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Author Topic: Global Surface Air Temperatures  (Read 339849 times)

Ned W

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Re: Global Surface Air Temperatures
« Reply #1600 on: September 18, 2017, 06:03:04 PM »
Just read through the Ned W/Jai discussion and I feel like a Yanomami tribesman from the Amazon rainforest who has just found himself at Wimbledon watching a tennis match without knowing the rules.
Eh.  The level of vitriol in that discussion was unpleasant, and it was off-topic for a thread on "global surface temperatures" anyway.  I started a new thread in the "Science" section of the ASIF, which hopefully will stay more on topic and have fewer insults. 

TerryM

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Re: Global Surface Air Temperatures
« Reply #1601 on: September 19, 2017, 01:04:23 PM »
Just read through the Ned W/Jai discussion and I feel like a Yanomami tribesman from the Amazon rainforest who has just found himself at Wimbledon watching a tennis match without knowing the rules.
Eh.  The level of vitriol in that discussion was unpleasant, and it was off-topic for a thread on "global surface temperatures" anyway.  I started a new thread in the "Science" section of the ASIF, which hopefully will stay more on topic and have fewer insults.


FWIW, I thought you handled the situation(s) admirably. I thoroughly enjoyed the discussion & might even have learned something. ;<}


Best to all
Terry

GeoffBeacon

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Re: Global Surface Air Temperatures
« Reply #1602 on: September 19, 2017, 02:15:59 PM »
I've been looking at Carbon Brief's Guest post: Why the 1.5C warming limit is not yet a geophysical impossibility

It's by Dr Richard Millar who is is a postdoctoral research fellow at the Oxford Martin Net Zero Carbon Investment Initiative.

I'm rather resistant to it's underlying message, which I think is erring on the side of least drama. Has anyone else this feeling?
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Shared Humanity

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Re: Global Surface Air Temperatures
« Reply #1603 on: September 19, 2017, 02:28:14 PM »
Just read through the Ned W/Jai discussion and I feel like a Yanomami tribesman from the Amazon rainforest who has just found himself at Wimbledon watching a tennis match without knowing the rules.
Eh.  The level of vitriol in that discussion was unpleasant, and it was off-topic for a thread on "global surface temperatures" anyway.  I started a new thread in the "Science" section of the ASIF, which hopefully will stay more on topic and have fewer insults.


FWIW, I thought you handled the situation(s) admirably. I thoroughly enjoyed the discussion & might even have learned something. ;<}


Best to all
Terry

My main point was not about the supposed vitriol but the back and forth nature of a discussion that presented information I have no hope of understanding. My second post was intended to highlight what I do understand and that is the relentless and rapidly accelerating warming of the planet. Whether Ned or Jai are more on point and whether I understand their thoughtful, informed points of view seems to have little impact on this simple fact.
« Last Edit: September 19, 2017, 02:51:01 PM by Shared Humanity »

Daniel B.

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Re: Global Surface Air Temperatures
« Reply #1604 on: September 19, 2017, 02:54:47 PM »
I've been looking at Carbon Brief's Guest post: Why the 1.5C warming limit is not yet a geophysical impossibility

It's by Dr Richard Millar who is is a postdoctoral research fellow at the Oxford Martin Net Zero Carbon Investment Initiative.

I'm rather resistant to it's underlying message, which I think is erring on the side of least drama. Has anyone else this feeling?

Not sure that he is erring on any side.  He is appearing to be rather candid, and making his contentions without fanfare or passion.  His claim is that if we can start reducing emissions in earnest by 2020, and fall to near-zero emissions by 2050, that we will maintain warming to below 1.5C.  This is a reasonable plan, that most can live with.

Ned W

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Re: Global Surface Air Temperatures
« Reply #1605 on: September 19, 2017, 04:12:29 PM »
I've been looking at Carbon Brief's Guest post: Why the 1.5C warming limit is not yet a geophysical impossibility

It's by Dr Richard Millar who is is a postdoctoral research fellow at the Oxford Martin Net Zero Carbon Investment Initiative.
The Millar et al. paper is here

I've only skimmed it so far and have not at all begun to really assimilate it.  As I understand it (disclaimer!) it's based on assumptions about the distribution of values for TCR and ECS that ultimately come from the IPCC AR5, which they note is consistent with observations but lower than (some) models:

