News BBC on tipping point?

  • Thread starter Andre
  • Start date

sylas

Science Advisor
1,632
6
So if we now think that El Nino is important for climate, why blame el nino for a single year? and why not talk about the La Nina's after 1998 that would affect the trends just as well. Right now we have a considerable El Nino, does that change trends?
Because El Nino and La Nina IS a short term factor. In the same way as the volcanic eruption of Pinatubo was responsible for the short term cooling spike seen in 1992/1993.

There's nothing new about this being seen as important for climate; it has consistently been a feature of the IPCC reports.

We do indeed have an El Nino forming at present; and if that continues -- and if we don't get a big eruption -- then there is a strong probability that 2010 will set a new record for the hottest measured global anomaly. It doesn't even need to be as strong as the 1998 El Nino event, given the boost from the long term trend.

The evidence at this point is that these events don't affect trends themselves; they are rather short term changes in the climate mode, not a cummulative effect that could give a trend. They are a significant source of short term variation.

And can the current ENSO (El Nino Southerly Oscillation) activity be responsible for some of the recent warming?
Some of the recent rise in temperature since 2008? Of course. But longer term warming? No. The short term changes in temperature are much stronger than the long term trend, and so it is entirely proper to recognize the role of such things for making one year warmer than another.

Cheers -- sylas
 

Redbelly98

Staff Emeritus
Science Advisor
Homework Helper
12,038
128
So if we now think that El Nino is important for climate, why blame el nino for a single year? and why not talk about the La Nina's after 1998 that would affect the trends just as well. Right now we have a considerable El Nino, does that change trends?

And can the current ENSO (El Nino Southerly Oscillation) activity be responsible for some of the recent warming? like some 72% perhaps
Andre, I was not blaming El Nino. I was objectively looking at a graph of the data. The 1998 data point is clearly no basis for making claims about trends.

My opinion:
This should be obvious to anybody who
1. has some minimal scientific training.​
AND
2. takes a look at the annual temperature graph.​
 
Last edited:

Redbelly98

Staff Emeritus
Science Advisor
Homework Helper
12,038
128
The demoralizing part will come in another decade perhaps when it becomes ovbious to everybody that climate cannot be tamed by being good.
That is a pretty strong claim. Can you back it up please? If temperatures continue upward, one could always argue that we didn't do enough, or that it takes more than 10 years for our efforts to have an effect. To say that our efforts can do no good sounds, well, rather speculative.
 

sylas

Science Advisor
1,632
6
I've seen this take on Trenberth's email before, and don't want to let it pass again, so I'm jumping in here -

This is not my reading of Trenbert's email or paper. Your use of the terms 'instrument' and 'measure' implying the problem is a lack of a mechanical adroitness. No doubt Trenberth would like better instrumentation, as does every physical scientist, but he is allowing for a more a fundamental problem. The query "do we have an adequate system?" in the paper is not just a call for better sea gauges. It also allows there may be some gap in the understanding of the climate system. Some part of it may be unknown or misunderstood.
It's not "mechanical adroitness"; just a lack of an adequate system for tracking energy flows.

If you are going to read the emails, don't just stop at the one email only. There's a lot of selection going on in the press and blogs right now which is actively contributing to distortions of what the scientists were actually saying; and singling out this one email is a case in point. In fact this email is part of a longish exchange of emails in a quite heated discussion, where Trenberth is challenged to explain himself, and where he does just that.

Better than the emails is the paper, where it is all spelled out in much more detail and in a form that is intended for wider readers, without making assumptions about colleagues Trenberth knows well.

The paper is explicitly a call for better tracking systems; not a set of questions about theory. He points out gaps in knowledge, of course; but they are not new gaps. They are questions of detail that have never been known, and which require adequate data on energy flows before answers can be given. The travesty is the lack of adequate systems to obtain that data -- especially given its evident importance. There are always questions, of course. The questions Trenberth wants to address are the questions of detail in energy flow, and the great imperative to address those questions is adequate data. Without that, they can't get the detail of short term and regional change.

