The blogosphere (and not only that) has been full of the “global warming is taking a break” meme lately. Although we have discussed this topic repeatedly, it is perhaps worthwhile reiterating two key points about the alleged pause here.
(1) This discussion focuses on just a short time period – starting 1998 or later – covering at most 11 years. Even under conditions of anthropogenic global warming (which would contribute a temperature rise of about 0.2 ºC over this period) a flat period or even cooling trend over such a short time span is nothing special and has happened repeatedly before (see 1987-1996). That simply is due to the fact that short-term natural variability has a similar magnitude (i.e. ~0.2 ºC) and can thus compensate for the anthropogenic effects. Of course, the warming trend keeps going up whilst natural variability just oscillates irregularly up and down, so over longer periods the warming trend wins and natural variability cancels out.
(2) It is highly questionable whether this “pause” is even real. It does show up to some extent (no cooling, but reduced 10-year warming trend) in the Hadley Center data, but it does not show in the GISS data, see Figure 1. There, the past ten 10-year trends (i.e. 1990-1999, 1991-2000 and so on) have all been between 0.17 and 0.34 ºC per decade, close to or above the expected anthropogenic trend, with the most recent one (1999-2008) equal to 0.19 ºC per decade – just as predicted by IPCC as response to anthropogenic forcing.
Figure 1. Global temperature according to NASA GISS data since 1980. The red line shows annual data, the larger red square a preliminary value for 2009, based on January-August. The green line shows the 25-year linear trend (0.19 ºC per decade). The blue lines show the two most recent ten-year trends (0.18 ºC per decade for 1998-2007, 0.19 ºC per decade for 1999-2008) and illustrate that these recent decadal trends are entirely consistent with the long-term trend and IPCC predictions. Even the highly “cherry-picked” 11-year period starting with the warm 1998 and ending with the cold 2008 still shows a warming trend of 0.11 ºC per decade (which may surprise some lay people who tend to connect the end points, rather than include all ten data points into a proper trend calculation).
Why do these two surface temperature data sets differ over recent years? We analysed this a while ago here, and the reason is the “hole in the Arctic” in the Hadley data, just where recent warming has been greatest.
Figure 2. The animated graph shows the temperature difference between the two 5-year periods 1999-2003 and 2004-2008. The largest warming has occurred over the Arctic in the past decade and is missing in the Hadley data.
If we want to relate global temperature to global forcings like greenhouse gases, we’d better not have a “hole” in our data set. That’s because global temperature follows a simple planetary heat budget, determined by the balance of what comes in and what goes out. But if data coverage is not really global, the heat budget is not closed. One would have to account for the heat flow across the boundary of the “hole”, i.e. in and out of the Arctic, and the whole thing becomes ill-determined (because we don’t know how much that is). Hence the GISS data are clearly more useful in this respect, and the supposed pause in warming turns out to be just an artifact of the “Arctic hole” in the Hadley data – we don’t even need to refer to natural variability to explain it.
Imagine you want to check whether the balance in your accounts is consistent with your income and spendings – and you find your bank accounts contain less money than you expected, so there is a puzzling shortfall. But then you realise you forgot one of your bank accounts when doing the sums – and voila, that is where the missing money is, so there is no shortfall after all. That missing bank account in the Hadley data is the Arctic – and we’ve shown that this is where the “missing warming” actually is, which is why there is no shortfall in the GISS data, and it is pointless to look for explanations for a warming pause.
It is noteworthy in this context that despite the record low in the brightness of the sun over the past three years (it’s been at its faintest since beginning of satellite measurements in the 1970s), a number of warming records have been broken during this time. March 2008 saw the warmest global land temperature of any March ever recorded in the past 130 years. June and August 2009 saw the warmest land and ocean temperatures in the Southern Hemisphere ever recorded for those months. The global ocean surface temperatures in 2009 broke all previous records for three consecutive months: June, July and August. The years 2007, 2008 and 2009 had the lowest summer Arctic sea ice cover ever recorded, and in 2008 for the first time in living memory the Northwest Passage and the Northeast Passage were simultaneously ice-free. This feat was repeated in 2009. Every single year of this century (2001-2008) has been warmer than all years of the 20th Century except 1998 (which sticks out well above the trend line due to a strong El Niño event).
