Just checking, but is your point essentially that because some people were wrong at one point during the infancy of the field of climatology, we should discount the abundant evidence present now?
Abundant evidence for what exactly? And many people are still predicting increasing greenhouse gasses will cause an ice age.
Skepticism is a valuable tool, but skepticism that persists in the face of an overwhelming amount of evidence to the contrary and without good reason is just dogma.
Again, overwhelming amount of evidence to the contrary, about what exactly?
You seem to believe that all scientists all agree on some same exact concept. They don't, whatever that is, other than 2 x CO2 = 1
°C.
Two things that might help me to come to a better understanding of what actual evidence you're basing your position on and whether or not it is a position worth considering:
1. What specific evidence would change your mind?
2. Would you mind linking some recent peer-reviewed literature that finds human emissions are not increasing the global mean temperature?
Let’s start with #2. I never said human emissions are not increasing the global mean temperature. I said they probably are, but there's no direct evidence to confirm the mild warming of the last 300 years or so is anything but natural. If any of that warming is due to increased greenhouse gasses it cannot determined how much is & isn't. It is up to the individual(s) making that claim that it is greenhouse warming, to provide the evidence. And an 'expert opinion' or 'a consensus', or a correlation is not science or evidence.
And #1.
What evidence would change my mind on what exactly? You’re not very specific at all. I've stated my position based on the theory they present & how it stands up against the evidence so far.
I can't ask you the same question because you've made no specific claims, other than I'm supposedly disagreeing with 10,000 scientists, & that’s not true & can’t be because they don’t all agree with each other.
Again, what I believe is, the equilibrium climate sensitivity for a doubling of atmospheric CO2 will result in an increase in the global average temperature of around 1°C. Maybe a tad more or less, depending on whether net feedback is a bit positive or negative. And the science is straight forward & settled on the fact that, however much warming 2 x CO2 results in, it would need to be increased by twice as much as before (doubled again from the new level) to get an equal response.
The science’s various & numerous climate modelling groups provide a range of projections for a doubling of CO2 of >>> 1.5°C to 4.5°C <<<, as promoted by the IPCC. The model spread is directly due to the high degree of uncertainty in the feedback response, primarily water vapour & cloud feedback.
Quote - Isaac M. Held and Brian J. Soden Geophysical Fluid Dynamics Laboratory/National Oceanic and Atmospheric Administration.
“Our uncertainty concerning climate sensitivity is disturbing. The range most often quoted for the equilibrium global mean surface temperature response to a doubling of CO2 concentrations in the atmosphere is 1.5◦C to 4.5◦C. All the models on which these estimates are based possess strong (positive) water vapor feedback. If this feedback is, in fact, substantially weaker than predicted in current models, sensitivities in the upper half of this range would be much less likely, a conclusion that would clearly have important policy implications…”
This IPCC graph for model projections clearly shows how (c)
well mixed greenhouse gases warm the tropical mid/upper troposphere at a significantly faster rate than the layers below down to the surface.
Figure 9.1. Zonal mean atmospheric temperature change from 1890 to 1999 (°C per century) as simulated by the PCM model from (a) solar forcing, (b) volcanoes,
(c) well mixed greenhouse gases, (d) tropospheric and stratospheric ozone changes, (e) direct sulphate aerosol forcing and (f) the sum of all forcings. Plot is from 1,000 hPa to 10 hPa (shown on left scale) and from 0 km to 30 km (shown on right).
IPCC:
Because the water vapour and temperature responses are tightly coupled in the troposphere (see Section 8.6.3.1), models with a larger (negative) lapse rate feedback also have a larger (positive) water vapour feedback….end
So, the models project water vapour feedback to be positive, to varying degrees, & this can be easily tested.
