# When it comes the average lifetime of chemicals in the atmosphere, is the mean lifetime ~1.4427 times the half-life? As with radioactivity?

There are so many websites giving numbers for 'average' lifetimes of global-warming or ozone-depleting chemicals in the atmosphere, yet they are rarely explicit in their definition(s)...

For instance, methane is usually stated to last 12.4 years.... But is this half-life (of a large amount) or mean lifetime (of a single molecule)?

• a part of the answer to this is in your question,for gasses"average LIFETIME" and for radioactivity "Half-Life". Apr 15 '21 at 6:11