evidence: The Australia-based Galileo Movement touts a series of "basic facts" on carbon dioxide that attempt to explain why the greenhouse gas can't contribute to climate change. [...] Claim: CO2 is Nature's colorless, odorless, tasteless gas essential for all life on Earth. It's not toxic. It doesn't make land, water or air dirty or unsafe to use. It does not cause disease. [...] It is worth noting, however, that even in the past CO2 had an impact on temperatures, given its role as a greenhouse gas.