1816

It is the 10th of April, 1815, and within moments, the sun is about to vanish. On an island located in present-day Indonesia, Mount Tambora erupts with a tremendous boom that can be heard over a distance of 2,000 kilometers. Massive plumes of sulfurous steam and ash shoot thousands of meters into the sky, forming ominous storm clouds infused with soot and lightning. This eruption would later be recognized as the largest in recorded history, but its impact is only just beginning. Ascending to great heights in the atmosphere, Tambora's emissions spread across the globe, obscuring the sun for nearly an entire year. The resulting hazy skies and cold weather of 1816 wreak havoc on agriculture, leading to widespread famines throughout the Northern Hemisphere. Nations struggle with epidemics, and artists create somber tributes to these seemingly apocalyptic times. This becomes known as the "year without summer," representing one of the darkest periods in human history.

However, despite the devastating consequences, why are some modern researchers considering ways to replicate this event? Clearly, no one wishes to recreate the famine and despair of that era. But certain scientists are intrigued by the idea of using sulfurous haze to block sunlight and potentially slow down the effects of global warming. This concept falls within the realm of geoengineering, which encompasses deliberate, large-scale interventions in Earth's natural systems aimed at mitigating climate change. Different geoengineering proposals target various systems. The notion of reducing global temperatures by limiting the amount of sunlight reaching the Earth falls under the category of solar radiation management.

Some of these proposals are grand in scale, such as creating controlled versions of volcanic plumes or constructing a massive sunshade in Earth's orbit. Others focus on more localized approaches, like enhancing marine clouds or increasing Earth's reflectivity through the creation of extensive white surfaces. While many of these ideas may sound peculiar, there is evidence to suggest their potential effectiveness, as demonstrated by natural occurrences such as the Tambora eruption. Scientists know that volcanic eruptions have historically caused periods of global cooling. Both the Pinatubo eruption in 1991 and the Krakatoa eruption in 1883 resulted in at least a half-degree Celsius reduction in global average temperatures that lasted up to a year. However, these cooling effects come with significant risks.

The Earth is a complex system where even minor changes can trigger countless unpredictable ripple effects. While we understand that cooling temperatures impact precipitation, extreme weather events, and other climate phenomena, it is challenging for even the most advanced computer models to accurately predict the precise nature and location of these consequences. What one country perceives as solar radiation management might be viewed as an unnatural disaster by another, potentially leading to extreme weather patterns or crop failures akin to those following the Tambora eruption. Furthermore, even if these schemes successfully cool the planet, solar radiation management does not address the underlying issue of greenhouse gas emissions driving global warming. These proposed solutions merely serve as highly experimental stopgaps, requiring the world to endure them for several decades while simultaneously working on actively removing CO2 from the atmosphere. Prematurely abandoning these measures could result in a rapid rebound in global temperatures, leading to an intense period of super warming. Consequently, solar radiation management carries considerable risks.

Currently, researchers are conducting small-scale experiments, such as enhancing marine clouds to safeguard the Great Barrier Reef from further heat stress and bleaching. Most scientists agree that our primary focus should be on reducing emissions and removing atmospheric CO2. Nevertheless, it is essential to continue studying these more aggressive approaches for several reasons. In desperate times, desperate measures may become necessary, and geoengineering might be seen as a last-resort option for civilization in the future. Additionally, some of these plans could be surprisingly simple to execute for a rogue actor with sufficient resources, making it crucial to be prepared if unauthorized geoengineering attempts occur. However, perhaps the most compelling reason to investigate the impacts of geoengineering is that humanity is already engaged in large-scale interventions in the atmosphere. Climate change itself can be seen as an unintentional geoengineering project fueled by centuries of burning fossil fuels. Unless we take decisive action to reduce emissions and actively remove CO2 from the atmosphere in a timely manner, the summers we once knew may never be the same again.