Comments on: How hot should it have really been over the last 5 years?

By: A toy model for forecasting global temperatures – 2011 redux, part 1 « BraveNewClimate

Wed, 02 Mar 2011 12:56:40 +0000

[...] little over two years ago, I wrote the following post on BNC: How hot should it have really been over the last 5 years? In it, I did some simple statistical tinkering to examine the (correlative) relationship between [...]

By: PeterPan

PeterPan — Fri, 08 Jan 2010 16:52:51 +0000

Re. Fig 2: Do you know why the difference between predicted and actual temperature is so big in 1998?

Thanks.

By: PeterPan

PeterPan — Fri, 08 Jan 2010 11:31:03 +0000

Thanks for linking this in SkepticalScience!, I like this more realistic example :)

By: Barry Brook

Barry Brook — Thu, 07 Jan 2010 01:02:43 +0000

Something fun to consider. Above I predicted the 2009 global temperature anomaly would be +0.75. So far, the D-N figures from NASA GISS have it at +0.71. Not bad, if I do say so myself.

By: Sun, Sun, Sun … here it comes – NOT « Greenfyre’s

Sun, Sun, Sun … here it comes – NOT « Greenfyre’s — Fri, 24 Jul 2009 04:44:16 +0000

[...] That’s the solar minima, the solar maxima are even more telling. The solar maximums peaked in 1957 (above) and have been declining ever since. If the sun were still the main climate driver we should have seen global temperatures peak in mid-20th century and decling ever since, the opposite of what we actually have. See also How hot should it have really been over the last 5 years? [...]

By: El Niño and sunspots return, sea ice doesn’t « BraveNewClimate.com

El Niño and sunspots return, sea ice doesn’t « BraveNewClimate.com — Sun, 05 Jul 2009 08:01:04 +0000

[...] us a blank face for essentially the whole year. Both of these factors (oceanic and solar) exert a mild to strong influence on year-to-year climate variability. The forcing effect of additional greenhouse gases is more subtle in the short term, but [...]

By: Hank Roberts

Hank Roberts — Sun, 29 Mar 2009 00:16:23 +0000

cross-reference:
http://www.realclimate.org/index.php/archives/2009/03/with-all-due-respect/langswitch_lang/sp#comment-116432

By: BFJ Cricklewood

BFJ Cricklewood — Wed, 18 Mar 2009 00:18:16 +0000

That looks to me like the first part of a (b) answer – a 10-year halt in GW is too soon to say GW has stopped. But what about the rest of your answer – ie, are you committed to a GW hypothesis no matter how long GW has halted, or do you have a cutoff point at which would accept the hypothesis is failing? And if so, what is this point?

By: Geoff Russell

Geoff Russell — Tue, 17 Mar 2009 21:23:00 +0000

Cricklewood: I have a model in my head of the planet tilted and spining on its axis while circling the sun. I can predict that, in Australia, it will get colder during the next few months. I can predict this with great certainty and that certainty will not disappear because of a week of hot days. Look at ANY time series of global temperature over long time periods and you can see the cycles as clear as day. Ice followed by warming followed by ice. When you are on your way to a warm period, the odd cold snap doesn’t destroy the pattern. Its just a consequence of the planet being a complex dynamic system.

The models do a pretty good job of “predicting” the past based on the raw physics, so they should also predict the future.

10 years is just a blink in the long period of thermal distribution in changes in forcing, just as a week is a blink on the way from summer to winter.

Look at some of the time series in:
http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_2.pdf

By: BFJ Cricklewood

BFJ Cricklewood — Tue, 17 Mar 2009 13:02:08 +0000

So would you maintain that
(a) the 10-year temperature plateau is actually predicted by the models, or
(b) merely that it doesn’t falsify the models, there being other equally long runs of years where other, larger effects have masked an assumed underlying CO2 effect?

If (b), would you maintain this regardless of how long temperatures failed to rise for, or is there some point (20? 50? …? years) after which you would judge the AGW hypothesis to have failed?

By: Barry Brook

Barry Brook — Sun, 15 Mar 2009 05:59:40 +0000

Simply because the last 5 years were the five most recent years — and so were able to be easily summarised in a small table.

