[Smokin' Joe]

1945-1976: Above ground nuclear testing

1800's: Significant volcanic eruptions/explosions

Both would place particulates high in the atmosphere, which would cause a reduction in sunlight reaching the surface.

Just my $0.02

[gondramB]

"1945-1976: Above ground nuclear testing "

I really wonder about that... the temperature was moving up the whole century til it stopped for 30 years.

[El Gato]

Both would place particulates high in the atmosphere,

But not so high as the Tunguska event, which is estimated at 10 km for the center of the explosion. Although it's the effect on the water vapor in the troposphere and mesosphere that the author argues is different between the volcanoes and nuclear tests on the one hand, and the Tunguska event.

He also argues that the effect is at permanent, or at least of longer lasting effect than events lower in the atmosphere.