by Al Gore
In the language of statisticians, a standard deviation quantifies how far the range, or spread, of a particular set of phenomena differs from the average spread. Extreme—in this case, either unusually hot or unusually cold—seasons naturally occur far less frequently than average or near-average seasons. Because seasons with extreme temperatures used to be so much less frequent, they nevertheless often surprised us, even though they fell within the normally expected range. Seasons that are three standard deviations from the average were exceedingly rare, but still did occur from time to time as part of the normal range.
The average temperature is warmer overall even though extremely cold events still continue to occur, though rarely. In other words, the entire distribution of temperatures has moved to much warmer values, and the bell curve of distribution has widened and flattened slightly, so that there is much more temperature variability than used to occur. But the most significant finding is that the frequency of extremely hot temperatures has gone up dramatically.
Hansen infers that the cause is global warming—and indeed, these results turn out to be perfectly consistent with what global warming science has long predicted. (In voluminous other studies, Hansen and climate scientists around the world have proven causality to a degree judged “unequivocal” and “indisputable” by virtually all of the world’s scientific community.) But the results themselves are based on observations of real temperatures in the real world. They cannot be argued with, and the implications are powerfully clear.
As the old saying has it in Tennessee, if you see a turtle on top of a fence post, it is highly likely that it didn’t get there by itself.* And now we are seeing turtles on every tenth fence post in every field in the world. They didn’t get there on their own. It is now abundantly obvious that all the extreme temperatures and the extreme weather events associated with them are like turtles on a fence post. They didn’t happen without human interference in the climate.
In 2012, new World Bank president Jim Yong Kim released a study showing temperatures will likely rise by 4 degrees C (7.2 degrees F) without bolder steps to reduce CO2, and that there is “no certainty that adaptation to a 4 degree world is possible.” Gerald Meehl, of the National Center for Atmospheric Research, uses a different metaphor to explain what is happening: if a baseball player who takes steroids hits a home run, it’s possible that he might have hit the home run even without the steroids. But the fact that he took the illegal performance-enhancing drug makes it much more likely that he will hit a home run in his next at bat. Within Meehl’s metaphor, the 90 million tons of global warming pollution that we are putting into the atmosphere every twenty-four hours are like steroids for the climate. An innovative 2012 study of the previous decade’s climate predictions showed that the “worst case” future projections are the ones most likely to occur.
The increases in the global average temperature and the greater frequency of extremely high temperatures that Hansen and others are documenting are also melting all of the ice-covered regions of the Earth. Only thirty years ago, the Arctic Ocean was almost completely covered by ice in summer as well as winter. Remember? Some called it the North Polar Ice Cap. Tell your grandchildren how it used to separate Eurasia from North America and the Atlantic from the Pacific all year round. Last year’s record low in the volume and the area it covered marked an acceleration of a melting pattern that has led to a 49 percent loss in three decades and could, in the view of many ice scientists, produce a 100 percent loss in as little as a decade.
Some shipping companies are excited that the fabled Northern Sea Route is now open for several months a year. A Chinese ship, the Snow Dragon, traversed the North Pole to Iceland and back in the summer of 2012. A high-speed fiber optic cable is now being installed to link the Tokyo stock markets with their counterparts in New York City so that computer-driven trades can be executed more quickly. Fishing fleets are preparing to exploit the rich biological resources of the Arctic Ocean, which until now have been protected by the ice. Navies from some countries are discussing the movement of military assets into the region, though discussions have also begun on the possibility of agreements to foster the peaceful resolution of issues involving the safety, sovereignty, and development of the Arctic Ocean as it becomes ice-free in summer.