The bottom line is: the observed warming over the last decade is 100% consistent with the expected anthropogenic warming trend of 0.2 ºC per decade, superimposed with short-term natural variability. It is no different in this respect from the two decades before. And with an El Niño developing in the Pacific right now, we wouldn’t be surprised if more temperature records were to be broken over the coming year or so.
Update: We were told there is a new paper by Simmons et al. in press with JGR that supports our analysis about the Hadley vs GISS trends (sorry, access to subscribers only).
Update: AP has just published an interesting story titled Statisticians reject global cooling, for which they “gave temperature data to four independent statisticians and asked them to look for trends, without telling them what the numbers represented”.
September (month end averages) NSIDC (sea ice extent)
2007 Northern Hemisphere = 4.3 million sq km
2008 Northern Hemisphere = 4.7 million sq km
2009 Northern Hemisphere = 5.4 million sq km
ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Sep/N_200709_extn.png
ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Sep/N_200809_extn.png
ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Sep/N_200909_extn.png
Please explain how this ice is getting thinner. Remember these are extent minimum averages.
[Response: Since ‘extent’ is not ‘thickness’ it’s hard to see your numbers justify any statement at all. However, if you are interested in thickness, you should look at thickness – i.e. ICEsat thickness estimates. – gavin]
What was the thickness of the ice, Karst?
Volume = Area x DEPTH.
“According to the polar 5 survey, ice thickened somewhat. Now, polar 5 was a linear and limited survey,”
It was also (IIRC) countered by even more limited but even more rigorously correct land survey:
http://news.bbc.co.uk/1/hi/sci/tech/7897392.stm
It’s a lot easier to say the thickness is “however long this rod had to go down before it left the ice” than to work it out by the differential reflections of radar echoes.
Gavin:
I believe it was Mark’s concern over thickness (not mine). I merely provided minimum extent data. The question merely followed and is as yet unanswered.
Mark:
Older ice is thicker ice, in general. When last years ice doesn’t melt, it becomes older, thicker, 2yr. ice and on and on. What the minimum (september) averages show is ice getting older. That is all I have to say in this matter.
Life is just a bowl of cherries — as selected by Karst:
September (month end averages) NSIDC (sea ice extent)
2007 Northern Hemisphere = 4.3 million sq km
2008 Northern Hemisphere = 4.7 million sq km
2009 Northern Hemisphere = 5.4 million sq km
From the same source Karst used:
http://nsidc.org/data/seaice_index/images/n_plot_tmb.png
Those last three dots — the ones Karst selected — are cherrypicked.
This has gone from surreal to ridiculous and on its way to sublime.
Mark said sea ice extent is not related to volume. I questioned that and said I thought extent is probably related/proportional to volume (implying directly, as opposed to inversely.) Mark replied I was wrong because V=L*W*D, and some other stuff. Then a bunch weighed in, most, it seems, insinuating or implying I am wrong, a couple insinuating I might be correct.
I’m not using democracy to determine physics; but I’m simply curious and would be appreciative of everyone’s position. Post a reply with a single letter for the multiple choice answers if you’re inclined.
A. Extent is directly related to volume.
B. Extent is usually directly related to volume
C. Extent is usually not related to volume.
D. Extent is not related to volume.
E. I’m unable to properly choose one of the above.
Then I’m inclined to follow Hank’s suggestion and quit talking about it.
Rod B … this statement by you:
Has been falsified by observation. So why are you asking us questions?
My answer, BTW, would be “F. It’s more complex than the simple picture you’re trying to paint”.
