Author Archives: niclewis

T cell cross-reactivity and the Herd immunity threshold

By Nic Lewis

An interesting new paper by Marc Lipsitch and co-authors, “Cross-reactive memory T cells and herd immunity to SARS-CoV-2”, has recently been published.[1] It discusses immunological and epidemiological aspects and implications of pre-existing cross-reactive adaptive immune system memory arising from previous exposure to circulating common cold coronaviruses. They argue that key potential impacts of cross- reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. I believe that they are mistaken on the herd immunity point, as I will show in this article. Continue reading

Herd immunity to COVID-19 and pre-existing immune responses

By Nic Lewis

I showed in my May 10th article Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. Continue reading

COVID-19: evidence shows that transmission by schoolchildren is low

By Nic Lewis

Much fuss has been made in the UK, not least by teachers’ unions, about recommencing physical school attendance. As this issue applies to many countries, I thought it worth highlighting research findings in Europe. Continue reading

New paper suggests historical period estimates of climate sensitivity are not biased low by unusual variability in sea surface temperature patterns

By Nic Lewis

An important new paper by Thorsten Mauritsen, Associate Professor at Stockholm University[i] and myself has just been accepted for publication (Lewis and Mauritsen 2020)[ii]. Its abstract reads: Continue reading

Emergent constraints on TCR and ECS from historical warming in CMIP5 and CMIP6 models

By Nic Lewis

This is a brief comment on a new paper[i] by a mathematician in the Exeter Climate Systems group, Femke Nijsse, and two better known colleagues, Peter Cox and Mark Williamson. I note that Earth Systems Dynamics published the paper despite one of the two peer reviewers recommending against acceptance without further major revisions. But neither of the reviewers appear to have raised the issue that I focus on here. Continue reading

Why herd immunity to COVID-19 is reached much earlier than thought – update

By Nic Lewis

I showed in my May 10th article Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. I opined, based on my modelling, that the HIT probably lay somewhere between 7% and 24%, and that evidence from Stockholm County suggested it was around 17% there, and had been reached. Mounting evidence supports my reasoning.[1]

I particularly want to highlight an important paper published on July 24th “Herd immunity thresholds estimated from unfolding epidemics” (Aguas et al.).[2] The author team is much the same as that of the earlier theoretical paper (Gomes et al.[3]) that prompted my May 10th article. Continue reading

The progress of the COVID-19 epidemic in Sweden: an analysis

By Nic Lewis

The course of the COVID-19 pandemic in Sweden is of great interest, as it is one of very few advanced nations where no lockdown order that heavily restricted people’s movements and other basic freedoms was imposed. As there has been much comment, some of it ill-informed, on how the COVID-19 epidemic has developed in Sweden, but relatively little detailed analysis published in English, it is worth exploring what their excellent publicly-available data reveal. Continue reading

Did lockdowns really save 3 million COVID-19 deaths, as Flaxman et al. claim?

By Nic Lewis

Key points about the recent Nature paper by Flaxman and other Imperial College modellers

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When does government intervention make sense for COVID-19?

By Nic Lewis

Introduction

I showed in my last article that inhomogeneity within a population in the susceptibility and infectivity of individuals would reduce the herd immunity threshold, in my view probably very substantially, and that evidence from Stockholm County appeared to support that view. In this article I will first provide other evidence pointing to such population inhomogeneity being very considerable. I will then go on to consider how the overshoot of infections beyond the herd immunity threshold could be reduced. Continue reading

Why herd immunity to COVID-19 is reached much earlier than thought

By Nic Lewis

Introduction

A study published in March by the COVID-19 Response Team from Imperial College (Ferguson20[1]) appears to have been largely responsible for driving government actions in the UK and, to a fair extent, in the US and some other countries. Until that report came out, the strategy of the UK government, at least, seems to have been to rely on the build up of ‘herd immunity’ to slow the growth of the epidemic and eventually cause it to peter out. Continue reading

A sensible COVID-19 exit strategy for the UK

By Nic Lewis

The current approach

A study by the COVID-19 Response Team from Imperial College (Ferguson et al. 2020[i]) appears to be largely responsible for driving UK government policy actions. The lockdown imposed in the UK appears, unsurprisingly, to have slowed the growth of COVID-19 infections, and may well soon lead to total active cases declining. However, it comes at huge economic and social costs, and substantial COVID-19-unrelated health costs.

Worse, the lockdown is merely a holding strategy, which offers no long term solution to the COVID-19 problem. The eventual total number of deaths for COVID-19 are not reduced relative to any less restrictive policy that likewise avoided the health system being overwhelmed. Deaths are merely spread over a longer period, assuming that eventually restrictions are lifted and people’s lives return to normal. Continue reading

Imperial College UK COVID-19 numbers don’t seem to add up

By Nic Lewis

Introduction and summary

A study published two weeks ago by the COVID-19 Response Team from Imperial College (Ferguson20[1]) appears to be largely responsible for driving UK government policy actions. The study is not peer reviewed; indeed, it seems not to have been externally reviewed at all. Moreover, the computer code used to produce the estimates in the study – which on Ferguson’s own admission is old, unverified and documented inadequately, if at all – has still not been published. That, in my view, shows a worrying approach to a matter of vital public concern.