Our median estimate climate response (TCR = 1.6 °C, ECS = 2.6 °C) is defined as the median of log-normal distributions consistent with IPCC-AR5 likely bounds on the TCR and ECS (TCR: 1.0–2.5 °C; ECS: 1.5–4.5 °C). From this, the likely above/below values are found from the 33rd and 67th percentiles of the distribution (TCR: 1.3–1.9 °C; ECS: 2.0–3.3 °C). The median TCR of this log-normal distribution is significantly lower than in the IPCC-AR5 ESM ensemble but is more consistent with observed warming to date than many ensemble members (see Supplementary Methods), indicative of the multiple lines of evidence used to derive the IPCC-AR5 uncertainty ranges.
Those values of TCR and ECS are reasonably realistic IMVHO (though others here will vehemently disagree) but I'm still dubious about Millar et al's conclusions regarding avoidance of 1.5 C warming.  I will wait to say more until I've had time to read further.

Shared Humanity

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Re: Global Surface Air Temperatures
« Reply #1606 on: September 19, 2017, 04:14:37 PM »

Not sure that he is erring on any side.  He is appearing to be rather candid, and making his contentions without fanfare or passion.  His claim is that if we can start reducing emissions in earnest by 2020, and fall to near-zero emissions by 2050, that we will maintain warming to below 1.5C.  This is a reasonable plan, that most can live with.

I am in agreement except with the last statement in bold. Most people in the U.S. are still opposed to such a plan.

AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1607 on: September 19, 2017, 05:07:45 PM »
I've been looking at Carbon Brief's Guest post: Why the 1.5C warming limit is not yet a geophysical impossibility

It's by Dr Richard Millar who is is a postdoctoral research fellow at the Oxford Martin Net Zero Carbon Investment Initiative.
The Millar et al. paper is here

I've only skimmed it so far and have not at all begun to really assimilate it.  As I understand it (disclaimer!) it's based on assumptions about the distribution of values for TCR and ECS that ultimately come from the IPCC AR5, which they note is consistent with observations but lower than (some) models:

Our median estimate climate response (TCR = 1.6 °C, ECS = 2.6 °C) is defined as the median of log-normal distributions consistent with IPCC-AR5 likely bounds on the TCR and ECS (TCR: 1.0–2.5 °C; ECS: 1.5–4.5 °C). From this, the likely above/below values are found from the 33rd and 67th percentiles of the distribution (TCR: 1.3–1.9 °C; ECS: 2.0–3.3 °C). The median TCR of this log-normal distribution is significantly lower than in the IPCC-AR5 ESM ensemble but is more consistent with observed warming to date than many ensemble members (see Supplementary Methods), indicative of the multiple lines of evidence used to derive the IPCC-AR5 uncertainty ranges.
Those values of TCR and ECS are reasonably realistic IMVHO (though others here will vehemently disagree) but I'm still dubious about Millar et al's conclusions regarding avoidance of 1.5 C warming.  I will wait to say more until I've had time to read further.

Ned,

You are correct that "... others here will vehemently disagree ..." that using AR5 median values for TCR and ECS is a good idea for calculating the remaining carbon budget, as Proistosescu & Huybers (2017), and others since AR5 was published, have clearly demonstrated that AR5 erred on the side of least drama w.r.t. these values:

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821

Extract: "The latest Intergovernmental Panel on Climate Change Assessment Report widened the equilibrium climate sensitivity (ECS) range from 2° to 4.5°C to an updated range of 1.5° to 4.5°C in order to account for the lack of consensus between estimates based on models and historical observations. The historical ECS estimates range from 1.5° to 3°C and are derived assuming a linear radiative response to warming. A Bayesian methodology applied to 24 models, however, documents curvature in the radiative response to warming from an evolving contribution of interannual to centennial modes of radiative response. Centennial modes display stronger amplifying feedbacks and ultimately contribute 28 to 68% (90% credible interval) of equilibrium warming, yet they comprise only 1 to 7% of current warming. Accounting for these unresolved centennial contributions brings historical records into agreement with model-derived ECS estimates."

See also the linked article entitled: "Why the climate is more sensitive to carbon dioxide than weather records suggest"

https://phys.org/news/2017-07-climate-sensitive-carbon-dioxide-weather.html

Extract: "According to their statistical analysis, historical weather observations reveal only a portion of the planet's full response to rising CO₂ levels. The true climate sensitivity will only become manifest on a time scale of centuries, due to effects that researchers call "slow climate feedbacks".

To understand this, it is important to know precisely what we mean when we talk about climate sensitivity. So-called "equilibrium climate sensitivity", or slow climate feedbacks, refers to the ultimate consequence of climate response – in other words, the final effects and environmental consequences that a given greenhouse gas concentration will deliver.

