Has BBC Reached the Global Warming Tipping Point?

[Andre]

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]

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]

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 http://www.aai.ee/~olavi/

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 http://www.agu.org/pubs/crossref/2006/2005GL025259.shtml, Wigley et al. (2005), Schneider von Deimling et al. (2006), http://www.sciencemag.org/cgi/content/abstract/310/5749/841, http://geotest.tamu.edu/userfiles/216/dessler09.pdf , Forster et al. (2006), http://www.iop.org/EJ/article/1748-9326/3/1/014001/erl8_1_014001.pdf?request-id=7ffdbae3-8892-4567-8067-33a2055ffc40, http://www.sciencemag.org/cgi/content/abstract/325/5939/460 , Gregory et al. (2002), Bony et al. (2006), http://www.agu.org/pubs/crossref/2008/2008GL035333.shtml, 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

 

[mheslep]

...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!...

On your summary of Trenberth's paper I almost entirely disagree. We'll have to leave it there.

 

[sylas]

...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]

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.

 

[Andre]

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

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

 

[sylas]

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

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 perceived 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

 

[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.

 

[Andre]

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.