Is net zero by 2050 possible?

Countries, states and companies have pledged to get their greenhouse gas emissions to net zero by 2050. What technologies, policies and investments would this require? Is it likely to be achieved? If not, is there a more achievable target? Dr. Melissa Lott, Sen Dir of Research, Center on Global Energy Policy, Columbia University SIPA., and Terry Keeley, Managing Director at BlackRock, discuss.