Nature absorbs more CO2 than it emits, but not enough to offset the amount we are putting out. Thus, the global CO2 concentration has been rising over the past 100+ years, especially in recent decades.

A higher CO2 concentration blocks more thermal radiation from exiting through Earth's atmosphere into space. When this energy is blocked, it stays on Earth, raising the temperature.

Using models that have made successful predictions in recent decades, we can predict that we are in for at least another 1 degree Celsius raise in global temperature, and very likely more if we don't work hard to counteract the issue (and stop emitting so much CO2).

This temperature increase will have very real, significant consequences, and we saw it coming many years ago. There is a reason all other developed countries in the world don't deny climate change.