Many So-Called 'Natural' Disasters Are Actually Caused by Humans—And They're Only Getting Worse

A 2015 study including Superstorm Sandy and Super Typhoon Yolanda showed that both were influenced by high sea surface temperatures that had a discernible human component.

Photo Credit: Ronnie Chua /

The following is an excerpt from the new book How the World Breaks by Stan & Paul Cox (The New Press, 2016): 

Attitudes toward geoclimatic hazards, and the disasters associated with them, have evolved dramatically over the centuries. Once treated exclusively as acts of angry or capricious deities (usually assumed to have been provoked by humans’ sinful acts), disasters came to be viewed during the Enlightenment as the inevitable consequences of natural processes; with the Industrial Revolution, disasters continued to be regarded as natural events, but ones that could be at least partly tamed with technology. As time went on, it became possible to redirect the flow of floodwaters, fortify unstable slopes, and maybe even knock an asteroid off course if it was to threaten us. Eventually, however, it became clear that fending off disaster can be a very tricky business, and that technological solutions often misfire or even trigger fresh calamities.

Our public policies are now falling even further behind as they fail to account for another, potentially even more jarring prospect: that the world economy is not only fostering disasters but also actually producing some of the geoclimatic hazards from which disasters emerge. There are greenhouse gases, of course, with their potential role in spawning heat waves, storms, floods, droughts, and, indirectly, landslides and wildfires. Non-greenhouse-gas air pollutants such as black carbon and sulfate aerosols play their own wild-card role in many of the new, disturbing weather patterns we are seeing—heating some places at some times, cooling others, and altering precipitation patterns in unpredictable, sometimes dangerous ways. And climate disruption is only one of several links between everyday human activities and hazards that look “natural.” The Lusi mud volcano is just one of many recent examples. Extensive manipulation of rivers and groundwater causes coastal lands to subside, increasing the threat of flooding at least as much as rising sea levels. That, along with destruction of coastal ecosystems, results in storm surge hazards where none existed before. Thousands of landslides are triggered every year by damming rivers, road construction, mining, quarrying, irrigation, burning, and logging. And in recent years, the dirty and green energy sectors both have been setting off earthquakes.

Nowhere do political or business leaders appear to be very interested in halting the production of new hazards and disasters. That is disturbing but not surprising, since doing so would mean curbing profitable activities and leaving valuable resources in the ground or under the sea. We have seen only a small sampling of humanity’s many recipes for cooking up natural-looking hazards. There are many more. In the arduous struggle to prevent, prepare for, and recover from disasters, communities and nations can no longer avoid the even more difficult question of deeper causes. In the words of the historian Ted Steinberg,“The next time the wind kicks up and the earth starts to roar, what will we tell ourselves? Will we rise up in indignation at what nature has done to us? Or will we reflect on our own roles as architects of destruction? It is how we answer these questions that will determine the future of calamity.”

Weather on Steroids

Tropical cyclones are among the most destructive of geoclimatic hazards, and it now seems they are being supercharged by climate change. Excess energy trapped by greenhouse gases can result not only in rising average global temperatures and locally extreme heat; it can also allow regions of the atmosphere to hold larger quantities of water vapor or generate stronger winds. The possibility that such energy could be dissipated by more powerful storms was once controversial but is now widely acknowledged. By the time Hurricane Katrina struck the Caribbean and U.S. Gulf Coast in 2005, researchers were already predicting that greenhouse warming could strengthen tropical cyclones. But in the broader public discussion, claims that Katrina was a symptom of anthropogenic climate change were loudly and effectively shouted down. A mere seven years later, similar views on Superstorm Sandy were widely accepted. People began talking openly about the possibility that natural disasters not only are not wholly natural, but that the underlying hazards themselves are increasingly created or aggravated by the normal operation of the human economy. Twelve months after Sandy, the record-shattering Typhoon Yolanda struck the Philippines; even as the storm was still raging over Southeast Asia, climate scientists were linking it to the warming global climate.

