Dangerous Earth: What We Wish We Knew about Volcanoes, Hurricanes, Climate Change, Earthquakes, and More
246
Dangerous Earth: What We Wish We Knew about Volcanoes, Hurricanes, Climate Change, Earthquakes, and More
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Overview
Today, we know more than ever before about the powerful forces that can cause catastrophe, but significant questions remain. Why can’t we better predict some natural disasters? What do scientists know about them already? What do they wish they knew? In Dangerous Earth, marine scientist and science communicator Ellen Prager explores the science of investigating volcanoes, earthquakes, tsunamis, hurricanes, landslides, rip currents, and—maybe the most perilous hazard of all—climate change. Each chapter considers a specific hazard, begins with a game-changing historical event (like the 1980 eruption of Mt. St. Helens or the landfall and impacts of Hurricane Harvey), and highlights what remains unknown about these dynamic phenomena. Along the way, we hear from scientists trying to read Earth’s warning signs, pass its messages along to the rest of us, and prevent catastrophic loss.
A sweeping tour of some of the most awesome forces on our planet—many tragic, yet nonetheless awe-inspiring—Dangerous Earth is an illuminating journey through the undiscovered, unresolved, and in some cases unimagined mysteries that continue to frustrate and fascinate the world’s leading scientists: the “wish-we-knews” that ignite both our curiosity and global change.
“If there is one main thread in Prager’s book it is that the main threat to humanity is climate change. The book is small, but it contains a wealth of information.” —Lars Backstrom, Geoscientist
“Prager . . . delves into the mysteries of our planet’s hazards and why they continue to perplex the world’s scientists.” —Katie Aberbach, Wesleyan
Product Details
| ISBN-13: | 9780226541723 |
|---|---|
| Publisher: | University of Chicago Press |
| Publication date: | 12/22/2022 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 246 |
| Sales rank: | 960,062 |
| File size: | 8 MB |
About the Author
Read an Excerpt
CHAPTER 1
Climate Change
Antarctica is a sleeping elephant that is starting to stir. When Antarctica fully wakens, it will likely be in a very bad mood. — Mark Serreze, director, National Snow and Ice Data Center
WEST ANTARCTICA, SUMMER 2002. It was unusually warm. But not all that unusual — over the past fifty years, summers in West Antarctica had become some 2.5°C warmer. The last several had been particularly balmy, and now strong mountain winds amplified the higher temperatures. Across the region's slow-flowing rivers of ice, or glaciers, meltwater trickled down through holes and cracks. As water percolated downward, the cracks grew wider and deeper. Soon meltwater reached the base of the glaciers. Normally, friction from the underlying bedrock slowed the delivery of ice from the vast West Antarctic ice sheet to the sea. But now as meltwater reached the base of the glaciers, it lubricated the flow and allowed the massive rivers of ice to march seaward more speedily.
At land's end, the glaciers pushed beyond the underlying rock to form massive ice shelves that floated buoyantly over the cold polar sea and blocked the flow of the glaciers behind (figure 1.1). In the summer of 2002, one such ice shelf, thousands of kilometers wide and 220 meters thick, lay o? Antarctica's horn-shaped peninsula, adjacent to the Weddell Sea. It was a section of the Larsen Ice Shelf known as Larsen B (Larsen A lay to the north, Larsen C to the south). Summers of melting and winters of freezing had created a slick sheet of ice on the surface of the Larsen B Ice Shelf. By February, late summer in the Southern Hemisphere, small ponds of meltwater lay like dotted lines along sutures between old glaciers whose slow flows had long ago coalesced.
As the warm days continued, the meltwater ponds grew. Water seeping down into the sutures caused fractures to form and deepen. Meanwhile, at the base of the shelf, relatively warm ocean water lapped against the ice, carving channels in its underside, and weakening it. Soon, within weeks, the massive Larsen B Ice Shelf began to splinter. As giant slabs and tall, narrow strips of ice broke off the shelf or calved, thunderous whumpfs echoed across the region. Wind, waves, and currents tossed and tipped the blocks of ice. Some of the newly born icebergs clustered like colossal shards of white glass swept together (figure 1.2). But it was just the beginning.
