Convert from uncia [Rome] to gigatonne

Unit Definition (uncia [Rome])
The uncia is the Roman ounce, equal to about 27.2875 grams of 0.9625 ounce avoirdupois. There were 12 ounces in a Roman pound, and the word uncia means a 12th part; its name gives us the ounce, of course, and also the inch.

Unit Definition (gigatonne)
The gigatonne is a metric unit of mass or weight equal to one billion metric tons (tonnes) or about 2.2046 trillion pounds. This very large unit is used, for example, in discussing the amounts of carbon added to the atmosphere by human activities.