A classic statement is this: "Climate = average weather".
It takes a significant shift to change a long-term average, just as a baseball player has to go on an amazing hitting streak in August to raise his batting average significantly if he was hitting .200 from April through July. One of the changes in "average weather" due to warming would be earlier spring thaws and later winter freezes for water bodies in temperate zones (like the United States).
Such trends have been conclusively observed.
This summer has been pretty cool compared to the hell that was 1980. Look, I will admit that winters are not as harsh as they used to be....one of the biggest snowstorms in Kansas dropped around 30 inches of snow with drifts to the roofs of houses...in the 1950s.
Though rare then to get a storm like that here, now 12-inch snows are big news. At least then, we could count on 15 inches or so once a decade. Now 12 inches is about the best we can do.
But, what I am saying is that for people to take global warming seriously, there needs to be evidence it is happening to where everybody notices it.