The problems of ice age etc will pale in comparison to all the wars we'll have because of climate change.
The biggest problem will be water. As the rain pattern changes (think, 5 consecutive Monsoon failures in Indian sub-continent, home to 2 Billion people), water wars will become common - aided by huge migrations. Trump will start looking like a dove on immigration.
Some estimates put world population around 1 Billion by 2100 AD. In other words, some 7 Billion will die untimely deaths.
Put bacteria in a jar of sugar water and watch. They keep growing and consuming sugar, until there is none left. They all die off. I'm fairly sure, humans are not very different from bacteria. This is my optimistic take - since bacteria don't kill each other.
The current general consciousness of humans that we live in a fishbowl (earth), will change with time. Mars and the rest of the Solar System awaits.