Greenhouse warming results in a significantly faster rate of warming in the upper troposphere than in the atmosphere below, down to the surface (negative lapse rate feedback). This warming in the upper tropical troposphere allows water vapour (the main greenhouse gas) to increase at that altitude (increase in humidity) & warms the upper tropical troposphere even more, raising the water vapour emissions layer (this is the altitude in the troposphere where water vapour no longer intercepts out going infrared radiation) to a higher altitude. This is positive water vapour feedback & it increases the direct warming from CO2 significantly.
Atmospheric Specific Humidity
Quote: Quote - Isaac M. Held and Brian J. Soden Geophysical Fluid Dynamics Laboratory/National Oceanic and Atmospheric Administration.
“Water vapour is the dominant greenhouse gas, the most important gaseous source of infrared opacity in the atmosphere. Models of the Earth’s climate indicate that this is an important positive feedback that increases the sensitivity of surface temperatures to carbon dioxide by nearly a factor of two when considered in isolation from other feedbacks, and possibly by as much as a factor of three or more when interactions with other feedbacks are considered. “…end
So what does the actual data show?
Radiosonde humidity data continues to show both specific & relative humidity declining in the mid/upper troposphere, not increasing. The opposite to the hypothesis projected by the models.
Atmospheric Moisture
Atmospheric Relative Humidity
Atmospheric Specific Humidity
The radiosonde temperature data also shows that the rate of temperature increase is not faster in the mid/upper troposphere than at the surface, as the positive water vapour hypothesis predicts, but slower. The opposite to the hypothesis projected by the models. And both the RSS & UAH satellite data sets show the same.
RSS Temperature Mid Troposphere TMT (tropics) Trend =
0.141K/decade
RSS Temperature Lower Troposphere. TLT (tropics) Trend =
0.154K/decade
UAH Mid Tropical Troposphere. Trend =
0.08 http://vortex.nsstc.uah.edu/data/msu/v6.0/tmt/uahncdc_mt_6.0.txt
UAH Lower Tropical Troposphere. Trend =
0.12 http://vortex.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt
So the above shows the positive water vapour feedback hypothesis is wrong.
So this brings us to the models projected positive cloud feedback. And recall what the IPCC says quote “
because of the inherently nonlinear nature of the response to feedbacks, the final impact on sensitivity is not simply the sum of these responses. The effect of multiple positive feedbacks is that they mutually amplify each other’s impact on climate sensitivity.”
Also IPCC: “The mean and standard deviation of climate sensitivity estimates derived from current GCMs are larger (3.2°C ± 0.7°C) essentially because the GCMs all predict a positive cloud feedback (Figure 8.14) but strongly disagree on its magnitude.”..end
Well there are some of the models that predict negative cloud feedback, actually.
Did you notice in the last video I posted how they said increased humidity results in more cloud? That is negative cloud feedback, & that makes sense, where as positive cloud feedback to increased humidity does not.
https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter02_FINAL.pdf
While trends of cloud cover are consistent between independent data sets in certain regions, substantial ambiguity and therefore low confidence remains in the observations of global-scale cloud variability and trends. {2.5.6}
https://www.ipcc.ch/ipccreports/tar/wg1/316.htm
the Second Assessment Report found that simulation of clouds and related processes remains a major source of uncertainty in atmospheric models. As discussed in Chapter 7, these processes continue to account for most of the uncertainty in predicting human-induced climate change.
Dr. Robert G. Brown of the Physics Department at Duke University
On water vapour feedback –
This last assumption (water vapour feedback) is finally dying a quiet and well deserved death. AFAIK, it is due to Hansen, who in his original papers predicting disaster assumed universally positive water vapor feedback (and for no particularly scientifically motivated reason that I can see, hypothesized truly absurd levels of water vapor feedback that doubled or tripled the CO_2-only warming of his then very simple models). Naturally, some of the GCMs out there have built into them parametric assumptions that preserve this much “climate sensitivity” — total ACO_2 warming plus feedback, usually at the expense of an overdriven response to e.g. volcanic aerosols necessary to explain periods of global cooling and to keep the model from having a runaway exponential instability (because one has to have a mechanism that keeps positive feedback water vapor from causing increase of water vapor without bound just from FLUCTUATIONS in water vapor content or global temperature — the climate cannot be a biased random walk where every time the temperature goes up a bit, average water vapor increases and hence resets the Earth’s average temperature a bit higher unless a competing process can completely erase the gain when the temperature fluctuates down a bit).
