Comparing with other sites, it seems like the main component of this calculation is filesize. The homepage is about 300kB, depending on how many images happen to be on it. The biggest permanent component is the font file, which is 134kB and therefore contributes over a third of the CO2 prodcued by this homepage without actually contributing much to the function and usability of the site. Is the font file necessary? Perhaps I should switch back to using Arial? It's interesting how seemingly innocent design choices can have such an impact on the environment. For now it will stay as pretty much no one looks at this site.