Much has been written about climate change, but one of the most overlooked pieces of the environmental puzzle is ice. This is mildly surprising, as in its own unspoken way, ice has plenty to say about the extent of global warming. As University of Michigan geophysicist Henry Pollack notes in his book “A World Without Ice” (Avery), “Ice asks no questions, presents no arguments, reads no newspapers, listens to no debates. It is not burdened by ideology and carries no political baggage as it crosses the threshold from solid to liquid. It just melts.”
In the book—and the following Failure interview—Pollack gives ice a voice, explaining in easily accessible terms why it is melting so rapidly, and how we might manage the unavoidable consequences. Along the way, he also floats a few thoughts about climate change skeptics, Climate Gate and the prospect of tens of millions of climate refugees.
Why is ice so important to the climate system?
Because ice is so reflective, it sends most of the sunshine falling on it right back to space. Therefore, when there is more ice on Earth, there is less solar energy available to warm Earth. When there is less ice, more sunshine is absorbed by the darker surfaces of Earth—the ocean, the land, and vegetation—and accordingly the planet warms. Additionally, the thick polar ice caps of Greenland and Antarctica spawn wind systems that influence the climate well beyond the margins of the ice.
Has there been an acceleration in terms of ice melting, and if so, why?
The annual summertime melting on Greenland, historically confined to the margins near sea level, has over the past two decades been climbing higher and spreading more widely. Today summer melting occurs at elevations greater than 2000 meters, and takes place over almost half the island.
The sea ice that covers the Arctic Ocean much of the year is also experiencing more summertime melting and breakup. Over the past three decades the summer ice loss has increased, so that compared to the late 1970s, only about 60% of the area and half the thickness of the sea ice remains at the end of the summer. If that rate of ice loss continues for another decade or two, we may see an ice-free Arctic Ocean in the summer, probably for the first time in human history.
Meanwhile, ice at the top of high mountains is in retreat around the world. Many of the tropical and mid-latitude glaciers, such as those in Africa, the Andes, the Alps, and in the Rocky Mountains will probably disappear in the next few decades. Ice loss is also occurring in the Himalayas, but because of their greater elevations and larger ice mass, some ice will endure beyond the end of the 21st century.
Why is Earth’s ice deteriorating so rapidly?
The atmosphere is warming because of the anthropogenic greenhouse effect. The burning of carbon-based fossil fuels emits carbon dioxide into the atmosphere, and enhances the heat-trapping capability of Earth’s atmosphere.
What does the melting of ice mean in terms of sea level rise?
Just as an ice cube afloat in a beverage glass does not raise the water level in the glass as it melts, neither does the accelerating seasonal melting and breakup of the Arctic sea ice raise sea level directly, because that ice is already afloat in the Arctic Ocean. But the melting of Greenland and the mountain glaciers around the world contributes additional water to the oceans, at a rate sufficient to raise sea level approximately 12 centimeters over the course of a century. Such a rise in sea level would on its own be disruptive but not catastrophic.
But melting ice is not the only cause of an increase in sea level. Two other factors play an even greater role. The first is simply the warming of ocean water around the globe, which causes the sea water to expand. This factor alone contributes more than half of the rise in sea level currently observed. The second factor is the direct loss of ice from Greenland and Antarctica directly into the sea, without first undergoing melting. Such additions of ice raise sea level the moment the ice discharges into the sea. The glaciers draining ice from Greenland and West Antarctica have been accelerating their discharge in the last two decades. Currently, sea level rise from all causes is at a rate of 34 centimeters per century. Were Greenland to return all its ice to the ocean, sea levels would rise a little more than seven meters. Such a rise would be catastrophic.
As the amount of ice on the planet diminishes, won’t temperature rise even more?
Yes indeed. This is because the sunshine reflected away from Earth by the ice will instead be absorbed by the darker materials once covered by the ice. This will warm the Earth at an even faster rate, causing the loss of even more ice. This self-reinforcing process is what scientists call a positive feedback.
How much time do we have to stabilize or reverse our emissions? Or might we be past the point of no return already?
Many climate scientists believe that to avoid very disruptive effects, the concentration of carbon dioxide in the atmosphere should not go beyond 450 parts per million (ppm). Today the concentration is near 390 ppm, and increasing at about 2-3 ppm each year. Simple arithmetic tells us that we have only two to three decades to decrease greenhouse gas emissions substantially if we are to avoid passing the 450 ppm threshold. And there are some who believe that even 450 ppm is a dangerous level, and argue that we should return to less than 350 ppm as soon as possible.
Also, because the climate system has considerable “momentum,” there will be some additional climate change even if we are somehow able to eliminate all greenhouse gas emissions. This change will result from the emissions of the past that are already in the atmosphere, and will remain present for another century or so.
How do you respond to climate change skeptics? And those that flat out deny climate change?
When I meet people who are truly puzzled by the “he-said she-said” exchanges about climate change, I try to zero in on what is troubling them: Do they think that the climate is not changing? Are they unconvinced that humans have anything to do with climate change? Or do they believe that the consequences of climate change will be benign, or even beneficial? Once I learn their concerns, I try to address those concerns in simple terms that carry no political baggage.
For the flat-out deniers, those who say, “My mind is made up—don’t bother me with the facts,” I cut the conversation short, usually with a comment to the effect that they can have their own opinions, but they cannot have their own facts.
How long before we begin to see climate refugees?
There are already climate refugees—those who are already feeling effects of changes in the hydrological cycle, particularly the changes that are leading to more severe droughts. And within a decade or two, we will see refugees leaving areas that depend on melting ice atop high mountains for part of their agricultural and domestic water. When the water supply disappears, or is greatly diminished, people are forced to move.
Another category of climate refugees are those that must abandon their homes because of rising sea levels. Particularly vulnerable are the people that live on low-lying islands in the Pacific and Indian oceans, where higher sea level is already damaging coastal infrastructure and degrading fresh water aquifers. A rise in sea level of only one meter would displace more than 100 million people worldwide.
What impact has the U.K. climate data scandal had in terms of public perception about climate change?
The impact on the scientific underpinnings of climate change is insignificant. There is more than ample redundancy of evidence, from many lines of inquiry pursued by diverse groups of climate scientists worldwide, to continue to support the principal conclusions about Earth’s changing climate and the likely causes and consequences. The discrediting of any single piece of evidence or any single research group does not change these bedrock conclusions.
But where Climate Gate has done some damage is in the political arena, where it has hardened the positions of the climate-change deniers. But the road towards getting a significant climate bill through the U.S. Senate—and then through a Conference Committee to reconcile it with the Waxman-Markey bill passed by the House of Representatives in 2009—has probably become rougher and steeper.