Question: which gas is most responsible for shielding us from excessive ultraviolet radiation?
Answer: In the late 1970s, scientists noticed levels of ozone gas (O3) dropping in the ozone layer, a region of the stratosphere some 15 to 30km above our heads. The ozone here absorbs most of the Sun's damaging ultraviolet (UV) radiation, shielding us from UVB and UVC rays.