I'd say the carbon footprint goes up more when Guinness ship to the UK, USA and Japan. They also tanker beer and have it sent to be bottled and canned in Belfast and in the UK.
It's an odd argument this as are you really saving carbon or money or whatever by producing everything locally?
Let's say there is one big brewery in the country and it acts as efficiently and as greenly as it can. Would it have less of a carbon footprint than a load of small regional breweries?
Maybe it would have less of a footprint as the supply trucks wouldn't have to deliver to loads of small breweries just one big one. They would use less water and be more able to put in steam recycling etc because of their size. The delivery of the product efficiently from one central location could be organized and a large brewery would be more able to afford green delivery vehicles. I could go on with more efficiencies of scale and process that a large brewery can have over a small one.
So the argument of small and local equals less of a carbon footprint might not be true. It's a commonly held view but I'm not sure it's actually true.