I'd also like to point out, even if some countries kept using fossil fuels, other nations could be carbon negative to cancel out any emissions. Here is a TED talk about Bhutan for example.
https://www.ted.com/talks/tshering_...sn_t_just_carbon_neutral_it_s_carbon_negative
https://www.ted.com/talks/tshering_...sn_t_just_carbon_neutral_it_s_carbon_negative