Now whenever disasters strike, greenhouse emissions are widely, but not universally, viewed as suspects. Some qualifications remain necessary. While the frequency of hurricanes, for example, is not thought to be affected yet by greenhouse emissions, it has been all but confirmed that their intensity can be strengthened by the warmer surface waters in the North Atlantic. Among several lines of evidence are Atlantic storm surge data going back to 1923 showing that Katrina-size storms are twice as frequent in warm years as in cold ones. A 2015 study including Superstorm Sandy and Super Typhoon Yolanda showed that both were influenced by high sea surface temperatures that had a discernible human component. When, in 2015, Hurricane Patricia exceeded even Yolanda’s intensity, the new record was attributed to unusually warm sea surface temperatures in the region of the Pacific where Patricia originated. That warming was attributed to a major El Niño event, but the implication is that greenhouse warming in the Pacific will similarly fuel stronger tropical cyclones. Record warm years are now routine, while record cool years no longer occur. To quote an Environmental Defense Fund vice president, “We can’t say that steroids caused any one home run by Barry Bonds, but steroids sure helped him hit more and hit them farther. Now we have weather on steroids.”

If climate science is making progress in figuring out the trend in tropical cyclones, it is still struggling to understand that quick-hitting scourge of the inland plains: the tornado. Individual twisters are notoriously difficult to study, but the kinds of weather fronts that spawn them are well understood. The towering storm clouds that are characteristic of such fronts feed on high convective available potential energy (CAPE) in the atmosphere.

Climate experts project that a warming atmosphere over North America in coming decades will generate higher CAPE levels and increase low-level wind shear (that is, wind currents passing each other in opposite directions, creating a potentially dangerous rotation) in the spring and fall across much of the continent east of the Rockies, with a very likely increase in the number of days per year in which the kind of severe thunderstorms that spin off tornadoes will occur. In any case, a longer storm season could itself constitute a disaster—in 2011, losses caused by the most severe thunderstorms across the United States were a staggering $47 billion.

Out-of-season tornadoes became a grim reality in the eastern and central United States in the 2015 Christmas season, when, under freakishly warm temperatures of fifteen to twenty-five degrees above normal and an atmosphere saturated with water vapor, a storm system grew to cover almost half the country at once. The giant storm was attributed to a strong El Niño in the Pacific being superimposed on a background of greenhouse warming. It incubated sixty-eight tornadoes across fifteen states, ranging in strength up to EF-4. Bob Henson and Jeff Masters of Weather Underground noted that “2015 is the first year in records going back to 1875 that has seen more confirmed tornado-related deaths in December than in the rest of the year combined.” As the storm front churned east, it also produced severe flooding and mudslides and brought blizzards behind it. On some lands flanking the Mississippi River, waters grew even deeper than in 1993’s record summer floods (and this in the dead of winter, not normally flood season on the river). Just before the first tornadoes struck on December 23, the New York Times, noting that the extreme warmth wave was expected to bring severe storms, twisters, and floods, had already labeled that anomalous Christmas week “a fitting end to the hottest year on record.”

