SIXTEEN
In 1998, I published a book called The Future in Plain Sight. I knew it was a fool’s errand to predict the future and so I chose to examine one simple question: whether the future was likely to be more or less stable than the present. In stable times, innovation and investment flourish, people look outward, cultural identities blur. In unstable times, innovation and investment shrivel, people turn inward and take out “insurance” of various forms, such as strengthened family and community ties. Society as a whole turns inward. The book outlined factors that would bear on future stability, one of which was climate change.
I included scenarios imagined for the year 2050 in order to dramatize how increased instability might transform life. My scenario from 2050 tried to show how forces set in motion by climate change might kill off California’s remaining redwoods, trees that had persisted on the West Coast for eight million years. Now, twenty-four years after publication, that very scenario seems to be unfolding.
One culprit is blobs. There have in fact been many bloblike marine heat waves around the world in recent decades, and a number of factors can cause extreme ocean warming, including an El Niño. Of particular interest, however, is the original Blob in the Northeast Pacific because it likely connects to changes in the Arctic, and those changes have produced a massive cascade of repercussions that are now threatening humans and entire ecosystems. At the tail end of this whip are the redwoods and their relationship with fog.
Redwoods are some of the largest, most durable life forms on earth. Weighing as much as 2,000 tons, they have developed fire- and pest-resistant bark and a root system from which a new redwood will grow even if the tree falls. There are living redwoods whose roots took hold at the dawn of human civilization. The tree’s strategy is to grow as tall as possible as rapidly as possible, stealing sunlight and moisture from competitors. The Achilles’ heel of that strategy is that the trees are poor pumpers of water, meaning that their upper branches and needles need to supplement what the trees get from their roots. This strategy was fine millions of years ago when the West was wetter, but as the West dried out, the redwoods died out everywhere except the coast, where they could get water from storms during the winter and from fog during the summer. So it turns out that one of nature’s most durable creations is utterly dependent on one of nature’s most fragile and evanescent atmospheric phenomena.
California’s coastal fogs have been a summer phenomenon for millions of years. That’s because the fogs are built on two profoundly stable pillars, the coast of a continent and an ocean, as well as one other pillar that proved very reliable until just very recently—trade winds. When things are operating normally—say for most of the past several million years—winds blowing from west to east over the North Pacific drive water toward the coast, causing cold water to well up to replace the surface water. When one current bumps into North America near southern Oregon, it splits in two, with one portion, dubbed the California Current, heading south along the coast, again drawing up colder water from below and cooling the air above it. The colder the air, the less capacity it has to hold water vapor, and when the air temperature drops to the dew point, as it typically does just before sunrise along the California coast in summer, a marine layer will take shape. Then, during the summer day, inland California heats up, and the rising hot air over the interior drags the fog in over the coast, bathing the redwoods in a protective, foggy dragon’s breath.
The fogs are a gift of a stable planetary setup of high- and low-pressure systems that extend across the Pacific, driving the current. The frequent reappearances of the Blob—three since 2013—represent an interruption of that setup. When the Blob appears, fogs retreat. This is the tail end of the whip, and it is open to question how many lashes redwoods can withstand.
The handle of the whip is global warming. More than 90 percent of the excess heat created by our overloading the atmosphere with greenhouse gases has ended up in the oceans. There, it has either amplified or set in motion myriad impacts, most of which are invisible to us on land. Let’s go through some of the most significant to show how the handle of the whip sets in motion lashes at the other end.
In simplest terms the warming of the oceans has raised the baseline for marine heat waves. Just as sea level rise (itself a product of warming of the oceans) raised the baseline so that storm surges have begun to overwhelm coastal defenses that stood for more than a century, so too has a warmer ocean helped push marine heat waves to extreme levels.
Oceanographers and geophysicists view the ocean and atmosphere as a coupled system, constantly interacting with each other. Climate change has altered these interactions, and some of the most significant changes are occurring in the Arctic. It only accounts for about 3 percent of the earth’s surface but, because of its unique composition, the Arctic has a disproportionately great influence on global climate. As noted previously, it has played an outsized role in some of the most extreme climatic events since the end of the last ice age. As the sea ice retreats, allowing the now dark surface of Arctic waters to absorb and release heat, and as the snow season shortens, allowing the same phenomenon to work on the land, the positive feedback of warming begetting more warming has resulted in temperatures in the Arctic increasing at several times the rate of the lower latitudes. This Arctic amplification has been long noted and much studied.
During the 2010s, a number of researchers, including Jennifer Francis, Marilena Oltmanns at the National Oceanographic Centre in the United Kingdom, and many others, published studies connecting the retreat of sea ice and the warming of the Arctic to other anomalous events around the world. One of these was the proliferation of warm blobs in the Northeast Pacific. A number of influences contribute to the formation of warm blobs, but among those the most dramatic has been the warming of the Arctic.
