass a law to help conserve the nation’s soil.
On the day of his speech, a dust storm rolled over the nation’s capitol to add a dramatic exclamation point to his argument. (History tells us Bennett was warned of the approaching storm, and timed his speech for its arrival.) Shortly after, Congress passed the Soil Conservation Act, which allowed the government to pay farmers to reduce production to conserve the soil.
The world may be waiting for a modern version of that dust storm before it acts against climate change, Thompson said.
“Most of what I see of human nature is that we don’t like to do anything until we have to, until there’s absolutely no other choice, your back’s against the wall, and then we’re pretty good,” he says. “I do wonder what it’s going to take to get everybody on the same page.”
Mosley-Thompson says she feels many people are finally coming together on the problems. “I’ve been at this business for almost three decades,” she says. “I would say the tide has turned tremendously in the last few years. Although we still have a long way to go, at least nearly everyone is talking about climate change.”
And despite what might seem like a doomsday scenario — reinforced almost daily by reports of ice shelf collapses, shrinking summer sea ice in the Arctic, melting permafrost and vanishing species — scientists are amazingly still hopeful.
“I’m absolutely convinced — when it’s clear what that job is and how we can solve it — the world can work together to accomplish it,” Thompson said.
Funding from the National Science Foundation has supported much of the research and scientists quoted in this story.
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