Several oil companies are thrilled at the prospect of new drilling opportunities and some are already moving their rigs into place. But the consequences of an accidental wellhead blowout at the bottom of the Arctic Ocean similar to BP’s disaster in 2010 would be far more catastrophic and far more difficult to deal with than in the Gulf of Mexico, or in any of the other numerous deepwater locations where wellhead blowouts have produced large oil spills. The relatively new and unperfected technology used for deepwater drilling involves more risk than conventional drilling because the pressures at the ocean’s bottom are so great. Drilling for oil at the bottom of the Arctic Ocean, and running the risk of a large spill in a pristine ecosystem where repair and rescue operations are all but impossible for much of the year, is an absurdly reckless endeavor. The CEO of the French multinational oil company Total broke ranks with his industry in 2012 and expressed his view that drilling for oil in the Arctic Ocean posed unacceptable ecological risks and should not be carried out.
The ecology of the Arctic Ocean is already experiencing significant changes. Scientists were shocked in 2012 at the discovery of the largest algae bloom ever recorded on Earth extending from open areas of the Arctic Ocean underneath the remaining ice cover—a phenomenon that has never been seen before and was considered impossible. The researchers explained that the most likely cause of this new occurrence was that the remaining ice is now thin enough, and has so many pools of water dotting its surface, that enough sunlight was penetrating to the ocean below to provide energy for algal growth.
The consequences of melting the North Polar Ice Cap will include large impacts on weather patterns extending far southward into the heavily populated temperate zones. The dramatically increased heat absorption in an Arctic Ocean that is ice-free in summer will have consequences for the location and pattern of the northern jet stream and storm track through the fall and winter seasons, modifying ocean currents and weather patterns throughout the northern hemisphere, and perhaps beyond. Moreover, if the world’s long familiar pattern of wind and ocean currents is pushed into a completely new design, the old one may never reemerge.
The land area surrounding the Arctic Ocean is also heating up, thawing frozen tundra that contains enormous amounts of carbon embodied in dead plants. They warm up and rot as the tundra thaws. Microbes turn the carbon into CO2 or methane, depending on the amount of soil moisture. Huge deposits of methane are also contained within frozen ice crystal formations called clathrates in the tundra, at the bottom of the many shallow frozen lakes and ponds surrounding the Arctic, and in some parts of the seabed underneath the Arctic Ocean. The bubbling methane carries heat energy upward, melting the underside of the ice—which then increases the heat absorption by the water when the sun’s rays are no longer reflected off the ice.
Scientists are struggling to quantify the amount of CO2 and methane that could be released, but the area involved is so vast that their work is extremely difficult. Already, however, they have found outgassing under way that exceeded what they expected at this early stage of global warming.
Moreover, scientists discovered in 2012 that there are likely to be enormous deposits of methane underneath the Antarctic ice sheet, in amounts that may be as large as the methane presently trapped in Arctic tundra and coastal sediments. Since the clathrates are kept in place by cold temperatures and high pressures, the thinning of the Antarctic ice sheets could, scientists fear, reduce pressures underneath the ice enough to trigger the release of methane.
The changes under way in Antarctica and Greenland are the focus of intense study by scientists who are trying to calculate how much sea levels will rise, and at what rate. Both ice sheets are being destabilized and are losing mass
at an increasing rate, which is leading to a much faster sea level rise than was predicted just a decade ago.
Throughout the history of urban civilization, the seas have been slowly and gently rising, as the warmer temperatures of the interglacial period have caused thermal expansion of the ocean’s volume, and the melting of some terrestrial ice. But with the rapid accumulation of CO2 and other greenhouse gases in the atmosphere during the last half century, global warming has accelerated and so has the melting of ice almost everywhere on the planet.
Predictions of the rate of sea level rise have been notoriously difficult, in part because many scientists use models calibrated using data derived from their studies of retreating glaciers at the end of the last Ice Age when conditions were very different from the ones we are now confronting. New real-time satellite measurements of ice mass in Greenland and Antarctica will soon improve scientific understanding of this process, but these measurements have been made for only a few years and more time is required to build confidence in what they are telling the scientific community. Recent observations in both west Antarctica and Greenland, however, already confirm a rapid and accelerating loss of ice. After a highly unusual melting event that affected 97 percent of Greenland’s surface in July 2012, Bob Corell, chairman of the Arctic Climate Impact Assessment, said, “It shocked the hell out of us.”
