air
atmosphere
blue
carbon
change
chimney
city
climate
cloud
coal
contaminate
contamination
dioxide
emission
energy
environment
environmental
exhaust
facility
factory
fossil
gas
global
greenhouse
heat
industrial
industry
nature
pale
pipe
plant
pollute
pollution
power
production
rise
sky
smog
smoke
space
station
tall
thick
town
toxic
urban
warming