Climate Change 2007: The Physical Science Basis
Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
Cambridge University Press, 996 pp., $90.00 (paper)
When the Rivers Run Dry: Water—The Defining Crisis of the Twenty-first Century
by Fred Pearce
Beacon, 324 pp., $16.00 (paper)
Too Smart for Our Own Good: The Ecological Predicament of Humankind
by Craig Dilworth
Cambridge University Press, 546 pp., $90.00; $29.99 (paper)
Black Soot and the Survival of Tibetan Glaciers
by Baiqing Xu, Junji Cao, James Hansen, and others
Proceedings of the National Academy of Sciences, December 29, 2009
On Avoiding Dangerous Anthropogenic Interference with the Climate System: Formidable Challenges Ahead
by Veerabhadran Ramanathan and Y. Feng
Proceedings of the National Academy of Sciences, September 23, 2008
The Great Melt: The Coming Transformation of the Arctic
by Alun Anderson
World Policy Journal, Winter 2009/2010
A full listing of sources appears at the end of this article.
It was not so long ago that the parts of the globe covered permanently with ice and snow, the Arctic, Antarctic, and Greater Himalayas (“the abode of the snows” in Sanskrit), were viewed as distant, frigid climes of little consequence. Only the most intrepid adventurers were drawn to such desolate regions as the Tibetan Plateau, which, when finally surveyed, proved to have the planet’s fourteen highest peaks. Because these mountains encompass the largest nonpolar ice mass in the world—embracing some 46,298 glaciers covering 17 percent of the area’s land and since time immemorial have held water in frozen reserve for the people of Asia—they have come to be known as “The Third Pole.”
There was a time when the immensity of such larger-than-life features of our natural world as oceans, deserts, mountains, and glaciers evoked awe and even fear. These days, however, these once seemingly eternal and invincible aspects of our planet’s architecture are on the defensive. And only belatedly are we beginning to understand how fragile and interconnected they actually are with myriad other elements of planetary life.
Through new scientific data, scholarly articles, books, NGO studies, and media reports, we now know that the melting of polar ice will lead to rising ocean levels and the inundation of many heavily populated areas in vulnerable lowland countries. But we are only beginning to become acquainted with the less-well-known consequences that are starting to flow out of the majestic arc of mountains that begins in Inner Asia with the Tianshan Range in western China and then wraps itself around the western tier of the Tibetan Plateau as it becomes the Hindu Kush in northern Afghanistan. It then joins the Karakorum in northern Pakistan to become the Himalayas above Nepal, Bhutan, and India before ending with the Hengduan Range in southwest China. (See map on page 48.)
Scientists are now warning that there could be a 43 percent decrease in land mass covered with ice in these mountains by 2070 and that in numerous and complex ways this loss will affect Asia’s ten major rivers—the Yellow, Yangtze, Mekong, Salween, Irrawaddy, Brahmaputra, Ganges, Indus, Amu Darya, and Tarim—around which many of the ancient civilizations of the world arose. It is here, among huge modern-day populations of Asia, that the melting of the Greater Himalayas’ glaciers will have the most significant impact during the coming decades and centuries.
Recent revelations that the Fourth Assessment Report of the UN’s Intergovernmental Panel on Climate Change (IPCC) erroneously claimed that there was a “likelihood” that Himalayan glaciers would disappear by 2035, “and perhaps sooner,” embarrassed the report’s authors; but they have not altered the reality that many glaciers in the region are, in fact, rapidly receding. Nor do they scientifically invalidate the panel’s overall conclusion that because “more than one-sixth of the world’s population live in glacier- or snowmelt-fed river basins and will be affected by the seasonal shifts in stream flow,” a serious downstream problem is unfolding.
Glacial ice-melt from the Greater Himalayas provides Asian river systems with important seasonal flows of water. A 2005 World Wildlife Fund report observes that in Nepal, India, and China, “glacial melt will affect freshwater flows with dramatic adverse effects on biodiversity, and people and livelihoods, with a possible long-term implication on regional food security.”
The Indus and Tarim rivers, for example, derive up to 50 percent of their annual flows from glacial melt. The Yangtze derives 18 percent, while the Salween derives 9 percent from such meltwaters. But what makes glacial melt so critical, even when it is a relatively small percentage of a river’s annual flow, is the timing at which it occurs. If these flows come during the rainy monsoon season, they may lead to floods. But if they come during the hot, dry spring and fall months, the so-called “shoulder seasons” just before and after the monsoon, they keep the volumes of river water more constant and are welcomed. For such rivers as the Ganges, Indus, and Kabul, meltwaters can account for as much as 70 percent of spring and fall flows.
As the science writer Fred Pearce puts it in When the Rivers Run Dry, by storing monsoon rain as snow and ice when it is not needed, and then releasing it slowly as water when it is, glaciers “provide a strong, regular flood pulse in the summer melting season.” Any disruption in these flows—especially when a monsoon is late, weak, or fails—significantly disturbs not only agriculture but industry, fisheries, transportation, and many other aspects of life for hundreds of millions of people downstream. That is the case this year in drought-stricken southwest China through which the Yangtze, Mekong, and Irrawaddy all flow.
