According to Ken Hersh, there is $50 trillion worth of energy infrastructure in place today. No government in the world can pay to replace that in a reasonable timeframe; it took a century to build it. Hersh argues that as a result, we should focus on replacing coal with natural gas in emerging economies (see: The single most impactful thing we could do is displace Chinese and US coal), on moving populations away from coastlines (see: Climate adaptation), and on leapfrog technologies (see: Look for leapfrog technologies that don’t require decades of new infrastructure).