A tropical volcano eruption may have caused the hottest July ever

Much has been said about the likelihood that the emerging El Niño would increase global temperatures this year.  However, new evidence suggests that an eruption of the Hunga-Tonga volcano in 2022 may have created a supercharged greenhouse effect — because it injected an unprecedented amount of water vapor into the atmosphere.

Most volcanoes, such as Mount Pinatubo's eruptions in 1991–1992, inject dust and sulfur dioxide particles into the atmosphere, resulting in a cooling effect that temporarily stopped warming and overrode an El Niño event.  The Hunga-Tonga eruption was different, injecting mostly water vapor.

Water vapor is actually the strongest greenhouse gas in terms of warming effect and is responsible for about half of Earth's surface temperature.  Without it, the Earth would be about 60 degrees Fahrenheit colder.

According to NASA, in a recent study, published in Geophysical Research Letters, it was estimated that the Hunga-Tonga eruption sent around 146 teragrams (1 teragram equals 1 trillion grams) of water vapor into Earth's stratosphere — equal to about 10 percent of the water already present in that atmospheric layer.

Another study suggested a 13-percent increase in stratospheric water mass and a fivefold increase of stratospheric aerosol load.

Because water vapor is the strongest greenhouse gas, and an unprecedented amount of it has been added to the atmosphere by the Hunga-Tonga eruption, is it any wonder that temperatures have been higher than normal this year, resulting in the warmest July ever?  According to the E.U.'s Copernicus Climate Change Service, July was found to be 1.5 degrees Celsius warmer than the average for the 1850–1900 period.  It represents the only time in modern history that nature performed a self-experiment on Earth that resulted in a large and fast observable warming. 

That temperature spike is higher than projections from El Niño–induced warming, and much higher than any warming that could be attributed to carbon dioxide emissions.  In fact, it is so insignificant that Copernicus doesn't even mention carbon dioxide in its report.  Water vapor is said to account for 66 to 85 percent of the greenhouse effect, compared to a range of 9 to 26 percent for CO2.

Dr. Ryan Maue, former chief scientist for NOAA, appointed by the White House, noted the water vapor warming impact on Twitter:

Everything was going fine until mid-March 2023, and then a dramatic 1°C warming spike in a matter of 2-weeks raised global temperatures to the record levels we are at today.

La Nina –> El Nino is certainly important for the Equatorial Pacific temperature increase. But, how is Hunga-Tonga affecting the Southern Hemisphere polar vortex? Not so good with the Antarctic sea ice down there.

And, the Northern Hemisphere is much warmer than normal especially in the Atlantic. How are all those trillions of gallons of water vapor in the stratosphere doing? How much is left, and how many more years of impacts?

Such an abrupt warming spike hasn't been attributed by science to either El Niño or carbon dioxide, but it can be attributed to the fact that in March, the Northern Hemisphere passed the spring (vernal)  equinox, bringing more sunlight and longer days, and with it, greater heating.  As anyone who has ever lived in the southern United States can tell you, higher humidity keeps temperatures higher, especially at night, and that raises the daily temperature average.  On a global scale, with more water vapor in the atmosphere thanks to Hunga-Tonga, it stands to reason that the increased greenhouse effect of that extra water vapor would raise global temperature.

Science is already rolling out a variety of studies looking at this massive humidification of Earth's atmosphere and the subsequent warming from it.  It remains to be seen how much more we might see and how long it will last.

While it will likely take a few months to a couple of years for Earth to "de-humidify" itself and bring temperatures down in the process, this episode is a dramatic illustration of how nature is still in control of our atmosphere, rather than we.

Anthony Watts (awatts@heartland.org) is a senior fellow for environment and climate at The Heartland Institute.

Image: PickPik.

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