Archives par mot-clé : Sensitivity

climate-debate

Scientists Document A DECLINE In Overall Greenhouse Effect Forcing From 1985-2014

by K. Richard, December 30, 2019 in NoTricksZone

CO2 concentrations rose from 345 ppm to 398 ppm in the 29 years from 1985 to 2014. Mainstream scientists sympathetic to the anthropogenic global warming (AGW) paradigm have nonetheless reported the overall greenhouse effect forcing has been flat to declining throughout this period.

 

1. Cess and Udelhofen, 2003  Due to the downward trend in cloud cover, absorbed shortwave radiation increased and the overall greenhouse effect’s forcing influence declined from 1985-1999. The authors consider these trends to be driven by natural variability.

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2. Song et al., 2016The overall greenhouse effect went on “hiatus” from 1992-2014, with the combined forcing effects of water vapor, cloud, and CO2 declining by -0.04 W/m² per year (-0.4 W/m² per decade) during this interval. Again, the main reason for the declining greenhouse effect trend was the downward trend in cloud cover.

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3. Kato et al., 2018   Downward longwave radiation (DLR), or the overall greenhouse effect, responds to variability in water vapor and cloud. CO2 isn’t mentioned in the paper as a factor influencing DLR. Total DLR was negative (-0.2 W/m²) during this decade, insinuating rising CO2 had no net warming climate impact. In contrast, downward shortwave forcing increased by +2.2 W/m² per decade from 1986-2000 and by +1.3 W/m² from 2005-2014. These positive shortwave absorption trends explain the warming during this period.

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climate-debate

CO2, GLOBAL WARMING, CLIMATE AND ENERGY

by Allan M.R. MacRae, B.A.Sc., M.Eng., P.Eng., June 2019 in WUWT

ABSTRACT

Global warming alarmism, which falsely assumes that increasing atmospheric CO2 causes catastrophic global warming, is disproved – essentially, it assumes that the future is causing the past. In reality, atmospheric CO2 changes lag global temperature changes at all measured time scales.

Nino34 Area Sea Surface Temperature changes, then tropical humidity changes, then atmospheric temperature changes, then CO2 changes.

The velocity dCO2/dt changes ~contemporaneously with global temperature changes and CO2 changes occur ~9 months later (MacRae 2008).

The process that causes the ~9-month average lag of CO2 changes after temperature changes is hypothesized and supported by observations.

The ~9-month lag, +/- several months, averages 1/4 of the full-period duration of the variable global temperature cycle, which averages ~3 years.

Based on the above observations, global temperatures drive atmospheric CO2 concentrations much more than CO2 drives temperature.

Climate sensitivity to increasing atmospheric CO2 must be very low, less than ~1C/(2*CO2) and probably much less.

There will be no catastrophic warming and no significant increase in chaotic weather due to increasing CO2 concentrations.

Increasing atmospheric CO2 clearly causes significantly improved crop yields, and may cause minor, beneficial global warming.

Atmospheric CO2 is not alarmingly high, it is too low for optimal plant growth and alarmingly low for the survival of carbon-based terrestrial life.

Other factors such as fossil fuel combustion, deforestation, etc may also increase atmospheric CO2. The increase of CO2 is clearly beneficial.

“Green energy” schemes are not green and produce little useful (dispatchable) energy, primarily because of the fatal flaw of intermittency.

There is no widely-available, cost-effective means of solving the flaw of intermittency in grid-connected wind and solar power generation.

Electric grids have been destabilized, electricity costs have soared and Excess Winter Deaths have increased due to green energy schemes.

HYPOTHESIS AND CONCLUSIONS

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Fig.1a – The very close relationship of dCO2/dt (red) vs global temperature (blue) is clearly apparent. Major volcanoes disrupt the relationship.

climate-debate

What’s the worst case? Climate sensitivity

by Judith Curry, April 1, 2019 in WUWT

Are values of equilibrium climate sensitivity > 4.5 C plausible?

For background, see these previous posts on climate sensitivity [link]

Here are some possibilistic arguments related to climate sensitivity.  I don’t think the ECS example is the best one to illustrate these ideas [see previous post], and I probably won’t include this example in anything I try to publish on this topic (my draft paper is getting too long anyways).  But possibilistic thinking does point you in some different directions when pondering the upper bound of plausible ECS values.

5. Climate sensitivity

Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations, after the climate system has reached equilibrium. The issue with regards to ECS is not scenario discovery; rather, the challenge is to clarify the upper bounds of possible and plausible worst cases.

The IPCC assessments of ECS have focused on a ‘likely’ (> 66% probability) range, which has mostly been unchanged since Charney et al. (1979), to be between 1.5 and 4.5 oC. The IPCC AR4 (2007) did not provide any insight into a worst-case value of ECS, stating that values substantially higher than 4.5 oC cannot be excluded, with tail values in Figure 9.20 exceeding 10 oC. The IPCC AR5 (2013) more clearly defined the upper range, with a 10% probability of exceeding 6 oC.

Since the IPCC AR5, there has been considerable debate as to whether ECS is on the lower end of the likely range (e.g., < 3 oC) or the higher end of the likely range (for a summary, see Lewis and Curry, 2018). The analysis here bypasses that particular debate and focuses on the upper extreme values of ECS.

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climate-debate

Why does climate sensitivity increase over time in models? A look at two possibilities

by A. Zaragoza Comendador, August 16, 2018 in WUWT

Note: if the terms used in this article seem confusing, check out the previous one.

Introduction

It’s well known that climate models show increasing sensitivity over time: for a given forcing, the true long-term temperature increase (ECS) is higher than what you’d estimate if you simply extrapolated from the past (ECS_hist). In other words, the ECS-to-ECS_hist ratio is above 1. This article tries to work out why climate models behave like that; that is to say, the variable I’m trying to explain is the ECS-to-ECS_hist ratio.

