Author Archives: niclewis

Brown and Caldeira: A closer look shows global warming will not be greater than we thought

A guest post by Nic Lewis Introduction Last week a paper predicting greater than expected global warming, by scientists Patrick Brown and Ken Caldeira, was published by Nature.[1]  The paper (henceforth referred to as BC17) says in its abstract: “Across-model relationships between currently observable attributes of the climate system and the simulated magnitude of future […]

Does a new paper really reconcile instrumental and model-based climate sensitivity estimates?

A guest post by Nic Lewis A new paper in Science Advances by Cristian Proistosescu and Peter Huybers “Slow climate mode reconciles historical and model-based estimates of climate sensitivity” (hereafter PH17) claims that accounting for the decline in feedback strength over time that occurs in most CMIP5 coupled global climate models (GCMs), brings observationally-based climate […]

The effect of Atlantic internal variability on TCR estimation – an unfinished study

A guest article by Frank Bosse (posted by Nic Lewis) A recent paper by the authors Stolpe, Medhaug and Knutti (thereafter S. 17) deals with a longstanding question: By how much are the Global Mean Surface Temperatures (GMST) influenced by the internal variability of the Atlantic (AMV/AMO) and the Pacific (PMV/PDO/IPO)? The authors analyze the […]

How dependent are GISTEMP trends on the gridding radius used?

A guest post by Nic Lewis Introduction Global surface temperature (GMST) changes and trends derived from the standard GISTEMP[1] record over its full 1880-2016 length exceed those per the HadCRUT4.5 and NOAA4.0.1 records, by 4% and 7% respectively.  Part of these differences will be due to use of different land and (in the case of […]

Was early onset industrial-era warming anthropogenic, as Abram et al. claim?

A guest post by Nic Lewis Introduction A recent PAGES 2k Consortium paper in Nature,[i] Abram et al., that claims human-induced, greenhouse gas driven warming commenced circa 180 years ago,[ii] has been attracting some attention. The study arrives at its start dates by using a change-point analysis method, SiZer, to assess when the most recent […]

Are energy budget TCR estimates biased low, as Richardson et al (2016) claim?

A guest post by Nic Lewis   Introduction and Summary In a recently published paper (REA16),[1] Mark Richardson et al. claim that recent observation-based energy budget estimates of the Earth’s transient climate response (TCR) are biased substantially low, with the true value some 24% higher. This claim is based purely on simulations by CMIP5 climate […]

Objective Bayesian parameter estimation: Incorporating prior information

A guest article by Nic Lewis Introduction In a recent article I discussed Bayesian parameter inference in the context of radiocarbon dating. I compared Subjective Bayesian methodology based on a known probability distribution, from which one or more values were drawn at random, with an Objective Bayesian approach using a noninformative prior that produced results […]

Marvel et al.: GISS did omit land use forcing

A guest article by Nic Lewis I reported in a previous post, here, a number of serious problems that I had identified in Marvel et al. (2015): Implications for climate sensitivity from the response to individual forcings. This Nature Climate Change paper concluded, based purely on simulations by the GISS-E2-R climate model, that estimates of […]

Bayesian parameter estimation: Radiocarbon dating re-examined

A guest article by Nic Lewis Introduction In April 2014 I published a guest article about statistical methods applicable to radiocarbon dating, which criticised existing Bayesian approaches to the problem. A standard – subjective Bayesian – method of inference about the true calendar age of a single artefact from a radiocarbon date determination (measurement) involved […]

Marvel et al. – Gavin Schmidt admits key error but disputes everything else

A guest article by Nicholas Lewis Introduction Gavin Schmidt has finally provided, at the GISS website, the iRF and ERF forcing values for a doubling of CO2 (F2xCO2) in GISS-E2-R, and related to this has made wholesale corrections to the results of Marvel et al. 2015 (MEA15). He has coupled this with a criticism at […]