Empirical estimation of anthropogenic and natural contributions to surface air temperature trends at different latitudes

TL;DR

This study uses empirical models to quantify natural climate variability and anthropogenic influences on surface air temperature trends across different latitudes and time periods, highlighting the dominance of greenhouse gases over longer intervals.

Contribution

It provides an empirical estimation of natural and anthropogenic contributions to temperature trends using autoregressive models on observational data across multiple latitudes.

Findings

Natural climate modes significantly influence short-term temperature trends.

Greenhouse gases dominate temperature trends over longer periods.

Contributions vary by latitude and time interval.

Abstract

How strong are quantitative contributions of the key natural modes of climate variability and the anthropogenic factor characterized by the changes of the radiative forcing of greenhouse gases in the atmosphere to the trends of the surface air temperature at different latitudes of the Northern and Southern Hemispheres on various time intervals? Such contributions to trends are estimated here from observation data with the simplest empirical models. Trivariate autoregressive models are fitted to the data since the 19th century and used to assess the impact of the anthropogenic forcing together with different natural climate modes including Atlantic Multidecadal Oscillation, El-Nino / Southern Oscillation, Interdecadal Pacific Oscillation, Pacific Decadal Oscillation, and Antarctic Oscillation. For relatively short intervals of the length of two or three decades, we note considerable contributions of the climate variability modes which are comparable to the contributions of the greenhouse gases and even exceed the latter. For longer intervals of about half a century and greater, the contributions of greenhouse gases dominate at all latitudes as follows from the present analysis of data for polar, middle and tropical regions.