Are there any estimates for the reduction of global solar insolation at the Earth's surface that a Tambora scale eruption would bring?

If our electrical power generation became heavily reliant on solar pv would it bring about a substantial reduction in output capacity?


1 Answer 1


Volcanic eruptions effectively inject large quantities of aerosols in the upper layers of the atmosphere, increasing Earth's albedo and reducing the intensity of the solar radiation reaching the surface. Such reduction would indeed lower the solar energy available to solar panels.

These effects of volcanic eruptions have been studied by Gao et al. (2008) and Crowley and Unterman (2013). Both studies were combined by the IPCC Working Group I during the assessment report 5 (2013), and summarized on the figure 8.18 (Chapter 8), together with other climatic forcings:

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You can see that the largest drop in effective radiative forcing happens in 1815 as a consequence of the Tambora eruption.

Unfortunately, that event goes out the scale of the plot. However, the data is available on Table AII.1.2 of Annex II, were we can see that the minimum value indeed happens in 1815 and reaches –11.629 W/m².

Considering the typical amount of energy received from the Sun under clear skies at seal level is roughly 1,000 W/m², the irradiation drop produced by Tambora would represent a drop of about 1% on the energy reaching the Earth's surface. Of course, much larger local effects could be observed due to transient and more localized dense ash clouds.

Therefore, at a global scale, if a new "year without summer" where to happen, photovoltaic energy output would drop by ~1%.

Of course, larger effects would take place if the eruption happens to be close to the most important areas for photovoltaic energy production.

  • $\begingroup$ just 1 % ? Seems almost minimal drop in production. Our solar panels drop in output much more during the monsoons. And we get some really really dark clouds when the monsoon depressions (synoptic scale events) pass through the subcontinent. $\endgroup$
    – user1066
    Commented Feb 10, 2019 at 1:47
  • 1
    $\begingroup$ @gansub I was also somehow surprised by the low number. A possible flaw of my answer is that the value used is the drop in radiative forcing, which is not exactly the same that the drop in energy reaching the surface. As all the energy captured by the atmosphere is still part of the radiative forcing but won't be available to solar panels. However, I don't think the difference will be too significant, as the ash is pretty short lived, and at a whole year timescale won't affect much. On the other hand, aerosols last very long and are accounted in this answer. $\endgroup$ Commented Feb 10, 2019 at 2:22
  • $\begingroup$ @gansub also the climate is very sensitive to forcing. Note that all the CO2 produce a change in the forcing of just 0.1%, and that makes a big difference specially in the long run. $\endgroup$ Commented Feb 10, 2019 at 2:24
  • $\begingroup$ @gansub I just found here a very similar question, and it arrived to a very similar answer (1.3% on the four months after the 1991 eruption of Pinatubo): earthscience.stackexchange.com/questions/8787/… $\endgroup$ Commented Feb 10, 2019 at 2:35
  • $\begingroup$ Fair enough. If you think about it the depth of the clouds(vertical) during the monsoon sometimes can easily be few kms.(what we call deep convection) and these systems can stick around for days making our solar panels worthless during those periods.Typically July August report the worst drop in PV output. It would be interesting to compare these losses vs. volcanic eruption losses. $\endgroup$
    – user1066
    Commented Feb 10, 2019 at 2:41

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