China and India have 36% of the world’s population and produce about 35% of global CO2 emissions, ranking first and third respectively in that category. The United States, with a little over 4% of the world’s population, produces about 16% of global CO2 emissions, good for second place.
A year ago, nearly 200 countries signed an agreement, known as the Paris Accord, to fight climate change by mitigating greenhouse gas emissions. They each promised to reduce their carbon output as soon as possible, and to do their best to keep global warming well below 2-degrees Celsius (or 3.6 degrees Fahrenheit).