The problem with holding countries, cities, and even individual companies accountable for their pledges to cut down on emissions is that monitoring emissions is a real challenge. We can estimate with relative accuracy how much a certain entity is emitting, but tracking down the exact amount remains difficult. The good news is scientists are getting close to being able to trace and monitor greenhouse-gas emissions thanks to advancements in technology. China is far ahead when it comes to such technology as the government publishes real-time emissions data on its 40,000 largest polluters. Through an app, citizens can access that data, which helps to motivate sluggish officials without additional regulation simply by marshaling citizen outrage.