Category Archives: Sensitivity & feedbacks

Nature Unbound VIII – Modern global warming

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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Marvel et al.’s new paper on estimating climate sensitivity from observations

by Nic Lewis

Recently a new model-based paper on climate sensitivity was published by Kate Marvel, Gavin Schmidt and others, titled ‘Internal variability and disequilibrium confound estimates of climate sensitivity from observations’.[1]

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Reply to Patrick Brown’s response to comments on his Nature article

by Nic Lewis

My reply to Patrick Brown’s response to my my comments on his Nature article.

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Greater future global warming (still) predicted from Earth’s recent energy budget

by Patrick Brown

A response to Nic Lewis’ post A closer look shows global warming will not be greater than we thought.

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

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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Update on the strength of aerosol forcing

by Frank Bosse

Increasing evidence of small aerosol forcing supports the importance of internal variability in explaining inter hemispheric differences in temperature variability.

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

by Nic Lewis

A new paper in Science Advances by Cristian Proistosescu and Peter Huybers (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 sensitivity estimates from historical records into line with model-derived estimates.

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How inconstant are climate feedbacks – and does it matter?

by Nic Lewis

Kyle Armour has a new paper out in Nature Climate Change: “Energy budget constraints on climate sensitivity in light of inconstant climate feedbacks”.

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Rethinking the Social Cost of Carbon

by Judith Curry

The Social Cost of Carbon is emerging as a major source of contention in the Trump Administration.

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Beyond Physics: Advanced Biology and Climate Change

by Clive Hambler

Reflections on the stabilization of Earth’s climate by life.

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Internal climate variability as a confounding factor in climate sensitivity estimates

by Frank Bosse

Towards eliminating multi-decadal natural oscillations in determination of the Transient Climate Response (TCR) to CO2.
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Tamino’s adjusted temperature records and the TCR

by Frank Bosse

Separating out the impacts of internal variability on evaluations of TCR.

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Dust deposition on ice sheets: a mechanism for termination of ice ages?

by Donald Rapp

In a recent paper, Ellis and Palmer (2016) proposed that deposition of dust on giant ice sheets, thus reducing their albedo, was a principal factor in the termination of Ice Ages over the past 800 kyrs.

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Broad consistency between patterns of fossil fuel emissions and atmospheric CO2

by Guido van der Werf

The 200% increase in fossil fuel emissions Murry Salby claims is about 20% in reality, and the constant CO2 growth rate he found actually increased by roughly 20% as well over the same time period.

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Atmospheric Radiation Measurement Program

by Judith Curry

The first 20 years.

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Are energy budget climate sensitivity values biased low?

by Nic Lewis

In a recently published paper (REA16),[i] 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.

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Towards reconciling climate sensitivity estimates from climate models and observatiions

by Judith Curry

A new paper purports to have resolved the discrepancy between climate response estimates from global climate models versus energy budget models.

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Assessment of Approaches to Updating the Social Cost of Carbon

by Judith Curry

Some new analyses are shedding some light on deficiencies in the approach to estimate the social cost of carbon.

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The cloud-climate conundrum

by Judith Curry

Four new papers remind us of the very large uncertainties surrounding cloud-climate feedbacks.

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Updated climate sensitivity estimates

by Nic Lewis

An update to the calculations in Lewis and Curry (2014).

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On inappropriate use of least squares regression

by Greg Goodman

Inappropriate use of linear regression can produce spurious and significantly low estimations of the true slope of a linear relationship if both variables have significant measurement error or other perturbing factors. This is precisely the case when attempting to regress modelled or observed radiative flux against surface temperatures in order to estimate sensitivity of the climate system. Continue reading

Are land + sea temperature averages meaningful?

by Greg Goodman

Several of the major datasets that claim to represent “global average surface temperature” are directly or effectively averaging land air temperatures with sea surface temperatures.

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Huge efficacy of land use forcing in one GISS-E2-R simulation: is an ocean model error involved?

by Nic Lewis

In a recent article here, which summarised a longer piece at ClimateAudit, 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.

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

by Nicholas Lewis

Different agents may have effects on global temperature (GMST) different to those which would be expected simply by reference to the radiative forcing they exert. This difference is encapsulated in the term “forcing efficacy”.

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How sensitive is global temperature to cumulative CO2 emissions?

by Nic Lewis

The mean carbon cycle behaviour of CMIP5 ESMs and EMICs may be quite unrealistic.

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