Since January 2022, the underwater eruption of Hunga Tonga-Hunga Ha’apai (HTHH) in Tonga has raised further concerns about global warming with its violent display of nature’s power. The eruption shot the standard volcanic mixture of ash, gas, and pulverized rock into the sky, but it came with an unexpected twist that has since sparked a climate concern: a significant splash of ocean water. As a result, the eruption injected an unprecedented amount of water vapor into the stratosphere, raising worries about its impact on global warming over the next five years. Initial estimates showed that 50-million metric tons of water were injected into the stratosphere but latest figures highlight that it was underestimated by a factor of three.
Typically, volcanic eruptions have a cooling effect on the planet due to the release of ash and sulfur dioxide that scatter sunlight, leading to global cooling. However, the HTHH eruption was unique. It ranked a 5.7 on the volcanic explosivity index, alongside historical eruptions like Vesuvius and Mount St. Helens, but it had a relatively low sulfur dioxide content. Instead, it injected an enormous amount of vaporized seawater into the stratosphere, which is the planet’s most common greenhouse gas.
Researchers found that the eruption boosted the water vapor content of the stratosphere by 10%–15%, according to a study published in Nature Climate Change. Using climate reconstructions and simulations, they estimated that the water vapor could increase the average global temperature by up to 0.035°C over the next five years. While this may seem like a small anomaly, in the context of the Paris Agreement’s 1.5°C target, it is a significant concern.
The planet was already 50% likely to warm past 1.5°C in the next five years, and the presence of HTHH’s water vapor increased the odds of temporarily exceeding that threshold to 57%, according to the simulation. Despite this potential impact, scientists emphasize that its contribution to surface warming is relatively small compared to human-caused greenhouse gas emissions. The study serves as a reminder that natural events can influence global temperatures, but the real challenge lies in addressing human-induced climate change.
As we reflect on the HTHH eruption and its implications, we are reminded of the delicate balance between natural and anthropogenic influences on our planet’s climate. It reinforces the urgent need for collective efforts to curb greenhouse gas emissions, invest in renewable energy, and promote sustainable practices worldwide.
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