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Global warming discussion III

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Why? The IPCC did it properly, and because they did it properly they reached the correct conclusions.
How would you know if they were doing it "properly", or even whether your interpretation of their conclusions are actually the same as the conclusions they claimed? The whole point of the discussion Pixel42 triggered was to try and understand what the numbers were; I should give credit for Pixel42 at least trying to look at numbers (even if the analysis wasn't very meaningful), which is far more than you have presented, which is just assertion.

You seem to be missing the point of scepticism. Unless you actually understand to some degree what was done, you are in no position to judge whether something is right or wrong. I've given you guys some leeway here, acknowledging that because you don't really understand the statistics, you have little choice but to believe the IPCC (or at least what you understand the IPCC to be telling you, which is unfortunately often filtered through activists who care little for actual science).

Again you would need to apply that to the model runs not the observations. Doing this would tell you how long a period you would need to look at to observe statistically significant acceleration. This time period is longer than the 20-30 years needed for the first derivative.
Once again, your strange belief in 30 years as being some magic number at which things become significant is hopelessly misguided. The difference between 15 years, 30 years and 60 years is not all that great. I've demonstrated that with actual numbers, you've demonstrated it by (1) assertion - worthless to a sceptic - and (2) by appeal to authority of the IPCC, which could carry some validity if you could actually back it up by showing what analysis you are referring to and we can then put the IPCC position in place of your assertion, but you have provided nothing.

As I mentioned earlier, what I have presented is utterly uncontroversial amongst actual scientists, even to the point that it is rarely discussed (because it is so blindingly obvious). Yet you dispute it. Earlier today I stumbled across a good example of a climate scientist highlighting this bizarre attachment to 30 years in a blog post from a couple of months back:

Natural Variability and Chaos – Four – The Thirty Year Myth

I note it is typically environmental activists who have this strange attachment to 30-year trends, with limited understanding of science, rather than *actual climate scientists*, although scienceofdoom does highlight a rather unhelpful cartoon by the IPCC which does appear to rather perpetuate the myth.

Also, it is quite inappropriate to use model runs to determine the error margins discussed. The error margins are sensitive to the autocorrelation structure of natural variability, and it is well known that the autocorrelation structure of models does not match the real world well at all. Unfortunately the observational record is too short to get really good accurate estimates of the autocorrelation function as well, which is why in practice nobody has correctly determined the population error margins. (Hopefully you understand the distinction between population error margins - the "true" error margins - and the sample error margins which I presented earlier, which are meaningful, but biased)

Regardless, the trend line you are trying to call "trend from IPCC model results" doesn't match what the model runs show for the period 2000 - 2015.
Ah, you're trying to cover up for CapelDodger's mistake now. I was responding to CapelDodger who referred to the "long-term trend", not what the model runs show for 2000-2015. Goalpost moving noted, though.
 
Natural Variability and Chaos – Four – The Thirty Year Myth

I note it is typically environmental activists who have this strange attachment to 30-year trends, with limited understanding of science, rather than *actual climate scientists*, although scienceofdoom does highlight a rather unhelpful cartoon by the IPCC which does appear to rather perpetuate the myth.

Deeply ironic that you would preface this statement with a link to a denier blog :eek:
 
"ScienceOfDoom" is classed as a "denier" blog by activists now is it?

Yup.

*Actual climate scientists* publish *actual climate science* in *actual climate science journals* - if your argument had the slightest shred of credibility you'd be able to point to an *actual published climate science paper* which says that 30 year trends aren't relevant.
 
From "The Science of Doom"
http://scienceofdoom.com/2015/02/04/the-holocaust-climate-science-and-proof/

"So when we need to demonstrate that the greenhouse effect is real, and that it increases with more GHGs we need some equations."

[snip]

"And equally obviously, anyone questioning the validity of the equation, or the results from the equation, is doing so from evil motives."

