[blam]

"Could something like this have cause what we would now call nuclear winter effect?"

Yes.

Astronomers Clube And Napier call this a 'cosmic winter' in their excellent book by the same title,Cosmic Winter

"Synopsis

"During five days in late June 1975, a swarm of boulders the size of motor cars struck the moon at a speed of 67,000 miles per hour. On 30 June 1908 an object crashed on Siberia with the force of a large hydrogen bomb. The moon was also struck on 25 June 1178 struck, this time by a missile whose energy was ten times that of the combined nuclear arsenals of the world. Why late June? What is the nature of such events? And what threat do they pose to mankind? The authors aim to reveal the answers in this book. They argue that rains of fire visit the earth from time to time, destroying civilizations and plunging mankind into Dark Ages. They uncover a lost tradition of celestial catastrophe, and underpin these claims with foundations based on the latest discoveries in space. They produce a risk assessment which reveals that civilization could well come to an abrupt end, destroyed by a rain of fire followed by an icy, cosmic winter."

[AntiGuv]

What about the "Mini-Ice Age" which occured in the Late Middle Ages? Could something like this have cause what we would now call nuclear winter effect?

The practical answer is: No. You need a very large strike on land to kick up enough debris to affect the climate for decades. That leaves a big mark, and creates a big boom, the kind of mark and boom people notice and write about...

In addition to that, a meteor that creates a huge tidal wave by definition falls into the ocean. Such a meteor kicks up no dust. You can't have it both ways..