The same year also fanned a continuing intensification of the country’s fire season. In August 2015, as numerous large, intense wildfires burned throughout the heat-and drought-stricken western United States, the U.S. Forest Service released a report projecting that the agency would spend half of its entire budget on firefighting that year, compared with only 16 percent twenty years earlier; furthermore, the report predicted, the expense would rise to two-thirds or more of the Forest Service budget by 2025. The reasons were clear, according to the report:“With a warming climate, fire seasons are now on average 78 days longer than in 1970. The U.S. burns twice as many acres as three decades ago and Forest Service scientists believe the acreage burned may double again by mid-century.” The Forest Service is part of the U.S. Department of Agriculture. Commenting on the report, agriculture secretary Tom Vilsack told the Washington Post “that to get a handle on the problem, extremely large or intense fires—which are only 1 to 2 percent of the total, but chew up 30 percent of firefighting costs—should be treated as natural disasters, much like hurricanes and floods are, and funded accordingly.” That proposal may have made budgetary sense to Vilsack, but it flew in the face of fire science. A growing body of research, some done in his own department, shows that the disastrous trend is not natural, but that the potential for wildfire is increased by the worsening heat and drought stress that comes with human-induced climate change. Based on historical data and tree-ring data going back a thousand years, a study published in Nature Climate Change in 2013 concluded that “drought has been, and remains, a primary driver of widespread wildfires” in the U.S. Southwest. The epic droughts that the western states have experienced in these early years of the greenhouse era, and with them the wildfires, are expected to worsen and extend across the country. In a 2012 paper published in the journal Forest Ecology and Management, Forest Service scientists, using future climate models, projected that “fire potential is expected to increase in the Southwest, Rocky Mountains, northern Great Plains, Southeast, and Pacific coast, mainly caused by future warming trends. Most pronounced increases occur in summer and autumn. Fire seasons will become longer in many regions.” The association among human-induced warming, drought, and wildfires is only one reason that Vilsack erred in calling the more frequent extreme fires “natural disasters.” Another is that U.S. forest lands all have long been under some degree of human management. Yet another, as acknowledged in the Forest Service’s own 2015 fiscal report, is that more and more houses and other buildings are being constructed in areas that are almost certainly doomed to burn at some point.

It’s a cruel irony on our greenhouse planet that an increased threat of drought in many regions coexists with a higher moisture content in the atmosphere overall. In recent years, that warmer, wetter atmosphere, the melting of Arctic sea ice, and unusual air circulation patterns—all associated with rising concentrations of greenhouse gases—have been bringing highly destructive winter storms and paralyzing quantities of ice and snow to parts of the United States, Europe, and China. By the winter of 2014–15, the repeated onslaughts were sorely testing the endurance of the U.S. Northeast’s residents. Research is increasingly finding what climate scientists call “teleconnections”: links among extreme climatic events across vast distances. In early 2014, the low-pressure system that persisted over Southeast Asia for weeks, which brought disastrous rains, caused the deadly landslide that hit Barangay Andap in the Philippines, and eventually grew into Tropical Depression Agaton, is also suspected of having played a teleconnected hand in the extraordinary onslaught of cold air, snow, and ice that plagued the United States and Europe that winter. The catastrophic deluges that struck Pakistan in 2010 were part of the same greenhouse-charged weather system that brought deadly heat, drought, and wildfires to Russia. Climate models project large increases in the number and size of floods in India, Bangladesh, and Pakistan in the coming century; by destroying crops, such flooding could halt or reverse the progress that is being made in South Asia to alleviate hunger and poverty.

A global increase in the annual number of catastrophic floods had become evident as early as 2002, when a group of National Oceanic and Atmospheric Administration (NOAA) scientists writing in Nature declared, “We find that the frequency of great floods increased substantially during the [late] twentieth century . . . and the model suggests that the trend will continue.” A more recent study, finding that prospects remain dire, concluded that in the twenty-first century severe flooding will be far more frequent and human exposure to flooding will be four to fourteen times as great as it was in the twentieth century, even when the effect of population increase is removed.