Sounds like a real scientist :D
 
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I don't know about anyone else but when it comes to climate I've always used the term denial in the Kübler-Ross sense of the word... But in all seriousness, the whole Holocaust thing is really just rank equivocation that is typical of the victimisation that pervades all forms of denial and conspiracy theorising. When people resort to such histrionics, it is usually a very good indicator that you are dealing with a denier, no matter how convincingly sciency they come across.
 
The whole point of the discussion Pixel42 triggered was to try and understand what the numbers were; I should give credit for Pixel42 at least trying to look at numbers (even if the analysis wasn't very meaningful), which is far more than you have presented, which is just assertion.
I did no analysis, I simply demonstrated that the range of values you get for the underlying trend if you look back 15 years over a five year period is far greater than the range of values you get if you look back 30 years from the same five year period.

The period over which an underlying trend can be reliably detected and measured depends on the size of the trend and the amplitude of the noise. In this case the expected trend is an average of 0.15 - 0.2C per decade, natural variations can cause as much as 0.2C difference from one year to the next, and the period over which some of the sources of those variations tend to cancel out is of the order of one or two decades. You don't need to be a mathematician to understand why 15 year trends are not going to be very informative, especially if you cherry pick start and/or end points for the 15 year period at peaks or troughs.

I've given you guys some leeway here, acknowledging that because you don't really understand the statistics, you have little choice but to believe the IPCC (or at least what you understand the IPCC to be telling you, which is unfortunately often filtered through activists who care little for actual science).
It may be nearly 40 years since I obtained my degree in Mathematics but I retain enough to recognise "arrogant cluelessness" when I see it. The amount in this thread has reduced since posters like mhaze, Poptech and r-j got themselves banned, but we still have Haig and a few other drivebys regularly depositing fresh samples. I do not see it in the posts of the majority of posters who take the time to read and understand what the IPCC, and the climatologists whose work it summarises, are actually saying.
 
From "The Science of Doom"
http://scienceofdoom.com/2015/02/04/the-holocaust-climate-science-and-proof/

"So when we need to demonstrate that the greenhouse effect is real, and that it increases with more GHGs we need some equations."

[snip]

"And equally obviously, anyone questioning the validity of the equation, or the results from the equation, is doing so from evil motives."

Sounds like a real scientist :D
Right. So in a blog where almost all of the posts are technical, including a complete mathematical description of the greenhouse effect (and why it is real) that you will not find on any other blog, you pick a post which is not technical, but discussing the tone of the climate debate, and you selectively quote a piece which is dripping with sarcasm.

OK, I will admit that writing a piece about the tone of the debate and laying on heavy sarcasm perhaps is a little counter-productive. You can see from the comments several people misunderstood the sarcastic sections.

But I asked a simple question. What exactly does scienceofdoom deny? Please point to a technical post to illustrate, rather than a post discussing civility in the climate debate.

Things to bear in mind. One, the blog is run by Dr Steve Carson, who used to work at the Geophysical Fluid Dynamics Laboratory in NOAA (but as far as I can tell left that job to become a science teacher - something I suspect he does very well judging from his technical blog posts). Also, he received an award via John Cook of SkepticalScience for his blogging:

Woody Guthrie award to Science of Doom

I've not seen any technical posts on the global warming threads of this forum that come anywhere close to his work. And I still don't even know what you lot thinks he denies.

Alternatively, you guys can stop scoring ridiculous own goals by poisoning the well before you know the first thing about the blogs in question. Just a thought.
 
Yup.

*Actual climate scientists* publish *actual climate science* in *actual climate science journals* - if your argument had the slightest shred of credibility you'd be able to point to an *actual published climate science paper* which says that 30 year trends aren't relevant.
Actual climate scientists publishing in actual climate science journals... like this one:

Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages
Hmm, wonder who that "SR Carson" dude is.

Incidentally, I would post an actual science paper showing that 30 year trends "aren't relevant" if I had made that argument. Since I didn't actually make that argument, I won't be any time soon.

Any other straw men you want to get off your chest before we move on?
 
