I find it difficult to reconcile the 1.2% GDP figure with this part: "The estimated $54 trillion in damage from 2.7 degrees of warming would grow to $69 trilli

I find it difficult to reconcile the 1.2% GDP figure with this part: "The estimated $54 trillion in damage from 2.7 degrees of warming would grow to $69 trillion if the world continues to warm by 3.6 degrees and beyond, the report found, although it does not specify the length of time represented by those costs." World GDP is currently $78 trillion, so the total cost of climate change is about 1 year's worth of ecenomic output. Perhaps the report is spreading this cost over 80 years to arrive at the 1.2% figure?