Arctic Sea Ice and the Mean Temperature of the Northern Hemisphere

TL;DR

This study quantifies the impact of Arctic sea ice loss on Northern Hemisphere temperature rise over six decades, highlighting a significant contribution of sea ice retreat to global warming beyond greenhouse gases alone.

Contribution

It provides a simple model estimating the specific effect of Arctic sea ice loss on temperature increase, emphasizing its larger role compared to greenhouse gases.

Findings

Sea ice loss accounts for approximately 0.7°C of warming.

Greenhouse gases contribute about 0.2°C of warming.

Temperature response to sea ice loss has a 10-20 year delay.

Abstract

The importance of snow cover and ice extent in the Northern Hemisphere was recognized by various authors leading to a positive feedback of surface reflectivity on climate. In fact, the retreat of Arctic sea ice is accompanied by enhanced solar input in the Arctic region, i.e. a decrease of the terrestrial albedo. We have studied this effect for the past six decades and estimate the corresponding global warming in the northern hemisphere. A simple 1-dimensional model is used that includes the simultaneous increase of the greenhouse gases. Our results indicate that the latter directly cause a temperature rise of only 0.2 K in 1955 to 2015, while a notably larger effect 0.7 +/- 0.2 K is found for the loss of Arctic sea ice in the same time. These numbers comprise most of the reported mean temperature rise of 1.2 +/- 0.2 K of the northern hemisphere. The origin of the sea-ice retreat is discussed, e.g. internal variability or feedback by the CO2 concentration increase. Our data also suggest a delayed response of the global surface temperature rise to the loss of sea ice with a time constant of approximately 10 to 20 years.