No one simple thing will “solve climate change”. Seeking one simple thing indicates a lack of understanding. There’s really no excuse for that any longer. There are SO many good, free courses online such as David Archer’s Climate Change: Understanding the Forecast, and great books like Kerry Emanuel’s What We Know About Climate Change, and Richard Alley’s earth: The Operators’ Manual which explain the problem. There are even great videos like Richard Alley
and David Suzuki
It’s not that complicated to understand. Our economies are based, in large measure, upon energy obtained from extracting and burning fossil fuels. While there are some emissions from cement production and agriculture (apart from agricultural machinery), and these need to be addressed, heating homes, making stuff, flying planes, and driving trains, trucks, and automobiles is where it comes from, and a lot of that is structural now, e.g., having suburbs.