Global warming discussion III

[Fudbucker]

I don't understand denialists. Even if the science was totally unclear, we know that humans can adversely affect the world's climate. One of the main causes of ozone layer depletion was wide-scale use of CFC's.

Even if you didn't know for sure, why would anyone think it's a good idea to pour gigatons of greenhouse gasses (and other crap) into the air?

 

[OCaptain]

So, what's the deal with this?

I'm not in the position to call BS on it, but it appears to be saying that there is a difference between what is measured and what is modelled, and that the measured suggests a warming hiatus.

http://www.nature.com/articles/natu...vuEYrapHPwKqTIxQ8zqCUgIX09-WGK2cnMLr61k6J20PG

 

[Red Baron Farms]

So, what's the deal with this?

I'm not in the position to call BS on it, but it appears to be saying that there is a difference between what is measured and what is modelled, and that the measured suggests a warming hiatus.

http://www.nature.com/articles/natu...vuEYrapHPwKqTIxQ8zqCUgIX09-WGK2cnMLr61k6J20PG

Did you read it?

 

[OCaptain]

Yup.

What I'm hoping to see is a bit of an analysis of how this paper fits within the larger framework of what we know about AGW.

 

[CapelDodger]

Even if you didn't know for sure, why would anyone think it's a good idea to pour gigatons of greenhouse gasses (and other crap) into the air?

The actual idea is to burn fossil-fuels for industrial and domestic purposes - which, in its own terms, is a good idea. Another idea is to turn a blind eye to any unwelcome consequences - which is a bad one.

The CFC example is not so much about climate as it is about humanity's capacity to materially affect Earth's atmosphere as a whole (not just in, say, London or Pittsburgh). At first glance that appears unlikely but the evidence is in - we're in charge now.

 

[CapelDodger]

Yup.

What I'm hoping to see is a bit of an analysis of how this paper fits within the larger framework of what we know about AGW.

From what I can see it may add some detail to our understanding of the climate system, particularly noise, but doesn't materially affect the basic theory.

Abstract :

"Most present-generation climate models simulate an increase in global-mean surface temperature (GMST) since 1998, whereas observations suggest a warming hiatus. It is unclear to what extent this mismatch is caused by incorrect model forcing, by incorrect model response to forcing or by random factors. Here we analyse simulations and observations of GMST from 1900 to 2012, and show that the distribution of simulated 15-year trends shows no systematic bias against the observations. Using a multiple regression approach that is physically motivated by surface energy balance, we isolate the impact of radiative forcing, climate feedback and ocean heat uptake on GMST—with the regression residual interpreted as internal variability—and assess all possible 15- and 62-year trends. The differences between simulated and observed trends are dominated by random internal variability over the shorter timescale and by variations in the radiative forcings used to drive models over the longer timescale. For either trend length, spread in simulated climate feedback leaves no traceable imprint on GMST trends or, consequently, on the difference between simulations and observations. The claim that climate models systematically overestimate the response to radiative forcing from increasing greenhouse gas concentrations therefore seems to be unfounded."

I wouldn't be at all surprised to find it being misrepresented as something else by the usual suspects, but that's life on this crazy planet of ours.

 

[Red Baron Farms]

Yup.

What I'm hoping to see is a bit of an analysis of how this paper fits within the larger framework of what we know about AGW.

Maybe this will help then?

The claim that climate models systematically overestimate the response to radiative forcing from increasing greenhouse gas concentrations therefore seems to be unfounded.

 

[lomiller]

I guess I'm just a bit surprised that the high bit goes back so long - looks like something around 7000 years?

Warming out of the last glaciations started ~18 000 years ago and reached near modern temperatures ~12 000 years ago, and except for a short downturn called the younger Dryas event ~11 000 years ago continued to warm slowly until the Holocene optimum ~8 000 years ago.

It's hard to tell with such a squished graph. It's like trying to look at stuff in the tail of a claims distribution - it's almost impossible to get it on a scale that makes it make sense while simultaneoulsy comparing it to the left end of the distribution for relativity.

Current CO2 and temperature rise are too fast to display properly even on a 10 000 year time scale so 100K+ year will be a single pixel vertical line.

It looks like the CO2 "leads" the temperature changes - not in terms of time scale, necessarily, but in terms of variability. I'm having a hard time putting this in to words. It looks like in past periods, the CO2 "pulls" the temperature. So when the CO2 spikes above, it "drags" the temperature behind it... and then when it falls below it "drags" the temperature down. I can envision it as a two balls attached by springs. The CO2 ball oscillates in a wave pattern around a central axis. The temperature ball is attached to both the CO2 ball and the axis, so it get's "dragged" by the motion of the CO2 ball... but not as far as it would if it weren't attached to the central axis. That's what I mean by the CO2 "leading" the temperature.