It's worth bearing in mind that if you are at all a skeptic about anthropogenic global warming, then you will be reading opinions you do not share. Trenberth is no doubt whatsoever about warming. In his own words from his paper: "global warming is unequivocally happening".

Look at the title of his paper. It is "An imperative for climate change planning: tracking Earth’s global energy". That is, in order to plan for climate change, it is imperative to track Earth's global energy. He really is focusing on the importance of measurements, and obtaining data.

Look at the abstract. (My bolding.)
Planned adaptation to climate change requires information about what is happening and why. While a long-term trend is for global warming, short-term periods of cooling can occur and have physical causes associated with natural variability. However, such natural variability means that energy is rearranged or changed within the climate system, and should be traceable. An assessment is given of our ability to track changes in reservoirs and flows of energy within the climate system. Arguments are given that developing the ability to do this is important, as it affects interpretations of global and especially regional climate change, and prospects for the future.

His focus is our ability to track changes. This information, this data, this measurement, is NEEDED in order to plan for adapting to climate change.

If you read any of this as needing data to be sure climate change is real, or to be sure that the planet really is warming, or to be sure that this is caused by anthropogenic effects, then you've not understood him at all. These are underlying basics that are thoroughly established to Trenberth's satisfaction; and indeed to the satisfaction of the vast majority of working climate scientists.

We can look at the alternative views of skeptics of AGW, of course, and we do it quite often. But that isn't the question here at all, when looking at Trenberth's concerns. It is entirely to do with tracking and measuring where Earth's energy goes, in detail, over short term variations and local regional changes.

Look at the top of page 20, right hand column. He starts out with the basic groundwork of what we do know.
The present-day climate is changing mainly in response to human-induced changes in the composition of the atmosphere as increases in greenhouse gases promote warming, while changes in aerosols can increase or diminish this warming regionally depending on the nature of the aerosols and their interactions with clouds. The current radiative imbalance at the TOA has increased from a very small imbalance only 40 years ago when carbon dioxide increases and radiative forcing were less than half of those today. The excess in heat does several things. ...
The warming, and the main cause of warming, is taken for granted. Sure, in principle, everything in science is open to question. But for working climate scientists, and Trenberth in particular, these are no longer the important unknowns. The unknowns are the modulating effects of aerosols and cloud -- which are smaller than the greenhouse warming but still significant and much less well known and hence a proper focus for investigation. He goes on to describe four effects of the known excess heat: only one of which is the increasing surface temperature.

But to get the detail of those effects, they must be measured, and on page 23 he comes back to his recurring complaint:
We cannot track energy in absolute terms because the accuracy of several measurements is simply not good enough.

sylas said:
Trenberth is, of course, in no doubt that the short term drop in temperature in 2008 is a local short term effect.
This contradicts statements in the paper. Yes if heat was somehow absorbed an ocean sink or melting ice, examples he gives, then the recent lack of temperature rise would be temporary. However he also allows:

(Trenberth 2009)
Was it compensated for temporarily by changes in clouds or aerosols, or other changes in atmospheric circulation that allowed more radiation to escape to space?
[highlights mine]

If the (excess) heat can escape to space now via some misunderstood mechanism it may (or may not) continue to do so.
This is not a contradiction at all; you've misunderstood him completely. Immediately prior to this he said:
The stock answer is that natural variability plays a key role [1] and there was a major La Nina event early in 2008 that led to the month of January having the lowest anomaly in global temperature since 2000. While this is true, it is an incomplete explanation. In particular, what are the physical processes?

He GIVES you the stock explanation. It really is short term natural variability for a cooler 2008. This is not in any credible doubt; and what is lacking is detail. We know the La Nina was involved; the question is... how does it do it, physically? Where does the energy go?

We KNOW the energy is there. The greenhouse forcing didn't suddenly stop, and there was no less sunlight. So all that energy was still coming in. HOW did that La Nina event lead to lowered temperatures? There are several credible possibilities.

