Disproof
This is a conspiracy theory. The document referred to in it is the US' White House "Request for Input to a Five-Year Plan for Research on Climate Intervention" and there is no indication in the document that supports the conspiratorial notion that the US is 'managing the climate to fight Russia'
In the Consolidated Appropriations Act, 2022, the White House Office of Science and Technology Policy (OSTP), in coordination with relevant Federal agencies, was directed by Congress to develop a five-year “scientific assessment of solar and other rapid climate interventions in the context of near-term climate risks and hazards",
There is no mention of Russia nor "the goal of combating the emerging dominance of Russia in agriculture" is mentioned.
This is part of a broader pro-Kremlin disinformation campaign against the West, particularly targeting the US. Pro-Kremlin disinformation outlets have a track-record of trying to discredit Western climate policies.