Why do we argue about climate change?
The reason there is so much contention regarding “global warming” is relatively simple to understand — in climate change science we basically cannot prove anything about how the climate will change as a result of adding extra greenhouse gases to the atmosphere. So, we are left to argue about unprovable claims. That’s really what it boils down to.
Now, we can measure and prove that greenhouse gases are increasing. And, in the laboratory, we can measure and prove that adding greenhouse gases to a jar of air will lead to further warming. We don’t argue about these.
But when it comes to how the actual climate system might respond to extra greenhouse gases, we’re out of luck in terms of “proof” because the climate’s complexities are innumerable and poorly understood.
Climate science is a murky science. When dealing with temperature variations and trends that might be influenced by humans, we do not have an instrument that tells us how much change is due to humans and how much to Mother Nature. Measuring the temperature change over long time periods is difficult enough, but we do not have a thermometer that says why these changes occur; i.e., we cannot appeal to direct evidence for the cause of change. So, we argue.
In other words, the real climate system is so massively complex, we do not have the explicit ability, as with so many other sciences, to test global-size theories in a laboratory. Without this ability, we tend to travel all sorts of other avenues to confirm what are essentially our unprovable views about climate. These avenues, indirect as they might be, tend to comfort our souls because we crave certainty over ambiguity.
Now, it is a fundamental characteristic of the scientific method, and therefore of the confidence we have in our theories, that when we finally understand a system, we are able to predict its behavior.