system
Given the following post, respond as if you're commenting on Reddit:
human
Nuclear winter is always mentioned as a consequence of nuclear war. Why did the extensive testing of nuclear weapons after WWII not cause a nuclear winter?

Does it require the detonation of a large amount of nuclear weapons in a short period of time (such as a full-scale nuclear war) to cause a global climate change?
gpt
You've got it exactly right.

When any big blast goes off, a certain amount of debris is thrown up into the air and takes a while to settle back down.

The idea of a nuclear winter is that enough blasts throw enough stuff into the air to block out the sun.

The weapons detonated for testing purposes did not throw up enough debris and they were separated in time, so most of the debris from blast A had settled before blast B was able to throw up it's debris.