If I understand this correctly, though I am having to fill in a gap in Nnadir's comment, the accumulated environmental damage due to coal exceeds 10T as of today. Assuming that is the right interpretation of the claim, Nnadir then goes on to suggest using that amount (which you point out is 5 weeks of world GDP) not to repair the damage but to prevent future damage by replacing Nuclear with coal.

Can we please have an estimate of the external environmental cost, and the internal operating cost, per GW-h for coal [cleanest technology] and nuclear [cleanest technology] as well as the cost of replacing generating capacity from coal to nuclear [per GW-h]? That way we can begin to thimk about the time scales involved.

Those whom the Gods wish to destroy They first make mad. -- Euripides