Kelsey Grammer and Wife Not Buying Climate Change Report

Kelsey Grammer all but said there's no need to worry about a potentially catastrophic impact on climate change ... 'cause it's all BS.

We got the "Frasier" star leaving a party Saturday night in Brentwood, and wanted to get his take on President Trump holding out at the G-20 summit on signing a deal to tackle climate change.

Kelsey -- with some help from his wife, Kayte -- said climate change is just science's way of keeping everyone on their toes. Kayte was more adamant ... straight-up saying it's all a myth.

We also tell Kelsey about Trump not believing his own administration's report -- involving 13 federal agencies and more than 300 climate scientists -- that said brace for the worse if nothing's done about climate change.