Part Four
ELEVEN
Guided by geophysics and geochemistry rather than politics and special interests, the changing climate continued to demand notice as the new millennium began. Seven years after the collapse of the Larsen A Ice Shelf, Antarctica’s Larsen B Ice Shelf disintegrated in 2002, removing an expanse of ice the size of Rhode Island from the Antarctic Peninsula. The ice shelf was already floating, and so its collapse did not raise sea levels. On the other hand, the shelf had held back the advance of the many land-based glaciers behind it, and once that cork was removed, the movement of those glaciers, whose ice does raise sea level when it reaches the ocean, accelerated by a factor of eight, giving scientists a firsthand view of one way in which changes in the Antarctic might rapidly raise sea levels.
In fact, iceberg calving and meltwater runoff from the great ice sheets of Antarctica and Greenland were already having a measurable effect on sea level rise (although it would be more than a decade before the IPCC would acknowledge their contribution to sea level rise in its Summary for Policymakers). Recall that in the first IPCC report in 1990, some scientists believed that the Antarctic ice sheets might expand over the next hundred years, which would have had the effect of lowering sea level (the logic behind this expectation was that rising temperatures in the cold regions might have the impact of increasing snowfall, which would ultimately thicken glaciers and ice sheets). Instead, by the new millennium, the shrinking ice sheets were becoming a significant factor in the acceleration of sea level rise.
Sea level rise is the most unambiguous signal of a changing climate simply because only a very few factors can influence it on a global scale. Changes in temperature in the oceans cause the volume of water to expand during warming periods and contract during cooling. During cool periods land ice increases, sequestering water that would otherwise flow to the oceans. During warm periods glaciers and ice sheets release that sequestered water as meltwater or through the increased calving of icebergs. Global sea level nets out all the various inputs, and it can be measured by satellite. If it is rising on a decade-by-decade scale, then the climate is warming.
Moreover, because most coastlines slope gradually, a small rise in sea level can have a dramatic impact on flooding and beach erosion. Florida is the flattest state in the nation, and estimates are that a further 1-foot rise in sea level could move the shoreline between 2,000 and 10,000 feet inland. Sea level has already risen about 8 inches in the past thirty years, and given the accelerating rate of this increase, the next foot of rise might happen in the next thirty years.
By the middle of the first decade of the 2000s, sea level was rising at roughly twice the rate of the decade before, and the rate of rise continued to accelerate. While previous sea level rise had been driven by thermal expansion as the oceans absorbed heat, during the oughts, meltwater from glaciers and ice sheets began to surpass thermal expansion as a contributor, though that only became clear to those studying sea level rise several years later. Moreover, given the inertia of the massive ice sheets, once they began to meaningfully contribute to sea level rise, inevitably that contribution would continue to increase for the foreseeable future regardless of any action humans might take to reduce emissions.
While glaciologists and oceanographers were struggling to find ways to monitor and analyze the contribution of ice sheet melting and iceberg calving to sea level rise, the effects of rising seas were already being felt in coastal communities. A study of sea level rise and flooding led by the University of Miami found that the frequency of floods caused by tides rather than rain in Miami Beach increased by 400 percent after 2006.
Perhaps the most dramatic indication that something was changing was the advent of floods that bubbled up from storm drains on days with clear skies. Dubbed “blue sky” and “sunny day” floods, these started happening in coastal towns in the Southeast during what were called “king tides.” In some cases, these were exacerbated by land subsidence as communities drained groundwater, but in all cases sea level rise was a factor.
Somewhat befuddling, however, is the fact that even after blue sky flooding became common, building in coastal Florida and other eastern seacoast areas continued to boom. After the housing bust of 2007–2008, Miami Beach and other coastal cities rebounded strongly, with pricey new waterside developments going up even as their affluent owners had to wade through occasional king tides to get to the lobby. Some of this might be explained by the complicated factors that made Florida a destination for flight capital from Russia, Asia, and South America. Still, one wonders what was going through a buyer’s mind if they still purchased an apartment after reading about king tides. Did such buyers think there will be fewer such events in the future?
Sea level rise provided a subtle, ominous reminder that climate was changing during the oughts, even if most of those in harm’s way blithely ignored the warning. Nature also provided other, more dramatic warnings that change was afoot. In 2003, Europe suffered the worst heat wave in nearly five hundred years. Some thirty-five thousand died as a direct result of the heat wave, and, subsequently, an additional thirty-five thousand deaths have been attributed to the sweltering temperatures. This event was the first of several major heat waves to hit Europe since 2000. Record-setting heat waves also hit parts of North America, Australia, and Asia, and the decade ended with an intense heat wave that impacted the entire Northern Hemisphere.
