Anthropogenic contributions to slow warming over 1998-2012

TL;DR

This study quantifies the relative impacts of natural variability and human factors on the slower global warming observed from 1998 to 2012, highlighting the significant role of human activities in climate change dynamics.

Contribution

It provides a comprehensive analysis of all relevant climate forcers during 1998-2012 using models, revealing the specific contributions of natural variability and human influences.

Findings

La Nina cooling contributed ~50% to warming slowdown

Solar cycle decline contributed ~26% to slowdown

Reduced ozone-depleting substances and methane explained about 25% of the slowdown

Abstract

The observed global mean surface temperature increase from 1998 to 2012 was slower than that since 1951. The relative contributions of all relevant factors including climate forcers, however, have not been comprehensively analyzed. Using a reduced-complexity climate model and an observationally constrained statistical model, we find that La Nina cooling and a descending solar cycle contributed approximately 50% and 26% of the total warming slowdown during 1998-2012 compared to 1951-2012. Furthermore, reduced ozone-depleting substances and methane accounted for roughly a quarter of the total warming slowdown, which can be explained by changes in atmospheric concentrations. We identify that human factors played an important role in slowing global warming during 1998-2012, shedding light on the evidence for controlling global warming by reducing greenhouse gas emissions.