The Future (54 page)

The word “desert,” by the way, is derived from the relationship of people to the land involved: deserts are
deserted
by people. Consider the significance of Greece, Italy, and the Fertile Crescent—the cradles of Western civilization—turned into deserts by
human alteration of the same natural climate feature that created the Sahara Desert beginning 7,300 years ago.

The jet stream that controls the location of storm tracks in most of North America and Eurasia is also being affected by the impact of global warming on atmospheric circulation patterns and the unusually chaotic weather patterns in these latitudes in recent years. There are actually two jet streams in both hemispheres—a subtropical jet stream flowing from east to west along the poleward margin of the barrel loop of the
Hadley cells (the trade winds), and the so-called polar jet stream—which flows from west to east on the poleward side of a second set of
barrel loop atmospheric currents known as the Ferrel cells.

The location of the northern polar jet stream (which North Americans and north Eurasians typically call
the
jet stream) is determined in part by the wall of cold air extending southward from the Arctic Circle. But in recent years, the melting of the Arctic ice cap has led to so much extra heat absorbed there that the northern boundary of the jet stream flowing across North America and Eurasia appears to have been profoundly and radically dislocated—changing storm tracks,
pulling cold Arctic air southward in winter, and disrupting precipitation patterns.

All of these energy transfer mechanisms—the wind and ocean currents, storms and cyclones, and atmospheric cells—define the shape and design of the Earth’s climate pattern that has remained relatively stable and constant since shortly before the Agricultural Revolution began. Yet global warming is changing all of the energy balances that have given definition to this climate envelope, and is both intensifying and changing the locations of the weather phenomena we are used to.

Some of these balances are being changed to such a degree that scientists worry that they could be pushed far enough out of the pattern we have always known that they could flip into a very new pattern that would produce weather phenomena with intensity, distribution, and timing that are completely unfamiliar to us and inconsistent with the assumptions upon which we have built our civilization.

By way of illustration, take a leather belt and hold one end in either hand; push your hands together until a loop forms sticking upward. As you move your hands and change the inflection of your wrists, the shape of the belt loop will vary but it will remain in the same basic shape. But if you inflect your wrists a little more, it will suddenly flip into a new basic pattern with the loop pointing downward instead of upward. The variations in climate that we have always known, large as they are, are like the variations in the belt loop pointing upward. There would still be similar variations if the loop pointed downward, but if we push the boundary conditions of the loops to a point that causes it to adopt an entirely new pattern, the consequences for our climate would be extreme indeed.

We have already been confronted by unwelcome surprises in our experimentation with changing the chemical composition of the Earth’s atmosphere. The sudden appearance of a continent-sized stratospheric
ozone hole above Antarctica in the 1980s raised the specter of a deadly threat to many forms of life on Earth, because it allowed powerful ultraviolet radiation normally blocked by the stratospheric ozone layer to reach the surface. And except for the fact that the progressive destruction of the stratospheric ozone layer was arrested, scientists say it would have spread to the stratosphere above highly populated areas.

Even though the Antarctic ozone hole lasted each year for only approximately two months, it had already
begun to produce a slight thinning of ozone in the stratosphere surrounding the entire planet. Scientists warned at the time that if the concentrations of chemicals causing ozone destruction continued to build, this dangerous thinning process would accelerate, and an even more
dangerous ozone hole above the Arctic might form on a more regular basis.

Luckily, almost immediately after this frightening discovery, President Ronald Reagan and Prime Minister Margaret Thatcher helped to organize a global conference in 1987 to negotiate and quickly approve a treaty (the Montreal Protocol) that required the phasing out of the group of industrial chemicals—including the best-known, chlorofluorocarbons (CFCs)—that two scientists, Sherwood Roland and Mario Molina, had proven conclusively in 1974 were
interacting with the unique atmospheric conditions in the cold stratosphere above Antarctica to produce this progressive destruction of the protective ozone layer that shields humans and other life-forms from deadly ultraviolet radiation.

