Sponsored climate discourse, driven by both climate contrarians and advocates, influences public attitudes towards climate change. We present an experimental study suggesting that the Facebook advertisement algorithm also influences climate discourse. The algorithm preferentially delivers ads to Facebook audiences in certain locations and demographics, at least partially based upon the ad image. Further, the algorithm is biased in terms of how it delivers ads featuring images of non-renewable sources of energy, and does not always fulfill targeting intentions as requested. This may result in inadvertent manipulation of ad delivery with consequences for climate discourse and algorithmic fairness.