If we can build (presumably) ships that are sealed enough to protect us from the great vacuum that is space, and that can last years in the great nothingness that is space, then we can certainly build habitats here on earth to survive the most extreme changes in climate.
At the end, a spaceship that will take us to another solar system is essentially a huge dwelling that contains everything we will need to restart life on another planet - there is no guarantee that we will find the necessary building blocks there. So we would not only have to take our food, but the plants that can produce the food, the animals that would provide meat, the bacteria that all plants and animals depend on, the birds and the bees - everything needed to bootstrap another earth.
And this assumes that we can find a planet that contains the right ingredients to support life. All the minerals that are necessary to grow life e.g. the right quantities of magnesium to create chlorophyll. If we were doing this, we might need a thousand years to get it right.
Put it another way, if you were a weary space traveller, and you happened upon an earth who surface had heated to, say, 25 degrees on average, would you settle there and try to make it work, or would you travel on?