Initial CO2 release should trail slightly because the initial CO2 release is triggered by orbital changes that do have a small warming effect on the planet.

CO2 and temperature are part of a feedback loop, so both respond to the other. In steady state the feedback loop acts to amplify the small changes in orbital forcing to something that can make significant changes in the earth’s climate. In transient state what’s going on is CO2 release cause temperature increase, which causes more CO2 to be released. As CO2 levels increase you need larger total release to get the same temperature increase so this cycle does eventually converge to a new stable state.

 

[lomiller]

So, what's the deal with this?

I'm not in the position to call BS on it, but it appears to be saying that there is a difference between what is measured and what is modelled, and that the measured suggests a warming hiatus.

That is not what it’s saying.

What it says is that surface temperature changes over short time spans like don’t necessarily follow the forcing that drive the trend over longer time spans.

This isn’t a property of the models it’s a property of the system being modeled. Climate is one form a chaotic system can take where over the long term things follow an attractor, but over shorter periods it will behave as a random variation above/below the attractor called internal variation.

This paper looks at this internal variation another way and comes to the same conclusion you get just doing statistical analysis on the data, that is individual 15 year trends don’t tell you anything about the longer term trend.

 

[Emily's Cat]

Lol. I said everything backwards. I got the blue line and the red line mixed up

Feedback also makes sense, so thank all of you for your really awesome explanations!

 

[macdoc]

Yup.

What I'm hoping to see is a bit of an analysis of how this paper fits within the larger framework of what we know about AGW.

One of the missing bits in many people's understanding is how small the SST aspect is.

Far and away the largest heat gain from AGW is in the ocean

Using a multiple regression approach that is physically motivated by surface energy balance, we isolate the impact of radiative forcing, climate feedback and ocean heat uptake on GMST—with the regression residual interpreted as internal variability—and assess all possible 15- and 62-year trends. The differences between simulated and observed trends are dominated by random internal variability over the shorter timescale and by variations in the radiative forcings used to drive models over the longer timescale. For either trend length, spread in simulated climate feedback leaves no traceable imprint on GMST trends or, consequently, on the difference between simulations and observations.

The ocean can both absorb more heat than average - La Nina or, in the case of El Nino, release massive heat back to the atmosphere. The scale of energies is astounding

This internal variability can produce transients in the short term but will stay on the trend line in the long term as the paper clearly states,

For either trend length, spread in simulated climate feedback leaves no traceable imprint on GMST trends or, consequently, on the difference between simulations and observations.

Picture and thousand words??

 

[CoolSceptic]

I pointed out to lomiller that 15 years ago is Jan 2000, which doesn't include 1998 and doesn't even suffer from autocorrelation with it (as 1999 does).

And I showed that this claim was complete nonsense. Oh and autocorrelation in climate extends far beyond a single year, so you are wrong on that too.

1998 has dropped off the short-term perch, so to speak.

And, as I pointed out, that makes absolutely no difference to a properly conducted analysis. Of course, if you are unaware how a properly conducted analysis is done, you may not appreciate this point.

To be fair, I feel sorry for you guys. It is clear from the basic statistical errors that you, lomiller and Pixel42 make that you do not have sufficient numeracy to assess whether the claims of climate scientists are correct or not. And those presenting a mainstream view are unlikely to correct you. And in that situation, I can understand why you defer to them. Here we are, largely anonymous individuals on an internet forum; there is no responsibility or expectation of competence.

However, we do expect a level of competence from scientific journals, and in climate we just don't get that. The latest howler:

Marotzke and Forster’s circular attribution of CMIP5 intermodel warming differences

This kind of incompetence in a prestigious journal is simply unacceptable and in the long run harms the reputation of science. It really doesn't matter about silly pedantic bun fights over stats on an internet forum. In some ways a degree of warming over the next 100 years, even by natural variation alone, would perhaps avoid enormous embarrassment to the scientific community. Unfortunately, I suspect it is more likely that will not happen.

 

[CapelDodger]

And I showed that this claim was complete nonsense.

No, you didn't. The last 15 years really is Jan 2000 (well, Feb 2000 now but who's counting) to Jan 2015.

Oh and autocorrelation in climate extends far beyond a single year, so you are wrong on that too.

Your evidence for that?

1998 has dropped off the short-term perch, so to speak.

And, as I pointed out, that makes absolutely no difference to a properly conducted analysis. Of course, if you are unaware how a properly conducted analysis is done, you may not appreciate this point.

You seem not to get the point that there's no point in any analysis of such a short period.

To be fair, I feel sorry for you guys. It is clear from the basic statistical errors that you, lomiller and Pixel42 make that you do not have sufficient numeracy to assess whether the claims of climate scientists are correct or not.

Simply dripping with essence of Dunning-Kruger.