I did no analysis
Yes, you did. You went and got some numbers and divided the max by the min and made some inferences. I know in the bigger scheme of things, it is pretty simplistic, but it still forms an analysis. And I explained why you should not have taken a ratio, and why you should use more than 5 samples when estimating spreads of values (a sample standard deviation calculated from just five samples, when used as an estimate of the population standard deviation, carries a VERY fat-tailed student's T distribution with five degrees of freedom)

The period over which an underlying trend can be reliably detected and measured depends on the size of the trend and the amplitude of the noise.
Hey look, this is good! This is EXACTLY the point I made earlier on. See, we have some points of agreement!

In this case the expected trend is an average of 0.15 - 0.2C per decade
OK, and this is similar to what I said, I had the 0.2 deg C per decade from IPCC, and CapelDodger (reasonably) added the 0.16 deg C per decade short term trend, so we're generally in agreement here too.

natural variations can cause as much as 0.2C difference from one year to the next
OK, I haven't checked this, but it doesn't sound unreasonable

and the period over which some of the sources of those variations tend to cancel out is of the order of one or two decades.
Ah, right. This is where we disagree. Whether variations "cancel out" or not is entirely dependent on the shape of the autocorrelation function of natural variability, which we do not know.

Furthermore, even with no assessment of the autocorrelation function, the variance on 15 year trends is only slightly greater than those of 30 year trends, which I demonstrated; a factor of about root 2. As detection is about magnitude of forcing over variability (something we agree on), this means that to be detected by thirty year trends, but not 15 year trends, you are tacitly admitting that you are right on the margins of detectability, due to this small difference.

You don't need to be a mathematician to understand why 15 year trends are not going to be very informative, especially if you cherry pick start and/or end points for the 15 year period at peaks or troughs.
A lot of assumptions here, many of which we agree on, but a couple of points we sharply disagree on. But progress of a sort...

It may be nearly 40 years since I obtained my degree in Mathematics but I retain enough to recognise "arrogant cluelessness" when I see it.
Well, I'm not the one dividing max and min of bipolar random variables. But then, maybe you missed that lecture, or have since forgotten it.

The amount in this thread has reduced since posters like mhaze, Poptech and r-j got themselves banned, but we still have Haig and a few other drivebys regularly depositing fresh samples. I do not see it in the posts of the majority of posters who take the time to read and understand what the IPCC, and the climatologists whose work it summarises, are actually saying.
Oh I don't disagree that many here parrot uncritically an activist-interpreted and filtered version of the IPCC output, which is always entertaining to see. I just doubt many understand what they are discussing (at either end of the debate spectrum), and when I see either a complete lack of analysis, or someone dividing the max and min of a bipolar RV, alarms go off.

Don't get me wrong - there are some great scientific minds on this forum. Notably I don't recall one of them venturing into this thread.
 
Yes, you did.
No I did not. I pointed out that the largest 15 year trend was greater than the smallest by a factor of three in order to emphasise how much wider the spread of values was compared to that for 30 year trends.

15 year trends: 0.04 to 0.12C per decade, a spread of 0.08C
30 year trends: 0.15 to 0.17C per decade, a spread of 0.02C

Whether variations "cancel out" or not is entirely dependent on the shape of the autocorrelation function of natural variability, which we do not know.
Solar activity varies over an approximate 11 year cycle (or 22 years if you're pedantic). The ENSO cycle is less predictable but on average produces an El Nino (of varying severity) about once every five years. Volcanic activity is not predictable. These sources of noise are more likely to cancel themselves out over periods of 30 years than over periods of 15 years.
 
CS
Don't get me wrong - there are some great scientific minds on this forum. Notably I don't recall one of them venturing into this thread.

Yourself excepted of course... :dl:

What a load of bollocks...hiding "we don't know enough" agenda behind word salad lice chasing. I dare say you might even get paid by the word. If not...then the price is appropriate to the intrinsic value of the content. At least there is chew toy value if naught else. Denier chew toys getting rare these days.
 
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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.


Because Arctic ice is almost entirely sea ice. When sea ice melts, it doesn't affect sea level (much, if at all), because it's already displacing an equivalent volume of water.
 
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