Category Archives: Sensitivity & feedbacks

Committed warming and the pattern effect

Posted on January 19, 2021 by niclewis | 52 comments

By Nic Lewis

A critique of the paper “Greater committed warming after accounting for the pattern effect”, by Zhou, Zelinka, Dessler and Wang. Continue reading →

Posted in Sensitivity & feedbacks

Disconnect in the relationship between GMST and ECS

Posted on November 11, 2020 by curryja | 142 comments

by Kenneth Fritsch

Abstract. An analysis is presented of he disconnection between the CMIP5 and CMIP6 Historical and Future periods when considering the relationship of the individual model GMST changes and the climate sensitivity. I have included a simple model that can account for the period disconnection using the negative forcing of aerosol/cloud effects in the Historical period that is carried forward into the Future period. I attribute some of the uncertainty in simulations of this simple model to endogenous model decision (selection) uncertainty that leads to variations in the changes of the negative forcing in the Historical period carried forward into the Future period.

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Posted in climate models, Sensitivity & feedbacks

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

Posted on August 24, 2020 by niclewis | 18 comments

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 →

Posted in Sensitivity & feedbacks

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

Posted on August 19, 2020 by niclewis | 65 comments

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 →

Posted in climate models, Scientific method, Sensitivity & feedbacks

Greening the planet and slouching towards Paris?

Posted on May 14, 2020 by curryja | 117 comments

by Patrick J. Michaels

A new paper finds higher than expected CO₂ fertilization inferred from leaf to global observations. The paper predicts that the Earth is going to gain nearly three times as much green matter as was predicted by the IPCC AR5.

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Posted in Sensitivity & feedbacks

Plausible scenarios for climate change: 2020-2050

Posted on February 13, 2020 by curryja | 229 comments

by Judith Curry

A range of scenarios for global mean surface temperature change between 2020 and 2050, derived using a semi-empirical approach. All three modes of natural climate variability – volcanoes, solar and internal variability – are expected to act in the direction of cooling during this period.

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Posted in climate models, Sensitivity & feedbacks, Solar, Uncertainty

Explaining the Discrepancies Between Hausfather et al. (2019) and Lewis&Curry (2018)

Posted on January 17, 2020 by curryja | 249 comments

by Ross McKitrick

Challenging the claim that a large set of climate model runs published since 1970’s are consistent with observations for the right reasons.

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Posted in climate models, Sensitivity & feedbacks

Two more degrees by 2100!

Posted on December 27, 2019 by curryja | 383 comments

by Vaughan Pratt

An alternative perspective on 3 degrees C?

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Posted in Sensitivity & feedbacks

3 degrees C?

Posted on December 23, 2019 by curryja | 261 comments

by Judith Curry

Is 3 C warming over the 21st century now the ‘best estimate’? A reframing of how we think about climate change over the 21st century, and my arguments for 1 C.

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Posted in Sensitivity & feedbacks

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

Posted on December 20, 2019 by niclewis | 67 comments

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 →

Posted in climate models, Sensitivity & feedbacks, Uncategorized

Tagged climate feedback, climate sensitivity

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

Posted on December 16, 2019 by niclewis | 113 comments

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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Posted in Sensitivity & feedbacks

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

Posted on October 18, 2019 by niclewis | 64 comments

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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Posted in Sensitivity & feedbacks, Uncategorized

Tagged climate feedback, climate sensitivity, regression, statistics

What’s the worst case? Climate sensitivity

Posted on April 1, 2019 by curryja | 95 comments

by Judith Curry

Are values of equilibrium climate sensitivity > 4.5 C plausible?

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Posted in Sensitivity & feedbacks

Why climate predictions are so difficult

Posted on March 30, 2019 by curryja | 110 comments

by Judith Curry

An insightful interview with Bjorn Stevens.

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Posted in climate models, Prediction, Sensitivity & feedbacks

Climate sensitivity calculator app

Posted on March 18, 2019 by curryja | 132 comments

by Alberto Zaragoza Comendador

How sensitive is the Earth’s climate to greenhouse gases? Speaking about carbon dioxide in particular, how much would air temperatures increase if we doubled atmospheric concentrations of said gas?

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Posted in Sensitivity & feedbacks

Reconstructing a dataset of observed global temperatures 1950-2016 from human and natural influences

Posted on January 3, 2019 by curryja | 191 comments

by Frank Bosse

A demonstration that multidecadal variation since 1950 leads to overestimation of the Transient Climate Response (TCR).

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Posted in Sensitivity & feedbacks

Climate sensitivity to cumulative carbon emissions

Posted on December 11, 2018 by niclewis | 220 comments

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 →

Posted in climate models, IPCC, Sensitivity & feedbacks

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

Posted on September 5, 2018 by niclewis | 150 comments

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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Posted in climate models, Sensitivity & feedbacks

Hothouse Earth

Posted on August 8, 2018 by curryja | 379 comments

by Judith Curry

We need to raise the bar on how we think about the possible worst case scenario for climate change.

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Posted in Sensitivity & feedbacks

Impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity

Posted on April 24, 2018 by niclewis | 283 comments

by Nic Lewis

We have now updated the LC15 paper with a new paper that has been published in the Journal of Climate “The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity“. The paper also addresses critiques of LC15.

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Posted in Sensitivity & feedbacks, Uncategorized

Emergent constraints on climate sensitivity in global models. Part III

Posted on March 29, 2018 by curryja | 78 comments

by Nic Lewis

The two strongest potentially credible constraints, and conclusions.

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Posted in Sensitivity & feedbacks

Emergent constraints on climate sensitivity: Part II

Posted on March 23, 2018 by curryja | 32 comments

by Nic Lewis

The four constraints that Caldwell assessed as credible.

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Posted in Sensitivity & feedbacks

Emergent constraints on climate sensitivity: Part I

Posted on March 19, 2018 by curryja | 119 comments

by Nic Lewis

Emergent constraints on climate sensitivity: their nature and assessment of validity.

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Posted in Sensitivity & feedbacks

Recent research on aerosol forcing of the CMIP5 models

Posted on March 11, 2018 by curryja | 169 comments

by Frank Bosse

A few days ago a paper (Sato et al) dealing with some aspects of the “Aerosol Cloud Interactions”, (ACI, also called “aerosol indirect effects”) was released. It bolsters the conclusions of earlier papers: the effective radiative forcing from ACI (ERFaci) is smaller than thought, perhaps near zero .

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Posted in Sensitivity & feedbacks

Nature Unbound VIII – Modern global warming

Posted on February 26, 2018 by curryja | 871 comments

by Javier

Summary: Modern Global Warming has been taking place for the past 300 years. It is the last of several multi-century warming periods that have happened during the Neoglacial cooling of the past 3000 years. Analysis of Holocene climate cycles shows that the period 1600-2100 AD should be a period of warming. The evidence suggests that Modern Global Warming is within Holocene variability, but the cryosphere displays a non-cyclical retreat that appears to have undone thousands of years of Neoglacial ice advance. The last 70 out of 300 years of Modern Global Warming are characterized by human-caused, extremely unusual, rapidly increasing CO₂ levels. In stark contrast with this rapidly accelerating anthropogenic forcing, global temperature and sea level appear to have continued their rising trend with no perceptible evidence of added acceleration. The evidence supports a higher sensitivity to CO₂ in the cryosphere, suggesting a negative feedback by H₂O, that prevents CO₂ from having the same effect elsewhere.

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Posted in Attribution, Sensitivity & feedbacks