These can include long-term climate feedback processes such as ice sheet disintegration with consequent changes in Earth's surface reflection (albedo), changes to vegetation patterns, and the release of greenhouse gases such as methane from soils, tundra or ocean sediments. These processes can take place on time scales of centuries or more. As such they can only be predicted using climate models based on prehistoric data and paleoclimate evidence.

On the other hand, when greenhouse gas forcing rises at a rate as high as 2–3 parts per million (ppm) of CO₂ per year, as is the case during the past decade or so, the rate of slow feedback processes may be accelerated.

Measurements of atmosphere and marine changes made since the Industrial Revolution (when humans first began the mass release of greenhouse gases) capture mainly the direct warming effects of CO₂, as well as short-term feedbacks such as changes to water vapour and clouds.
A study led by climatologist James Hansen concluded that climate sensitivity is about 3℃ for a doubling of CO₂ when considering only short-term feedbacks. However, it's potentially as high as 6℃ when considering a final equilibrium involving much of the West and East Antarctic ice melting, if and when global greenhouse levels transcend the 500-700ppm CO₂ range."

Edit: Please note that in the first attached image that the bar for observational ICS values entitled "Marvel et al 2016; Otto et. al. accounting for efficacy" has a median value for ICS of about 3.25C (and an upper value close to 8C); which is close to the median value on the bar entitled "PH17 (w/Lewis Comments)" for the modeled value of ICS.  However, the median value of the modeled ECS value for the bar entitled "PH 17" [Proistosescu & Huybers (2017)] is close to 3.7C (with an upper value close above 6C).  This is all evidence that AR5 errs on the side of least drama.

Edit 2:  The first attached image is from: "Sensible Questions on Climate Sensitivity"

http://www.realclimate.org/index.php/archives/2017/08/sensible-questions-on-climate-sensitivity/
« Last Edit: September 19, 2017, 05:14:43 PM by AbruptSLR »
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jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1608 on: September 19, 2017, 05:54:09 PM »
Glen Peters has a good blog post on this recent paper

http://www.cicero.uio.no/no/posts/nyheter/commentary-did-15c-suddenly-get-easier

We know that global average temperatures may increase as much as 0.25°C per decade, and that would mean it would take 20 years (two decades) to go from about 1°C today to 1.5°C. Since we emit about 40 billion tonnes CO2 per year, that would give a budget of about 800 billion tonnes of CO2 if we assumed emissions remained constant.

so, their definition of budget is:

The amount of emissions we can produce before GMST crosses the 1.5C threshold.

which is like saying, "we are moving at 200 Km per hour and cannot possibly stop in time to prevent a collision with a brick wall, but we DO have 170 meters until we crash"  So we have a 'budget' of 170 meters.

Also see his excellent post on the difference between *exceed* and *avoid* CO2 budgets

http://www.cicero.uio.no/no/posts/klima/should-climate-policy-aim-to-avoid-2c-or-to-exceed-2c

Note (of all people) posted this:  https://twitter.com/RichardTol/status/910125828410888192

A carbon budget should be a function of cumulative emissions and climate sensitivity, not of the actual temperature.

(perhaps I should repost in "Conservative Scientists and its Consequences" thread. . .  >:( )

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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1609 on: September 21, 2017, 05:01:40 PM »
The linked article emphasizes that CMIP5 projections have not 'exaggerated' global warming:

Title: "Factcheck: Climate models have not ‘exaggerated’ global warming"

https://www.carbonbrief.org/factcheck-climate-models-have-not-exaggerated-global-warming

Extract: "The results of model/observation comparisons differ greatly based on the dataset used, the model outputs analysed – model air temperatures or blended model air/ocean temperatures – and the time period examined. While the Millar et al study points out some sizable differences between the HadCRUT record and the model air temperature field, this should not be generalised to conclude that warming projections are unreliable or that warming has been ‘exaggerated by faulty models’. The paper’s real focus is on carbon budgets and carbon cycle accuracy, rather than model/observation comparisons of the warming associated with increased atmospheric greenhouse gas concentrations, and their results have little bearing on our understanding of climate sensitivity."
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1610 on: September 21, 2017, 06:43:27 PM »
Ed Hawkins (Climate Lab Book) also has a new post addressing this model/data comparison problem, based on Medhaug et al. 2017

Are the models “running too hot”?

Short answer: No, the models are not "running too hot".

I actually hate the graph included in that post (it's from Medhaug 2017) which IMHO would likely confuse the casual reader more than necessary.  The key point is the similarity between the darkest orange thin line (Estimated GMST) and the dark blue thin line (CMIP5 GMST with forcing and variability). 


AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1611 on: September 21, 2017, 10:29:04 PM »
I note that Hawkins et al (2017) defines the pre-industrial baseline to be from 1720-1800 for determining GMSTA, and indicates that as the AR5 projections are baselined to the 1896-2005 baseline, one needs to add about 0.6C to the AR5 GMSTA projections to reference them to the pre-industrial baseline.  I note that means that climate sensitivity is slightly higher than previously thought (when using 1850-1900 observations as a baseline).

Hawkins, E., P. Ortega, E. Suckling, A. Schurer, G. Hegerl, P. Jones, M. Joshi, T. Osborn, V. Masson-Delmotte, J. Mignot, P. Thorne, and G. van Oldenborgh (2017), "Estimating changes in global temperature since the pre-industrial period", Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-16-0007.1

http://journals.ametsoc.org/doi/10.1175/BAMS-D-16-0007.1
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0007.1

Abstract: "Better defining (or altogether avoiding) the term ‘pre-industrial’ would aid interpretation of internationally agreed global temperature limits and estimation of the required constraints to avoid reaching those limits.
The United Nations Framework Convention on Climate Change (UNFCCC) process agreed in Paris to limit global surface temperature rise to ‘well below 2°C above pre-industrial levels’. But what period is ‘pre-industrial’? Some-what remarkably, this is not defined within the UNFCCC’s many agreements and protocols. Nor is it defined in the IPCC’s Fifth Assessment Report (AR5) in the evaluation of when particular temperature levels might be reached because no robust definition of the period exists. Here we discuss the important factors to consider when defining a pre-industrial period, based on estimates of historical radiative forcings and the availability of climate observations. There is no perfect period, but we suggest that 1720-1800 is the most suitable choice when discussing global temperature limits. We then estimate the change in global average temperature since pre-industrial using a range of approaches based on observations, radiative forcings, global climate model simulations and proxy evidence. Our assessment is that this pre-industrial period was likely 0.55–0.80°C cooler than 1986-2005 and that 2015 was likely the first year in which global average temperature was more than 1°C above pre-industrial levels. We provide some recommendations for how this assessment might be improved in future and suggest that reframing temperature limits with a modern baseline would be inherently less uncertain and more policy-relevant."
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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1612 on: September 24, 2017, 03:14:54 AM »
Per the linked websites, August 2017 GISTEMP was the second warmest August in 137 years of modern record-keeping:

https://www.skepticalscience.com/2017-SkS-Weekly-News-Roundup_38.html

&

https://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt
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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1613 on: October 06, 2017, 04:55:25 PM »
The linked article notes how relatively well current climate models match current observations (see attached table); however, I warn that as GMSTA approaches/exceeds 2C model projections become increasingly nonlinear and the best models indicate that climate sensitivity increases with increasing GMSTA:

Title: "Analysis: How well have climate models projected global warming?"

https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming

Extract: "Climate models published since 1973 have generally been quite skillful in projecting future warming. While some were too low and some too high, they all show outcomes reasonably close to what has actually occurred, especially when discrepancies between predicted and actual CO2 concentrations and other climate forcings are taken into account.

Models are far from perfect and will continue to be improved over time. They also show a fairly large range of future warming that cannot easily be narrowed using just the changes in climate that we have observed."
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Sigmetnow

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Re: Global Surface Air Temperatures
« Reply #1614 on: October 08, 2017, 04:54:53 PM »
Limited to Arctic air temps in the satellite era, but shows the trend beautifully.
(Also posted in 2017 Melting Season.)

Monthly Arctic air temperature (925hPa) rankings over the satellite era (from 1979)

Additional temperature graphics  http://sites.uci.edu/zlabe/arctic-temperatures/
https://twitter.com/ZLabe/status/915964532282974208
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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1615 on: October 17, 2017, 06:04:57 PM »
The GISS LOTI value of 80 was recently posted for September 2017.  This give a GMSTA above pre-industrial of 1.15C for a 12-month running GISS LOTI assuming the following conversion (To convert 1951-1980 temp departures to pre-industrial add: + 0.256 Celsius).  This is not good news considering that the ENSO condition is currently on the cold side of neutral.
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rboyd

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Re: Global Surface Air Temperatures
« Reply #1616 on: October 18, 2017, 03:19:22 AM »
If this is anywhere near accurate, then October is not looking good GMST (the black line) wise. The northern hemisphere is looking particularly warm.

http://www.karstenhaustein.com/climate.php
« Last Edit: October 18, 2017, 03:28:11 AM by rboyd »