Now, there’s probably too many hyphens and underscores in the text. So it will be more readable if I clarify that, every time I talk simply about ‘correlation’, I mean the correlation of thing X with the ECS-to-ECS_hist ratio. If other kind of correlation is mentioned, I’ll say so explicitly.

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climate-debate

Climatology’s startling error – an update

by Christopher Monckton of Brenchley, July 30, 2018 in WUWT

How climatologists forgot the Sun was shining

Climatologists trying to predict global warming forgot the sunshine in their sums. After correction of this startling error of physics, global warming will not be 2 to 4.5 K per CO2doubling, as climate models imagine. It will be a small, slow, harmless and net-beneficial 1.17 K.

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climate-debate

THE SUN ALLERGY OF CLIMATE RESEARCHERS

by  Ulli Kulke, June 29, 2018 in GWPF

Henrik Svensmark, head of solar research at Denmark’s Technical University in Copenhagen, is one of them. And he ventures far ahead in the climate debate, the research with perhaps the greatest significance of our time. His research is contested, of course. Nevertheless, Svensmark and his critics agree that the topic “sun” deserves more attention in climate research. The participants are particularly interested in the complex interplay between our central star and ionizing emissaries from the depths of the galaxy – “cosmic radiation”.

Svensmark says: “The climate is influenced more by changes in cosmic radiation than by carbon dioxide”. CO2 has an effect, of course, “but it is far less than most current climate models assume, and also less than the influence of cosmic radiation”. In his opinion, a doubling of the greenhouse gas in the atmosphere would cause an increase in global temperature of at most one degree, and not two degrees, as is now generally accepted.

In other words, the “climate sensitivity” of carbon dioxide is only half as high as assumed (…)

climate-debate

Ross McKitrick: All those warming-climate predictions suddenly have a big, new problem

by Ross McKitrick, June 20, 2018 in FinancialPost

One of the most important numbers in the world goes by the catchy title of Equilibrium Climate Sensitivity, or ECS. It is a measure of how much the climate responds to greenhouse gases. More formally, it is defined as the increase, in degrees Celsius, of average temperatures around the world, after doubling the amount of carbon dioxide in the atmosphere and allowing the atmosphere and the oceans to adjust fully to the change. The reason it’s important is that it is the ultimate justification for governmental policies to fight climate change.

The United Nations Intergovernmental Panel on Climate Change (IPCC) says ECS is likely between 1.5 and 4.5 degrees Celsius, but it can’t be more precise than that. Which is too bad, because an enormous amount of public policy depends on its value. People who study the impacts of global warming have found that if ECS is low — say, less than two — then the impacts of global warming on the economy will be mostly small and, in many places, mildly beneficial.

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climate-debate

Atomic Physicist: Human CO2 Emissions Have An Equilibrium Climate Sensitivity Of A ‘Not Important’ 0.02 K

by K. Richard, June 4, 2018 in NoTricksZone

Dr. Boris M. Smirnov, a prominent atomic physicist, has authored 20 physics textbooks during the last two decades.  His latest scientific paper suggests that the traditional “absorption band” model for calculating the effect of atmospheric CO2 during the radiative transfer process is flawed.  New calculations reveal that the climate’s sensitivity to a doubling of the CO2 concentration is just 0.4 K, and the human contribution to that value is a negligible 0.02 K.

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climate-debate

Is climate alarmist consensus about to shatter?

by A. Watts, May 2, 2008 in WUWT

A new study by climatologists Nicholas Lewis and Judith Curry concludes that Earth’s “equilibrium climate sensitivity” (ECS) to more atmospheric carbon dioxide is as much as 50% lower than climate alarmists have been claiming. That their paper was published in the Journal of Climate  suggests that the asserted “97% consensus” of climate experts may be eroding.

Or as Cornwall Alliance founder Cal Beisner puts it (paraphrasing Winston Churchill) it may not be the beginning of the end of climate alarmism. But it could be the end of the beginning of alarmism as the dominant, ever-victorious tenet of our times.

Indeed, say other noted climatologists, there are good reasons to think ECS and alarmist errors are even greater than 50 percent. For one thing, there is no persuasive reason to assume our planet’s climate system (…)

climate-debate

New Lewis & Curry Study Concludes Climate Sensitivity is Low

by Ph.D. Roy W. Spencer, Apritl 24, 2018 in Global Warming

Global warming “problem” cut by 50%

As readers here are aware, I don’t usually critique published climate papers unless they are especially important to the climate debate. Too many papers are either not that important, or not that convincing to me.

The holy grail of the climate debate is equilibrium climate sensitivity (ECS): just how much warming (and thus associated climate change) will occur in response to an eventual doubling of the CO2 concentration in the atmosphere?

Yesterday’s early online release of a new paper by Nicholas Lewis and Judith Curry (“The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity“, Journal of Climate) represents one of those seminal papers.

climate-debate

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

by J. Curry and N. Lewis, April 24, 2018 in ClimateAudit

There has been considerable scientific investigation of the magnitude of the warming of Earth’s climate by changes in atmospheric carbon dioxide (CO2) concentration. Two standard metrics summarize the sensitivity of global surface temperature to an externally imposed radiative forcing. Equilibrium climate sensitivity (ECS) represents the equilibrium change in surface temperature to a doubling of atmospheric CO2 concentration. Transient climate response (TCR), a shorter-term measure over 70 years, represents warming at the time CO2 concentration has doubled when it is increased by 1% a year.

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See also here

climate-debate

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-debate

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.

climate-debate

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.

climate-debate

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.

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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.

climate-debate

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

climate-debate

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.

climate-debate

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.

climate-debate

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.

climate and geology

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.

climate-debate

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.