A new study estimates that the projections used for establishing the emissions targets for the Paris Agreement could have been too conservative.
- A new study says global-warming projections for the end of the century could be up to 15% higher than previously thought.
- The authors found that the climate models that best represented the current situation showed the most warming in the future.
The world may be a lot hotter by the end of the century than scientists previously thought.
That's according to a new study in the journal Nature, which predicts that global warming by the year 2100 could be up to 15% higher than the highest projections from the Intergovernmental Panel on Climate Change (IPCC).
The study's authors, Patrick Brown and Ken Caldeira, from the Carnegie Institution for Science in California, estimate the steepest emissions scenario will lead the planet be 0.5 degrees Celsius warmer than the IPCC projections, which were the numbers used to formulate the Paris agreement.
The authors also reduced the uncertainty of the IPCC's projections by a third.
Scientists use climate modeling to predict future warming based on estimates of how much greenhouse gas humans spew into the atmosphere, and what its effects will be over time. But models aren't always perfect. The study's authors note that there is sometimes a discrepancy between what the models say and what scientists actually observe happening in the atmosphere.
For their calculations, Brown and Caldeira analyzed the Earth's current energy budget — the absorption and re-emission of radiation from sunlight in the Earth's atmosphere — and input that data into a number of different climate models.
The authors found that if humans keep pumping greenhouse gases like carbon dioxide and methane into the atmosphere unabated, the world could wind up 15% warmer than the previous high estimate.
When climate models are constrained by what scientists actually observe, the authors said, they generally project more warming. The models that most accurately reflect today's climate therefore tend to be the ones that predict the most warming by the end of the century.
Under the Paris agreement, which was created almost exactly two years ago, 195 countries set a goal to limit global warming to 2 degrees Celsius above pre-industrial levels by cutting emissions. President Donald Trump has since vowed to withdraw the US from the agreement, though that process will take years.
This new research suggests humans will probably have to reduce emissions even more steeply to avoid crossing the thresholds agreed to in Paris.