Extreme Temperature Diary- Friday August 4th, 2023/Main Topic: How Much Did the Tonga Eruption Push Earth Toward +1.5°C?

The main purpose of this ongoing blog will be to track planetary extreme, or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: How Much Did the Tonga Eruption Push Earth Toward +1.5°C?

Dear Diary. During these very hot days in the summer of 2023 I do see that climate change denialists were latching onto one item to further their debating cause. Many were suggesting that the eruption of the Tonga volcano in January 2022 was the main culprit for the Earth’s average temperature getting close to if not exceeding +1.5°C above preindustrial conditions this July, our first United Nations line in the sand that we dare not cross, due to the tremendous amount of water vapor spewed unto the atmosphere from the eruption.

We often see that major volcanic eruptions briefly cool the planet because they spew copious amounts of ash and soot high into the stratosphere, blocking the sun’s rays. The eruption of Mount Pinatubo in the early 1990s cooled the Earth for a few years before the longer-term trend of global warming recommenced during the mid 1990s. The Tonga eruption was from an underseas volcano, so high volumes of sea water instantly became steam and were thrust high into the atmosphere along with some ash. Water vapor is actually a stronger greenhouse gas than carbon dioxide.

So exactly how much did the Tonga eruption warm the planet? For that answer, here is an Eos article. For climate deniers, this figure is not much but significant enough to warrant some concern because the added warmth will only make our climate that much worse:

Tonga Eruption May Temporarily Push Earth Closer to 1.5°C of Warming – Eos

Tonga Eruption May Temporarily Push Earth Closer to 1.5°C of Warming

The underwater eruption of Hunga Tonga–Hunga Ha‘apai sent megatons of water vapor into the stratosphere, contributing to an increase in global warming over the next 5 years.

By J. Besl

16 March 2023

The volcanic ash plume from the Hunga Tonga–Hunga Haʻapai eruption sent water vapor into the stratosphere. Credit: NASA Earth Observatory

When Hunga Tonga–Hunga Ha‘apai (HTHH) erupted in January 2022, it shot the standard volcanic cocktail of ash, gas, and pulverized rock into the sky. But the eruption included one extra ingredient that’s now causing climate concerns: a significant splash of ocean water. The underwater caldera shot 146 metric megatons of water into the stratosphere like a geyser, potentially contributing to atmospheric warming over the next 5 years, according to a new study published in Nature Climate Change.

Earth’s average temperature is teetering on the edge of surpassing its preindustrial level by 1.5°C—the target set by the United Nations in the Paris Agreement. In May 2022, the World Meteorological Organization announced there was a 50% chance of exceeding the 1.5°C threshold over the next 5 years. The new study showed that slight warming caused by the HTHH eruption increased the likelihood of Earth temporarily tipping past that mark by another 7%.

Straight to the Stratosphere

HTHH ranked a 5.7 on the volcanic explosivity index, alongside other historymakers like Vesuvius (79 CE) and Mount St. Helens (1980). Explosive volcanoes inject ash and sulfur dioxide into the atmosphere, typically leading to global cooling. Mount Tambora’s sulfur dioxide plume in 1815, for example, inhibited sunlight from reaching Earth, triggering the “year without a summer.”

The HTHH eruption was unusual. Unlike other eruptions its size, HTHH had a relatively low sulfur dioxide content. Researchers assumed it led to only 0.004°C of global cooling in 2022.

HTHH also exploded just below the ocean surface, injecting vaporized seawater into the stratosphere like a syringe. Though seemingly innocuous, water vapor is the planet’s most common greenhouse gas. Whereas volcanic sulfates commonly block sunlight from reaching Earth, water vapor keeps it from leaving.

The HTHH blast sent water vapor and other gases to at least 40 kilometers (25 miles) above Earth’s surface and punched through the boundary of the stratosphere. In this atmospheric layer, cool, heavy air rests below less dense warmer air. Because there is little turbulence to stir the system, “you can get a perturbation lasting for, in an atmospheric sense, quite a long time,” said Stuart Jenkins, an atmospheric physicist at the University of Oxford and lead author of the new study. The eruption boosted the water vapor content of the stratosphere by 10%–15%, according to the study.

“If we’re only a quarter of a degree from 1.5°C, those four hundredths of a degree do actually make a tangible difference.”

Using reconstructions of global climate, Jenkins and his colleagues established the monthly baseline conditions for the 7 years prior to the eruption, then simulated the effect of water vapor in the stratosphere for 7 years after the event. The researchers assumed that the injected water vapor would settle out of the stratosphere in that time. Their model parameters are conservative, Jenkins said, and assumed the volcanic plume spread widely between altitudes and latitudes.

The model calculated the monthly change in Earth’s energy balance caused by the eruption and showed that water vapor could increase the average global temperature by up to 0.035°C over the next 5 years. That’s a large anomaly for a single event, but it’s not outside the usual level of noise in the climate system, Jenkins said. But in the context of the Paris Agreement, it’s a big concern.

“If we’re only a quarter of a degree from 1.5°C, those four hundredths of a degree do actually make a tangible difference,” he said. The planet was already 50% likely to warm past 1.5°C in the next 5 years, and the presence of HTHH’s water vapor increased the odds of temporarily exceeding that threshold to 57%, according to the simulation.

What About 1.5°C?

The volcano launched an “unprecedented” amount of water vapor into the stratosphere, said Patrick Sheese, a climate physicist at the University of Toronto who was not involved in the study. But the event’s impact can’t compare with that of human emissions, he said. Even if the eruption increases temperatures as the simulation predicted, that’s only a small, temporary lift toward the 1.5°C threshold. Decades of research have shown that humans are still responsible for most of the warming.

The study “is just another reminder that nature isn’t going to help us out of climate change.”

The first year that world temperatures breach the Paris Agreement will inevitably spur a flurry of headlines. But as the study showed, part of that warming is caused by natural anomalies. Any number of phenomena can sway global temperatures, from El Niño conditions in the Pacific Ocean to wildfires in Siberia. The HTHH eruption may nudge the temperature past 1.5°C of warming, but that doesn’t mean the Paris Agreement has failed yet; the event demonstrated how close the world is to its agreed-upon tipping point.

The study “is just another reminder that nature isn’t going to help us out of climate change,” Sheese said. “This clearly is up to us to fix.”

—J. Besl (@J_Besl), Science Writer


Here are some other “ET’s” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:

Here is more brand-new July 2023 climatology:

Here is more climate and news from Friday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Today’s News on Sustainable and Traditional Energy from Fossil Fuel:

More on the Environment:

More from the Weather Department:

More on other science and the beauty of Earth and this universe:

If you like these posts and my work on record temperature ratios, please contribute via my PayPal widget on this site. Thanks in advance for any support. 

Guy Walton… “The Climate Guy”

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