E
VEN THOUGH THE
Montreal Protocol has been a historic success, it is important to understand the precise mechanism through which these chemicals led to the stratospheric ozone hole in the first place—because of new threats to the ozone layer from global warming. To begin with, there is a third and final set of barrel loop atmospheric cells at both the North Pole and the South Pole, called polar cells, within which the winds form a vortex around each pole.

The south polar vortex is much stronger and more coherent, especially in the austral winter, because Antarctica is land surrounded by ocean—whereas the Arctic is ocean surrounded by land—and while the Arctic Ocean is covered, at least in winter, by a thin layer of ice only several feet thick, Antarctica is covered year-round by two kilometers of ice. That also makes it the continent with the highest average altitude,
which means it is closer to the top of the sky and
radiates the reflected sunlight back into space more powerfully. Consequently, the air above Antarctica is much colder than anywhere else on Earth, which produces an unusually high concentration of ice crystals in the stratosphere there.

The tight vortex formed by the Antarctic circumpolar wind currents during winter holds the CFCs and ice crystals in place above the continent, almost like a bowl. And it is on the surface of these ice crystals that the CFCs react with stratospheric ozone. One other crucial ingredient must be present before the chemical reaction that destroys the ozone starts taking place: a little bit of sunlight.

At the end of the southern hemisphere winter, around the middle of September, when the first rays of sunlight strike the ice crystals held in this “bowl,” the chemical reaction is ignited. Then it quickly spreads, destroying virtually all of the stratospheric ozone inside the bowl. As the atmosphere absorbs more heat, the vortex formed by the wind currents weakens and the bowl breaks up, signaling the end of the ozone hole for that year. Some large blobs of ozone-free air sometimes move northward, like the blobs in an old lava lamp from the 1960s—exposing populated areas in the southern hemisphere
like Australia and Patagonia to high levels of ultraviolet radiation
when air with low concentrations of ozone is no longer able to provide a screen for those at the surface.

Stratospheric ozone depletion and global warming have always been considered almost completely separate phenomena, but in 2012 scientists discovered that global warming is producing an unexpected and unwelcome threat to the stratospheric ozone layer—this time above highly populated areas in the temperate zone of the northern hemisphere.

Just as the extra heat energy absorbed in the tropics is causing the updraft of the Hadley cells to nudge the top of the troposphere higher, the extra heat energy being absorbed in the temperate zone of the northern hemisphere is causing more powerful thunderstorms to punch through the top of the troposphere,
injecting water vapor into the stratosphere, where it freezes into a new and dangerous concentration of ice crystals—thus creating the conditions for triggering stratospheric ozone loss by providing the surfaces on which the CFCs still in the atmosphere can come into contact with stratospheric ozone and sunlight to destroy the protective ozone layer. This new phenomenon has begun to appear at a time when the stratosphere is also getting colder, in inverse proportion to the warming of the lower atmosphere. Long predicted by climate
models, stratospheric cooling is a result of
the Earth’s atmosphere attempting to maintain its energy “balance.” Much more work will need to be performed before this troubling surprise is fully understood, but it already illustrates the recklessness of this “planetary experiment” that humanity has under way. We are not only playing with fire, but ice as well. As Robert Frost wrote, “
Some say the world will end in fire; some say in ice.” Either one, he added, “would suffice.”

The idea that we are engaged in an unplanned experiment with the planet was first articulated by Roger Revelle, who was my teacher and mentor on global warming. In 1957, Revelle wrote with his coauthor, Hans Suess, that, “Human beings are now carrying out a large scale geophysical experiment.” They also noted, “The increase of atmospheric CO
₂
from this cause [combustion of fossil fuels] is at present small but may become significant during
future decades if industrial fuel combustion continues to rise exponentially.”

