picture stuff that is picked up by satellites, and again if you look at the web site, the national oceanographic administration, you will see this extraordinary time lapse or satellite imagery of the reduction of the arctic over a number of years and it is quite striking freezes up and it melts in the summer. but in general each summer it melts a little bit more and doesn't freeze up quite as much in the previous winter and did you get the sense that the arctic ice islam slowly or in some places quickly disappearing and the question is what your in the summer will there be no ice at all. when i started working on these issues the answer to that question tended to be maybe 2060, 2070. and as i worked on this issue over the years, that sort of consensus estimate has come down 2014 colin 2030 come some people even say that it could happen as early as 2020. so there is the sense that part of the world we've always considered to be frozen, and changing and yet it is changing on our watch before our eyes and your lifetime and that is a fairly remarkable thing to see. >> is it dangerous? >> is it dangerous to the glo