Archives par mot-clé : Sensitivity

Emergent constraints on climate sensitivity in global climate models, Part 3

by Nic Lewis, March 29, 2018 in ClimateAudit (Steve McIntyre)


The two strongest potentially credible constraints, and conclusions

In Part 1 of this article the nature and validity of emergent constraints[1] on equilibrium climate sensitivity (ECS) in GCMs were discussed, drawing mainly on the analysis and assessment of 19 such constraints in Caldwell et al. (2018),[2] who concluded that only four of them were credible. An extract of the rows of Table 1 of Part 1 detailing those four emergent constraints is given below.[3]

Climate scientist admits embarrassment over future climate uncertainty

by J. Cartwright, March 16, 2018 in A. Watts WUWT


WUWT readers may recall this chart which clearly illustrates just how uncertain climate science really is.

t seems that some climate academics are a bit embarrassed that they haven’t been able to pin down climate sensitivity. From EU Horizon Magazine

Climate sensitivity – reducing the uncertainty of uncertainty

by Jon Cartwright

A study published in January 2018 claims to halve the uncertainty around how much our planet’s temperature will change in response to rising carbon dioxide (CO2) levels, potentially giving governments more confidence to prepare for the future.

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

by Nic Lewis, February 5, 2018 in ClimateAudit


Recently a new model-based paper on climate sensitivity was published by Kate Marvel, Gavin Schmidt (the head of NASA GISS) and others, titled ‘Internal variability and disequilibrium confound estimates of climate sensitivity from observations’. It appears to me that the novel part of its analysis is faulty, and that the part which isn’t faulty isn’t novel.

Emergent constraint on equilibrium climate sensitivity from global temperature variability

by P.M. Cox et al., January 18, 2018 in Nature


Equilibrium climate sensitivity (ECS) remains one of the most important unknowns in climate change science. ECS is defined as the global mean warming that would occur if the atmospheric carbon dioxide (CO2) concentration were instantly doubled and the climate were then brought to equilibrium with that new level of CO2.

(…)

This metric of variability can also be calculated from observational records of global warming3, which enables tighter constraints to be placed on ECS, reducing the probability of ECS being less than 1.5 degrees Celsius to less than 3 per cent, and the probability of ECS exceeding 4.5 degrees Celsius to less than 1 per cent.

Study: no acceleration in global warming, climate sensitivity to CO2 too high

by Anthony Watts, November 29, 2017 in WUWT


New research yields old result: Climate warming slow, steady. Observed value is half that of CMIP5 climate models.

The rate at which Earth’s atmosphere is warming has not significantly accelerated over the past 23 years, according to research at The University of Alabama in Huntsville (UAH).

If you take away the transient cooling in 1983 and 1992 caused by two major volcanic eruptions in the preceding years, the remaining underlying warming trend in the bottom eight kilometers (almost five miles) of the atmosphere was 0.096 C (about 0.17° Fahrenheit) per decade between January 1979 and June 2017.

That was unexpectedly close to the 0.09 C warming trend found when similar research was published in 1994 with only 15 years of data, said Dr. John Christy, director of UAH’s Earth System Science Center.

See also here

Israeli Astrophysicist rejects UN IPCC – Finds ‘the sun completely overturns the way we should see global warming’

by Dr. Shaviv, November 9, 2017 in ClimateDepot


(…)The body of evidence however clearly shows that the climate sensitivity is on the low side, about 1 to 1.5 degree increase per CO2 doubling. People in the climate community are scratching their heads trying to understand the so called hiatus in the warming. Where is the heat hiding? While in reality it simply points to a low sensitivity.

CO2 Contributed Only 0.12°C To Global Temps Since 1850

by Kenneth Richard, July 17, 2017


A Swiss scientist known to have published hundreds of scientific papers in physics journals has authored a new scholarly paper that casts serious doubts on the effectiveness of CO2 as a greenhouse gas influencing Earth’s temperatures.

This paper has been added to a growing volume of peer-reviewed scientific papers that seriously question estimates of a high climate sensitivity to significant increases in CO2 concentrations.

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

by Nic Lewis, July 8, 2017 in Climate Audit


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 sensitivity estimates from historical records into line with model-derived estimates. It is not the first paper to attempt to do so, but it makes a rather bold claim and, partly because Science Advances seeks press coverage for its articles, has been attracting considerable attention.

Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model

by J. Krissansen-Totton and D.C. Catling, May 22,  2017, in Nature


The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH since 100 Myr ago.

How inconstant are climate feedbacks – and does it matter?

by Nic Lewis, April 18, 2017


There is as yet no observational evidence that climate sensitivity increases with time in the real climate system – although this cannot be ruled out – nor is it fully understood why it increases in most AOGCMs. In any event, even if real-world climate sensitivity does increase with time, in the longer run other factors that are not reflected in ECS, such as melting ice sheets, are probably more important. Therefore, while time-varying climate sensitivity is of considerable interest from a theoretical point of view, for practical purposes its influence is likely to be very modest.

Published measurements of climate sensitivity declining

by Laterite, June 20, 2015


The climate sensitivity due to CO2 is expressed as the temperature change in °C associated with a doubling of the concentration of carbon dioxide in Earth’s atmosphere. The equilibrium climate sensitivity (ECS) refers to the equilibrium change in global mean near-surface air temperature that would result from a sustained doubling of the atmospheric carbon dioxide concentration.  The transient climate response (TCR) is defined as the average temperature response over a twenty-year period centered at CO2 doubling in a transient simulation with CO2 increasing at 1% per year. The transient response is lower than the equilibrium sensitivity, due to the “inertia” of ocean heat uptake.

Also, this post

“[T]here is growing evidence of much smaller climate sensitivity to CO2; and even if these drastic emissions reductions occurred, we see little impact on the climate in the 21st century (even if you believe the climate models).”

The Logarithmic Effect of Carbon Dioxide

by David Archibald, March 8, 2010


The greenhouse gasses keep the Earth 30° C warmer than it would otherwise be without them in the atmosphere, so instead of the average surface temperature being -15° C, it is 15° C. Carbon dioxide contributes 10% of the effect so that is 3° C. The pre-industrial level of carbon dioxide in the atmosphere was 280 ppm. So roughly, if the heating effect was a linear relationship, each 100 ppm contributes 1° C. With the atmospheric concentration rising by 2 ppm annually, it would go up by 100 ppm every 50 years and we would all fry as per the IPCC predictions.

But the relationship isn’t linear, it is logarithmic. In 2006, Willis Eschenbach posted this graph on Climate Audit showing the logarithmic heating effect of carbon dioxide relative to atmospheric concentration