Grabbed from comments in a blog, here http://www.jonfr.com/volcano/?p=969:
http://www.ruv.is/frett/ekkert-akvedid-um-folksflutninga
According to the article, 2000 tons are being ejected every second. That’s approximately 700 cu m per second, 2,500,000 per hour and 60,000,000 per day. A guesstimate based on this would be a total of about 150,000,000 – 200,000,000 cu m (0,15 – 0,20 cu km), a comfortable VEI 4 and more than the entire output of Eyjafjallajökull in a little over 48 hours.