I was delighted to come across this set of breathtaking images from the NASA Earth Observatory a few weeks ago, and have been waiting for a moment to share them amid the hectic start of the semester. Aside from being stunned by how pretty they are, I was fascinated by the range and richness of what these graphics show about the world.
Luminous swirls of color atop the darkened continents represent the density, on a particular late-August day, of several different types of aerosols — fine particles so small as to be suspended and pushed by the motion of air. All but invisible on their own, these bits of material are lofted into the atmosphere by various processes: winds whip ocean water into a fine salt spray, for example, and the ashy residues of fire are carried upward as smoke on a billowing pillar of heat.
Here’s a version of the same map with a few simple labels to highlight some of the most eye-catching features:
How much has changed in a few short weeks, during which all of the tropical cyclones visible here have dissipated — replaced by the likes of Florence and Mangkhut? This duo has wreaked havoc over the last few days as the cyclones tore into the Carolinas, the Philippines and southern China. My heart goes out to everyone still dealing with storms and their aftermath on mainlands or on islands, and to those left standing on the long, long road back toward anything like “normal.”
The regionally specific names for these massive cyclonic storms — “hurricane” in the west, “typhoon” in the east — come to English by way of other tongues, rooted in opposite sides of the planet. Typhoon seems to stem from some variant on a Chinese term (大风 literally ‘great wind’, pronounced daai fung in the Cantonese dialect*). Meanwhile, the mythology of the Taíno and other indigenous groups in and around the Caribbean and Gulf of Mexico use a range of related words and deity names to describe and explain the great whirling storms, fueled by divine rages; the Spanish colonists ultimately transliterated one of these terms and brought it back to Europe as el juracán.
To a linguist, this might beg the question of whether the experience of a typhoon is different in some subtle but fundamental way from the experience of a hurricane, couched as the two terms are in vastly different cultures, histories and geographies. After all, some of those bracing through Mangkhut this week were locked away in a dense forest of swaying highrise towers, wondering whether the new bridge would survive; surely such an experience engenders a different flavor of fear than the experience of the folks who stayed behind to weather Florence Down East or along the Gullah coast (where the waters are now rising from the other direction).
Regardless of whether such environmental phenomena are perceived differently by people in different places as a matter of culture, it is clearly true that the same natural phenomenon may have different physical impacts depending on where it occurs. Features visible in the NASA maps hint at this. The dust of the Saharan Desert, shown in purple, is carried aloft into air near where planetary topography and climate tends to seed most of the dangerous Atlantic hurricanes. Meanwhile, the large purple cloud on the far side of the map is the result of winds racing over Western China’s Taklamakan Desert, picking up dust that may make its way through high jet streams across the Pacific to North America’s other shore — where these particles seem to help create many of the rare soaking rainstorms on which the dry West Coast desperately depends.
Each desert’s unique geography and mineralogy cause it to play a different role in global weather — the particles in the Sahara’s heaviest dust-laden plumes may have the power to weaken the formation of deadly storms heading toward North America’s East Coast. The Taklamakan’s dust, a world away, is situated in a way that may help raindrops fall on the West.
At the same time, the root causes of a similar-seeming phenomenon can be fundamentally different as a function of place. For example, the graphics show that same North American West Coast festooned in trailing tongues of glowing orange, representing the smoke from the massive wildfires now raging there. But southern-central Africa is shrouded in a fog of the same blazing orange, labeled instead as “Agricultural burning.” Here, says NASA, the fires and their smoke are the product of an attempt to restore fertility to the soil for the next round of planting, in a manner following thousands of years of tradition (though I’ll have a lot more to say about that in a planned future blog post about the global topsoil problem). These two regions, half a world apart and both burning, find themselves wrapped in a superficially similar haze of airborne toxins for a season at a time, whether as the result of accident, negligence and decades of misguided land management practices — or whether simply as the result of millions of people doing what they’ve always done to make a living.
Looking past the differences in specifics and causation, we can see both of these situations as clear examples of how human action has shaped and is still shaping the environment; this environmental change in turn shapes the health, wealth and culture of people. Cycles of action and reaction can expand into unexpected feedback loops (does more smoke mean less rain, causing more accidental fires?) or into impacts in seemingly unrelated areas (does more air pollution have implications for the health and productivity of crops?).
That idea of tight connections between human activity, the natural world and the changing health of both is at the core of the field of Planetary Health, a relatively new field of study in which I am taking a course this semester at DKU. So far we have spent the first few weeks of the class covering some of the basics of how researchers study health at the population level and on a planet-wide scale, while using international reports and daily current events discussions to get ourselves used to thinking about environmental health problems as the products of many linked natural and human systems. The goal is to begin to see how the broad natural cycles of the world interact with one another, and how human-driven changes to those cycles will in turn cascade back into impacts on us, in both predictable and unexpected ways.
The rapid advancement of technology in the last few centuries has enabled us to change the planet at a rate that has never been seen before in history, from forest cover to land use to climate to mining to urbanization. This speed and continued acceleration makes it all the more critical to clearly understand the links and balances between our actions and their complex impacts on nature — the state of which will always come back around to influence our own health and well-being. Our ability to understand these systems, and thereby work to protect ourselves, will depend not only on our knowledge of the fascinating particularities of place, but also on our ability to tie those to a bigger picture of how the planet operates. Together, unified, these two kinds of knowledge are far more powerful than either type alone.
Images: NASA Earth Observatory graphics by Joshua Stevens, using GEOS data from the Global Modeling and Assimilation Office at NASA GSFC.
*Here’s a bunch of people arguing on the Internet about the possible origins of the word “typhoon”, a story which is further complicated by the possible loan of variations on the word backward into some Chinese dialects from English, and some similar roots in several Indo-European languages. If you have any credible sources that would clarify this, I’d love to see them in a comment.