... how do know global warming isn't partly natural?
With all the evidence this world is showing us the reality is clear. Unlike you, who should have already studied the data and know this answer, the world scientific community is not stupid and know, with certainty, today’s climate change problem is all the result of mankind.
No amount of evidence will convince you since you, politically, religiously, do not want this to be despite the glaring reality. If you had been paying attention these many years you too would know this climate change is anthropic and no amount of stupid is going to change this.
Take a few hours to dredge up the overwhelmingly easy to find evidence of anthropic climate change. Stop being intellectually lazy, lift the scales from your eyes and see the reality your god set in front of you. The present rush to climate change on this planet, change that will cause the extinction of many millions of species, including all mammalia, is man made.
“There’s simply no polite way to tell people they’ve dedicated their lives to an illusion,”
-Daniel Dennett
Stop Tzar Vladimir the Condemned!