One of the Pink Panther movies finds Inspector Clouseau disguised as a local dentist who is summoned by an unsuspecting and villainous Chief Inspector Dreyfus to extract a bad tooth.   An accidental release of laughing gas puts both characters into hysterics and could possibly be one of the best-humorous scenes in movie history. Nitrous oxide, often used as a dentist’s anesthetic, has become the largest ozone-depleting substance emitted from human activity.  Laughing gas is produced by natural and human-related sources and is a by-product of agricultural fertilization and microbial action in wet tropical forests.  Science magazine reported that a study by NOAA indicated that emissions of N2O have eroded the ozone layer and is expected to continue through the twenty-first century. The passage of another cold front today will have enough "oumph" to pop some afternoon showers.  Once the ridge of high pressure bops in behind the front we will temporarily clear-out. Through the rest of March and into April and early May, we'll enjoy numerous cold fronts and wind-shift lines.  Speaking of cold, the extremely cold early-March weather in Kentucky in '94 caused chilled air to infiltrate Mammoth Cave causing thermal contraction of the rocks and loosening a 100-ton limestone slab, causing it to crash into the Rotunda Area. The average last freeze temperature for our area is March 5. On June 1, '93, St. Cloud, Minnesota recorded its latest ever freezing temperature.