Global Warming Increases Earth’s Sensitivity to Greenhouse Gases

By SEAN DUFFY

(CN) – A warmer climate increases the planet’s sensitivity to changes in carbon dioxide levels, a factor that will likely come into play as average global temperatures continue to surge.

This relationship was tested by researchers who examined global mean temperatures and the Earth’s energy balance over nearly the last 800,000 years. In a study published Nov. 9, the scientists presented their analysis of reconstructions of past temperatures and carbon dioxide levels to demonstrate how changes in the planet’s energy balance dynamically affects the climate system.

The team used marine sediment cores, ice cores, and computer simulations to project the last eight glacial cycles, and extracted greenhouse gas concentrations from air bubbles in ice cores. The greenhouse gas concentrations were then incorporated with astronomical factors that affect the planetary heat budget to calculate the Earth’s energy balance over that period.

“Our results imply that the Earth’s sensitivity to variations in atmospheric carbon dioxide increases as the climate warms,” said lead author Tobias Friedrich. “The associated increased climate sensitivity needs to be taken into account for future projections of warming induced by human activities.”

Based on estimates of the Earth’s climate sensitivity, the team projects that by the year 2100, average global temperatures will rise about 10.5 degree Fahrenheit above pre-industrial values – if humans continue to produce greenhouse gas emissions at current levels.

This level of warming overlaps with the higher range of estimates presented by the Intergovernmental Panel on Climate Change, and far exceeds the 3.6 degrees Fahrenheit above pre-industrial averages that the 2015 Paris climate agreement was designed to avoid given the more severe weather events and overall damage the planet would begin to experience.

However, several studies have also shown that the collective global action expected as part of the Paris climate agreement is not sufficient to prevent the planet from warming to 3.6 degrees Fahrenheit above pre-industrial averages and experiencing the side effects, making Thursday’s findings even more significant.

The United States’ involvement in the Paris agreement is also in question after the election of President Donald Trump, whose campaign rhetoric suggested that he might be open to withdrawing or limiting the nation’s role in environmentally inspired greenhouse gas reduction and offsetting global climate change.

“The only way is to reduce greenhouse gas emissions as soon as possible,” Friedrich said.