Category Archives: climate models

Compensation between cloud feedback + ECS and aerosol-cloud forcing in CMIP6 models

Posted on March 5, 2021 by niclewis | 45 comments

By Nic Lewis

An important paper, Wang et al.[1], on the relationships between cloud feedback, climate sensitivity (ECS) and aerosol-cloud interaction in the latest generation of global climate models (CMIP6) has just been published. The key conclusion of the paper is:

The seeming consistency of global-mean temperature evolution between more positive cloud feedback (high ECS) models and observations requires a strong aerosol indirect cooling effect that leads to an interhemispheric temperature evolution that is inconsistent with observations.

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Posted in climate models, 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 confirmation that climate models overstate atmospheric warming

Posted on August 25, 2020 by curryja | 148 comments

by Ross McKitrick

Two new peer-reviewed papers from independent teams confirm that climate models overstate atmospheric warming and the problem has gotten worse over time, not better.

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Posted in climate models

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

Structural errors in global climate models

Posted on June 20, 2020 by curryja | 99 comments

by Gerald Browning

Climate model sensitivity to CO2 is heavily dependent on artificial parameterizations (e.g. clouds, convection) that are implemented in global climate models that utilize the wrong atmospheric dynamical system and excessive dissipation.

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Posted in climate models

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

Inconsistency between historical and future CMIP5 simulations

Posted on February 11, 2020 by curryja | 81 comments

by Kenneth Fritsch

Identification of significant differences between the historical and future CMIP5 simulations for intrinsic climate sensitivities.

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Posted in climate models

Analysis of a carbon forecast gone wrong: the case of the IPCC FAR

Posted on January 31, 2020 by curryja | 140 comments

by Alberto Zaragoza Comendador

The IPCC’s First Assessment Report (FAR) made forecasts or projections of future concentrations of carbon dioxide that turned out to be too high.

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Posted in climate models

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

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

Escape from model land

Posted on October 29, 2019 by curryja | 348 comments

by Judith Curry

“Letting go of the phantastic mathematical objects and achievables of model- land can lead to more relevant information on the real world and thus better-informed decision- making.” – Erica Thompson and Lenny Smith

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Posted in climate models, Uncertainty

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

Is ocean warming accelerating faster than thought?

Posted on January 21, 2019 by niclewis | 92 comments

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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Posted in climate models, IPCC, Oceans

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

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

Posted on October 18, 2018 by niclewis | 121 comments

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 →

Posted in climate models, IPCC

A Test of the Tropical 200-300 mb Warming Rate in Climate Models

Posted on September 17, 2018 by curryja | 250 comments

by Ross McKitrick

I sat down to write a description of my new paper with John Christy, but when I looked up a reference via Google Scholar something odd cropped up that requires a brief digression.

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Posted in climate models

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

Uncertainty in climate projections

Posted on August 20, 2018 by curryja | 251 comments

by Judith Curry

My article Climate Uncertainty and Risk has now been published in the Summer 2018 edition of CLIVAR Variations.

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Posted in climate models, Uncertainty

Climate uncertainty & risk

Posted on July 8, 2018 by curryja | 537 comments

by Judith Curry

I’ve been invited to write an article on climate uncertainty and risk.

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Posted in climate models, Policy, Uncertainty

Of boundary and initial conditions

Posted on June 25, 2018 by curryja | 318 comments

by Dan Hughes and Tomas Milanovic

Further reflections on the application of the divergence theorem to the Earth’s climate system.

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Posted in climate models

Energy budgets, climate system domains and internal variability

Posted on May 22, 2018 by curryja | 437 comments

by Dan Hughes

It is not a boundary value problem.

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Posted in climate models

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

Posted on December 15, 2017 by curryja | 245 comments

by Nic Lewis

A critique of a recent paper by Brown and Caldeira published in Nature that predicted greater than expected global warming.

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Posted in climate models, Sensitivity & feedbacks

Are Climate Models Overstating Warming?

Posted on September 26, 2017 by curryja | 402 comments

by Ross McKitrick

A number of authors, including the IPCC, have argued that climate models have systematically overstated the rate of global warming in recent decades. A recent paper by Millar et al. (2017) presented the same finding in a diagram of temperature change versus cumulative carbon emissions since 1870.

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Posted in climate models

Prospects for a Prolonged Slowdown in Global Warming in the Early 21st Century

Posted on November 30, 2016 by curryja | 274 comments

by Nic Lewis

[W]e estimate that the warming slowdown (< 0.1 K/decade trend beginning in 1998) could persist, due to internal variability cooling, through 2020, 2025 or 2030 with probabilities 16%, 11%, and 6%, respectively. – Knutson et al.

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Posted in Attribution, climate models

Climate models for lawyers

Posted on November 12, 2016 by curryja | 315 comments

by Judith Curry

I have been asked to write an Expert Report on climate models.

***SEE UPDATE

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Posted in climate models