There are a wide range of potential climate change scenarios. The upper extremes of temperature increase (6 celsius) pose major challenges for humanity within the century, due to food shortages (droughts, changing growing seasons, collapsing fish stocks), flooded cities, and the social upheaval & wars that likely accompany catastrophic changes. The lower range of temperature change (1.5 celsius) suggest difficulties, perhaps even major ones, especially for poorer nations. Read the most recent IPCC report for more detail: https://www.ipcc.ch/sr15/. The important thing is to work on two fronts: reduce greenhouse gas emissions and begin planning for crises.