Hi Marc,
yes, see what Carl suggested, though this might not always help. I realized Yahoo is very inconsistent and this method simply works for some, and not for others (as far as I can see - randomly...).
In such case, use the URL you used for the previous version which worked. If you just change the URL from your backed up header.php from previous Meteotemplate version and copy that URL to the new header.php it will work.
If still not, then let me know and I will look at your particular location and try to determine a URL which you would then hard-code in your header.php.
With regards to CO2, I am not sure I understand exactly what the problem is