Glad to hear it was useful! George said there were 10 OWLs available to borrow from the Transition group, so shouldn't be hard to get hold of one. I lent mine to David Till. Your questions had me thinking! We all have a long way to go to get to 20% CO2 of 1990 levels, let alone zero! Think of it as 3% reduction per year till 2050. Part of that can be better technology, part lifestyle choice. All the best. Nick