It turns out that apart from causing marine die-offs and aberrant weather, the changes in the Arctic also can interfere with the coastal fogs that have sustained redwoods for millions of years. As noted, the jet stream’s vigor is determined by the temperature contrast between the Arctic and the lower latitudes. As the Arctic has warmed, that contrast has diminished, which has slowed the jet stream and dampened its meanders so that it maintains a configuration for a longer period. As we have seen, a slower, more persistently patterned jet stream means that a weak high-pressure system that ordinarily forms in the Northwest United States in the fall and winter can both intensify and remain in place for far longer than it used to.
As this ridge becomes larger, it sets in motion a self-reinforcing cycle. Storms get diverted to the Far North, while the high pressure dampens winds over the Pacific. This lessens ocean water mixing, which allows the Blob to both expand and become warmer. In turn, the warm water bolsters the perpetuation of the high-pressure system. This cycle impacts the California Current and its related fogs.
With less wind to drive the system, the California Current warms and weakens, and with warmer temperatures, the marine layer becomes less reliable, and the West Coast bakes. The redwoods, some of them more than two thousand years old, clinging to their last redoubt on a band of the Oregon and California coast, find themselves struggling for the moisture that sustained them through millions of summers. The tail end of the whip.
As noted earlier, the advent of the Northeast Pacific warm Blob and its accompanying ridge are also implicated in the series of extremely cold and stormy winters in the U.S. Midwest and Northeast in recent years. Just as the RRR and its ilk push the storm track farther north, the distortion of the jet stream has also caused it to roust cold that should have settled in over the Arctic and ship it to the midlatitudes. The phenomenon has been misnamed “polar vortex.” The polar vortex is actually a barrier of sorts, formed by the steep temperature gradient that ordinarily bottles cold air in the Arctic and that defines the track of the jet stream. As that temperature gradient decreases, that barrier can break down and Arctic air can spill south, creating the bizarre situation in which the Arctic is bathed in unseasonable warmth while the lower latitudes freeze.
The repercussions of a warming Arctic can become truly confusing. For instance, 3,000 miles east of the Blob in the Pacific Northwest, another blob has been forming in recent years in the North Atlantic. It’s also related to the warming of the Arctic, but, paradoxically, this blob consists of intensely cold water and centers southeast of Greenland. Seen from space in satellite imagery, it shows up as a blue blob, one lonely instance of cooling against warming oceans throughout the Northern Hemisphere. Except it’s not ocean water, and it poses a potentially catastrophic threat to northern Europe.
One artifact of the warming of the Arctic has been the accelerated melting of the Greenland Ice Sheet. The meltwater from the ice sheet as well as from the many glaciers in eastern Canada flows into the North Atlantic and is collected and pooled by ocean currents. This fresh water is lighter than salt water and tends to stay on the surface. And even though it is meltwater, it is far colder than the ocean water it sits atop. The profoundly disturbing fact is that it shouldn’t be there.
Ordinarily, this is near the part of the ocean where the remnants of the Gulf Stream sink, forming what is called “deep water” as part of the planetary system of a river of water within the oceans called the thermohaline circulation. What happens during this part of the circulation is that as the Gulf Stream travels northward it steadily evaporates, releasing heat, and, as it does, it becomes saltier than the surrounding ocean water. More saline water is heavier than less saline water, and at a certain point in the North Atlantic between Greenland and Iceland it begins to sink. This process is partially a function of a sill on the bottom of the ocean. As the saltier water spills over that sill it “entrains,” or drags, the rest of the current behind it. This entraining is a critical part of the heat distribution system of the ocean. The North Atlantic part of the thermohaline system is called the Atlantic Meridional Overturning Circulation, or AMOC.
As Wallace Broecker, Gerald Bond, Willi Dansgaard, and others have reconstructed events, in the past this part of the circulation has been periodically interrupted when the surface of the ocean has been flooded with fresh water from the melting of ice sheets or, in some cases, flotillas of icebergs. When that has happened the thermohaline circulation has shut down, and that in turn has plunged much of the Northern Hemisphere into a deep freeze.
That pool of cold fresh water presents a worrisome sign that something like that may be happening now. Michael Mann and colleagues collected data on sea surface temperatures and, in 2015, published a new index for the AMOC in Nature Climate Change. It showed that since 1970 the AMOC has lost considerable vigor. Separately, Stefan Rahmstorf, the German climate modeler, has, with colleagues, published several papers on the slowdown. In a 2018 paper in Nature, his team argued that shutdowns in the AMOC have resulted in the most rapid and violent climate shifts in the past 2.6 million years. Estimates are that the current has lost about 15 percent of its normal vigor. The problem for humanity is that no one can confidently estimate at what point this system tips into shutdown or what that would mean for those of us living today. Rahmstorf and colleagues have followed up with a new study published in Nature in 2021. It asserts that the Atlantic overturning is the weakest it’s been in a millennium, and they estimate that it might further weaken by 25 to 45 percent by the end of the century.