The inference you have made is as follows: "If the (excess) heat can escape to space now via some misunderstood mechanism it may (or may not) continue to do so." That's not Trenberth's inference, or mine either. Trenberth is quite sure about the La Nina association, and recognizes that it definitely will not all just keep going on. It will go away at the next El Nino (which is now, as it turns out, and so we are hotting up again of course, just like we always do with El Nino).

The question Trenberth is asking is simply this: during these La Nina events, what is the actual energy flow that gives this short term cooling? It's not about some strange "misunderstood" mechanism. It's rather that we don't have the tracking systems in place to tell which mechanisms are the ones involved.

I've missed it if anyone in this thread attempted to say global warming stopped over the long term. The OP BBC piece phrase was "For the last 11 years we have not observed any increase", Andre used the term "stagnate", and Trenberth leaves it as an open question:
(Trenberth 2009) last paragraph:

A climate information system that firstly determines what
is taking place
and then establishes why is better able to
provide a sound basis for predictions and which can
answer important questions such as ‘Has global warming
really slowed or not?’
[highlights mine]
Trenberth is right. Andre, and Hudson, are wrong; or at least misleading.

We simply do not have the statistical data to say that global warming has "stagnated" or "slowed". As I showed in a previous post, this is a straight statistical question. We know the process involves both long term trend plus short term variations. And the trend may not be constant. So how can we tell whether it has really slowed or not? Most people seem to think you tell by just looking at trends with the data.

They are wrong. Statistically, the natural variation is too great to let you determine what the trend is doing from a short period of measurement, like eleven years. Heck, in all seriousness, the data is actually consistent with the global warming trend having accelerated!

That's what Trenberth is saying. Statistically you cannot tell what warming is doing by looking at eleven years of global anomalies. The skeptics take it for granted that global warming has "slowed" or "stagnated" or something else; which is incorrect. A short trend line does not let you infer that.

Trenberth notes that the only way you can possibly tell this is by actually understanding the natural variation, rather than simply treating it as a random process of some kind... which is what you do to estimate confidence limits on the trend calculations. So Trenberth is saying that it is imperative to get the tracking systems in place that actually let us measure where the energy is going. That's the key to understanding what is going on, because the trend is masked over the short term by natural variations.

Cheers -- sylas
 
4,453
57
That is a pretty strong claim. Can you back it up please? If temperatures continue upward, one could always argue that we didn't do enough, or that it takes more than 10 years for our efforts to have an effect. To say that our efforts can do no good sounds, well, rather speculative.
No it is not. The essence is the predominance of negative feedback, which precludes the "amplification" of the basic planck reaction of some 1.1 - 1.2 degrees per doubling CO2 as per Lindzen and Choi 2009 and diverse publications of Karner
 
4,453
57
Andre, I was not blaming El Nino. I was objectively looking at a graph of the data. The 1998 data point is clearly no basis for making claims about trends.

My opinion:
This should be obvious to anybody who
1. has some minimal scientific training.​
AND
2. takes a look at the annual temperature graph.​
Again, once more, maybe the essence is that Trenberth acknowledges no warming:

... we can't account for the lack of warming at the moment ...
would that depend on any starting year?
 

sylas

Science Advisor
1,632
6
Again, once more, maybe the essence is that Trenberth acknowledges no warming:



would that depend on any starting year?
Of course it would. Reading the actual context of that quote makes it abundantly clear that Trenberth is specifically talking about accounting for where energy flows during the short term variations which dominate climate over the short term. The context also shows that Trenberth is in no doubt whatsoever that this is about short term variation on top of an unambiguous warming trend.

More detail in [post=2499641]msg #29[/post]. A comparison of my msg #29 with Andre's use of a half-a-sentence and no context demonstrates just how badly you can misrepresent someone when you cherry pick phrases and ignore meanings. Sheesh.