And then there were the storms. On August 29, 2005, Hurricane Katrina hit New Orleans after barreling across the southernmost part of Florida. It had lost some of its punch, top wind speed having dropped from 174 miles per hour to 125 miles per hour, but a concatenation of other factors gave the United States and the world a lesson in the damage that can occur when a major hurricane hits a major city.
New Orleans is a gift of civil engineering, as much of the city lies below sea level. The Mississippi River passes through as an elevated highway (as John McPhee memorably described it), with the river and tidal areas walled off from the city by hundreds of miles of levees. Before Katrina, many worried that the Mississippi River posed the biggest threat to the city. Instead, it turned out that the inundation came from the south, in the form of a 19-foot storm surge. Throughout the city and surrounding areas, the levees proved inadequate. Some were overtopped, one was rammed by a loose barge, others fell victim to scouring and were undermined by the erosive power of torrents of water, and others failed because engineers had overestimated the density and composition of the soils at their base. Twenty-eight failed in the first day, a number that soon grew to fifty.
The ensuing damage was biblical. More than 70 percent of the city’s houses were damaged, with 56 percent suffering major damage. Eighty percent of the city was underwater during the worst of the flooding, and St. Bernard Parish was entirely submerged. With no place to live, half the population left. Before the hurricane New Orleans had a population of 452,000. In 2019, fourteen years later, the population was still lower by 160,000, 35 percent less than it was before the storm.
Economically, Katrina was the costliest natural disaster in U.S. history. Total damage resulting from the storm has been estimated at $125 billion. New Orleans accounted for $70 billion of that tab. New Orleans is one of the most strategically important cities in the United States. It’s the last gateway of America’s largest river, which drains 41 percent of the contiguous forty-eight states and carries 60 percent of our grain exports. The Port of New Orleans supports 150,000 jobs and sees 500 million tons of shipped goods pass through each year. With every resource imaginable devoted to restoring its damaged infrastructure, it still took a year before the port could handle pre-storm levels of traffic.
There was a climate change lesson from Katrina, but it never registered, buried by the flood of other stories related to the flood—human interest stories; stories about the disproportionate damage to poorer parts of the community; stories about people trapped on their roofs, stories about looting, violence, and police overreaction; stories about pet rescues; stories about the diaspora that followed the storm. All were worthy of attention, but their sheer volume obscured the stark warning that the storm offered.
The climate message of Katrina was simple: preparations that enabled your city to withstand nature’s blows throughout your hometown’s history will not be sufficient for what nature has in store. It was a message that would be delivered to New York with Hurricane Sandy seven years later, and then to Houston with the arrival of Hurricane Harvey in 2017.
The combination of sea level rise, increased storm frequency, and increased storm intensity accompanying a warming globe has shown that coastal defenses built to withstand the storm surges of the past will not be adequate for tides and surges of the future. Nor is this message about weather preparedness confined to coastal cities. As many nations around the world are discovering, dams designed to contain floods based on historical data may not be adequate for the scale of floods that follow intensified rains. Harvey’s 10-foot storm surge was exacerbated by an astounding 60 inches of rain that fell on the Houston area over a matter of days.
Katrina’s most important message can be summed up in one word: thresholds. Had New Orleans’s defenses been a bit higher, and their base better designed, the damages might have been measured in the millions rather than the tens of billions. A storm surge of 11 feet is 10 percent higher than one of 10 feet. If, to take a hypothetical example, levees protecting a city are built to contain a worst case of 10 feet, even a 5 percent increase in storm surge can up potential damages a thousandfold. These same thresholds apply to protection from winds, heat waves, droughts, and other weather-related phenomena. Beyond certain thresholds, an incremental increase can produce exponential increases in damage.
It’s not just the United States that is learning that defenses built for the climate of the past ten thousand years may not be adequate in the new climate regime. The sea walls protecting the Chinese megacity of Shanghai were built to defend the city from a once-in-a-two-hundred-year flood. The combination of sea level rise and subsidence will mean that the city can expect such floods as frequently as every twenty years by the second half of this century according to Gao Shu, a coastal defense expert, as reported by the Chinese publication Sixth Tone. A recent analysis undertaken by Financial Times estimated that sea level rise and attendant floods and tides could inflict nearly a trillion dollars in economic damage (relative to 2019 GDP) to the Shanghai area alone, with other low-lying coastal cities exposed to hundreds of billions of dollars in additional damage.