But the exact same method, as applied to the last 30 years, is also plotted, in figure 2. So I guess I’ve focused on 5 years and 30 years. The last 10 years is within there if you prefer this period — or any other 10 year run. Regarding the last 10 years, as you can see from Fig 2, the match between predicted and observed is excellent for 2002 and 2003, and a little too high for 1999-2001. The prediction for 1998 (11 years ago) is way too low — indeed, it is the most anomalous year for the model predictions of the 30 year series by a long way (perhaps because the regional [low latitude] ENSO forcing was higher than the normalised index would indicate).

In regards to the last 10 years, it is not unusual compared to other runs of years within that 30 year sequence, as nicely illustrated here:
http://www.skepticalscience.com/Global-warming-stopped-in-1981.html

Solar forcing, ENSO, volcanoes — they all played their part then, too. See Fig 1 & 2. (e.g. 1982 volcano, 1983 super El Nino, 1988 El Nino, 1991 volcano, peak solar cycle in 1979, 1990, 2001 and solar forcing troughs in 1985, 1996, 2008).

By: BFJ Cricklewood

BFJ Cricklewood — Sun, 15 Mar 2009 05:27:56 +0000

This doesn't really address my question, perhaps I need to restate it more clearly. The most interesting data is the last 10 or so years, interesting because it shows no GW, thereby breaking from previous patterns and current understanding. Why then do you focus on only the last 5?

By: BFJ Cricklewood

BFJ Cricklewood — Fri, 13 Mar 2009 07:42:47 +0000

(Note to your webmaster: although I am subscribed to this post, I do not get notification emails).

By: Barry Brook

Barry Brook — Thu, 12 Mar 2009 06:56:10 +0000

I ‘corrected’ the last 5 years for ENSO and TSI simply because these were the most recent 5 years — I didn’t want to bother to expand it to include all 30 years. But it would be simple enough to do (if slightly tedious). You can try it yourself if you want — I’ve supplied the coefficients.

But the model is fit to 30 years of data (as far back as the satellite record goes), so it’s actually about a 30 year period I’m addressing.

By: BFJ Cricklewood

BFJ Cricklewood — Thu, 12 Mar 2009 06:51:18 +0000

Granted, until now a moveable 30-year window shows GW. But now the temperature record for the last 10+ shows no GW. Yet above you refer only to the last 5. Why is that?

By: Barry Brook

Barry Brook — Wed, 11 Mar 2009 16:30:29 +0000

Well, to be more precise, climatologists say GW has occurred over the last 30+ years, of which the last 5 years is a(n incomplete) part. And you can move the 30 year window backwards in time.

By: BFJ Cricklewood

BFJ Cricklewood — Wed, 11 Mar 2009 16:27:12 +0000

The general state of play, then, is that though we lack of sufficient data on OHC to be able to rationally say GW has occurred for the last decade, climatologists continue to say it anyway.

By: BFJ Cricklewood

BFJ Cricklewood — Wed, 04 Mar 2009 06:33:04 +0000

Yes I quite realise the point of looking at long term data for evidence of trends amoungst other variability.
My point above though, persuant on one you raised in a related thread, is rather that :

* Surface temperatures have leveled out for a decade or so.
* This need not mean that GW has stopped, since additional heat could have gone into the oceans instead.
* To show that though, we would need to show a correlation between the leveling off of surface temperatures, and an increase in the rate of OHC increases.
* But since as you say we cannot (yet?) do this, we therefore also cannot (yet) say that GW has occurred for this period.

By: Hank Roberts

Hank Roberts — Mon, 02 Mar 2009 03:52:02 +0000

http://www.agu.org/pubs/crossref/2009/2008GL036801.shtml

“… Specifically, a conspicuous absence of Indian Ocean temperature conditions conducive to enhanced tropical moisture transport has deprived southeastern Australia of its normal rainfall quota. In the case of the “Big Dry”, its unprecedented intensity is also related to recent higher temperatures.”

Citation: Ummenhofer, C. C., M. H. England, P. C. McIntosh, G. A. Meyers, M. J. Pook, J. S. Risbey, A. S. Gupta, and A. S. Taschetto (2009), What causes southeast Australia’s worst droughts?, Geophys. Res. Lett., 36, L04706, doi:10.1029/2008GL036801.

By: Barry Brook

Barry Brook — Thu, 26 Feb 2009 09:19:06 +0000

In the short term, yes, it is — short-term variability overwhelms the GHG warming trend. Hence the need to look at long-term trends. Look at Fig 2 and see how apparent the trend is over the 30 year period. That’s kind of the point of this post. Glad you got it.