Oceans could reduce that figure a bit. Carbon naturally captured and stored in the deep ocean could cut committed warming by 0.4 degrees F (0.2 C).
There is some risk that warming this century cannot be kept to 1.5 degrees C beyond pre-industrial temperatures. In fact, there is a 13 percent chance we are already committed to 1.5-C warming by 2100.
"Our estimates are based on things that have already happened, things we can observe, and they point to the part of future warming that is already committed to by past emissions," said Mauritsen. "Future carbon dioxide emissions will then add extra warming on top of that commitment."
Materials provided by University of Colorado at Boulder. Note: Content may be edited for style and length.