What is the percentage of carbon dioxide in the atmosphere and how much has that changed in the past 100 years? Something worth looking into.

About 420 ppm, an increase of about 120 ppm in the past 100 years? This is a strange question since it is obvious that it’s heavily “looked into” and easy to look up, and simultaneously hard to figure out what rhetorical point is being made in asking people to cite it out of context.

0.04% vs 0.03%

Illustrates how silly the comment is that I was replying to.

Huh?

There are plenty of systems where the difference between 0.04% and 0.03% is dramatic, after all it’s an increase of 30% — and what matters is not the paltry decimal representation but rather the effects.

For example: consider concentration of sodium in human blood. The normal range is 0.31%-0.33% by weight. By 0.4% you’re pretty much dead.

Or consider chromium, an essential trace element: the normal amount is practically infinitessimal, in blood it’s 0.0000007% by weight, approximately. But not enough and you end up with diabetes or cardiovascular disease.

“0.04% vs 0.03%” is not an effective takedown of global warming.

Exactly. Represented as decimal numbers, we could also say that is only 0.0004 vs 0.0003, which looks like even less. Seeing that there is a 30% difference is the important thing here.

I can look it up (and so can you) but it is irrelevant for this conversation.

This matters if you are a climate scientist and are constructing a model to make predictions or shape policy. But for this conversation, all we need to know is that the percentage has increased because of human activity (specifically as a result of fossil fuel extraction and usage for energy consumption) and this increase is enough to cause significant warming, shaping the climate, and escalating wild fire intensity and frequency.

>This feels like another clear case of climate denialism.

"Feels like" and "clear case" don't mix. Just say "I'm bluffing".