The spat between the TV host and first daughter began after she tweeted: 'FACT: Greenhouse gases generated by the U.S. will slide 9.2% this year'
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She might have been referring to total greenhouse emissions, but the CO2 decline from fossil fuel combustion looks to be a little larger than 9.2%, at least through August.

https://www.eia.gov/totalenergy/data/monthly/pdf/sec11_3.pdf...

Through August, US CO2 emissions, million metric tons.
       Coal   NatGas   Oil  Total 
2019    740    1124   1579   3451
2020    576    1111   1343   3037

2020 percent change from 2019
       Coal   NatGas   Oil   Total
       -22%     -1%   -15%   -12%

The decrease in coal emissions is just a continuation of the trend of natural gas power plants replacing coal-fired plants. That trend started way before the pandemic hit.

Preliminary information on September electricity production, as well as natural gas and petroleum consumption, show continued declines on fossil fuel CO2 emissions. However, those declines are not as great as they were earlier in the year. Fossil fuel use is recovering in several areas. It is still too early to tell exactly what the year-end numbers will show, but -9.2% looks completely possible.

- Pete