Current worldwide human CO2 emissions are about 30,000,000,000,000 (3x1013) kg/year. That's 30 billion tonnes/year or nearly 1,000 tonnes/second, a bit more than can be explained by southeast Asian peat fires. The daily average CO2 concentration at Mauna Loa just hit 400 ppm (0.04%) for the first time.
Schmitt's denial of global warming is a disappointment. So was his support for the "flag burning" amendment some years ago. Obviously his politics are pretty right wing.
But he does demonstrate that NASA "insiders" can take public stances that differ from the "party line" and survive...