Despite what the photographs suggest, the Earth is not perfectly round. Our home planet is actually a lumpy “oblate spheroid” that bulges slightly at the equator and flattens at the poles, like a ball of clay crushed between your fingers. But as fossil fuel pollution alters the Earth’s climate, it is also altering the shape of the planet. This is according to a study published last month in the journal JGR Solid Earth. The findings suggest that the overall shape of Earth’s solid surface is becoming rounder at an accelerating rate as rising global temperatures drive the melting of polar ice. While the shape of the planet has never been fixed, this rapid change underscores the power of human-driven warming. “These findings are important because they help scientists understand how the planet responds to melting glaciers and changing water,” Christopher Kotsakis, a professor of geodesy at the Aristotle University of Thessaloniki in Greece and an author of the study, wrote in his study. “This type of knowledge is essential for tracking climate change and its impact on the long-term behavior of the Earth.” Our rounded blue Kotsakis marble set out to determine whether the recent acceleration of polar ice melt and the resulting redistribution of meltwater has measurably changed the shape of Earth’s solid surface, specifically the flatness of the poles and the bulge around the equator. He developed a new method for analyzing data from the Global Navigation Satellite System (GNSS), which directly measures surface motion. The analysis suggests that the poles are rising, with a rate of rise between 2011 and 2015 of about 0.02 to 0.04 inches (0.5 to 1 millimeter) per year. At the same time, Earth’s equatorial bulge appears to be shrinking at a similar rate. Today, those rates are likely even higher, as findings suggest the Earth is rounding faster with each passing decade. The rate of change between 2011 and 2015 was actually greater than the rate between 1997 and 2000. It appears that every 10 years, polar uplift accelerates by about 0.01 inch (0.25 mm) per year, and equatorial contraction accelerates by 0.02 inch (0.4 mm) per year. These may seem like minuscule changes considering the planet is nearly 8,000 miles (12,800 kilometers) wide, but they show that there has been a measurable and accelerating increase in the Earth’s roundness in recent history. This makes sense if the driving force is the melting of polar ice, which has also accelerated significantly in recent decades. As the ice sheets shrink and the poles lose mass, pressure is taken off the Earth’s solid surface, allowing the crust to rise. Meanwhile, all that meltwater flowing toward the equator puts more pressure on the crust there, leading to subsidence. The rapid climate changes observed in recent decades are notable (and extremely alarming) on their own, but the fact that a single species is capable of altering the physical properties of the planet is nothing short of astonishing. It’s important to note, however, that this study only looked at how Earth’s solid surface is changing. If you take the ocean into account, the planet’s equatorial bulge is actually growing as meltwater accumulates there. A Fundamentally Altered Earth While we tend to focus on the numerous ways that fossil fuel emissions are reshaping Earth’s climate, researchers are finding increasing evidence to suggest that climate change is altering the most fundamental features of the planet, such as its axis, its rotation, and its gravitational field. The rapid climate changes observed in recent decades are notable (and extremely alarming) on their own, but the fact that a single species is capable of altering the physical properties of the planet is nothing short of astonishing. To be clear, the human-driven rounding identified by this new study does not pose any immediate threat to life on Earth, but it does speak to the incredible influence we have over our home.
