Greenhouse gases like carbon dioxide and methane are increasing the average temperature of the planet. Some scientists have recently suggested that the pace of that change is increasing. Now a new study has provided support for that idea; this research has indicated that as levels of carbon dioxide increase in the atmosphere, the climate-warming effects of the gas become more potent. The findings have been reported in Science, and they emphasize the need for urgent action to reduce the release of greenhouse gases.
This study used computational models that focused on the stratosphere, a portion of the upper atmosphere that is known to cool down as carbon dioxide levels increase. This cooling effect then traps more heat in lower levels of the atmopshere, in a kind of positive feedback loop that boosts the heating impact of carbon dioxide.
It was thought that the amount of heating trapped by carbon dioxide, or radiative forcing, would increase consistently, and at a rate that would not change over time. This research has shown differently, and that, "radiative forcing is not constant but changes as the climate responds to increases in carbon dioxide," said Ryan Kramer, a physical scientist at the National Oceanic and Atmospheric Administration's (NOAA) Geophysical Fluid Dynamics Laboratory.
The researchers estimated that radiative forcing is increasing by around 25 percent every time atmospheric carbon dioxide levels double, and that since the preindustrial era, it has increased by around ten percent. The work also explains some discrepancies in previous models.
Climate model simulations created by The Coupled Model Intercomparison Projects (CMIP) were used in this work. They include coordinated experiments that have been performed by dozens of comprehensive climate models that support IPCC (Intergovernmental Panel on Climate Change) assessments. Other analytical models were also employed to confirm these conclusions.
Sources: Rosenstiel School of Marine, Atmospheric, and Earth Science; Science