Evidence suggests that earth climate is warming. Which activity do scientists believe contributes most to global warming?

May 3, 2018

The release of greenhouse gases from fossil fuels.

Explanation:

Anthropogenic climate change is largely caused by the release of GHG's from burning coal, oil, and natural gas (mostly the first two).

Factories and power plants burn coal and oil, gasoline for cars is derived from oil, and much of the US's electricity and heating comes from natural gas.

$C {O}_{\text{2}}$ is the gas that we release the most, thus causing the most climate change, but we also release plenty of methane and nitrous oxide (${N}_{\text{2}} O$) into the atmosphere, both of which are also potent GHG's.

Much of the methane we release is from agriculture due to our raising of about 1.5 billion cows, and 770 million pigs. Natural gas also releases methane when fracking for it, since 4% of the extracted material is methane that escapes into the atmosphere.

These are the main sources, but the activity that contributes most is burning fossil fuels, which releases $C {O}_{\text{2}}$ and ${N}_{\text{2}} O$. In the US, the largest contributor to these emissions is in transportation.