This pollution buildup is causing global climate change that, left unchecked would spread the frequency and severity of heat waves, floods, droughts and storms;
(global climate change; left; unchecked) (This pollution buildup; is causing; global climate change that, left unchecked would spread the frequency and severity of heat waves, floods, droughts and storms)
global climate change This pollution buildup
left is causing
unchecked
global climate change that, left unchecked would spread the frequency and severity of heat waves, floods, droughts and storms