The short term variations are on the way up again, by the way. If there's a new record warm year soon, will that mean global warming has accelerated? Let me answer for you: NO IT WON'T. You cannot figure out the actual trend by looking at individual years or individual decades. It's statistically not possible. That is precisely why Trenberth is calling so strongly for a measuring system that will enable scientists -- ALL scientists -- to have data about where energy flows as temperature fluctuates up and down from year to year.

Just using a global temperature trend tells you almost nothing about trend unless you look at at least 15 years of data, and more than that if you want to know if trend is increasing or decreasing. But if we have data that enables us to track precisely physically where energy goes, then we have the basis for understanding these short term variations, and separating them out from trend on shorter time scales.

Cheers -- sylas
 

sylas

Science Advisor
1,632
6
No it is not. The essence is the predominance of negative feedback, which precludes the "amplification" of the basic planck reaction of some 1.1 - 1.2 degrees per doubling CO2 as per Lindzen and Choi 2009 and diverse publications of Karner
As opposed to the predominance of positive feedback, which means the lower bound of sensitivity for doubling CO2 is well above 1.2 degrees as per Annan et al. (2006), Wigley et al. (2005), Schneider von Deimling et al. (2006), Soden et al. (2004), http://geotest.tamu.edu/userfiles/216/dessler09.pdf [Broken], Forster et al. (2006), Bender (2008), http://www.sciencemag.org/cgi/content/abstract/325/5939/460 [Broken], Gregory et al. (2002), Bony et al. (2006), Dessler et al. (2008), and Minschwaner et al. (2006).

And by the way. Just to anticipate a repeat of not-so-subtle hints by some other contributors (not Andre, I hasten to add!) that anyone claiming to know too much is merely googling; this was not obtained by google. These are all papers already on my own computer, which I have obtained and checked out for myself well before writing this, and some of which I have discussed already in various threads. Had I used google I would expect to find a lot more, even if I limited myself to stuff published in the last 12 months. As long as we are going to drop papers into threads without discussion as a some kind of authority argument, this helps indicate what that technique would really show.

This is becoming a science based discussion, rather than political discussion. I think it would be more appropriate, given the focus of PF on actually learning about the science, not to merely dump references as some way of closing off discussion or overwhelming it; but to actually discuss the content of particular methods for inferring feedback (there are many different independent methods giving support to the same conclusion represented in the above papers) in a more focused science thread, with one or two papers as a backup for more detail.

Cheers -- sylas
 
Last edited by a moderator:

mheslep

Gold Member
254
728
...Statistically, the natural variation is too great to let you determine what the trend is doing from a short period of measurement, like eleven years.
Yep, then why make this following statement?
sylas said:
...Heck, in all seriousness, the data is actually consistent with the global warming trend having accelerated!...
On your summary of Trenberth's paper I almost entirely disagree. We'll have to leave it there.
 

sylas

Science Advisor
1,632
6
...Statistically, the natural variation is too great to let you determine what the trend is doing from a short period of measurement, like eleven years.
Yep, then why make this following statement?
...Heck, in all seriousness, the data is actually consistent with the global warming trend having accelerated!...
Because the second statement helps explain the first, to show just how large the confidence limits are.

You can quantify this mathematically, and I gave the numbers back in [post=2498365]msg #22[/post]. Here it is for you again, with all numbers in degrees per decade.
  • Regression trend since 1998 with HadCRUT3: 0.032
  • Regression trend since 1998 with GISS: 0.115
  • 95% confidence limits given autocorrelation: 0.2

So as you can see, even using the dataset with the least amount of warming, the trend is still apparently somewhere between -0.17 and 0.23

The thirty year trend is enough to nail down the values better, as the confidence limits are about 0.05, and the values (since 1979) are 0.15 (HadCRUT) and 0.16 (GISS). That gives you a trend of somewhere from 0.10 to 0.22 degrees per decade, 95% confidence, with the trend since 1998 being anything from complete reversal to a significant acceleration. OK?