As the days progressed, more meltwater ponded and flowed into the fractures on what remained of the Larsen B Ice Shelf. Crevices became deeper and wider. Then suddenly, all of the meltwater drained away. A tumultuous sound rang out and a huge portion of the ice shelf broke free; other parts simply disintegrated. It was as if a monstrous bite, the size of Rhode Island (more than 3,000 square kilometers), had been taken out of the Larsen B Ice Shelf. By March, the ice shelf was essentially a floating expanse of icebergs and slush. Scientists across the world were shocked.
The 2002 collapse of West Antarctica's Larsen B Ice Shelf was unprecedented in modern history. Researchers are still trying to piece together exactly how it happened. A smaller collapse had occurred in 1995. For scientists studying ice sheet dynamics, these events were a game-changer.
The loss of ice at the Larsen B Shelf did not directly affect sea level (only land-based ice or snow, melting and flowing into the ocean, adds to its volume). However, as would be shown by measurements years later, the 2002 collapse released the brake on the land-based glacier behind it, allowing the river of ice to flow six times faster toward the sea.
The scale and speed of the 2002 Larsen B Ice Shelf breakup were startling. But what it and the 1995 event suggested was even more worrying: similar processes could play out on other, larger ice shelves.
And they already are. Ice is also fracturing and melting at the even more massive shelves buttressing the Pine Island and Thwaites Glaciers. In fact, a giant cavity beneath the Thwaites Glacier was recently discovered. It is two-thirds the area of Manhattan, about 40 square kilometers, and 300 meters deep. Scientists estimate that billions of tons of ice were lost within just the previous three years, an indication that the glacier is melting even faster than previously thought. The complete melting of the Pine Island and Thwaites Glaciers could potentially raise the ocean by more than 3 meters. If West Antarctica's Ross Ice Shelf (about half a million square kilometers, or the size of Spain) were to collapse and release the glaciers behind it, the flow of ice to the ocean could raise sea level another 3 meters or more.
In July 2017, a Delaware-size chunk of the Larsen C Ice Shelf, some 6,500 square kilometers, broke away. Scientists took note because it happened in the Antarctic winter. It is unclear what will happen next at the Larsen and other ice shelves in Antarctica, but very close attention is being paid, especially to those fronting large land-based glaciers.
The Earth's climate is changing. Among the big unknowns: How much of the vast expanses of snow and ice in Antarctica and Greenland will melt? How fast, and by what processes? And how far and how fast will sea level rise because of it?
Climate Change: The Known
Weather and climate have affected humankind for as long as our species has inhabited the planet. For much of that time, myth and folklore were used to explain the vagaries of the atmosphere or to predict its behavior. Today, scientists have real-time access to weather stations across the globe, along with data from satellites, ships, custom-equipped aircraft, weather balloons, ocean-voyaging and stationary buoys, and remotely operated vehicles. As never before, we are observing and monitoring the Earth and its atmosphere. Yet critical questions remain. To better understand what remains unknown, it is helpful first to consider some aspects of the Earth's climate that are well understood.
The Atmosphere and Carbon Dioxide
The atmosphere. It extends from the planet's surface to the edge of space and is only about 100 kilometers thick. Compared to the Earth, whose radius is nearly 6,400 kilometers, the atmosphere is wafer thin (see plate 1). Yet it is this thin layer of nitrogen, oxygen, and trace gases that provides for our every breath and prevents the planet from plunging into a frigid Mars-like cold. But the atmosphere is not an immobile source of life — it changes over time and space. Its never-ending fluctuations give rise to the day-to-day changes that form our weather and the longer-term variations that constitute climate. And variations in the makeup of the atmosphere influence and can drive change in the Earth's climate. This is not a big unknown, like the nature of dark matter, whether life exists on other planets, or what Batman wears under his tight-fitting rubber suit. For hundreds of years, scientists have been studying the Earth's atmosphere and how it affects our planet.
