This is just wrong. You are free to argue that 3° warming is no big deal, like one of your sibling comments does, but saying that humans are not responsible for climate change is factually wrong.
You might want to check the news. The arctic has melted, temperatures have topped 100 degrees. The sea ice, where still present, is less than an inch thick. Commercial shipping is happening in winter without the aid of icebreaking ships. The Polar Vortex has gotten completely destabilized, sending the Jet Stream careening deep into southern latitudes (which is why Texas froze).
This is ecological doom knocking at our door. There are multiple, overlapping positive feedback loops occurring. You really should be paying attention and not just smugly pretending that you can "own the libs".
The reality that most of the increase in CO2 in the atmosphere compared to pre-industrial levels is due to humans. We know this because different CO2 sources have different carbon isotope ratios.
The reality that increased CO2 results in increased warming. We know this from various experiments and direct measurements.
The reality were we have satellites that can measure the incoming and outgoing solar energy and see that the Earth is gaining energy.
We have good measurements of various recent phenomena.
We have bad, inferred, or proxy data of various past phenomena.
We have limited data on cyclic global and extraterrestrial phenomena.
We mash these data into computer simulations of the earth, hit "run", and observe the result.
Herein lies the problem: we're feeding good, not so good, and incomplete data into an incomplete model of a chaotic system the size of the entire planet and projecting this data many years into the future to a result of impressively narrow margins.
We frequently update these models as we learn about new phenomena and interactions. We refine the data we input as we learn to better calibrate or infer its correctness. We run the simulation again and observe the results.
While the desire to improve our methods in the face of new information is a very scientific process, I think the objection is that there is a combination of a tremendous amount of hubris to trust such a large model of such a chaotic system, as well as an incentive structure that is tremendously vulnerable to abuse or corruption.
Of course it is absolutely scientific to be skeptical; that is, after all, a crucial component of the scientific process. That skepticism of this particular process exists is not only to be expected, but should also welcomed.
However, there is exceedingly little dissent within the scientific community. This alone should raise skepticism.
Now, I'm not talking about dissent about CO2's thermal properties or ways in which we measure things. Obviously these are testable, so we can maintain a certain level of confidence in their methods or results.
The global models—and actual, physical global system—are not testable. We cannot "try a little of this and a little of that" to pull apart how the emergent sum of all the parts affect this great chaotic system.
So we have a majority of the scientific community vociferously defending our projections—mostly because of unrelated but adjacent social reasons—and very few pushing the narrative that yes, in fact this is a very brittle process that ultimately thrives on faith.
At least, this is how I imagine a reasoned skeptic may form the justification for their skepticism...
There is evidence in the geological record that CO2 increases lagged temperature increases. There is evidence in the geological record that CO2 levels, and temperatures, were much higher than they are today.
Water vapor and the sun are the two biggest inputs into the greenhouse effect on Earth, not CO2. CO2 is infinitesimal by comparison.