According to
this article , worldwide statistics are hard to come by. You will note the following:
The OIV produces the best overall statistics on the worldwide wine situation. Unfortunately they are currently two years old, and their accuracy varies, depending on the thoroughness of the country that reported them. One thing that is missing is solid varietal information. Since many countries do not track varietals, currently neither does OIV.
Nevertheless, the article includes some links that might help you. The link to the OIV is
here.