Climate sensitivity of Earth to solar irradiance: update

TL;DR

This study updates the Earth's climate sensitivity to solar irradiance using recent data, revealing higher sensitivity than no-feedback models and identifying feedback mechanisms and response times.

Contribution

It introduces new dynamic and non-radiative flux factors in sensitivity analysis and compares observed feedback effects with climate model assumptions.

Findings

Sensitivity is about twice that of no-feedback models, indicating positive feedback.

Volcano forcing shows evidence of negative feedback.

Response times are fractions of a year, much shorter than climate model assumptions.

Abstract

This paper is a continuation of a study by Douglass and Clader. We extend the analysis through December 2003 using the latest updates of the observational temperature and solar irradiance data sets in addition to a new volcano proxy data set. We have re-determined the solar effect on the temperature from satellite measurements of the solar irradiance and the temperature of the lower troposphere the sensitivity to solar irradiance. This re-analysis calculates two newly recognized dynamic and non-radiative flux factors which must be applied to the observed sensitivity. The sensitivity is about twice that expected from a no-feedback Stefan-Boltzmann radiation balance model, which implies positive feedback. The sensitivity to volcano forcing is also determined. Preliminary results indicate that negative feedback is present in this case. Response times of fractions of a year are found for both solar and volcano forcing. We note that climate models generally assume relaxation times of 5 to 10 years and we comment on the consequences of this large disparity. We also have determined a linear trend in the data.