According to researchers from the University of Colorado Boulder, even if we magically stop emitting all greenhouse gasses right now, the Earth is still on course to warm by at least 1.3°C (2.3°F).
The finding comes from a sophisticated new analysis, published in Nature Climate Change, that shows we might already be on course to significant warming by the end of the century – beyond the target set during the Paris climate agreement. The new work is not based on any prediction models, simply on what’s currently in the atmosphere.
“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 Thorsten Mauritsen, from the Max Planck Institute for Meteorology, in a statement. "Future carbon dioxide emissions will then add extra warming on top of that commitment.”
The researchers' estimates include the amount of carbon dioxide in the atmosphere, the capacity of the oceans to absorb carbon, and the effect of fine dust particles in reflecting or absorbing light. Their analysis also shows how the oceans could help reduce carbon dioxide in the atmosphere, cutting warming by 0.2°C (0.4°F).
This is, of course, on the assumption that things won’t change in the future. For example, if emission rates continue at the current level for the next 15 years, we are likely going to see a 1.5°C (2.7°F) increase. The study suggests there’s already a one-in-eight chance that this will happen.
Obviously, things might change for the better or worse. Models based on economic factors, population growth, and carbon usage are a lot bleaker. Another study published in Nature Climate Change suggests that the likelihood that we can actually keep the temperature below 2°C (3.6°F) is around 5 percent.
“This ‘committed warming’ is critical to understand because it can tell us and policymakers how long we have, at current emission rates, before the planet will warm to certain thresholds,” added co-author Robert Pincus, a scientist with the Cooperative Institute for Research in Environmental Sciences. “The window of opportunity on a 1.5-degree[C] target is closing.”
The Paris climate agreement is a cooperative effort by nations around the world to stop global temperatures rising beyond 2°C, with efforts to keep it under 1.5°C. Policymakers need to be willing to curb emission much faster if we want to achieve that goal.