Climate scientists are struggling to find the right words for very bad news

When they can’t agree, they form “contact groups” outside the hall, trying to strike an agreement and move the process along. They are trying to reach consensus on what it would mean — and what it would take — to limit the warming of the planet to just 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, when 1 degree Celsius has already occurred and greenhouse gas emissions remain at record highs. “It’s the biggest peer-review exercise there is,” said Jonathan Lynn, head of communications for the United Nations' Intergovernmental Panel on Climate Change. “It involves hundreds or even thousands of people looking at it.”