By all measurable data, Global warming is a fact. The sheer amount of information on this phenomenon (especially the most recent from 2016) leaves little room to doubt that this rapid increase in the temperature of our planet is due to human intervention. I firmly believe that it is in our purview to reverse or modify this trend: human ingenuity has throughout history saved us from our worst fates and mistakes, and very little we have done so far could have more profound consequences that running out of a planet to live.
Disconcertingly often, the spectre of climate change is lensed through too human a perspective – as if a snowball flung on a congressional floor has some form of scientific persuasive power. Even when accepting the fact of the rising temperatures, some glance at the undiminished azure of their closest skies and take it as reassurance. The danger intrinsic to these anecdotally and qualitatively informed positions is one of missing contexts and narrowing scopes. We owe a lot of our sustained success across history to our ability to recognise certain patterns- but when those patterns occur across too long a time scale, or threaten to escape the frames of reference we’ve always known, they begin to lose meaning on a phenomenal or felt level.
In the case of rising global temperatures, the delicacy of this balance only becomes more striking when one realises their precariously thin margins of livability which we have always relied upon – knowingly or not. Precisely because of how reliable the mild 20-30 °F diurnal oscillations that most places on Earth experience have been, it becomes altogether too easy to view the limits of daily temperatures as ironclad. In truth, we owe a great deal of this to the meticulous fine tuning of our own atmosphere, a point made incredibly stark by some of our more recent speculations of space colonisation; in this light, the surly bonds of earth seem anything but, when contrast with the 100° temperature fluctuations and 0.087 psi characteristic of Mars’ surface.
In fact, this becomes an interesting approach to understand the far-reaching implications of current global warming without being confined to the narrow lens of human experience; i.e., observing it within the larger context of our two closest planetary neighbors: Venus and Mars. Venus, despite being so similar to Earth, is a hot and hellish world, while its Mars’ thin atmosphere which is largely responsible for its aforementioned difficulties. Recent missions from ESA and NASA have shed new light on the processes that made these planets so hostile to life- and from this tale we can derive important conclusions regarding some of the possible ends of ours.
As residual effects of the Sun’s creation, the formation of the inner planetary trio of Venus, Earth, and Mars is thought to have largely followed the development of our central star. According to the standard model of planetary formation, the Sun formed out of a dense interstellar molecular cloud comprised predominantly of hydrogen, helium, water and refractory materials (Iron, Mg-silicates etc.) that crystallized in a dust of small particles. As the proto-star continued its collapse, due to the law of angular momentum, two to ten percent of the stellar gas moved to orbit the star in a flattened disk. This disk of dust and gas ultimately housed enough mass for the accretion of our interior planets from planetesimals to the bodies we know today.
Venus, having been formed by accretion at about the same time as Earth, would have been initially composed of the same materials as our planet. Venus was initially cooler than what it is now, had a greater abundance of water, and had most of its carbon dioxide locked up in rocks. Since Venus is slightly closer to the Sun than the Earth, its water never liquefied and remained in the atmosphere, heating the atmosphere through a classic greenhouse effect. Its electric field, being much larger than Earth’s, also accounts for the escape of the ions and other particles necessary to form water. As Venus heated up, some of the carbon dioxide in the rocks was released into the atmosphere, enhancing the greenhouse effect. The increased temperature caused the release of more carbon dioxide out of the rocks (as well as any water), and a runaway feedback loop began.
Water eventually began escaping the atmosphere and lessened its contribution to Venus’ temperature rise, but by then, there was already enough carbon dioxide in the atmosphere that it could maintain this feedback loop on its own, and so it continued increasing with no mechanism to stop it. Recent measurements show that the pressure of Venus’ atmosphere is 90 times greater than that of Earth’s, with CO2 comprising 96.5% of it, while the surface temperature is 737K (464C): a hellish world indeed.
Carbon sinks in Earth’s carbon cycle absorb significant amounts of carbon dioxide out of the atmosphere and help maintain the greenhouse gas in an equilibrium state through negative feedback loops. This is why Earth, though as rich in total carbon dioxide content as Venus, has so little of it (0.4%) in its atmosphere. The carbon cycle on Earth has remained unchanged for most of its history, enabling the existence of breathable air and life. However, starting 150 years ago, the amount of CO2 in our atmosphere began increasing beyond dangerous levels. Venus shows us what the extreme greenhouse effect does to a planet; its lifelessness is the result of physical processes very different from our Earth, but we cannot ignore that increasing CO2 in our atmosphere could result in something disconcertingly similar.
For millions of years the natural carbon sinks in our planet have controlled the carbon emissions that occur spontaneously in nature. In the last 150 years, human activity has been increasing the concentration of greenhouse gases in the atmosphere (mostly carbon dioxide, resulting from the combustion of coal, oil, and gas). There is no scientific debate on this point, according to the American Chemical Society: “Data for the past 2000 years show that the atmospheric concentrations of CO2, CH4, and N2O – three important long-lived greenhouse gases – have increased substantially since about 1750. Rates of increase in levels of these gases are dramatic. CO2, for instance, never increased more than 30 ppm during any previous 1,000-year period in this record but has already risen by 30 ppm in the past two decades.” It is obvious that more greenhouse gases are dumped in our atmosphere than ever before, to an extent far beyond the absorption capabilities of our natural protections.
The use of fossil fuels is the largest contributing factor changing our climate, but it is not the only one; in our attempts to conquer an indifferent nature, humans have a long history of altering the landscape and perturbing its equilibrium: agriculture, tropical deforestation and overgrazing started millennia ago. However, we continue these practices to this day at an alarming and uncontrolled rate. It is true that such efforts have allowed our species to thrive and reach today’s levels of development, but with the knowledge and welfare that results from our current position, also comes the responsibility to ensure the benefits are sustainable. Earth is the only world we know; it is our ethical responsibility to take care of and protect it, both for ourselves and future generations.
Featured Image: NASA