I'm curious why you think this might be significant. All global root server traffic amounts to < 1gbps. Under contrived conditions you could easily serve it all from a single laptop computer, but even if we assume that realistically it's being served by a large, distributed collection of servers each drawing ~250 W continuously and each housed in one of those ridiculous corporate datacenters with a PUE over 2.0, you're still looking at a global energy cost comparable to one tankful of motor fuel per day, or much less than the energy used by one single commercial airplane.