Answer :
It’s a law because it is a type of science it has been proven over time that we humans are heating up the earths atmosphere you can take records from a year like let’s say 1935 compared to now the Antarctic is melting twice as fast because of the use of fossil fuels and burning of them into the atmosphere using those are not a sufficient way for the future of our plants use of natural resources that are very limited. and it heats up the ozone layer in the earth if it was a theory we wouldn’t see the gradual change of the ice melting quite at a rapid pace currently