The word “experiment” is worth a little reflection. There are ethical prohibitions against human experimentation that puts lives at risk or seriously damages those who are subjects of the experimentation. Since there are millions of lives put at risk by the “unplanned experiment” that is radically changing the Earth’s atmosphere and threatening the future of human civilization, surely the same ethical principle should apply.

Climate science
began more than 150 years ago when the legendary Irish scientist John Tyndall discovered that carbon dioxide traps heat. The actual mechanism by which this occurs is more complicated than the popular metaphor of a “greenhouse effect”; the bonds holding together the atoms of the CO
₂
molecule absorb and radiate energy at infrared wavelengths, impeding the flow of energy from the surface outward toward space much like a blanket.

But the consequences are the same—the CO
₂
in the atmosphere, like the glass in a greenhouse, retains heat that comes in from the sun. Tyndall’s historic finding occurred the same year, 1859, as the drilling of the
first oil well by Colonel Edwin Drake in Pennsylvania.

Thirty-seven years later, in 1896, the Swedish chemist Svante Arrhenius cited Tyndall in a landmark paper in which he addressed the following question: “Is the mean temperature of the ground in any way
influenced by the presence of heat-absorbing gasses in the atmosphere?” Arrhenius performed more than 10,000 calculations by hand in order to arrive at his conclusion that a
doubling of CO
₂
concentrations in the atmosphere would raise global average temperatures by several degrees Celsius.

In the second half of the twentieth century, in the midst of the postwar burst of industrialization, research into global warming picked up considerably. The International Geophysical Year of 1957–58 led to the establishment by Roger Revelle and Charles David Keeling of a historic project to begin the long-term systematic measurement of CO
₂
concentrations in the global atmosphere. The results were astonishing. After only a few years of measurements it became obvious that the
concentration was increasing steadily by a significant amount, a result confirmed in the following years by installation of observation stations all over the world.

Because most of the landmass and deciduous vegetation is in the northern hemisphere, the CO
₂
concentration shows an annual cycle of CO
₂
intake and outgassing by the terrestrial biosphere, which is so much larger north of the equator than south. As a result, the CO
₂
concentration in the northern hemisphere goes up in winter (when uptake of CO
₂
by leaves and plants is low) and down in summer (when the trees and grasses are once again pulling CO
₂
from the air).

But the observations also showed clearly that the overall concentration of
CO
₂
throughout this yearly seasonal cycle was being shifted steadily upward. After the first seven years of the iconic measurements contained in what is now known as the Keeling Curve, the low point in the annual cycle was already higher than the high point when the measurements began. Fifty-six years later, these measurements still continue every day—from the top of Mauna Loa; at the South Pole; in American Samoa; in Trinidad Head, California; and in Barrow, Alaska. In addition,
there are sixty other “distributed cooperative” sets of measurements, including aircraft profiles, ship transects, balloons, and trains. The project is now overseen, by the way, by an outstanding scientist, Ralph Keeling, who happens to be Dave’s son. He is also now monitoring the small but steady reduction in the concentration of oxygen in the atmosphere—not a cause for concern in itself, but yet another validation of the underlying climate science,
which has long predicted this result, and an effective cross-check on the accuracy of the CO
₂
measurements.

Ten years after Revelle and Keeling began measuring CO
₂
in the atmosphere, I had the privilege of becoming Revelle’s student in college and was deeply impressed by the clarity with which he described this phenomenon and the prescience with which he projected what would happen in the future if the exponential increase in fossil fuel combustion and consequent CO
₂
emissions continued.

A decade after leaving college, I began holding hearings about global warming in Congress, and in 1987–88, I first ran for president in order to focus more attention on the need to solve the climate crisis. In June of 1988, NASA scientist Jim Hansen testified that the evidence of human-caused global warming had become statistically significant in observations of rising global temperatures. Six months later, in December, the United Nations established a global scientific body—the Intergovernmental Panel on Climate Change (IPCC)—to provide authoritative summaries of the evidence being found by scientific studies around the world.