James Hansen, for one, surmises that we are witnessing an exponential process of ice mass loss, and that, as a result, the most relevant statistic is the doubling time of the observed loss. Based on his preliminary analysis of the data, Hansen believes it is likely that we will see a “multi-meter” sea level rise in this century. Others note that the last time temperatures on Earth were consistently as high as they are now, sea level was twenty to thirty feet higher than the present—although it took millennia for the seas to rise that much.
Because so many countries were settled by migrants, and in some cases colonialists, arriving by ship—and because trade and supply routes rely so heavily on oceangoing vessels—a disproportionate percentage of the world’s largest cities are located near the sea. In fact, 50 percent of the world’s population lives within fifteen miles of the coast, and according to the U.S. National Academy of Sciences, “Coastal populations around the world are also growing at a phenomenal pace. Already, nearly two-thirds of the world’s population—almost 3.6 billion people—live on or within 100 miles of a coastline. Estimates are that in three decades, 6 billion people—that is, nearly 75 percent of the world’s population—will live along coasts. In much of the developing world, coastal populations are exploding.”
Those in low-lying areas are therefore especially vulnerable to the increases in sea level produced mainly by the melting and breakup of large masses of ice in Antarctica and Greenland. A recent study by Deborah Balk and her colleagues at the CUNY Institute for Demographic Research showed that approximately 634 million people live in low-elevation coastal zones and that the ten nations with the most people in threatened areas are: China, India, Bangladesh, Vietnam, Indonesia, Japan, Egypt, the United States, Thailand, and the Philippines. Moreover, two thirds of the world’s cities with more than five million people are at least partly in vulnerable low-elevation areas.
Some of the populations who live on low-lying islands in the Pacific and Indian oceans and in coastal deltas are already beginning to relocate. Large island populations are also at risk in the Philippines and Indonesia. The number of climate refugees is expected to grow and could potentially involve more than 200 million people in this century, especially because of those who will have to move away from the mega-deltas of South Asia, Southeast Asia, China, and Egypt. Refugees from coastal areas of Bangladesh have already crowded into the capital city of Dhaka, and many have moved farther north across the border into northeastern India, where their arrival has contributed to the worsening of preexisting tensions based on religious and complex tribal conflicts. In 2012, these conflicts generated contagious fear that was spread by text messaging and email into cities throughout India.
All these regions and others are also threatened by climate-related flooding during storm surges as stronger cyclones (known as hurricanes in the U.S.) gain energy from warmer seas. Even small vertical increases are magnified by storm surges that carry the ocean inland. And with stronger storms, these surges are already having a bigger impact. In 2011, for example, New York City was put on emergency alert as a hurricane threatened to flood its subway system. In 2012, Superstorm Sandy did. London has long since built barriers between the ocean and the Thames River that can be closed to protect the city against such surges—at least for a while; the city is already discussing plans for further steps.
As noted in Chapter 4, the surge in population growth in the balance of this century will be completely in urban areas. The cities with the highest population at risk from rising seas are, in order: Calcutta, Mumbai, Dhaka, Guangzhou, Ho Chi Minh City, Shanghai, Bangkok, Rangoon, Miami, and Hai Phong. The cities with the most exposed assets vulnerable to sea level rise are: Miami, Guangzhou, New York/Newark, Calcutta, Shanghai, Mumbai, Tianjin, Tokyo, Hong Kong, and Bangkok.
In addition, as the chief scientific advisor in the United Kingdom, Sir John Beddington, recently noted, many climate refugees have migrated to low-lying coastal cities vulnerable to increased climate-related flooding and rising seas. They are unknowingly relocating into areas from which they may once again become climate refugees.
