On the Warming of the Southern Hemisphere since 1955 and Recent Slowing-Down: Role of Sea Ice, Sun Spot and El Nino Variability

TL;DR

This study estimates the impact of sea ice retreat, solar variability, and El Nino on Southern Hemisphere warming since 1955, highlighting the role of ice-albedo feedback and recent slowdown in temperature increase.

Contribution

It provides a semi-quantitative model estimating the ice-albedo feedback's contribution to SH warming and links solar and El Nino variability to temperature fluctuations.

Findings

Ice-albedo feedback contributed approximately 0.5 K to warming from 1955-2015.

Greenhouse gases contributed about 0.2 K to the same period.

Recent slowdown in temperature increase is predicted to continue, reducing future warming rate by 33%.

Abstract

The importance of the sea ice retreat in the polar regions for the global warming and the role of ice-albedo feedback was recognized by various authors [1,2]. Similar to a recent study of the phenomenon in the Arctic [3] we present a semi-quantitative estimate of the mechanism for the Southern Hemisphere (SH). Using a simple model, we estimate the contribution of ice-albedo feedback to the mean temperature increase in the SH to be 0.5 +/- 0.1 K in the years 1955 to 2015, while from the simultaneous growth of the greenhouse gases (GHG) we derive a direct warming of only 0.2 +/- 0.05 K in the same period. These numbers are in nice accordance with the reported mean temperature rise of 0.75 +/- 0.1 K of the SH in 2015 since 1955 (and relative to 1880). Our data also confirm previously noticed correlations between the annual fluctuations of solar intensity and El Nino observations on the one hand and the annual variability of the SH surface temperature on the other hand. Our calculations indicate a slowing down of the temperature increase during the past few years that is likely to persist. Assuming a continuation of the present trends for the southern sea ice and GHG concentration we predict the further temperature rise to decrease by 33 % in 2015 to 2025 as compared to the previous decade.