F. Fail: arguing with Mark pleases him and goes on as long as you’re willing;
and
G. Gavin gave the appropriate link, where it’s explained — look DOWN the page, til you get to the answer.
Somewhat off-topic, but “… the rate of climate change over the next century could be higher than previously anticipated …”:
Nitrogen Cycle: Key Ingredient In Climate Model Refines Global Predictions
http://www.sciencedaily.com/releases/2009/10/091009204032.htm
#305 Rod Black
Hmm…, sort of reminds me of word play
https://www.realclimate.org/index.php/archives/2007/10/did-you-stop-beating-your-wife-yes-no/
http://uscentrist.org/news/2007/word-play/
https://www.realclimate.org/index.php/archives/2007/11/did-we-call-it-or-what/
Rod, think of it this way: extent is the book cover, volume is the thickness and/or content of the book.
As per your statement:
1. What does sea ice riding the extent mean, or have to do with anything, and if it does have something to do with something, in what reality?
2. Extent is not volume.
3. Read 2 again.
September 2009, should be in the warming “pause” zone?
Fun to be so accurate with predictions when September is #1 in temperature world wide
http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt
Can some contrarian x’plain this?
I need a bit of Sunday night comedy….
305 Rod, extent is NOT related to volume because ice melts ONLY in the thickness dimension. Your visualization of ice being a big lump with a standard shape and defined edges is just plain wrong. The ice is fragmented and the Arctic ocean is a bowl. Thus, volume will decrease tremendously before any significant change in extent is noted. The ice just gets thinner and more spread out. That’s what happened over the last 30 years or so. The thickness decreased by 50% or so over the last 5 years alone! Thickness has to drop to zero to affect extent. Take a bowl of water, add some big ice cubes, and agitate. The extent of ice in your bowl will be essentially unchanged even as 90% of the ice’s volume melts. Only after the ice has fragmented and spread out does extent start to drop appreciably. You can see this in action on any lake. The ice cover’s extent stays near 100%, then near 100%, then near 100%, then suddenly it’s near 0%. Again, ice ONLY melts in the thickness dimension.
310
David B. Benson says:
11 October 2009 at 7:10 PM
“Somewhat off-topic, but “… the rate of climate change over the next century could be higher than previously anticipated …”:”
I have lost count of the number of times I have seen this or similar statements. Do not people who propogate these statements realise that it is like crying wolf? The average person in the street will start to ignore them and regard them for what they are: Scaremongering.
Rod B, do you know the definition of ‘extent’? If you do, you can trivially answer your own question. If not, read up. In neither case bother the rest of us.
This “extent vs volume” argument is ridiculous. Surely those claiming that greater extent means greater volume can see how silly they are being? I’m not a scientist (surprise!) but even I can see how silly it is.
My attempt at a basic analogy to show why the argument is silly:
Take a 1m x 1m x 1m block of ice – a volume of 1m^3. The top surface area is thus 1m^2. Now take that block and cut it horizontally into 10cm deep slabs, then arrange those slabs side by side. You’ll end up with say a 5m x 2m x 10cm slab of ice, giving a top surface area of 10m^2. The volume is still 1m^3 however.
So now we have ice that can occupy a surface area of 1m^2 or 10m^2 without any change in volume. Extent is not “area”, but “area containing at least 15% ice”, so lets arrange those slabs so there is one 1m^2 slab of ice in every 2m^2 area of floor. Each 2m^2 has more than 15% ice cover and as such counts. Now our 1m^2 block of ice can have an extent of 40m^2, and this is without any change in volume of the ice.
So, from this mental experiment we can conclude that volume is totally independent of extent as the same volume of ice can represent many different “extents” depending on how that volume of ice is divided up, and different volumes can represent the same extent depending on how the volume is arranged spatially.
Basically, there are three different terms in use here “area”, “extent” and “volume” all of which are related to each other but not proportional. Greater extent does NOT always mean greater volume. In fact it is possible to have greater extent and LESS volume. In my example, simply take each clab and cut it again so it is now only 5cm deep and Discard the rest. We now have half as much volume occupying 40m^2 compared to a 1m x 1m x 1m block occupying 2m^2 area of floor.
