Honestly? Because this chart didn’t explain that this isn’t part of some normal cycle or that humans are directly involved in some way. Many people don’t understand that.
Since I was a kid “El Niño” came around every few years and the hot air mass caused unusual summer storms and wacky winter snow conditions. This was explained as a 3-6 year cycle or something, nothing to worry about. A lot of people know about it because the weatherman loves the story.
Secondly, and I know this is a common thought: if humans are 100% solely responsible for tomorrow’s temperature reading, what precisely can any single person do today, and tomorrow, and next week to have the most significant impact? And how much will it cost that person relative to the benefit he or she will receive? It’s very unclear and this is a PR problem with the communication coming from many climate change activists.
People think a trend that’s been happening for 70 years, and is accelerating, is part of some harmless natural cycle that’s never been noticed before in the entirety of human history? I guess that’s possible because a lot of people are incredibly dumb, but mainly I think it’s just plain old denial.
It’s really hard not to be a total misanthrope.
Seeing a massive deviation from many years should be an obvious sign that it is not normal and there should be concern.
Not to mention scientists have been clearly calling for reduction in pollution and greenhouse games for over a century, starting with companies that are the most polluting. So a single person can vote for policies that hold companies accountable, because individuals cannot solve the problem on their own.