Mount Toba eruption had minimal global climate impact, new research suggests

Revisiting the Toba Catastrophe Theory

The Mount Toba eruption, occurring approximately 74,000 years ago, was the largest volcanic event in the last 2.6 million years, releasing thousands of cubic kilometers of magma. Historically, some theories proposed that this eruption caused significant global cooling, nearly leading to the extinction of early human populations.

New Evidence from Lake Sediments

Geoscientist Jinheum Park and his team investigated mud cores from a crater lake on the Kenya-Tanzania border to find geological records of the eruption's impact. Their findings suggest that the effects of the Mount Toba eruption were short-lived, lasting less than two years, and resulted in a global temperature decrease of only about half a degree Celsius.

Mechanism of Volcanic Cooling

Volcanic eruptions inject sulfur dioxide into the stratosphere, forming aerosols that reflect sunlight and cause cooling. However, Park explains that for eruptions exceeding a certain magnitude, larger sulfate aerosols settle quickly due to their weight. This rapid settling reduces their effectiveness in scattering solar radiation, limiting the overall cooling effect.

Challenges in Geological Interpretation

Estimates of Toba's sulfur output have varied widely, leading to diverse computer model predictions ranging from near-extinction events to minor inconveniences. Geological evidence from seafloor or lake cores has also been difficult to interpret accurately. Underwater mud cores often present challenges in precisely dating and constraining abrupt events like volcanic eruptions, as sediment mixing can obscure short-term climate signals.