Late last month, those with an internet connection could watch, via webcam, a disaster unfolding. Flames fanned by strong winds raced through chaparral and pines toward one of the country’s most famed scientific institutions: The Lick Observatory, which sits atop Mount Hamilton on the outskirts of San Jose, California. 

Built in the late 1800s with a $700,000 endowment from an eccentric philanthropist named James Lick, it was the first permanently inhabited mountaintop observatory in the world. Over the years, astronomers peering through its famed 36-inch telescope made numerous discoveries, including many of the smaller moons of Jupiter.  

Firefighters managed to stop the fire before it destroyed the historic observatory, but the blazes have continued to wreak havoc throughout Northern California. The fire that almost torched Lick Observatory is part of a vast mosaic of wildfires called the SCU Lightning Complex. As of the end of August, those conflagrations had burned more than 376,000 acres. And yet, they are but a handful of the nearly 7,200 fires touched off in the state this year. 

Wildfires are, of course, not a new phenomenon in California or most of the western US. Years of fire suppression and the rapid expansion of cities into the so-called wildland-urban interface have surely played a key role in this season’s extreme fire activity. But something fundamental has changed. Fire season arrives earlier and lasts longer. The fires themselves are burning longer and hotter. Even more unusual, many of the recent wildfires were started by “dry lightning” strikes—a virtually unprecedented phenomenon in the Bay Area. The firestorms also spawned “firenados,” cyclones of flame that speed across the landscape. 

This year’s extreme fire activity is not just limited to California. Last week, NASA released a series of images, taken by a satellite called Terra, that showed a massive swath of Earth enfolded in giant plumes of smoke emanating from thousands of forest fires burning in the western United States. 

While this column is typically devoted to subjects far beyond Earth’s surface, lately the stars seem remote—not to mention hard to see through the veil of smoke. This month, I find myself dwelling less on what’s out there and more on our home planet. In particular, I am ruminating on the thin layer that separates and protects the living things on Earth’s surface from the lifeless void of space: our atmosphere.         

Imagine, if you will, one of the Lick Observatory’s telescopes transported to the surface of the moon and aimed back at Earth. Such an exercise brings to my mind an essay published in 1973 by the physician and essayist Lewis Thomas. Written a year after the US’s final moon landing, no piece of writing that I know of so evocatively describes the isolated beauty of our home planet and articulates the importance of its life-giving atmosphere. "Viewed from the distance of the moon,” wrote Thomas in "The World’s Biggest Membrane,” “the astonishing thing about the earth, catching the breath, is that it is alive. The photographs show the dry, pounded surface of the moon in the foreground, dead as an old bone. Aloft, floating free beneath the moist, gleaming membrane of bright-blue sky, is the rising earth, the only exuberant thing in this part of the cosmos." 

That term, membrane, is as apt a metaphor as I can imagine. To most, the word probably conjures a barrier or a wrapper. But to the biologist, a membrane is far more than packaging. It is a hallmark of living things. Life quite simply cannot exist without something to hold all of the component parts together. 

Thomas continues: “When the earth came alive, it began constructing its own membrane, for the general purpose of editing the sun.” Perhaps only a writer would have chosen the verb ‘edited,’ but it is exactly right. The editing that is carried out by the atmosphere is highly selective, allowing wavelengths of light conducive to life to pass through while filtering out those that are harmful. Again, Thomas: “It is hard to feel affection for something as totally impersonal as the atmosphere, and yet there it is, as much a part and product of life as wine or bread. Taken all in all, the sky is a miraculous achievement. It works, and for what it is designed to accomplish, it is as infallible as anything in nature.” 

Though the word designed may give strict materialists pause, there is no dispute with Thomas’s idea that the atmosphere performs its “job” magnificently. 

But how exactly did this membrane arise?  

Scientists believe that it happened in three distinct stages. The first atmosphere arose in Earth’s early turbulent history, when the planet was a mere half-billion or so years old. At that time, the pelting of the surface by rocks from space roiled the lithosphere, triggering volcanoes, which belched huge quantities of sulfurous gases into the air. Squalls of acid rain fell, weathering the planet’s volcanic rock, giving rise to chemicals necessary for life.

For years, astrobiologists believed that the early atmosphere was rich in methane, carbon monoxide, hydrogen sulfide, and ammonia—a smothering, poisonous cocktail utterly hostile to life. But recent evidence from researchers at the Rensselaer Polytechnic Institute in New York proposes otherwise. By analyzing long-lived compounds formed early in Earth’s history called zircons, the Rensselaer researchers found evidence that the ancient atmosphere may have been rich enough in oxygen to support life.

Two and a half billion years later, the atmosphere entered its second phase. The planet cooled and water vapor began to condense, forming the planet’s oceans. Tiny organisms called cyanobacteria flourished in the primordial oceans, transforming carbon dioxide into oxygen. As millennia passed, the photosynthetic reactions within these small cells steadily increased the amount of oxygen in the atmosphere. By 2.6 billion years ago, the planet’s membrane was on a path to resembling the atmosphere we know today. Larger multicellular photosynthetic organisms appeared on the scene about 1.5 billion years ago, converting carbon dioxide to oxygen. In that transition from a reducing to an oxidizing environment, multicellular life began to thrive. Oxygen levels continued to climb until roughly 400 million years ago, when they reached today’s concentrations. 

For the past two and a half centuries, humankind, like the cyanobacteria of eons past, has dramatically altered the makeup of the world’s biggest membrane. Rather than injecting oxygen, we have—by way of our cars, houses, office buildings, factories, farms, and hundreds of other sources—drastically increased the concentration of carbon dioxide and other heat-trapping gases in the atmosphere.  

In other words, we have entered a distinct and frightful fourth stage of the atmosphere’s evolution. In the past 50 years—a mere heartbeat in the 4.5-billion-year history of the planet—our carbon output has risen by 90 percent, most of it attributable to an unchecked increase in the combustion of fossil fuels.   

The excess carbon we’re churning out has hampered the atmosphere’s ability to edit the sun, setting the stage for greater numbers of extreme weather events. Days before the lightning-triggered outbreak of fires across the Bay Area, the temperature in Death Valley National Park soared to 130°F—possibly the highest temperature ever recorded on Earth. The previous week, sudden “derecho” windstorms destroyed hundreds of buildings and wiped out nearly half of Iowa’s corn and soybean crop. On August 27, Hurricane Laura, the most powerful storm to hit Louisiana in a century and a half, made landfall and cut a path of destruction through the state.         

Whether one is looking back at Earth from space or standing firmly on its surface, the message is becoming ever more obvious: The rising temperatures, the increasing frequency of crippling droughts and destructive storms, the growing swaths of flame-scarred land—all are signs of our future burning up before our eyes.