Rise and Fall

In a 2013 article, Wolfgang Kron of Munich Reinsurance Company made an extraordinary claim: “There are few natural catastrophes that are not somehow related to coasts. While not all of them occur right on the borderline between land and sea, their causes can be found either in meteorological events produced over the water or in geological events that happen at the crustal plate boundaries along the continents or mid-ocean ridges.” In the hazardous century ahead, it is indeed coastal areas that are expected to be imperiled most severely (but not exclusively; some other places, ones distant from any coast, can expect a heightened probability of geoclimatic disasters such as wildfires, tornadoes and landslides). The obvious aggravating factors affecting coasts will be the melting of polar ice caps and glaciers and the more rapid swelling of shallow coastal waters as they warm. The greater the relative sea level rise, the bigger the threat from heavy precipitation, storm surges, and tsunamis. The terrible flooding that struck Bangkok in 2011 could become the norm if sea levels rise as projected. By 2050, moderate flooding of Thailand’s Chayo Praya River at a level not even reaching that experienced in 2011 could cause far more damage, inundating almost half of the sprawling metropolitan region; in 2100, floodwaters could cover two-thirds of the area. In Venice, Italy, “alarm level” floods, which now occur about four times a year, would happen 250 times every year in the event of a sea level rise of less than two feet. All told, with a worst-case scenario like the global six-foot sea rise that could happen if warming goes unaddressed, we could see 10 million people on the U.S. Atlantic coast and 18 million Europeans evacuating their homes, and 120 million people forced out of their homes across Asia.

More than 100 million people live at elevations within one meter of sea level, and, as if increasing sea levels weren’t bad enough, the land under many of the world’s great coastal cities is sinking to meet the sea. Much of the subsiding urban land is in river deltas. A delta is not a fixed geographical feature; a satellite image of any delta is just a snapshot of soil and water on the move. Over the past two thousand years, delta growth was accelerated by upstream cutting of forests and tilling of agricultural lands, both of which expose soil to rainfall and allow it to be washed into rivers and their tributaries. But in recent decades, most deltas have stopped expanding, and some are shrinking. That’s because the constant flux of sediments that is required to replenish them is being interrupted, primarily by damming of rivers. One-quarter to one-third of sediment flux through the world’s rivers is being trapped in reservoirs behind an estimated 45,000 large dams. And dam building is gaining momentum worldwide. Even as they are being robbed of sediment, many coastal lands are sinking as well, and that is putting a lot of people and property at risk in many of the world’s largest cities. (The world’s forty most important deltas account for only 0.4 percent of the Earth’s land area but are inhabited by 4.6 percent of the human population.) Pumping of fresh groundwater for irrigation, residential, and industrial uses is allowing the underlying sands and clays that held the water to undergo slow-motion collapse. Removal or degradation of dunes, wetlands, and mangroves has made matters worse. Other local factors, such as extensive petroleum extraction in the Niger River delta and industrial dredging in Italy’s Po River, are accelerating subsidence. In many places, the land is subsiding as fast as or faster than the adjacent sea is rising. In fact, a 2006 survey of the world’s deltas led by a group at the University of New Hampshire concluded that climate-induced sea level rise has so far been a “relatively minor influence” on the condition of delta regions when compared with human manipulation of landscapes and water resources.

Of the ten world cities projected to have the largest populations exposed to coastal flooding by 2070, nine are in Asia. (The one non-Asian city, number nine on the list, is Miami.) Where Bangkok’s outskirts meet the South China Sea, twelve hundred acres of native mangrove forest have been cut, leaving the city even more vulnerable to storm surges. In the period 1951–80, China’s east coast was hit with up to fifty storm surge disasters. Surges are becoming more dangerous with sea level rise, but now the impacts of rising seas are expected to be eclipsed by other human-induced changes that continue to lower coastal lands in some areas of China: urban development, inadequate enforcement of groundwater protection laws, and the decreasing ability of the country’s great rivers to carry sediment all the way to their deltas—largely a result of river course alterations and sediment capture by numerous upstream dams. Seven thousand miles of coastline already have some sort of engineered protection against flooding from the sea. The Yangtze River delta and the Jiangsu coastal plain upstream from it currently enjoy the highest level of engineered protection; without it, twenty thousand square miles in that region would be flooded by only a one-foot sea level rise. But if there is a three-foot global ocean rise and China’s barriers are not raised, current defenses won’t be enough: those twenty thousand square miles will go under.

Copyright © 2016 by Stan Cox and Paul Cox. This excerpt originally appeared in How the World Breaks: Life in Catastrophe’s Path, from the Caribbean to Siberia, published by The New Press Reprinted here with permission.


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