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Co2 makes the world greener nasa study
https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth

what concentration of CO2 toxic for humans. (60,000 PPM present value ->400PPM)
http://principia-scientific.org/at-what-concentration-does-co2-becomes-toxic-to-humans/

this is not only CO2 but more broadly climate change talk from the co-founder of Greenpeace. It's a good place to start and see if the man says the truth wit further research.

This man talks about the uncertainty in how things are measured in climate science. the change of 0.8C increase in the last 150years is hard to measure at this accuracy before the satellite data that started 20-30 years ago and other stuff. I think he makes good points.

another one that discusses possible lies and exaggerations that can give you some ideas on the issues and what to search for.

Hope this helps, tell me what do you think when you study this, I am curious :)