How dark would it be living in an impact winter?

Where would an asteroid have to hit earth to cause an impact winter? gives a great breakdown of the effects of an impact winter, but I'd like to know some more specifics about just how dark it would really be.


This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

  • $\begingroup$ Define "dark". Are you talking about actual light levels, or are you talking about how bad it would be for people? $\endgroup$ – Nicol Bolas May 11 '16 at 4:55
  • $\begingroup$ @NicolBolas light levels $\endgroup$ – socrates May 11 '16 at 5:53

Strangely, not very dark at all.

The "year without summer" in 1816 was caused by the volcanic ejecta from Mount Tambora blocking a small fraction of the sunlight which strikes the Earth. Days and nights were marked by strange phenomena, such as spectacular sunsets caused by sunlight reflecting and scattering through the fine particles suspended in the atmosphere, but there are no remarks about not being able to see during the day, or nights being unusually dark.

Instead, there was a deep and lingering cold, which affected plant growth and caused widespread unrest throughout many nations as crops failed and hunger spread. Fortunately for us, this effect only lasted one year...

The Dinosaur Killer asteroid kicked so much particulate matter into the atmosphere that it was indeed dark for a short while (not just dust from the strike, but forest fires from the burning vegetation and water vapour blasted out of the ocean). The heavy particulate matter fell out rapidly, as you would expect, and even smoke from the fires dissipated quickly. After a period of days to perhaps months, the atmosphere would look clear to the unaided eye, but the ring particles are up there scattering the incoming sunlight and reducing the temperature.

Your biggest problem would not be light, but getting warm coat and finding a source of food.

  • $\begingroup$ Can you add some references (preferably to the Tambora eruption), as per the hard-science tag? Thanks. $\endgroup$ – HDE 226868 May 9 '16 at 2:26

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