At the moment, estimates of climate sensitivity are struggling to retain any net positive feedback from water vapor in the face of data that already solidly excludes the kind of absurd feedback levels Hansen originally hypothesized. Even the question of net negative feedback from water vapor, long considered to be anathema in climate science (except for a few mavericks who managed to publish papers suggesting that clouds could easily lead to net negative feedback through the dual mechanism of latent heat transport and modulation of albedo) is no longer completely off of the table.
A Test of the Tropical 200-300 mb Warming Rate in Climate Models by Ross McKitrick
We confirmed, among other things, that based on modern econometric testing methods
the gap between models and observations in the tropical troposphere is statistically significant.
https://judithcurry.com/2018/09/17/a-test-of-the-tropical-200-300-mb-warming-rate-in-climate-models/
Are Climate Models Overstating Warming? by Ross McKitrick
Summary
Millar et al. attracted controversy for stating that
climate models have shown too much warming in recent decades, even though others (
including the IPCC) have said the same thing. Zeke Hausfather disputed this using an adjustment to model outputs developed by Cowtan et al. The combination of the adjustment and the recent El Nino creates a visual impression of coherence. But other measures not affected by the issues raised in Cowtan et al. support the existence of a warm bias in models. Gridcell extreme frequencies in CMIP5 models do not overlap with observations. And satellite-measured temperature trends in the lower troposphere run below the CMIP5 rates in the same way that the HadCRUT4 surface data do, including in the tropics.
The model-observational discrepancy is real, and needs to be taken into account especially when using models for policy guidance.
https://judithcurry.com/2017/09/26/are-climate-models-overstating-warming/
How inconstant are climate feedbacks – and does it matter? by Nic Lewis
Conclusions
It has in fact been found that when CMIP5 models are forced with specified SST anomalies matching the pattern of warming over the historical period, they produce net climate feedbacks of the order of 2 Wm-2K-1, closely consistent with the modest ECS best estimates from good observationally-based energy budget studies.[18] The real questions seem to be w
hy do AOGCMs simulate very different warming patterns under increased CO2 concentration than those that have actually occurred during the historical period, and why do their net feedback strengths differ so much between these warming patterns.
https://judithcurry.com/2017/04/18/how-inconstant-are-climate-feedbacks-and-does-it-matter/
New Lewis & Curry Study Concludes Climate Sensitivity is Low
April 24th, 2018 by Roy W. Spencer, Ph. D.
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.
It is an extension of a
previously published paper by Lewis & Curry, adding more data, and addressing criticisms of their earlier work. Its methodology isn’t entirely original, since previous (but somewhat preliminary) work along the same lines (
Otto et al., 2013) has resulted in observational estimates of relatively low climate sensitivity compared to the IPCC climate models.
But what is notable to me is (1) the comprehensive extent to which methodological and data uncertainties have been addressed, and (2) the fact it was published in the relatively mainstream and consensus-defending
Journal of Climate.
Basically, the paper concludes that the amount of surface and deep-ocean warming that has occurred since the mid- to late-1800s is consistent with low equilibrium climate sensitivity (ECS) to an assumed doubling of atmospheric CO2. They get a median estimate of 1.66 deg. C (1.50 deg. C without uncertain infilled Arctic data), which is only about half of the average of the IPCC climate models. It is just within the oft-quoted range of 1.5 to 4.5 deg. C that the IPCC has high confidence ECS should occupy.
http://www.drroyspencer.com/2018/04/new-lewis-curry-study-concludes-climate-sensitivity-is-low/