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COVID-19: Updated data implies that UK modelling hugely overestimates the expected death rates from infection

By Nic Lewis

Introduction

There has been much media coverage about the danger to life posed by the COVID-19 coronavirus pandemic. While it is clearly a serious threat, one should consider whether the best evidence supports the current degree of panic and hence government policy. Much of the concern in the UK resulted from a non-peer reviewed study published by the COVID-19 Response Team from Imperial College (Ferguson et al 2020[1]). In this article, I examine whether data from the Diamond Princess cruise ship – arguably the most useful data set available – support the fatality rate assumptions underlying the Imperial study. I find that it does not do so. The likely fatality rates for age groups from 60 upwards, which account for the vast bulk of projected deaths, appear to be much lower than those in the Ferguson et al. study. Continue reading

Comment by Cowtan & Jacobs on Lewis & Curry 2018 and Reply: Part 2

By Nic Lewis

In an earlier article here I discussed a Comment on Lewis and Curry 2018 (LC18) by Kevin Cowtan and Peter Jacobs (CJ20), and a Reply from myself and Judith Curry recently published by Journal of Climate (copy available here). I wrote that I would defer dealing with the differences between observed and CMIP5 model-simulated historical warming, which formed the basis of CJ20’s numerical analysis, until a subsequent article. I now do so. Continue reading

Comment by Cowtan & Jacobs on Lewis & Curry 2018 and Reply: Part 1

By Nic Lewis

A comment on LC18 (recent paper by Lewis and Curry on climate sensitivity)  by Cowtan and Jacobs has been published, along with our response.

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Gregory et al 2019: Unsound claims about bias in climate feedback and climate sensitivity estimation

By Nic Lewis

The recently published open-access paper “How accurately can the climate sensitivity to CO2 be estimated from historical climate change?” by Gregory et al.[i] makes a number of assertions, many uncontentious but others in my view unjustified, misleading or definitely incorrect.

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Resplandy et al. Part 5: Final outcome

By Nic Lewis

The editors of Nature have retracted the Resplandy et al. paper.

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Is ocean warming accelerating faster than thought?

by Nic Lewis

*** UPDATE : response to comments by Zeke Hausfather appended

There are a number of statements in Cheng et al. (2019) ‘How fast are the oceans warming’, (‘the paper’) that appear to be mistaken and/or potentially misleading. My analysis of these issues is followed by a reply from the paper’s authors.

Contrary to what the paper indicates:

  • Contemporary estimates of the trend in 0–2000 m depth ocean heat content over 1971–2010 are closely in line with that assessed in the IPCC AR5 report five years ago
  • Contemporary estimates of the trend in 0–2000 m depth ocean heat content over 2005–2017 are significantly (> 95% probability) smaller than the mean CMIP5 model simulation trend.

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Climate sensitivity to cumulative carbon emissions

By Nic Lewis

An observational estimate of transient (multidecadal) warming relative to cumulative CO2 emissions is little over half that per IPCC AR5 projections.

AR5 claims that CO2-caused warming would be undiminished for 1000 years after emissions cease, but observations indicate that it would halve. Continue reading

Resplandy et al. Part 4: Further developments

By Nic Lewis

There have been further interesting developments in this story Continue reading

Resplandy et al. Part 3: Findings regarding statistical issues and the authors’ planned correction

By Nic Lewis

Introduction

The Resplandy et al. (2018) ocean heat uptake study (henceforth Resplandy18) is based on measured changes in the O2/N2 ratio of air sampled each year, compared to air stored in high pressure tanks originally sampled in the late 1980s and early 1990s, and in atmospheric CO2 concentration. These are combined to produce an estimate (ΔAPOObs) of changes in atmospheric potential oxygen since 1991 (ΔAPO). They break this series down into four components, including one attributable to ocean warming (ΔAPOClimate). By estimating the other three, they isolate the implied ΔAPOClimate and use it to estimate the change in ocean heat content. In two recent articles, here and here, I set out why I thought the trend in ΔAPOClimate – from which they derived their ocean heat uptake estimate – was overstated, and its uncertainty greatly understated. Continue reading

Resplandy et al. Part 2: Regression in the presence of trend and scale systematic errors

by Nic Lewis

In a recent article I set out why I thought that the trend in ΔAPOClimate was overstated, and its uncertainty greatly understated, in the Resplandy et al. ocean heat uptake study. In this article I expand on the brief explanation of the points made about “trend errors” and “scale systematic errors” given in my original article, as these are key issues involved in estimating the trend in ΔAPOClimate and its uncertainty.

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A major problem with the Resplandy et al. ocean heat uptake paper

by Nic Lewis

Obviously doubtful claims about new research regarding ocean content reveal how unquestioning Nature, climate scientists and the MSM are. Continue reading

Remarkable changes to carbon emission budgets in the IPCC Special Report on Global Warming of 1.5C

by Nic Lewis

A close reading of Chapters 1 and 2 of the IPCC Special Report on Global Warming of 1.5°C (SR15) reveals some interesting changes from the IPCC 5th Assessment Report (AR5), and other science-relevant statements. This article highlights statements in SR15 relating to carbon emission budgets for meeting the 1.5°C and 2°C targets.

It seems fairly extraordinary to me that the AR5 post-2010 carbon budget for 1.5°C, which was only published four years ago, has in effect been now been increased by ~700 GtCO2 – equal to 21st century emissions to date – despite SR15’s projections of future warming being based very largely on the transient climate response to cumulative emissions (TCRE) range exhibited by the models used in AR5. Continue reading

Warming patterns are unlikely to explain low historical estimates of climate sensitivity

By Nic Lewis

A critique of of a new paper by Andrews  et al., Accounting for changing temperature patterns increases historical estimates of climate sensitivity.

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