<p>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. </p>

<p>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. </p>

<p>Reference: </p>

<ol>
<li>Minnis et al., 1993, "Radiative climate forcing by the Mt. Pinatubo eruption", Science, vol. 259, 1411-1415, doi: <a href="http://dx.doi.org/10.1126/science.259.5100.1411" rel="nofollow noreferrer">10.1126/science.259.5100.1411</a> </li>
<li>Kremser et al., 2016, "Stratospheric aerosol - observations, processes and impact on climate, Review of Geophysics, vol. 54, 278-335, doi:<a href="http://dx.doi.org/10.1002/2015rg000511" rel="nofollow noreferrer">10.1002/2015rg000511</a></li>
</ol>

CC BY-SA 4.0
2018-06-13T17:56:21.017Z
this means the reduction was about 0,2% after pinatubo erupted more about solar radiation here https://en.wikipedia.org/wiki/Solar_irradiance
trond hansen
CC BY-SA 4.0
2018-06-14T09:12:47.530Z
@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.
Harish
CC BY-SA 4.0
2018-06-14T09:22:11.470Z
@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.
Harish
CC BY-SA 4.0
2018-06-14T12:19:23.387Z
it was the drop in temparature of 0,5C it fits a drop in radiation of about 0,2% https://en.wikipedia.org/wiki/Mount_Pinatubo
trond hansen
CC BY-SA 4.0
2018-06-12T11:35:33.177Z
2018-06-14T09:08:05.487Z
2018-06-14T09:08:05.487Z
Harish
<p>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.</p>

<p>Everyone is happy, bliss abounds.</p>

<p>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?</p>

CC BY-SA 3.0
2016-09-27T14:43:18.100Z
Welcome to Earth Science SE. I think http://sustainability.stackexchange.com/ might be a better site for the question. In any case, let's see what this community decides.
arkaia
CC BY-SA 3.0
2016-09-27T14:48:04.957Z
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.
PoloHoleSet
CC BY-SA 3.0
2016-09-27T14:52:21.150Z
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.
arkaia
CC BY-SA 3.0
2016-09-27T23:41:08.920Z
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
Gordon Stanger
CC BY-SA 3.0
2016-09-28T13:00:44.850Z
@AndrewMattson [sustainability.se] 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.
410 gone
CC BY-SA 4.0
2018-06-12T13:46:40.643Z
There's also an engineering question here too, because of the damage risk to the collectors from the immediate ashfall.
Spencer
CC BY-SA 4.0
2019-02-10T02:52:28.450Z
Related question (using Tambora eruption as reference): https://earthscience.stackexchange.com/q/16213/11908
Camilo Rada
<atmosphere><climate><volcanic-hazard><solar-terrestrial-physics>
Would a global cooling event disable solar energy usage?
PoloHoleSet
# Would a global cooling event disable solar energy usage?

(Asked by: username_0 on 2016-09-27)

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?

**Tags:** atmosphere, climate, volcanic-hazard, solar-terrestrial-physics

> **Comments:**
> **username_1**: Welcome to Earth Science SE. I think http://sustainability.stackexchange.com/ might be a better site for the question. In any case, let's see what this community decides.  
> **username_0**: 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.  
> **username_1**: 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.  
> **username_2**: 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  
> **username_3**: @AndrewMattson [sustainability.se] 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.  
> **username_4**: There's also an engineering question here too, because of the damage risk to the collectors from the immediate ashfall.  
> **username_5**: Related question (using Tambora eruption as reference): https://earthscience.stackexchange.com/q/16213/11908  

---

## 1 answers

### Answer by username_6 on 2018-06-12. Score: 4 | Accepted answer

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.

Reference:

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](http://dx.doi.org/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](http://dx.doi.org/10.1002/2015rg000511)

> **Comments:**
> **username_7**: this means the reduction was about 0,2% after pinatubo erupted more about solar radiation here https://en.wikipedia.org/wiki/Solar_irradiance  
> **username_6**: @username_7 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.  
> **username_6**: @username_7 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.  
> **username_7**: it was the drop in temparature of 0,5C it fits a drop in radiation of about 0,2% https://en.wikipedia.org/wiki/Mount_Pinatubo  

---

