The planet is just proceeding along its evolutionary course. At this point, there's a pretty thick atmosphere that is about one-fifth oxygen, and there's abundant carbon-based life. But that hasn't always been the case, and won't always be the case. Being only 13, you might be witness to significant changes in the abundance of life, and to the climate...but nothing you live to see will be conditions that have never existed before.
The planet's surface conditions aren't terribly significant, from the planet's perspective. But from YOUR perspective, the biggest threat to your quality of life will come from other humans and their attempts at government. You could well face an economic collapse, displacement from your home, an interruption to your food or water supplies, or a war or two.
Short of a collision with a rogue planetoid, Earth can handle whatever comes - but YOUR most serious worry is the other humans you share the surface with.