Until now, the formidable glaciers of the world hardly seemed vulnerable. While they may appear immobile, they are actually “rivers of ice,” as the great Swiss geologist Louis Agassiz described them, and are constantly moving downward from their “accumulation zones” high on mountainsides where snows fall and are compressed into “firn,” the blue ice that gives glaciers their air of frozen purity. Pushed by their own immense weight, and aided by meltwaters, which seep down crevasses to lubricate the interface between ice and rock, glaciers make their slow gravity-driven progress downward, carving out whole valleys as they move and gathering up so much debris before them and on their surfaces that they often look more like conveyor belts for rocks than icefalls.
A glacier’s lower reaches are known as its “ablation zone,” because it is here that it “calves,” or sloughs off, giant pieces of itself in a process that can give off unearthly noises—like a giant door creaking open or even a cannon shot. After these terrestrial icebergs break off, the ice begins the final stage of its long odyssey to the sea, as meltwaters flow into the river systems of the vast and populous Asian continent.
As long as the buildup of new ice in a glacier’s accumulation zone remains greater than losses in its ablation zone, “mass balance,” or equilibrium, is maintained. But most of the world’s “reference glaciers”—those two hundred–plus that have been under observation over the past sixty years by the Switzerland-based UN World Glacier Monitoring Service—have begun to record significant losses.
Only now, as these glaciers have been put in jeopardy by man’s voracious appetite for energy, are we starting to become more aware of the critical links between the thirsty, riverine lowland population centers of East, Southeast, and South Asia and the high-altitude ice fields of the Greater Himalayas. And it has been climate change that has drawn our attention to the connection.
The amount of heat-trapping greenhouse gases (GHGs) emitted annually is now roughly twice what the earth can recycle through natural processes of reabsorption. By interfering with the planet’s ability to reflect incoming solar heat from the earth’s atmosphere, over the past century these gases have caused an average rise in global temperature of three quarters of a degree centigrade (0.74°C). But scientists who construct models of global warming to predict future outcomes also believe that because of an ongoing delayed reaction, existing GHG emissions (those released before 2005) alone—quite aside from future emissions—will, during the next century, cause an additional threefold temperature rise, of approximately 2.4°C. Furthermore, they contend, unless current emissions rates are radically curbed, it is even possible that future average temperatures could rise by as much as 4.3°C.
A few degrees here and there may not seem like much to a layman; but ecosystems, especially those involving ice, are so delicately balanced that even shifts of a degree or two have profound impacts, as we are now beginning to discern.
One of the most respected, pioneering scientists concerned with global warming is Veerabhadran Ramanathan at the University of California–San Diego’s Scripps Institution of Oceanography. He and his colleague Y. Feng point out that these estimated aggregate temperature rises surpass “the currently perceived threshold range of 1°C to 3°C for dangerous anthropogenic interference with many of the climate-tipping elements such as the summer arctic sea ice, Himalayan-Tibetan glaciers, and the Greenland Ice Sheet.” In other words, we are close to passing a tipping point—one that many scientists formerly put much lower, at an increase of 1.5–2.0°C—and are entering a danger zone where ice systems on the planet will be put even more irrevocably in peril.
What is more, when it comes to the Greater Himalayan region, climatologists tell us that global temperature averages are a very deceptive measure. For reasons that scientists are just beginning to understand, far greater temperature rises occur as a result of global warming in certain high-altitude regions than elsewhere. On the Tibetan Plateau, warming has increased at upward of three times the global average.
Two of the world’s leading glaciologists, Lonnie Thompson, distinguished university professor at Ohio State University’s Byrd Polar Research Center, and Yao Tandong, director of the Chinese Academy of Sciences’ Institute of Tibetan Plateau Research, both of whom have worked extensively in the Himalayas studying oxygen isotopes in glacial ice cores, have concluded that temperatures in these mountains are likely to rise as much as 5–6°C over the next one hundred years. Needless to say, such precipitous rises would only accelerate melting and lead to an even more drastic loss in ice mass, as well as an increase in a potentially catastrophic series of outbursts of water from glacial lakes, downriver flooding, and then, eventually, to diminished flows and periods of drought, affecting human communities both upstream and down. As Zheng Guoguang, head of the China Meteorological Bureau, recently put it, “If the warming continues, millions of people in western China will face floods in the short term and drought in the long run.”
“The current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia,” writes Thompson in the Proceedings of the National Academy of Sciences. “The continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth’s climate system.” This change, he writes, “may signal that the climate system has exceeded a critical threshold and that most low-latitude, high-altitude glaciers are likely to disappear in the near future.”
As important as rising temperatures are in understanding what is happening to Tibetan Plateau glaciers, another major factor is also causing damage: black carbon.
Atmospheric brown clouds, or ABCs, are aerosol suspensions of very small particles created by the inefficient combustion of coal, kerosene, and diesel oil, as well as biofuels from home cooking fires. In India, emissions from these sources increased sixfold between 1930 and 2000 and this particulate matter now causes the brown clouds that regularly hang like a pall over densely populated areas of the Indian subcontinent and China.