During the past several years, the frequency of zodiac lights and noctilucent clouds have been increasing for observers in the mid-latitudes. Here is an example of the ZL I captured near Santa Fe, NM last year: http://www.astrobin.com/81543/.
Both phenomena occur in the upper reaches of the atmosphere where meteor vapor and ice crystals reflect sunlight. Could it be that the globle temperature pause of the past 15 years or so is related to this potential blocking of incoming solar radiation in the upper atmosphere?
I think it has something to due with the weakening heliospheric magnetic field. In the past, increased sitings of noctilucent clouds preceded significant global cooling episodes, so there is a relationship, IMO.