The evidence for man made global warming (AGW) has only reached the assumption stage: CO2 acts like a greenhouse gas, and more greenhouse gasses should reduce our planet's ability to cool itself.
But there are far too many variables that affect the climate to prove exactly what CO2 does, or does not do.
Even a worst case assumption (that CO2 caused all the warming in the past 45 years) does not add up to CAGW -- because the past 45 years had mild, harmless global warming.
And if you examine the actual warming, it most affected colder areas of the Northern Hemisphere, mainly in the six coldest months of the year, and mainly at night -- that adds up to beneficial warming.
Add the greening of the planet from more CO2 in the atmosphere, and the past 45 years of climate change were good news.
If CO2 caused any of the warming, then we, and our plants, should celebrate CO2 enrichment of the atmosphere.
If
CO2 caused none of the warming, we should celebrate our more moderate
climate, and hope that mild, harmless warming continues.
The only alternative to global warming is global cooling -- our planet is not in thermodynamic equilibrium, so the climate is ALWAYS changing.
Throughout history there is strong anecdotal evidence that people do not like a cooler climate, as in the Little Ice Age Centuries.
We
should be thankful we are living in a mild warming period during an
interglacial -- one of the best climates this planet has had for humans,
animals and plants.