There are sensationalists, as with any issue in society. However, this doesn’t cast doubt on whether CO2 is a greenhouse gas that traps heat in our atmosphere.
We know the levels of CO2 in our atmosphere over the last 500,000 years or so. It has always fluctuated between 175 and 300 parts per million (ppm).
We are currently over 400 ppm which is a 30-40% increase. Fires have always occurred in nature, but that has never driven CO2 to levels we are seeing now. Obviously, something is different. That difference is the fact we are burning fossil fuels.
Also, temperature has also fluctuated with CO2, mostly due to the difference in CO2 solubility in cold vs. warm water.
So we already know that temperature fluctuates, and the main culprit is thought to be the Milankovitch cycles which involve changes in the Earth’s orbit, tilt, and other factors. This is why the ice ages and interglacial periods are somewhat clock like. So we already have a strong understanding of what causes natural changes in temperature.
What we are seeing now is an increase in a gas that traps heat in an atmosphere. Basic physics tells us that this will increase global temperatures because that is what greenhouse gases do. This was understood clear back in the 1800’s. The first rough calculations estimated in the late 1800’s suggested a 2C increase in global temps for each doubling in CO2.