In addition to rising sea levels, weather pattern disruptions, increased drought and flooding, disruptions in food production, and the increased spread of disease, I suspect there may be another, unanticipated consequence of global warming: an increase in powerful earthquakes.
In fact, the past decade has seen a spate of powerful earthquakes occurring at a greater frequency than the historical average:
“According to long-term records (since about 1900), we expect about 16 major earthquakes in any given year. That includes 15 earthquakes in the magnitude 7 range and one earthquake magnitude 8.0 or greater. In the past 40-50 years, our records show that we have exceeded the long-term average number of major earthquakes about a dozen times.” USGS
“The annual number of “great” earthquakes nearly tripled over the last decade, providing a reminder to Americans that unruptured faults like those in the northwest United States might be due for a Big One. Between 2004 and 2014, 18 earthquakes with magnitudes of 8.0 or more rattled subduction zones around the globe. That’s an increase of 265 percent over the average rate of the previous century, which saw 71 great quakes, according to a report to the annual meeting of the Geological Society of America…” NBC News
Nonetheless, scientist have been quick to point out that this is just a fluke, that over time the number of earthquakes has remained relatively constant, and that the increase in large earthquakes is just due to chance:
“Large earthquakes greater than 8.0 in magnitude have struck the Earth at a record high rate since 2004 but scientists have analyzed the historical record and found that the increase in seismic activity was likely due to mere chance. Peter Shearer at Scripps Institution of Oceanography and Philip Stark at the University of California, Berkeley examined the global frequency of large magnitude earthquakes from 1900 to 2011. They discovered that while the frequency of magnitude 8.0 and higher earthquakes has been slightly elevated since 2004 – at a rate of about 1.2 to 1.4 earthquakes per year – the increased rate was not statistically different from what one might expect to see from random chance. The results of the study were published on January 17, 2012 in Proceedings of the National Academy of Sciences.
Devastating earthquakes greater than 8.0 in magnitude are infrequent and occur at a rate of about one earthquake per year. However, the occurrence of several of these large earthquakes over the past decade, including two quakes in 2004, two quakes in 2006 and four quakes in 2007 has caused people to question if the frequency of high magnitude earthquakes has increased in the early part of this century.
…the scientists could find no plausible physical mechanism that could explain the possible occurrence of global seismic swarms. Hence, even though large earthquakes are infrequent and difficult to analyze, the scientist concluded that the global frequency of large earthquakes is no higher today than it has been in the past.” EarthSky
I disagree with this assessment, and here is why:
Global warming, caused largely by the increase in atmospheric CO2, is causing glaciers and ice caps to melt at an alarming rate. That is changing the mass balance of the Earth, as the great mass of ice at the poles is redistributed around the globe. Since the Earth is a rotating object with enormous angular momentum, changing its mass balance is likely to put stress on the floating, movable plates that make up the crust.
Imagine if you have a perfectly balanced rotating object, like a top. On the top and the bottom, there are a series of weights (the ice caps). Imagine if you remove one or more of those weights. Experience tells us that the top will begin to wobble, because it is now out of balance. If that top had a movable skin made of separate, loosely connected segments, we can reasonably conclude that the segments may begin to shift.
That, I believe, is what’s happening to the Earth. Whether the change in mass balance from melting ice caps is enough to make our planet wobble, I can’t say. But I’m pretty sure it’s enough to make the floating tectonic plates shift a bit. In addition, as ice caps melt, the crust beneath them rebounds. This not only alters the pressure on that portion of crust, it may also alter the relationship with surrounding plates. Perhaps it could even alter the flow of magma beneath them. Both consequences might allow those plates to move more freely.
This is all conjecture, of course. I’m not a geologist. However, it’s important to remember that, on the Earth, everything is connected. Changing one thing changes everything.
Ten years ago, well before this recent spate of powerful earthquakes, I predicted an increase in strong earthquakes as a consequence of global warming. That prediction has come to pass. I suspect there will be more strong earthquakes, and that the increase in frequency will continue until the Earth reaches a new weight-balanced equilibrium. That could take several centuries.
The next two decades will show whether I am right or wrong.
Addendum: After writing this post, I came upon an article by a professor of geophysics who has come to the same conclusion as I have, and he cites evidence to support it. Although the actual mechanism discussed in the article is slightly different than I proposed, the underlying reason is the same: redistribution of mass.
