ROME (Reuters) -Leaders of the Group of 20 major economies will say they aim to cap global warming at the 1.5 degrees Celsius level scientists say is vital to avoid disaster, but will largely avoid firm commitments, according to a draft statement seen by Reuters. The joint statement on the need for climate action reflects tough negotiations among diplomats as the leaders gathered for a two-day summit in Rome, but the draft details few concrete actions to limit carbon emissions. The statement also says the leaders recognised “the key relevance” of achieving net zero carbon emissions by the middle of this century.