I have a theory in Enemy of the World the 2nd Doctor meets his double Salamander a man who in 2018 came to power thanks to a famine caused by a environmental disaster and he took over the United Zones Organization. But here we are and not in that world well later in Inferno the Government was drilling to the Earth's crust for energy then the 3rd Doctor traveled to a parallel fascist Earth and saw the horrible effects the project will have on the Earth and stops it when he gets home. So it's possible that by stopping the drilling the Doctor could had stopped the events which lead to the environmental disasters in Enemy of the World and he stopped that future he once visited from coming to be.