Nov 3 (Reuters) - Hundreds of companies around the world have promised to cut carbon emissions, but the deadlines they have set are years away and it is hard to tell if it is enough. According to scientists at the United Nations, the world"s net emissions must drop to zero by 2050 to limit the rise in global temperature to no more than 1.5 degrees Celsius, compared with pre-industrial levels. Following is a gist of some of the targets set by global companies as world leaders and officials meet at the U.N. climate gathering in Scotland.GHG - Greenhouse gasesScope 1 - Direct emissionsScope 2 - Indirect emissionsScope 3 - Indirect emissions produced by co, products, supply chain