Los Angeles LED street lights

In 2013 Los Angeles completed the world's largest LED (light emitting diode) street light replacement project, replacing more than 140,000 streetlight fixtures across the city. According to L.A.'s Bureau of Street Lighting, the switch has resulted in a 63.1 percent reduction in energy use and carbon emissions have been reduced by 47,583 metric tons a year.

That a massive city like L.A. can achieve significant energy and emissions reductions from simply swapping out its light bulbs demonstrates that green technology retrofits like LED are a great way for any city -- small, medium and large --  to combat climate change while at the same time saving on costs and improving the safety and aesthetics of the city.