Author Archives: niclewis

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 […]

Marvel et al.: Implications of forcing efficacies for climate sensitivity estimates – update

A guest article by Nicholas Lewis Introduction In a recent article I discussed the December 2015 Marvel et al.[1] paper, which contends that estimates of the transient climate response (TCR) and equilibrium climate sensitivity (ECS) derived from recent observations of changes in global mean surface temperature (GMST) are biased low. Marvel et al. reached this […]