Ned Nikolov & Karl Zeller: Exact Calculations of Climate Sensitivities Reveal the True Cause of Recent Warming

I’m delighted Ned Nikolov and Karl Zeller have chosen the Talkshop as the venue for the publication of this new open peer review paper on climate sensitivity. Scientific advance at the cutting edge has always been the most important aim of this blog, and I think this paper truly is an advance in our understanding of the climate system and the factors which support and modulate surface temperature on Earth and other rocky planets. 

The paper is mathematically rigorous, but is also accessible to everyone, thanks to Ned and Karl’s exemplary effort to fully explain their concepts and definitions in terms which can be understood by any interested reader who has some familiarity with the climate debate. Building on the bedrock of their 2014 and 2017 papers, this new work extends the applicability and validates the postulates of those previous papers by examining the causes of variability in planetary surface temperature and incorporating the previous findings in quantifying and deriving equations to model them. They find that Earth is sensitive to changes in cloud cover, which affects the amount of solar shortwave radiation reaching the surface, but not very sensitive to changes in Total Solar Irradiance arriving at the top of the atmosphere. They also find that the sensitivity to changes in CO₂ levels has been heavily overestimated by current climate models. They show that a doubling of atmospheric CO₂ concentration from 280 ppm to 560 ppm will cause an undetectable global warming of 0.004K.

A PDF of the paper can be downloaded here:  ECS_Universal_Equations.

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Exact Formulas for Estimating the Equilibrium Climate Sensitivity of Rocky Planets & Moons to Total Solar Irradiance, Absorbed Shortwave Radiation, Planetary Albedo and Surface Atmospheric Pressure.
Ned Nikolov, Ph.D. and Karl Zeller, Ph.D.
April, 2022

1. Introduction

The term “Equilibrium Climate Sensitivity” (ECS) has become a synonym for the steady-state response of global surface temperature to a modeled long-wave radiative forcing caused by a doubling of atmospheric CO₂ concentration with respect to an assumed pre-industrial level of 280 ppm. According to climate models based on the Greenhouse theory, an increase of atmospheric CO₂ from 280 ppm to 560 ppm would produce a net radiative forcing (i.e. an atmospheric radiant-heat trapping) of 3.74 W m^-2 (Gregory et al. 2004) resulting in a global surface warming between 2.5 K and 4.0 K with a central estimate of 3.0 K according to IPCC AR6 (see p. 11 in Climate Change 2021: The Physical Science Basis. Summary for Policymakers). This implies an average unit ECS of 3.0/3.74 = 0.8 K / (W m^-2) with a range of 0.67 ≤ ECS ≤ 1.07 K / (W m^-2). Contemporary climate science and IPCC Assessment Reports do not discuss global temperature sensitivities to changes in cloud albedo, absorbed solar radiation or total surface atmospheric pressure. Consequently, no equations have been derived/proposed thus far to calculate these sensitivities. Part of the reason is that variations of cloud albedo are typically viewed in modern climate science as internal feedback to a climatic change induced by external forcing such as increasing anthropogenic carbon emissions. This notion is based on the 19^th-Century Greenhouse theory (Arrhenius 1896) adopted by IPCC, which attributes most of the observed warming during the 20^th Century and especially over the past 40 years to rising atmospheric  CO₂ concentrations believed to trap outgoing long-wave radiation in the Earth’s troposphere and reduce the rate of surface infrared cooling to Space.

However, a plethora of studies published during the past 15 years have shown through both satellite and surface observations that the absorption of solar radiation by the Earth-atmosphere system has increased significantly since 1982 due to a decreased cloud cover/albedo, a phenomenon often referred to as “global brightening” (e.g. Goode & Pallé 2007; Wild 2009; Herman et al. 2013; Stanhill et al. 2014; Hofer et al. 2017; Pfeifroth et al. 2018; Pokrovsky 2019;  Delgado-Bonal et al. 2020; Dübal & Vahrenholt 2021;  Yuan et al. 2021).