This kind of incompetence in a prestigious journal is simply unacceptable ...

No doubt they'd be mortified to hear it, but then they're not likely to, are they? Whereas you've heard of them. It's all down to prestige, really. You earn it and keep it or you don't got it. They still have it and you don't. Makes you think,doesn't it?

It's rather obvious that you've only recently been introduced to the world of statistics since you've only recently begun to entertain us with your expertise in the subject. A little knowledge, as the saying goes, is a hilarious thing.

 

[CoolSceptic]

No, you didn't. The last 15 years really is Jan 2000 (well, Feb 2000 now but who's counting) to Jan 2015.

You seem confused. I showed differencing single months the way you did gets ridiculous answers whatever you cherry pick. But you need some statistical abilities to realise that.

Your evidence for that?

That claim isn't controversial, just ask any mainstream climate scientist. Since you are far more likely to believe them than me, even if I do present you with evidence.

You seem not to get the point that there's no point in any analysis of such a short period.

Once again, quite wrong. There is no magic time period at which analysis becomes pointless. A 40W/m^2 forcing would be detectable on a daily measure of temperature.

To understand whether something is pointless, you need to know what the forcings are, and what the uncertainties are. I even demonstrated the difference between the difference in sample variance of 15 year trends and 30 year trends, and code to calculate it. (The difference isn't actually that great; just under 50%, which is the difference between the forcing that you would be able to detect).

It's rather obvious that you've only recently been introduced to the world of statistics since you've only recently begun to entertain us with your expertise in the subject. A little knowledge, as the saying goes, is a hilarious thing.

Pretty sure I've been posting occasionally here and elsewhere about stats (and other related topics) for several years now. I usually avoid this thread because of the astonishing levels of arrogant cluelessness on display.

 

[CapelDodger]

So, what's the deal with this?

I'm not in the position to call BS on it, but it appears to be saying that there is a difference between what is measured and what is modelled, and that the measured suggests a warming hiatus.

http://www.nature.com/articles/natu...vuEYrapHPwKqTIxQ8zqCUgIX09-WGK2cnMLr61k6J20PG

SkS have a user-friendly piece on it :

http://www.skepticalscience.com/climate-climate-models-overestimate-warming-unfounded.html

"Choosing a 15-year period over which to examine surface temperatures is arbitrary. You can get almost any trend depending on which year you choose as the starting point.

Well there's a thing .

That's why it's important to look at other 15-year periods in Earth's temperature record to see whether or not the most recent one is unusual, the new paper explains.

The authors looked at every possible 15-year period since the beginning of the 20th century. The first spans the period 1900-1914, the next one 1901-1915 and so on, right up to 2012.

The paper uses surface temperature data from the HadCRUT4 record, jointly produced by the UK Met Office and the Climatic Research Unit at the University of East Anglia (UEA).

For each 15-year period, the authors compared the temperature change we've seen in the real world with what the climate models suggest should have happened.

Over the 112-year record, the authors find no obvious pattern in whether real-world temperature trends are closer to the upper end of what model project, or the lower end.

In other words, while the models aren't capable of capturing all the "wiggles" along the path of rising temperatures, they are slightly too cool just as often as they're slightly too warm."

Short version : 15 year trends don't mean diddly.

 

[bit_pattern]

However, we do expect a level of competence from scientific journals, and in climate we just don't get that. The latest howler:

Marotzke and Forster’s circular attribution of CMIP5 intermodel warming differences

This kind of incompetence in a prestigious journal is simply unacceptable and in the long run harms the reputation of science.

If it's such a howler then why doesn't McIntyre or Lewis write up a rebuttal and have it published rather than blogging about it?

 

[Mikemcc]

If we are talking about statistical competency I'll plump for Tamino:

https://tamino.wordpress.com/2015/01/20/its-the-trend-stupid-3/

Pause, what pause?

 

[macdoc]

The 900 lb gorilla lurking that WILL surface somewhere.....5 C above average on a good chunk of the Pacific...any care to guess the Hiroshima thermal units that represents????!!

And some are noodling on about .066 sst .....

 

[researcherTony]

Question:

Point # 1 - With all this ice melting. 2015 Sept all Arctic ice may be all gone for the first time (summer time).

Point #2 - Most of the carbon goes into the ocean and the heat goes there too.

So why is the ocean rate of rise still growing so slowly, like in millimeters.

 

[macdoc]

Ummm...there is a lot of ocean?

Ask Miami about accelerating in rate of change...they are up to 17 mm per annum now from 5 or less.

http://www.rsmas.miami.edu/blog/2014/10/03/sea-level-rise-in-miami/

As to point 2.....somehow "most" doesn't seem to apply to your carbon comment....280 to 400 PPM+ rise means there's an awful lot of "residue" left in the air each year..