Greenhouse gases fuelling long-term global warming

The Earth is known to be able to restore its temperature equilibrium after a period of natural warming. But the phenomenon tends to be overwhelmed locally by external drivers like greenhouse gases that can cause sustained changes in global temperature in the long run, a study has found.

Researchers at NASA's Jet Propulsion Laboratory in Pasadena, California, and Duke University in Durham, North Carolina, combined global climate models with satellite measurements of changes in the energy approaching and leaving the Earth at the top of the atmosphere over the past 15 years to study the human impacts on global temperatures in the long run.

The satellite data were from the Clouds and the Earth's Radiant Energy System (CERES) instruments on NASA's Aqua and Terra spacecraft.

Scientists have long known that as the Earth warms, it is able to restore its temperature equilibrium through a phenomenon known as the Planck Response.

The phenomenon is an overall increase in infrared energy that the Earth emits as it warms. The response acts as a safety valve of sorts, allowing more of the accumulating heat to be released through the top of the Earth's atmosphere into space.

"Our analysis confirmed that the Planck Response plays the dominant role in restoring global temperature stability, but to our surprise, we found that it tends to be overwhelmed locally by heat-trapping changes in clouds, water vapour, and snow and ice," said lead author Patrick Brown, a doctoral student at Duke's Nicholas School of the Environment.

"This study underscores that large, sustained changes in global temperature like those observed over the last century require drivers such as increased greenhouse gas concentrations," Brown added.

The study findings were published this month in the Journal of Climate.