Imagine that we've improved the level quality, affordability, and ease of use of photo-voltaic solar, and it's use is widely distributed in the USA. We've improved the grid for power distribution, we increase wind, hydro, geothermal sources for 24-hour generation and create a storage network to the point where fossil fuel generation is only needed for, say, 20% of our energy needs, and peak/backup needs.

Everyone is happy, bliss abounds.

Would such a system be vulnerable to a natural disaster? If there was another Krakatoa event, with an equivalent amount of ash thrown into the atmosphere, how much, percentage-wise, of a reduction in solar intensity would we see, and for how long?

  • $\begingroup$ Welcome to Earth Science SE. I think sustainability.stackexchange.com might be a better site for the question. In any case, let's see what this community decides. $\endgroup$
    – arkaia
    Sep 27, 2016 at 14:43
  • $\begingroup$ Sounds good. Look like sustainability is more about personal choices in one's lifestyle, as opposed to societal policy, planning and the science of it, but if that's the best fit, no objections here. $\endgroup$ Sep 27, 2016 at 14:48
  • $\begingroup$ As you mention, sustainability might also not be the best option. I would just keep it here for now and see if you get a decent answer. $\endgroup$
    – arkaia
    Sep 27, 2016 at 14:52
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    $\begingroup$ Whatever answers we get, I hope they will include (a) a spectral intensity graph, showing the wavelengths of usable solar energy vs the wavelengths of atmospheric particulate absorbtion, and (b) the latitudinal effect of warmer climate decreasing photovoltaic efficiency - and how that would shift after a major volcanic eruption $\endgroup$ Sep 27, 2016 at 23:41
  • 1
    $\begingroup$ @AndrewMattson Sustainable Living is for the macro issues you describe, as well as the lifestyle ones. But this is an Earth Science question anyway, really, as you're asking about the absorption of insolation. $\endgroup$
    – 410 gone
    Sep 28, 2016 at 13:00

1 Answer 1


I am not sure about the size of Krakatoa eruption but the eruption of Mt. Pinatubo in Indonesia around 12th June 1991 is considered as the largest eruption in the past 100 years. Global average of decrease in solar radiation after 4 months of eruption was about 2.7 +/- 1 W/m^2. Global average surface reaching solar radiation is about 198 W/m^2. In other words, Mt. Pinatubo eruption caused about 1.3% decrease.

The number 2.7 W/m^2 is a global average, so the decrease might have been more in tropical regions and less at high latitudes. It took about three years for stratospheric aerosol amount to return to the background level.


  1. Minnis et al., 1993, "Radiative climate forcing by the Mt. Pinatubo eruption", Science, vol. 259, 1411-1415, doi: 10.1126/science.259.5100.1411
  2. Kremser et al., 2016, "Stratospheric aerosol - observations, processes and impact on climate, Review of Geophysics, vol. 54, 278-335, doi:10.1002/2015rg000511
  • $\begingroup$ this means the reduction was about 0,2% after pinatubo erupted more about solar radiation here en.wikipedia.org/wiki/Solar_irradiance $\endgroup$ Jun 13, 2018 at 17:56
  • $\begingroup$ @trondhansen I am not sure how you arrived at number 0.2% but in general direct impact is always small. It is the feedback loop that causes temperature rise (or decrease) in spite of a small change in the energy budget. $\endgroup$
    – Harish
    Jun 14, 2018 at 9:12
  • $\begingroup$ @trondhansen I think you used 1000 W/m^2 as a number for surface reaching solar radiation. 1000 W/m^2 surface reaching solar radiation is only momentarily at noontime in a tropical region but in general values are much lower than 1000 W/m^2. During the night, there is no solar radiation, so accounting for higher latitudes and night-time no radiation, 24-hour global average surface reaching solar radiation is about 198 W/m^2. $\endgroup$
    – Harish
    Jun 14, 2018 at 9:22
  • $\begingroup$ it was the drop in temparature of 0,5C it fits a drop in radiation of about 0,2% en.wikipedia.org/wiki/Mount_Pinatubo $\endgroup$ Jun 14, 2018 at 12:19

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