In the early 1800s, mathematician and physicist Joseph Fourier recognized that as the sun's energy or radiation passes through the atmosphere and strikes the Earth's surface, it heats up the planet. Without the atmosphere, though, the planet would regularly turn frigid. Fourier was the first to recognize that the atmosphere insulates Earth from heat loss — like a blanket. Then in 1859, scientist John Tyndall discovered something astonishing about one of the trace gases in our atmosphere — carbon dioxide. While the other major components of the atmosphere, nitrogen and oxygen, are essentially transparent to long-wave radiation, carbon dioxide is not. Carbon dioxide, along with water vapor, even in small quantities, absorbs long-wave energy, which is stored as heat. Several decades later, Swedish chemist Svante Arrhenius went further, suggesting that increased levels of carbon dioxide in the atmosphere could alter Earth's surface temperatures. Since that time, observations and experimental evidence have repeatedly confirmed these early discoveries.
Here's how it works. Incoming solar radiation (short-wave) passes through the atmosphere and strikes the Earth. Some of this energy is reflected back, especially from light-colored surfaces like ice or snow. But much is absorbed as heat and then re-emitted as longer-wave infrared radiation (we don't see such energy, much like ultraviolet light). Somewhat like the glass in a greenhouse, carbon dioxide, water vapor, methane, and other gases trap (absorb and re-emit) this long-wave energy as heat in the atmosphere. Again, some is lost to space, but much of the absorbed heat is directed back toward the planet — warming the air, ocean, and land.
The result of heat-absorbing greenhouse gases in our atmosphere: a fertile, warm Earth versus desolate, frigid Mars. But there's a catch. Humans are at times too smart for their own good. We discovered the power (pun intended) that comes from burning fossil fuels. And when fossil fuels are burned, they release additional carbon dioxide into the atmosphere, and more carbon dioxide captures more heat.
Ever wonder why they are called fossil fuels? Hundreds of millions of years ago on a very warm Earth, algae and other simple plantlike organisms flourished. After these carbon-based organisms died, some were buried deep beneath the land and seas. Over time, with decomposition, pressure, and heat, they transformed into oil, natural gas, and coal. These fuels are thus the preserved remains of prehistoric plants and other organisms — fossils. When fossil fuels are burned, the carbon they contain combines with oxygen, and carbon dioxide is released into the atmosphere — the very same gas that Tyndall and Arrhenius first showed traps radiant heat.
The burning of fossil fuels is not the only way humans add carbon dioxide to the atmosphere. But it is by far the largest anthropogenic source of carbon dioxide, followed by deforestation. Natural sources include the decomposition of organic material, volcanic emissions, weathering of rocks, respiration, and processes within the oceans.
Our best modern record of carbon dioxide concentrations in the atmosphere comes from the observatory at Mauna Loa in Hawaii. In the 1950s, Scripps Institution of Oceanography scientist Charles David Keeling and his colleagues began measuring the concentration of carbon dioxide in the atmosphere there and at other locations. Early on, they discovered a small daily variation in carbon dioxide concentrations. In the daytime, plants take up carbon dioxide through photosynthesis, then at night they release it via respiration. Later measurements revealed a similar seasonal variation. Carbon dioxide in the atmosphere decreases in the late spring and summer as it's taken up by growing plants. In the winter, carbon dioxide concentrations increase in the atmosphere because some plants die and decompose, and the release of carbon dioxide through respiration is greater than photosynthetic uptake. Over time, another and more startling pattern in the Mauna Loa carbon dioxide data became apparent: since industrial times the amount of carbon dioxide in our atmosphere has been rising, from about 300 parts per million to more than 400 parts per million.
Concurrently, the Earth's average temperature has risen more than 1°C since 1880. More important, the pace of warming has accelerated since 1950, with the last several years being the warmest ever recorded. Today, whether you look at the atmosphere or the ocean, at direct measurement or satellite data, the same tale is being told: carbon dioxide in the atmosphere is increasing and the climate is warming at a rate unprecedented in modern times.
People often argue that Earth has, throughout its history, gone through cycles of cold and warmth. Why then is today different from the past?