And if you think that sounds implausible... try figuring the 11 year trend from 1999 to 2009 inclusive. Use both datasets, to get the two estimates.

Cheers -- sylas
 

Redbelly98

Staff Emeritus
Science Advisor
Homework Helper
12,038
128
Again, once more, maybe the essence is that Trenberth acknowledges no warming:

... we can't account for the lack of warming at the moment ...
would that depend on any starting year?
Certainly. GW is a long-term effect. To acknowledge that there is no warming at the moment, or even over the past few years, says nothing about the long term warming trend that we are in.
 
4,453
57
Paul must therefore be using HadCRUT3, which is fair enough for a BBC writer, as this is from the UK met office. The linear trend for the last eleven years does show a small increase -- even if you start in 1998! The regression gives 0.032 C/decade.

If you do the estimate with the GISS dataset, then you get a warming trend over 1998 through 2008 of 0.115 C/decade.
For completeness, not for disputing, the trends of the satellite data between Jan 1998 and November 2009 seem to be (in degrees K per decade), http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt [Broken]

But it will still be interesting to see what happens to the trend if ALL percieved effects of the ENSO would be removed, thinking especially of the La Nina dip immediately after the 1998 El Nino maximum.
 
Last edited by a moderator:

sylas

Science Advisor
1,632
6
For completeness, not for disputing, the trends of the satellite data between Jan 1998 and November 2009 seem to be (in degrees K per decade), http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt [Broken]
That sounds about right... and of course, these numbers are equally meaningless as indicators of long term trend, just like the surface temperature. They are figures for the atmosphere, and the uncertainty limits are even larger than at the surface. I have not attempted to estimate confidence limits for them myself as yet, however.

It's still useful data; because the short term variations are real and something we'd like to understand also!

One thing I find interesting is that the Large El Nino spike in 1998 is larger in the atmospheric data (lower troposphere) than at the surface. Your links are to atmospheric datasets. Even allowing for the larger errors in atmospheric measurements, this is still interesting and may be a clue to the processes involved. I don't know.

But it will still be interesting to see what happens to the trend if ALL percieved effects of the ENSO would be removed, thinking especially of the La Nina dip immediately after the 1998 El Nino maximum.
I agree! There have been attempts to do this kind of thing, using statistical arguments and the southern oscillation index.

I think Trenberth is right. What we REALLY want is better data, so that we can figure out precisely where the energy goes during these ENSO variations. I like statistics, but scientifically I find argument based on correlations to be very unsatisfying. I want to know the physics. To test models for the physics of how temperature is actually changing, we need to track the energy flows. Then we'll have a much better way of identifying and removing the ENSO effect.

Cheers -- sylas
 
Last edited by a moderator:

DrClapeyron

12 out of the 40 threads on the first page of P&WA are about global warming (email scandal, cap and trade, investing confidence in climate experts, etc).

One tipping point seems to be that all Republicans in the US oppose climate change bills while Democrats support climate change bills, but at the same time no significant pieces of legislation have resulted in the 20 some odd years of the global warming debate.
 
4,453
57
12 out of the 40 threads on the first page of P&WA are about global warming (email scandal, cap and trade, investing confidence in climate experts, etc).

One tipping point seems to be that all Republicans in the US oppose climate change bills while Democrats support climate change bills, but at the same time no significant pieces of legislation have resulted in the 20 some odd years of the global warming debate.
And there is your problem. It's politics and nobody can't affort to be wrong.

Eventually nature will tell who is wrong and nature is not democratic, I'm afraid.
 

Related Threads for: BBC on tipping point?

  • Last Post
Replies
8
Views
3K
  • Last Post
Replies
2
Views
343
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
11
Views
6K
  • Last Post
Replies
7
Views
2K
  • Last Post
Replies
1
Views
446
  • Last Post
5
Replies
106
Views
17K
  • Last Post
Replies
4
Views
2K

Hot Threads

Top