is it natural AND man increased? or some other variation of that?
National Geographic Channel’s Naked Science program recently showed on how Solar Weather has an impact, as do cosmic rays.
The episode I’m referring to is titled “Solar Force”
http://channel.nationalgeographic.com/series/naked-science/3146/Overview
It mentions something that surprised me, the Ozone layer that we are damaging with pollution and with orbital launches will repair itself, if we quit poking holes in it. But the really interesting thing is that it is actually a greenhouse gas. one that stops harmful levels of solar radiation from getting in to harm us, but it also stops all the heat from escaping. so it’s a mixed blessing, rapid sunburns and chromosomal damage with high heat loss cooling the planet, or slower tanning with higher temperatures… interesting mix of concerns there.
The sun itself caused the mini ice age, that 400 year ice age that destroyed the Viking colonies on Greenland and ended about the time the Industrial Revolution started.
Really, quite the interesting episode, and a series with a fair bit of solid science behind each episode.