Confused about the new IPCC's carbon budget? So am I.

When the IPCC's new report on the physical basis of climate change was released in late September, media attention focused on a conclusion from the Summary for Policymakers that the world had emitted just over half of the allowable emissions if global warming is to be kept to 2 degrees Celsius (2°C) of warming. Unfortunately, because many people think if you have a budget you should spend every last dollar, the "carbon budget" message could be interpreted as saying there is plenty of budget left to spend. The respected climate researcher Ken Caldeira told Climate Progress that the carbon budget concept is dangerous for two reasons: