According to a 2020 DW article:
President Vladimir Putin has repeatedly denied the scientific consensus that climate change is caused by man-made emissions. Last month, in his year-end press conference, he said "nobody knows the origins of global climate change."
They have more quotes from that conference, held in late 2019:
Putin cast doubt on the man-made origins of global warming, saying "nobody knows the origins of global climate change."
"We know that in the history of our Earth there have been periods of warming and cooling and it could depend on processes in the universe," Putin said. "A small angle in the axis in the rotation of the Earth or its orbit around the Sun could push the planet into serious climate changes."
France24 quotes & paraphrases him in 2017 as saying similar things
One day after visiting the Franz Josef Land archipelago in the Arctic, Putin claimed that icebergs had been melting for decades and suggested that global warming was not mankind’s fault.
“The warming, it had already started by the 1930s,” Putin said in comments broadcast from an Arctic forum held in the northern Russian city of Arkhangelsk.
“That’s when there were no such anthropological factors, such emissions, and the warming had already started.”
The Kremlin strongman added: “The issue is not stopping it... because that’s impossible, since it could be tied to some global cycles on Earth or even of planetary significance. The issue is to somehow adapt to it.”
I don't recall Putin saying such things in the more distant past, but I haven't been paying much attention to Putin's stance on climate change. So, for how long has he been saying this?