Spot The Volcano, 1815 Edition

Guest Post by Willis Eschenbach

It’s been a while since I played “Spot The Volcano”. The premise of the game is that the decrease in temperatures from volcanic eruptions is nowhere near as large as people claim. So I ask people to see if they can identify when a volcano erupted based on the temperature records of the time.

Now, I say that the main reason the temperature drop from volcanic eruptions is so small is that when we get a reduction in downwelling radiation from any cause, the equatorial oceans start to cool. When that happens the clouds form later in the day, allowing in more sunshine. And the net result is that any cooling from the volcanic eruption is mostly offset by the increase in incoming solar energy.

With that in mind, I thought I’d take a look to see what records we have for the largest volcanic eruption in modern times. This was the eruption of the Indonesian island of Tambora in April of 1815. To my surprise, I found that we have no less than forty-two temperature records from that time. As you might imagine, most of these are from Europe. The list of the forty-two stations is appended in the end-notes.

So I took the records for the period during which the Tambora eruption occurred, and I “standardized” them so that they all had an average value of zero and a standard deviation of one. Then I plotted them all on one graph. Here is that result.

WILLIS USED TO WORK EAST OF TAMBORA IN THE SOLOMON ISLANDS
THIS IS HOW HE LOOKS IN THE NORTHERN HEMISPHERE
AND HERE IS THE VIEW OF TAMBORA FROM THE FOLKS WHOSE DATA HE CHERRYPICKED: