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.
by K. Richard, December 31, 2018 in NoTricksZone
Climate models postulate that increasing CO2 concentrations will intensify the Earth’s water cycle. This intensification is believed to eventually result in dangerous (3°C and up) global warming. Observational evidence has thus far falsified these IPCC-endorsed claims.
by Judith Curry, December 11, 2018 in ClimateEtc.
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.
by A. Zaragoza Comendador, August 16, 2018 in WUWT
Note: if the terms used in this article seem confusing, check out the previous one.
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.
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.
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 (…)
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.
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.
by Eric Worrall, May 16, 2018 in WUWT
The researchers claim adding historical data derived fudge factors to correct the discrepancy between climate models and historical observations, producing a Frankenmodel mix of fudge factors and defective physics, will make climate predictions more reliable (…)
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 (…)
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.
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.
See also here
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 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), 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.
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.
by K. Richard, October 16, 2017 in NoTricksZone
A recently highlighted paper published by atmospheric scientists Scafetta et al., (2017) featured a graph (above) documenting post-2000 trends in the published estimates of the Earth’s climate sensitivity to a doubling of CO2 concentrations (from 280 parts per million to 560 ppm).