For the moment, this cold blob has contributed to more intense storms in Europe, while the slowdown in the AMOC has contributed to a rise in sea level on the northeast coast of the United States. Sea level seeks uniformity, but there are persistent patterns that distort sea levels in areas around the world. As Michael Mann has explained, when the AMOC is vigorous it creates a downslope that draws water away from the coast. Conversely, when it slows down, that slope decreases so that water piles up by the coast, raising measured sea level.
Thus, the Northern Hemisphere enters the 2020s with dueling blobs, both hot and very cold, with the cold blob the product of heating in the Arctic and itself perhaps the harbinger of a sudden cooling in parts of the North Atlantic. For average Americans, and even for those deeply involved in climate change, these competing forces are hard to reconcile.
The heating of the oceans and the tropics may be pushing storm tracks northward, leaving the Mediterranean regions around the world hotter and drier. Three massive zones of evaporation, transport, and condensation (one can visualize this as a series of belts, each taking up close to 30 degrees of latitude covering the distance from the equator to the North Pole) drive poleward atmospheric circulation away from the equator. As the air and oceans warm, these belts have been shifting poleward on both sides of the equator, leaving a rain shadow in some areas where rain used to fall (e.g., the California coast in the Northern Hemisphere and southern Australia in the South) as clouds drop their moisture nearer the poles.
On the other hand, the slowdown in the AMOC may be pushing tropical rain belts southward. Taken together, what is happening is that the interconnected systems that distribute heat and moisture around the planet are adjusting to the increased energy the warming of the planet represents. It is happening now, and people and ecosystems around the world are feeling the adjustments in freakish and extreme weather events.
The future began knocking on the door in the 1980s, and while the public ignored the knocking, climate scientists noticed that the record-setting years might be a signal that climate theory about greenhouse gases and warming might be climate fact. That knocking became a pounding in the 1990s, and the science community recognized that it meant that climate change was not a future event. Even with a global effort to understand what was happening, the changes occurring outpaced that ability of science to connect the dots. The Northeast Pacific Ocean blob showed up, and oceanographers, geophysicists, and meteorologists scrambled to understand how it came about and what it meant. It wasn’t predicted.
For all the surprising weather and geophysical anomalies, there were many that science had predicted that showed up much earlier than expected. Perhaps the most dramatic and consequential examples of such unwelcome visitors from the future have been the signals of distress coming from the West Antarctic Ice Sheet. Events there that were predicted to unfold more than a century from now seem to be happening now.
As noted earlier, in the 1990s, scientists saw that the so-called ice streams that transport ice within the West Antarctic Ice Sheet seemed to be accelerating. WAIS delivers ice to the ocean primarily through the massive Thwaites and Pine Island glaciers. Thwaites is about the size of Florida and Pine Island about two-thirds as big. What surprised scientists was the speed with which the glaciers were delivering ice to the ocean and the changes that were occurring within the ice sheets. This discovery set in motion a global scramble to determine what was going on. Also driving this scramble: none of the models could account for the enormous and rapid shifts in sea level rise evident from the fossil record.
In 2011, Jeremy Bassis and C. C. Walker published a paper in the Proceedings of the Royal Society A, offering a mechanism for the accelerating disintegration of glaciers. Stable marine ice sheets such as WAIS typically have ice shelves extending into the seas from the ends of major glaciers. If the ice shelf is in a bay it can act as a cork of sorts, slowing the advance of the masses of ice continually being transported toward the sea. Glaciologists noticed that the breakup of the Larsen B Ice Shelf and the breakup of the ice tongue in front of Greenland’s gigantic Jakobshavn Glacier resulted in a dramatic increase in iceberg calving. Bassis and Walker offered an explanation for the increase. They argued that the breakup of such ice shelves exposed ice cliffs in the main body of the glacier and that the structural properties of the ice could not sustain a cliff more than about 300 feet high. Once exposed, an ice cliff taller than that will fracture and collapse from its own weight, leading to a flood of icebergs.
Since this argument was put forward, a number of scientists have refined and developed the theory, linking it to other aspects of ice transport toward the sea. While uncertainties remain, the picture that has emerged during the 2010s is that as the ocean and air warm, melting and runoff deliver water into and through the ice shelves, leading to a complicated series of interactions that ultimately thin and weaken the shelves from below. Once they disintegrate, the back pressure on the glaciers is relieved and they begin to move more rapidly toward the sea.
