The number of Berkshire Hathaway shares held by Warren Buffett are roughly as follows: [1] [2]

  Class A — 250,000 shares out of       640,000 shares outstanding
  Class B —  10,000 shares out of 1,330,000,000 shares outstanding

Class A shares have 10,000 times the voting power of Class B shares, so Warren Buffett controls just under 33% of voting power overall.

If Warren Buffett had abstained, the climate report measure would have still been defeated by the remaining votes against.

[1]: https://www.investopedia.com/articles/company-insights/08291...

[2]: https://www.berkshirehathaway.com/2020ar/202010-k.pdf