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"You take a million, billion tonnes of flaming inferno and turn it into 'twinkle, twinkle little star' ..."

Thu, 18 Jun 2009

Maps and Coastlines in Debian

As mentioned before, I've started working on Debian Meteorology, adding "standard" meteorology-related packages to Debian. Part of the aim of this is to jump-start an effort of integrating the FLOSS in the field: all the usual libraries that people working in the field use and expect to be on the supercomputers and workstations they use.

So, two packages I've been working on are Magics++ and zyGrib, which are plotting and visualisaton tools. respectively. So they both contain coastline maps of the world. Digging deeper shows they use the same files : a binary database called 'GSHHS', or Global Self-consistent Hierarchical High-resolution Shorelines. Some scope for integration here.

So, I start investigating GSHHS in order to create a 'coastline data' package to be shared. It turns out that building GSHHS depends on GMT, the Generic Mapping Tools, already present in Debian, and this coastline issue has been explored before, and a package gmt-coast-low created.

"gmt-coast-low" is 5.5 MB in size, and as its name suggests, there was once a "gmt-coast-high", but this has since been dropped for taking up too much space in the Debian archive (in its place, a script which will download this data for you has been created. But the files in gmt-coastline-low are in netCDF rather than GSHHS's own binary format; what to do? Posting a mail for help and it turns out that another package is being considered, Basemap, an add-on for Mathplotlib, that also includes the GSHHS data.

I've summarized the files, sizes and versions here in the Debian Wiki. Offhand it appears that there is scope for re-adding a gmt-coastline-high package (with perhaps additional small datafiles on states boundaries, etc. seen in Basemap), though some questions remain:

  • Is 170 MB of arch-independent data too much these days in the Debian archive, especially since it appears at least 4 packages can use it ?
  • It seems that some packages would need to be patched to bring them up to date with the latest format version for the database. What format should the data be in, this special binary format (quite simple) or netCDF ?

Tue, 31 Mar 2009

With Speed and Violence: Why Scientists fear Tipping Points in Climate Change, by Fred Pearce

I bought With Speed and Violence: Why Scientists fear Tipping Points in Climate Change to investigate the concept of tipping points in climate change: how real are they, and what ones might exist. A lot of points are labelled 'tipping points', such as the melting of the Arctic; but, if we successfully reduced CO2 to pre-industrial levels, would they revert, or would we have passed a point of no return?

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Mon, 08 Dec 2008

Storm World: Hurricanes, Politics and the Battle over Global Warming

Storm World, by Chris Mooney is an account of the development of the science of Hurricanes and their links to Global warming, against the background of Katrina and the politics of global warming.

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Fri, 02 May 2008

CO2 reconsidered

Just up on arxiv.org this week appeared Warming the early Earth - CO2 considered, by von Paris et al.. Just a preprint, and i'm working through its 53 pages now, put its likely to put the cat among the pidgeons:

Abstract: Despite a fainter Sun, the surface of the early Earth was mostly ice-free. Proposed solutions to this so-called "faint young Sun problem" have usually involved higher amounts of greenhouse gases than present in the modern-day atmosphere. However, geological evidence seemed to indicate that the atmospheric CO2 concentrations during the Archaean and Proterozoic were far too low to keep the surface from freezing. With a radiative-convective model including new, updated thermal absorption coefficients, we found that the amount of CO2 necessary to obtain 273 K at the surface is reduced up to an order of magnitude compared to previous studies. For the late Archaean and early Proterozoic period of the Earth, we calculate that CO2 partial pressures of only about 2.9 mb are required to keep its surface from freezing which is compatible with the amount inferred from sediment studies. This conclusion was not significantly changed when we varied model parameters such as relative humidity or surface albedo, obtaining CO2 partial pressures for the late Archaean between 1.5 and 5.5 mb. Thus, the contradiction between sediment data and model results disappears.

The suspected composition of the eary Earth (the Archean, when life is believed to have started, 3.8 to 2.5 billion years ago), has alternated between CO2 and other reducing gases, such as methane.

Originally CO2 was thought to be the main greenhouse gas, making life possible. However the high CO2 levels required were a problem; high CO2 levels would have created siderite (FeCO3) in the top layers of soil as iron interacted with CO2 in the oxygen-free air. Since then methane has top billing as the greenhouse gas responsible, with significant hydrogen levels a possibility. Over time, methane has come out on top. And thats what I wrote when I did my literature review for my PhD. Now I'm tidying it up a bit, and that section may be in for a rewrite.

But what does it mean for our Climate change models of today?