Contrary to most popular thinking, the rate of sea level rise is not uniform around the world, because some of the tectonic plates on which the landmasses rest are still slowly “rebounding” from the last Ice Age.† Scandinavia and eastern Canada, for example, were pushed down by the weight of the last glaciation and are still moving slowly upward long after the ice retreated. Conversely, areas at the opposite ends of the same tectonic plates—the coastal nations of Western Europe and the mid-Atlantic states of the U.S., for example—are slowly sinking, in a kind of seesaw effect. Cities like Venice, Italy, and Galveston, Texas, are also sinking—for a mixture of complicated reasons.
Because warmer oceans expand when their molecules push apart from one another (thermal expansion of the oceans has contributed significantly to the relatively small increases in sea level we have experienced thus far), areas of the ocean with large accumulations of warmer water are experiencing more rapid sea level increases—the coast of the U.S. between South Carolina and Rhode Island, for example. But all the increases in sea level thus far are nothing compared to what scientists warn is in store for the entire world as Antarctica and Greenland are affected by the sharp increases in global temperatures now in store.
Many agricultural areas in low-lying coastal regions and areas adjacent to river deltas are already suffering impacts from rising seas because of saltwater invasion of the freshwater aquifers on which their farms depend. In 2012, the combination of sea level rise and sharply diminished flows in the Mississippi River, due to the drought in the U.S., led to saltwater intrusion into drinking water wells and aquifers in southern Mississippi.
The characteristics of the seawater itself are also being profoundly altered by global warming. Approximately 30 percent of human-caused CO2 emissions end up in the ocean, where they dissolve into a weak acid, building up in such enormous volumes that it has nevertheless already made the world’s oceans more acidic than at any time in the last 55 million years, which was during one of the five previous great extinction events in the history of the Earth. And the rate of acidification is faster than at any time in the last 300 million years.
One of the immediate concerns is that the higher levels of acidity are reducing the concentration of carbonate ions that are essential to species that make shells and coral reefs. All such structures are made from various forms of calcium carbonate, which the coral polyps and shell-making creatures scavenge from seawater. But the increasing acidity of the ocean interferes with the solidifying of these hard structures. The director of the U.S. National Oceanic
and Atmospheric Administration, Jane Lubchenco, calls ocean acidification global warming’s “evil twin.”
The warmer ocean temperatures—also caused by man-made global warming—are especially stressful to the specialized algae that form the brightly colored skin of coral reefs and live in an intricate symbiosis with the coral polyps. When water temperatures rise too high, these specialized algae—known as zooxanthellae (also called zoox)—leave the skin of the coral, rendering it transparent and revealing the white bony skeleton underneath. These events are known as coral bleaching. Reefs can and do recover from bleaching events, but several events in the space of a few years can and do kill the reefs.
Coral reefs are particularly important because, according to experts, approximately one quarter of all ocean species spend at least part of their lifecycles in, on, and around reefs. Shockingly, scientists warn that the world is in danger of killing almost all of the coral reefs in the ocean within a generation. Between 1977 and 2001, 80 percent of the coral reefs in the Caribbean were lost. All of the rest, experts say, are threatened with destruction before the middle of the century. And the same fate threatens reefs in every ocean, including the largest of all, the Great Barrier Reef off the eastern coast of Australia. In 2012, the Australian Institute of Marine Science announced that half of the Great Barrier Reef corals had died in just the previous twenty-seven years.
The most visible and familiar reefs are warm-water reefs at relatively shallow depths. However, there may be an equal or even larger number of deeper, cold-water reefs. Because of their depth, they have been less studied and documented, but scientists say that since colder water absorbs more CO2 than warmer water (just as a cold container of soda stays more carbonated than a warm one), many of the cold-water reefs may be in even greater danger. Some scientists hold out hope that coral reefs might yet survive, but many of their colleagues are now convinced that virtually all corals are likely to be killed off by the combination of higher ocean acidity, higher temperatures, pollution, and overfishing of species important to reef health.
