In 2019 Q2, power generation from coal provided 21% of the US’ electricity, while natural gas provided 36%.

Compared to 2005, a year commonly used to benchmark progress in reducing emissions, the carbon intensity of the US power sector was down more than 38% in 2019 Q2

The result shows that the trend that started in 2016, when natural gas replaced coal as the main source of energy production, has continued.

“We’re in the middle of an energy transition right now, and the biggest part of that story in the US is how swiftly coal has been declining over the past decade,” Costa Samaras, an assistant professor of Civil and Environmental Engineering at Carnegie Mellon, said in a media statement. “The decline of coal can be attributed to the rise of natural gas, the continued improvement of renewables, and energy efficiency efforts.”

This means that emissions from electricity production have also dropped because burning natural gas generates about half of the direct CO2 emissions per unit of energy roduced than coal does.

According to the Carnegie Mellon scientists, the carbon intensity of the sector, measured in pounds of CO2 emissions per megawatt-hour, dropped by 9% from last year.

The decrease in emissions -the experts found- is also a result of the continued growth of the renewable sector. Compared to 2018 Q2, generation from solar increased 10% and generation from wind increased by 7%.

Together, wind and solar accounted for 11% of US power generation in 2019 Q2. Hydropower was responsible for 8% of the electricity.

Nuclear power, on the other hand, remained the largest zero-carbon source of electricity in America, accounting for 20% of total generation.

The study by Samara and his team is part of the Pittsburgh-based university’s Power Sector Carbon Index, which compiles information from disparate datasets and standardizes the calculation of carbon intensity so that it is possible to track the performance of the sector.