I seem to have endless debates where I support climate science and the current science that says:

1) The Earth is on a warming trend. 2) At least 90% of that warming is caused by Human activity. 3) The overwhelming majority of that heat is because of the release of CO2 and CH4 (Methane) into the atmosphere. 4) We ae at least 90% certain of this meaning that there is very little doubt.

Are there any credible or widely accepted sources that question these? My friends seem to think that there is a lot of debate on these topics and I don't a single credible source of refutation so maybe my biases are blinding me to the actual science. Is my understanding of these phenomena wrong or oversimplified?

Lastly, and this is only a side question: how much credence does science give to An Inconvenient Truth? Is it wacko science as some of my friends claim?