For a city to run entirely on renewable energy, it means each building in the municipal area must adhere to the strict guidelines put in place. Sure, it's not an easy, or even convenient goal in the short term, but the lasting effects are increasingly important—especially in a year that saw Cairo and Antarctica share the same 63.5 degree Fahrenheit temperature on the same day. That's why news that Chicago and Atlanta just announced they would be operating with 100 percent renewable energy in the near future is as relevant as it is exciting.

For Chicago, a city with over 2.7 million residents (9.5 million people including the metro area), the lofty goal of running entirely on renewable energy by 2025 gives many Americans hope. Indeed, hundreds of thousands recently marched around the country for the unifying goal of attacking climate change. "By committing the energy used to power our public buildings to wind and solar energy, we are sending a clear signal that we remain committed to building a 21st century economy here in Chicago," said Chicago Mayer, Rahm Emanuel, in a statement. Were Chicago to accomplish their goal, they would be the largest city in America to run entirely on renewable energy.

Atlanta was the other major U.S. city that announced plans this week to live in a greener future. By setting 2035 as the year they plan on running completely on renewable energy, the ninth largest metropolitan area in the U.S. will exist on sources such as solar and wind, among others. “We know that moving to clean energy will create good jobs, clean up our air and water and lower our residents’ utility bills,” said city council member Kwanza Hall in a statement, a man who is also a Democratic candidate for mayor. “We never thought we’d be away from landline phones or desktop computers, but today we carry our smart phones around and they’re more powerful than anything we used to have. We have to set an ambitious goal or we’re never going to get there.”

After lawmakers in Atlanta made their announcement on Monday, the city became the 27th one in America to pledge a 100-percent renewable energy goal.