Throughout humanity's history, our energy use has steadily increased, now reaching a point where it's affecting the climate. Even if we do switch to renewable energy, we'll continue to generate waste heat that will be put into the environment, continuing to warm our planet. Researchers calculated that if energy use increases by 1% per year, it would make a planet like Earth uninhabitable within 1,000 years. Going to space will be the only way to continue growth.