Alright, another strange Jellyfish question. This occurred in Viareggio, again in Italy, durring the early summer of last year. I was swimming in the sea, in which at first I did not see a single jellyfish, when all at once I was swimming in what was something like two parts jellyfish to one part water, if you get my drift. I know that now sudden blooms of medusae in the Mediterranean have been becoming common, but here's where it gets a little weird: every last one of them were dead, and their tentacles missing. What could have caused this? At first the only explaination I could think up was that perhaps they die after breeding, and that their tentacles had been chewed off. Which, nonetheless, makes little sense to me. And seeing that a creature whose body is 97% water decays quite rapidly as it is, I wouldn't think that their tentacles just happened to rot away first. I supposed it's worth noting that, although varying in size, all of the dead jellyfish were of the same species. All other types of jellyfish I saw that day in the area were alive and intact. Any ideas?

I look after a pendulum clock at the University of Cambridge which I hope will achieve an accuracy of less than 1 second of error per year (www.trin.cam.ac.uk/clock). It has a temperature-compensated pendulum, but is sensitive to air pressure variation.

If the mean global temperature was to rise by, say, 4 °C, would there be any change to mean air pressure at sea level? Put simply, would global warming cause the clock to speed up or slow down?

Hugh Hunt, Keeper of the Clock, Trinity College, University of Cambridge, UK

Given that past temperatures have been both higher and lower than present levels and have increased rapidly in the past, for both longer and in greater amounts than at present, how is it possible to identify warming caused by humans.

DURING THE TIME UP TO SATS EXAMS THERE WAS A QUESTION ABOUT GLOBAL WARMING AND MELTING ICE CAPS.  IT SAID THAT AS THE CAPS SHRINK LEVELS WILL RISE BUT, I SAW IT AND THOUGHT FOR A BIT. ACCORDING TO ARCHIMEDES, THE LEVEL WOULD STAY THE SAME. THE CAPS WOULD MELT BUT, BECAUSE THEM MELTING WOULD RESULT IN LEVELS STAYING THE SAME WOULDN'T IT?  I TRIED THIS WITH A GLASS OF WATER AND AN ICE CUBE AND THE WATER DID NOT RISE. DOES ANYONE HAVE AN EXPLINATION OR IS IT JUST TOTAL RUBBISH?                                                                                                                                                                                                  Felix, 12 From Norwich

I have a very conservative relative who lives in FL.  She now believes that global warming is all a liberal conspiracy plot because the weather report announces snow sometime tonight or tomorrow (she's in Orlando).  I'd like to explain to her that these crazy and unusual weather occurrences are a consequence of global warming, but don't know how.  Please help!

Thanks

50 years ago at school we were told that "permafrost" is a remnant of the last Ice Age. At what rate is the permafrost decaying and how does it decay?

In my area the ground freezes to a depth of less than 1.5 meters. This sets the standards of how deep to bury utilities and by May the ground is generally frost free. In areas of permafrost the top layers generally melt and re freeze in the winter. The depth to which the ground freezes in this area evidently is quite deep. What is the minimum depth of sustainable permafrost, and what average temperature is required to maintain that?

Given that this temperature is likely to be considerably higher than that required to drive the frozen level down to the existing "deepest" levels one can speculate that the temperature is in fact changing. Given that the "edge" (both surface and depth) of permafrost is retreating, can one not create a time scale and projection of global temperature changes over a very long period. On this scale could one see the affect of the recent influx of green house gasses?

With talk of solar shades and other reflecting technologies, I wonder what impact - if any - existing materials have on global temperature.

With winter approaching and temperatures in the region of -10oC to -20oC expected, I want to know what the most effiecient way of heating my home is.

As I see it there are broadly two options, I can set my heating to, say, 17oC (while I`m out) and increasing to 21oC, 30 minutes before I return home. Or, I can let the house cool own more, to say 5oC through the day, using less energy, but then to return to 21oC I`ll burn more fuel.

So I repeat my question, what is the most efficient way of heating my house? I feel that this is of increased importance due to the impact of ineffiecient energy use and global warming.