Volcano rumbles – Watts?

This is an impressive scientific achievement, and the authors deserve recognition for solving such a long-standing puzzle.

However, I laughed when I read a basic study in the Proceedings of the National Academy of Sciences titled “Mysterious Eruption of 1831 AD Identified as Zavaritskii Crater on Simushir Island (Thousand Islands) ”.

What makes me laugh is their claim that volcanoes caused global temperatures to drop by 1°C (1.8°F, aka “nearly two degrees”). I've seen a lot of volcanoes erupt. Here is a link to my research on volcanic eruptions and temperature. I found no consistent response in global mean surface temperatures. I thought “This should be fun”. I looked at the study to see what evidence they had.

They used land temperature data from Berkeley Earth to verify their claims…the problem is, even using their method, the Berkeley data don't support their claims. The image and caption in Figure 1 below are from their research.

Figure 1. Original title: Figure S1: Time series of instrumental temperature anomalies from 1790 to 1840 AD. The years 1831 to 1833 are shades of gray. Instrument temperature records from Berkeley Earth [www.berkeleyearth.org, (8)] and displays estimated global average land temperatures. These represent annual temperature anomalies relative to the CE mean of 1790-1807 (a period without major volcanic eruptions).

Even though I squinted at Figure 1, I didn't see a 1°C drop in temperature after 1831. Not even close.

Also, Berkeley's data is monthly, but they use annual averages. This throws away a lot of valuable data.

So I decided to take a closer look at the temperature records of all major volcanic eruptions over the past two centuries. This eruption information is maintained by the Smithsonian Institution in its World Volcanoes Database. I only used the largest volcanoes, those with a Volcanic Explosion Index of 6 or higher. Here is that record, compared to the same Berkeley Earth temperature data set used in their study.

Figure 2. Large volcanic eruptions and Berkeley Earth global monthly surface temperature anomaly records.

This is the curious part. Among these seven large volcanoes, only one had a significant drop in temperature after the volcano. This is Mount Pinatubo, the poster child for the idea that volcanic eruptions affect global average surface temperatures. All the rest of these large volcanoes show no unusual behavior. Even the two largest volcanic eruptions in the Berkeley Earth record, Tambora in 1812 and Krakatoa in 1883, did not show global cooling. After every volcanic eruption, temperatures actually rise.

Anyway…that's why I laughed when they said they found that the 1831 volcano caused temperatures to drop 1°C (1.8°F). I don't even have to look at the record above to know that the likelihood of a significant impact is slim.

In fact, Figure 2 shows that Zavaritsky volcano occurred midway through the cooling period and that post-volcanic and pre-volcanic cooling were indistinguishable.

I said that this lack of temperature response to volcanic eruptions could be explained by my hypothesis that various sudden events regulate the temperature of the Earth. In particular, when temperatures drop due to volcanic eruptions that inject aerosols into the stratosphere, the climate responds with cumulus cloud fields and thunderstorms forming later in the day. This allows more sunlight to be absorbed by the surface, preventing the volcano from cooling.

To look at the problem of temperature changes caused by volcanic eruptions in a different way, I looked at UAH MSU satellite atmospheric records. Figure 3 shows eruptions and temperatures from top to bottom in four different atmospheric layers: stratosphere, tropopause, midtroposphere, and lower troposphere.

Figure 3. UAH MSU satellite-based atmospheric temperature anomalies, arranged in order of altitude from highest (top) to lowest (bottom). The red line shows eruption dates with a Volcanic Explosive Index (VEI) of 5 or higher. The number after the name shows the VEI of the eruption.

Now, this shows a strange property of the atmosphere – there is almost no correlation between the temperature anomalies in the stratosphere (top panel) and the rest of the lower atmosphere (bottom three panels). There were clear signs of volcanoes in the stratosphere in 1982 and 1991…but when the volcanoes reached down into the lower troposphere, the story was very different. There, only the Mount Pinatubo/Hudson pair experienced a temperature drop after the eruption, and even that was not significantly different from many other temperature drops during the period.

When the impact of stratospheric aerosols injected by an eruption causes them to fall to the surface, we get Figure 4.

Figure 4. Close-up of the most recent end of the data shown in Figure 2, with additional eruptions. The vertical red line shows satellite-era VEI 5 ​​and VEI 6 volcanic eruptions and Berkeley Earth global monthly land surface temperature records.

If the St. Helens eruption caused the subsequent cooling, did the El Chijun eruption cause the subsequent warming? We again see temperatures drop by about 0.5°C after Mount Pinatubo, but beyond that there is no clear indication that the eruption affects global average surface temperatures.

Yes, I know this goes against the wisdom of revelation. That wisdom says:

Eruptions –> Stratospheric SO2 aerosols –> Increased albedo –> Less sunlight –> More cooling

Sounds logical, but it ignores the fact that climate is a dynamic system, constantly changing and adapting to various forcings and factors. The wisdom revealed soon stops. I said this is what happened:

Eruptions –> Stratospheric SO2 aerosols –> Increased albedo –> Decreased sunlight –> Cooling –> Delayed daily formation of tropical cumulus cloud fields –> Decreased albedo –> Increased sunlight –> Decreased cooling

add

Eruptions –> Stratospheric SO2 aerosols –> Increased albedo –> Decreased sunlight –> Cooling –> Delayed or absent daily tropical thunderstorm formation –> Reduced thunderstorm cooling –> Reduced cooling

Both emerging phenomena, daily sun-reflecting tropical cumulus cloud fields and cooling thunderstorms, could counter the cooling effects of volcanic stratospheric aerosols and prevent large swings in global surface temperatures.

I provide interesting evidence for this hypothesis in the post below.