Understanding the Differences Between TOA and Surface Energy Budget Attributions of Surface Warming

Sergio A Sejas,Hanjie Fan,Ming Cai,Xiaoming Hu

doi:10.3389/feart.2021.725816

Abstract

Energy budget decompositions have widely been used to evaluate individual process contributions to surface warming. Conventionally, the top-of-atmosphere (TOA) energy budget has been used to carry out such attribution, while other studies use the surface energy budget instead. However, the two perspectives do not provide the same interpretation of process contributions to surface warming, particularly when executing a spatial analysis. These differences cloud our understanding and inhibit our ability to shrink the inter-model spread. Changes to the TOA energy budget are equivalent to the sum of the changes in the atmospheric and surface energy budgets. Therefore, we show that the major discrepancies between the surface and TOA perspectives are due to non-negligible changes in the atmospheric energy budget that differ from their counterparts at the surface. The TOA lapse-rate feedback is the manifestation of multiple processes that produce a vertically non-uniform warming response such that it accounts for the asymmetry between the changes in the atmospheric and surface energy budgets. Using the climate feedback-response analysis method, we are able to decompose the lapse-rate feedback into contributions by individual processes. Combining the process contributions that are hidden within the lapse-rate feedback with their respective direct impacts on the TOA energy budget allows for a very consistent picture of process contributions to surface warming and its inter-model spread as that given by the surface energy budget approach.

Highlights

The Intergovernmental Panel on Climate Change (IPCC) Assessment Report (AR) five states that the warming of the climate system is unequivocal [IPCC, 2013]
Comparing TOA and Surface Perspectives dioxide (CO2), due to human activities (Hartmann et al, 2013). This anthropogenic increase in CO2 is the primary driver of the surface warming, which is corroborated by simple climate models and complex coupled global climate models demonstrating that increasing the CO2 concentration leads to a warming of the surface (Manabe and Wetherald 1975; Robock 1983; Washington and Meehl 1984; Schlesinger and Mitchell 1987; Manabe et al, 1991)
We show that the differences between the two methodologies are explained by non-negligible changes to the atmospheric energy budget

Summary

Introduction

The Intergovernmental Panel on Climate Change (IPCC) Assessment Report (AR) five states that the warming of the climate system is unequivocal [IPCC, 2013]. A particular emphasis has been placed in the climate literature on understanding the surface warming response to an increase of CO2, and understanding how the different climate feedbacks triggered by the CO2 increase contribute to the surface temperature response With this purpose in mind, many climate feedback analysis methods have been developed to attribute and understand the contributions of individual climate feedbacks to surface warming (Wetherald and Manabe 1988; Cess et al, 1996; Aires and Rossow 2003; Gregory et al, 2004; Soden et al, 2008; Lu and Cai 2009a; Lahellec and Dufresne 2013). The advantages and disadvantages of these methods have been previously discussed (Aires and Rossow 2003; Soden et al, 2004; Stephens 2005; Bony et al, 2006; Bates 2007; Cai and Lu 2009; Klocke et al, 2013; Lahellec and Dufresne 2013, 2014)

Objectives

Results

Conclusion