NASA satellite data shows the volcano threw more than 146 teragrams of water – enough to fill 58,000 Olympic swimming pools – into the second layer of Earth’s atmosphere, known as the stratosphere, where the layer is located. ozone and just above where planes fly. The study indicated that the amount released is equivalent to 10% of the water already present in the stratosphere.
“This is the first time this type of injection has occurred in the entire satellite era,” which includes water vapor data dating back to 1995, said Luis Millán, lead author of the study and atmospheric scientist at NASA. “We had never seen anything like it before, so it was quite impressive.”
Volcanic eruptions eject many types of gases and particles. Most eruptions, including Hunga Tonga, release particles that cool the Earth’s surface by reflecting sunlight back into space, but they usually dissipate after two to three years. Very few, however, blow water vapor that high. This water vapor can persist in the atmosphere for longer – five to 10 years – and trap heat on the Earth’s surface.
Millán speculates that the water vapor could begin to have a warming effect on the planet’s surface temperature once the accompanying cooling particles dissipate in about three years. He does not know how much the temperature would increase, because it depends on the evolution of the water vapor plume. The team suspects that the increased warming will last for a few years, until circulation patterns in the stratosphere push water vapor into the troposphere, the layer where Earth’s weather occurs.
“It’s just a temporary warm-up, and then it’ll go back to what it was supposed to go back to,” Millán said. “It’s not going to make climate change worse.”
NASA atmospheric scientist Ryan Kramer added that, given the many factors that drive temperature changes on timescales of years, the volcano’s warming effect could also be lost in the noise, in depending on its magnitude.
On a shorter time scale, increased water vapor could also exacerbate ozone depletion in the stratosphere, said Susan Strahan, an atmospheric chemist at the University of Maryland-Baltimore County and NASA .
Stratospheric ozone protects the Earth’s surface from harmful ultraviolet rays. Chemicals that deplete the ozone layer were largely eliminated by the Montreal Protocol of 1987 and subsequent amendments.
Strahan, who was not involved in the study, explained that excess water vapor will affect many chemical reactions that control stratospheric ozone concentrations. NASA satellite data in July already shows a decrease in ozone levels, compared to previous years, where excess water vapor is most concentrated. She added that a full analysis should be conducted to unravel the cause.
“There are probably impacts right now, but what we need [is] a model to tell us is by which mechanism(s) the impacts occurred. Meteorology and chemistry will almost certainly play roles – the questions are how much, where, when? Strahan said in an email.
Strahan also said excess water vapor could promote the formation of special noctilescent clouds, which appear as shimmering, ghostly streaks across the night sky. They occur about 50 miles in the atmosphere, higher than the stratosphere, and are among the rarest, driest, and tallest clouds on Earth. For many people, clouds provide a remarkable sighting of the sky. However, researchers think any noticeable changes in these clouds would not become apparent until later, depending on how long it takes for water vapor to rise into the atmosphere where the clouds are forming.
Overall, Millán said the excess water vapor was not really of concern in itself, but “something interesting going on”. He and his colleagues are taking the opportunity to test their computer models that help us understand climate change and weather forecasting in general.
“We have these massive amounts of water vapor moving through the stratosphere, and we can test how well the patterns reflect its movements through the atmosphere,” Millán said. “This volcano will give a lot of work to many researchers.”