The disappearance of the ice shelves leaves an ice cliff exposed at the terminus of the glacier, and at this point a self-reinforcing process can lead to runaway acceleration of the glacier. In the case of the Thwaites and Pine Island glaciers, the more ice that breaks off, the higher the remaining ice cliff (because of the slope of the land underneath the glacier). The higher the cliff, the more ice will hive off.
Thwaites alone now contributes about 4 percent of annual sea level rise. Its acceleration has already forced reappraisals of future sea level rise that themselves are just a few years old. For instance, a study led by glaciologist W. Tad Pfeffer published in Science in 2008 estimated that the Antarctic might contribute 60 centimeters of sea level rise by 2100. By 2013, that estimate was raised by 50 percent to 90 centimeters. Expect it to be raised again.
The push to understand Thwaites is yet another example of what is becoming an all-too-familiar phenomenon. In the space of a few decades, what was isolated speculation about something long in the future became a present-day threat and an urgent matter for science in real time. So urgent that the United States and the United Kingdom have jointly set up a mission to study Thwaites. The International Thwaites Glacier Collaboration involves sixty scientists who over the next five years will try to understand the ways in which this giant unstable glacier might contribute to rapid sea level rise.
Over the past three decades, the vast global network of scientists and scientific institutions has mobilized to understand all the ins and outs of the global climate system and its vulnerabilities. Writing for RealClimate, Stefan Rahmstorf pointed out that in 2018 there were roughly twenty thousand peer-reviewed papers published on climate change. That works out to fifty-five papers a day, more than two every hour for every day of the year, meaning that studies are accumulating far more rapidly than any one human could read them.
The picture emerging from these thousands of studies is of a climate system quite different from the one we thought we had, and also of a climate threat far more dire and more imminent than was anticipated by the IPCC’s first assessment in 1990. Then, the Greenland Ice Sheet seemed stable, and the conventional wisdom was that the Antarctic ice sheets might well grow as the climate warmed. In 1990, sea level was rising at about 1.2 millimeters per year, not far off the same pace it had been rising for more than a century. At that time, the paradigm for climate change was that it would arrive at a stately, incremental pace. It was believed that the permafrost would remain stable for the next hundred years.
Then, as the scientific world mobilized, the news that past climate shifts were violent and extremely rapid was confirmed. In 1996, the Greenland Ice Sheet began losing mass, a process that has accelerated dramatically as the years have passed and is now more than seven times the rate it was at the end of the 1990s, according to the National Oceanic and Atmospheric Administration (NOAA). WAIS was discovered to be losing mass not long after that, and more recently, evidence has surfaced that the East Antarctic Ice Sheet, the mother of all ice sheets, is losing mass as well. By the mid-1990s it became obvious that permafrost was melting throughout the Arctic, and by the 2010s it became conventional wisdom that most of the world’s top layer of permafrost would disappear by 2100. By the middle of the 1990s, the rate of sea level rise had more than doubled; by the early part of the new millennium, the rate had tripled; and now it is close to quadruple the rate of rise in 1990.
Indeed, in many cases the worst-case scenarios of the early 1990s have become the conventional wisdom of today. The current intermediate case for sea level rise in 2100 is roughly the same as the high case in the first IPCC assessment. NOAA’s worst case of 2.5 meters is more than four times as high as the high case for the IPCC of 2007. Even these numbers are not the worst case.
During the 2010s, the IPCC made big strides in catching up to the science, if not reality. As noted earlier, the reports themselves are supposed to represent the state-of-the-art science, but for most of their history, most notably with the fourth assessment in 2007, the Summaries for Policymakers have been far more conservative than the chapters, and some of the chapters lagged the actual state of knowledge. Perhaps because of the very strong reaction to the fourth assessment’s lowball estimates of future sea level rise, subsequent reports have been less equivocal about the severity of the threat the world faces. In October 2018, the IPCC issued a special report, Global Warming of 1.5°C, which focused on how hard it would be to keep warming to that level, how harsh those consequences might be for humanity and nature, and how much more harsh life would be should warming continue to 2 degrees Celsius. While written in the maddening, plodding prose of a document subject to a thousand editors, this time its message was loud and clear: you don’t want to go there. Then, in August 2021, the IPCC began releasing draft elements of its Sixth Assessment Report, the message of which UN Secretary-General António Guterres described as a “code red for humanity.”
Scientific knowledge continues to advance, but there won’t be a straight-line path to perfect understanding. Accounting for all the variables that go into weather, much less climate, far exceeds the capacity of even the most advanced supercomputers. A quip that circulated among climate scientists about their work went “It’s not rocket science; it’s much harder than that.” Even as climate scientists discover new connections among the various gears of climate and new geophysical processes that underlie the dynamics of the ice sheets, the climate offers new anomalies and conundrums. Science has mobilized, but its clock will never catch up to reality. The best we can hope for is that science doesn’t lose ground as climate continues to change.