Methane is just a small part of the space industry’s overall impact on the climate — and that impact is not well understood. Exhaust particles emitted high above the earth can have an “umbrella” effect, preventing sunlight from reaching the ground, said Martin Ross, an atmospheric scientist at the nonprofit Aerospace Corp. Because of uncertainty around that and other aspects of space flight, scientists aren’t sure whether the industry causes net heating or cooling in the lower atmosphere, he said.