The expense for preventing this flooding is prohibitive. Gao, quoted in Sixth Tone, also noted that the price of bolstering these defenses rises exponentially if a wall has to be doubled in height from 1 to 2 meters. With some 15,000 kilometers of coast to protect with sea walls, the increased tab is beyond the reach of the Chinese government. In a refreshing sign of a new way of approaching problems, China is looking at biological coastal defenses such as mangroves and marshes as a less expensive alternative.
Another threshold involves crops. Yields begin to drop precipitously as temperatures rise. A study of cereal crops in China showed that a 1 degree Celsius increase in nighttime temperatures led to a 10 percent drop in yields. Another couple of degrees increase in all-day temperatures and many crops won’t grow at all.
Beyond certain thresholds, incremental increases lead to nonlinear impacts that can be near impossible to predict. The failure of a rice crop might lead to starvation, bankruptcy for farmers and their suppliers, and a cascade of repercussions including social unrest and the fall of governments. This is exactly what happened to end the thirty-one-year Suharto regime in 1998 after a devastating El Niño ruined the rice crop.
These thresholds are real. Some, like the heat tolerances of cereal crops, are hard, natural limits, while others are more movable, involving the assumptions about weather made during the design of infrastructure. Whether natural or artificial, however, these thresholds make predicting the costs of climate change almost impossible because the cascade of repercussions of a threshold breached will be wildly unpredictable. I came upon this truth myself when I was working on a report attempting to predict the future costs of rapid climate change sponsored by the reinsurance industry and various international and public institutions.
The first decade of the new millennium unveiled other unwelcome aspects of climate change beyond accelerating sea level rise and the problem of thresholds. One was a lesson about the costs of what might be described as second-derivative impacts. In the 1990s, Paul Epstein, the World Health Organization, and many others warned about the relationship between climate change and disease in animals and plants. In the first decade of the 2000s, the United States got a vivid lesson in the relationship between climate change, plant disease, and wildfires.
Global warming sets the stage for larger and more intense fires in several ways. The heat dries out the vegetation and the soils. It also spurs population explosions for various bark beetles that can kill entire forests, thereby providing a ready supply of fuel waiting for a spark. A warming globe allows bark beetles to invade areas where cold temperatures previously kept them at bay, and warmer winters mean that fewer of these pests die off each year. And with extreme weather come more intense winds, which can make fires uncontrollable once they get going.
The record of the first decade of the millennium underscores the impact of these unholy synergies. In 2002, Arizona, which had suffered infestations of beetles killing ponderosa and piñon pines, suffered its worst fire in history. Colorado, also beleaguered by bark beetle infestations, suffered its worst fire that year. Two years later, the Taylor Complex Fire in eastern Alaska burned 1.3 million acres. That fire was the largest in North America for a ten-year stretch. Then in 2007, Georgia, Florida, and Utah also had their worst fires ever. In between there were plenty of second and third worsts in states such as California and Oregon, and right after the start of the next decade, Texas suffered its worst, while a new record for largest forest fire was set in Arizona, and a series of three fires set and subsequently broke the record for largest wildfires in New Mexico history.
As we now know, the frequency, scale, and intensity of wildfires have only increased in subsequent years as drought has become a recurrent feature of North American climate, not just in the West, but in the Midwest and South as well. The connection between climate change, beetle infestations, and wildfires was well covered by the press in the early 2000s, but any lessons that might have been drawn about the wisdom of building in potential fire zones went unheeded. Even as the incidence of fires rose, some of the most fire-prone areas of Arizona, California, and other states enjoyed a building boom, briefly interrupted not by worries about wildfires but by the housing bust that accompanied the crash of 2008.
The drumbeat of natural disasters continued to become louder and more urgent throughout the decade. A survey by Munich Re held that 2008 had a record forty category 5 natural disasters—in terms of financial and human impacts—only one of which, an earthquake in Japan, was not related to weather. As we will see, the public continued to ignore any connection to changing climate.
Not heeding nature’s warning signals about climate change seemed to be the unifying theme of the first decade of the new millennium. People and businesses might be given a grudging pass for not taking climate change into account in the 1990s, particularly in the early part of the decade, as a picture of the warming world was emerging from background clutter amid plenty of competing claims on attention. By 2010, however, the message from nature was loud and clear: climate change was already here and promised to get more dangerous and expensive.