date: Fri, 16 Jul 2004 11:07:05 +0100 from: Sarah Raper subject: Re: next to: Tom Wigley On 15 Jul 2004, at 13:41, Tom Wigley wrote: > Sarah, > > I will cover the new points and add the refs. They are > important in case we get some of these authors as > reviewers. It is hard to add text specifically to knock > the TAR method. One problem is that it should be > a differential equation at the outset. My addition changes > it to a differential equation -- but in a rather roundabout > way. The reason that the TAR method is OK is that > if the time scale is >> 100 years (as it seems to be) then > the d/dt term drops out. Praps I can add a little bit about > this at the end. > > What is annoying to me is that the TAR method is > conceptually flawed and it happens to work not becoz of > cleverness and forward thinking by Jonathan, but by a > fluke. > > Oh well. EXACTLY! As you say never mind. > > Jane Leggett, who is funding some of my MAGICC work, > wondered about sensitivity proportional to remaining > V instead of A. To test this I can use proporional to V**n > for different 'n'.. Then we could cite the J. Glac. paper too. > This is only one line of code. > > What 'n' range? I used this but the better reference is probably Bahr, D. B., Meier, M.F., and Peckham, S.D.;1997 The Physical Basis of Glacier Volume-Area scaling. J. Geophys. Res 102 20355-20362. From memory they find V=A**alfa where alfa is 1.36 for glaciers and 1.25 for icecaps. The original data for the glacier part comes from Ohmura and Chen I will try to send you the graph and if I can get the pdf I will also send you that. In the J. Glac paper I used 1/1.36 = 0.735 in A=V**0.735. FOR GLACIER Will look in paper for n range but for this purpose we combine glacier and icecaps don't we. > > Here is what I said to Jane ..... > > ------------------ > >> The linear with volume vs linear with area is something I will look >> into. There >> is a paper that Sarah is first author on in J. Glaciology a few years >> back where >> we note that one can use A = V**n. I can put this in the code to see >> the >> sensitivity to 'n'. My intuition says it will be small. To 2100, >> volume has no >> effect, so 'n' cannot be important. For large times the paths must >> tend to the >> initial volume, so 'n' can have no effect there either. Still, it is >> easy to do the >> full sums to check this out. Good point. > > > ---------------------------- > > Tom. > >