Our record of instrument-measured temperatures goes back only about 100 to 150 years. To compare today's rate of warming or current concentrations of carbon dioxide with those of the more distant past, scientists must find indicators or proxies that record previous atmospheric conditions. These include plants or other organisms that are sensitive to temperature or other climate variables and preserve records of their growth over time, such as corals, trees, and foraminifera (small shelled marine organisms). Bubbles of air trapped within layers of ice, undisturbed layers of sediment in lakebeds or oceans, and accumulations of ice, dust, pollen, and volcanic ash may also been used to establish prehistoric temperatures, dates, and carbon dioxide concentrations.
By combining the data from such indicators and from modern observations, scientists are able to construct a record of global temperatures and carbon dioxide concentrations going back hundreds of millions of years. The detail or resolution diminishes as you go further back in time, but even so the data reveal a great deal about Earth's distant past. For instance, based on data from Antarctic ice cores, over the last eight hundred thousand years and up until now, carbon dioxide concentrations in the Earth's atmosphere has varied between about 170 and 300 parts per million.
But going way back, some fifty million years ago, data indicate the concentration of carbon dioxide in the atmosphere was about 1,000 parts per million. Back then, there were no ice sheets, temperatures were 8 to 12°C warmer than today, and sea level was some 75 meters higher — the Earth was definitely less hospitable than it is today. Some three million years ago, carbon dioxide concentrations were similar to what we see today (350 to 400 parts per million). Temperatures were 1 to 3°C warmer than now and sea level was up to 20 meters higher. Again, it was not a very hospitable world for modern society as we know it. During the last peak interglacial (warm) period, 125,000 years ago, carbon dioxide concentrations were about 300 parts per million, temperatures were slightly warmer (1 to 2°C), and sea level was some 5 meters higher than today. The takeaway: in Earth's past, when carbon dioxide levels in the atmosphere were higher than or at levels similar to today, the planet was warmer, more sea-covered, and certainly a less roomy, hospitable home for its residents.
So what drove climate change millions or even thousands of years ago? It wasn't anthropogenic releases of carbon dioxide. Data suggest that back then the climate system was driven by other factors, including changes in solar output, massive volcanic emissions, the distribution of land and sea, ocean circulation, and tectonic upheavals followed by weathering. On time scales of about ten thousand to a hundred thousand years, orbital variations play an important role, particularly in forcing glacial and interglacial periods; these include the varying shape of Earth's elliptical orbit about the sun, the tilt of the Earth's rotational axis, and the wobble of the Earth's spin. Carbon dioxide played a role as well, but rather than driving change it appears to have either enhanced or reduced the effects of the other variables through feedback mechanisms. Today, these same forcing factors are present, but they are being overshadowed by the influence of carbon dioxide in the atmosphere.
Since 1950 the concentration of carbon dioxide in the atmosphere has risen to greater than 400 parts per million — a level far higher than it has been in hundreds of thousands of years. To investigate in more detail how Earth's climate has responded to this increase, scientists have reconstructed a precise record of temperature change for the last thousand years using both global proxy data and observations (figure 1.3). Here the data is especially revealing. In the Northern Hemisphere, a long-term gradual decline in temperature continued until about a hundred years ago. Then something happened. The temperature began to increase and at an accelerated pace. There have been similar periods of warming in Earth's past, following ice ages, but the amount of warming that has occurred over the last century, back then took ten times longer, on average a thousand years. So here's the point: It is not the actual temperature that is the issue. Rather it is the rapid pace at which the global thermometer is rising that is unusual and problematic.
(Continues…)
Excerpted from "Dangerous Earth"
by .
Copyright © 2020 Ellen Prager.
Excerpted by permission of The University of Chicago Press.
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Table of Contents
Note to Readers1. Earthly Dangers and Science
2. Climate Change
3. Volcanoes
4. Earthquakes and Tsunamis
5. Hurricanes
6. Rogue Waves, Landslides, Rip Currents, Sinkholes, and Sharks
7. Knowing Enough to Act
Acknowledgments
Recommended Reading and References