[Publius]

In 1986 the US and the Soviet Union signed an agreement not to use weather or earthquake weapons against each other. If these weapons don't exist, then why the agreement?

[norsky]

In 1986 the US and the Soviet Union signed an agreement not to use weather or earthquake weapons against each other. If these weapons don't exist, then why the agreement?

...........

Meaning, they will work harder to out do each other, like the other agreements

[Spunky]

"If these weapons don't exist, then why the agreement?"

Here is why an agreement was made.

Signed in Geneva May 18, 1977
Entered into force October 5, 1978
Narrative
Treaty Text
Annex
Understandings
Signatory List
Narrative
Use of environmental modification techniques for hostile purposes does not play a major role in military planning at the present time. Such techniques might be developed in the future, however, and would pose a threat of serious damage unless action was taken to prohibit their use. In July 1972 the U.S. Government renounced the use of climate modification techniques for hostile purposes, even if their development were proved to be feasible in the future.

Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques
https://2009-2017.state.gov/t/isn/4783.htm