To really settle this, split the 1m^3 block of ice up into small enough blocks spread over a large enough area that no single 1m^2 of floor area contains more than 15% ice coverage. TADA! 0m^2 ice extent without any change in ice volume!
RichardC – Water and snow at the same temperature will emit the same radiant energy – NO wait, I think snow is actually closer to being a perfect blackbody, so snow should emit more radiation.
Solar heating will raise the temperatue of the water but by a small amount because of heat capacity. That is a large amount of heat which must be lost before and during freezing. This keeps temperature warmer during the fall/winter, which will tend to increase radiation to space, but that is what happens everywhere when the temperature increases (with modulation by varying water vapor, clouds, vertical distribution of temperature increase, etc.), which is why the climate doesn’t simply change without end in response to a (change in) forcing but instead tends to reach a new equilibrium where fluxes are balanced over time, provided the positive feedback is not too large.
——–
PS I still need help with this:
OT but … I wanted to send a friend the web address for the “FAQ on climate models” parts I and II; I found part II but part I is missing – there is this website:
https://www.realclimate.org/index.php/archives/2008/11/faq-on-climate-models/
but it is not what it should be. Where did it go?
Please, help. Thank you.
Here’s the problem and we all know it. If there is a cooling trend, even if it’s only small, relative one, that will be enough for the professional deniers to scream that “it’s all a HOAX!” and further delay any mitigation efforts. I mean, look how difficult it’s been to get ANYTHING at all substantial done about it up to now even in the face of obviously increasing temperatures.
I’ll tell ya, I don’t hold much hope out for anything real EVER happening with regard to climate change amelioration.
“F. Fail: arguing with Mark pleases him and goes on as long as you’re willing;”
F- Epic Fail: I hate terrible arguments. They piss me off.
Thank you so VERY much Hank, for that leap to a conclusion. I take it that since you’re still arguing with Rod that global warming is good that you too live to argue and get your jollies from it..?
“Mark said sea ice extent is not related to volume.”
U: Unmarked.
Super fail.
I said that sea ice volume isn’t proportional on sea ice area.
Funny how you miss that out of your “exhaustive” list of possibilities.
“Older ice is thicker ice, in general.”
True.
“When last years ice doesn’t melt, it becomes older, thicker, 2yr. ice and on and on.”
True.
” What the minimum (september) averages show is ice getting older”
False. It won’t be older until next year.
” That is all I have to say in this matter.”
Based on past actions, no.
You’ll continue to parrot the same old snake oil until the sea ice minimum reaches 0. Then you’ll probably go on about how sea ice is mending each winter because it’s coming back.
One question comes to mind regarding this. During the melt process of the sea ice it develops cracks within itself, how much can an 1km2 fresh and solid ice expand during this process? It actually turns whiter during the process (if its not snow covered), thus changing the albedo, the air streams above it, and the movements of ice flows (though mainly they are due currents) somewhat. Does this have an effect large enough to explain my failed guess at lablemmings? Well now there’s two queestions, the other was meant to be rhetorical, you decide which one.
“Here’s the problem and we all know it. If there is a cooling trend, even if it’s only small, relative one, that will be enough for the professional deniers to scream that “it’s all a HOAX!” and further delay any mitigation efforts.”
Ron R, that’s not the problem: the data WILL show that. Because reality IS doing that.
The problem is that deniers are entirely credulous when it comes to anything that might mean there’s no AGW.
That’s the sole problem.
E.g. if RodB were as skeptical of his arguments as he is of the IPCC’s we’d have a lot less noise on the boards.
“Scaremongering” is a strange word for a self-proclaimed scientist to use in regard to published research.
Well here is an intersting post that suggests that the main post here is based on cherry-picked data. http://masterresource.org/?p=5240 . It summarizes in an easy to understand manner the data for all major temperature indexes and their trends for a a variety of periods over the last twenty years or so.
[Response: Vaguely ok, but he has failed to take the clear auto-correlation in the monthly data series into account and so his statements about significance are all biased to be over-definitive. – gavin]
#314 Richard Steckis
So are you saying that the US Department of Energy, The Oak Ridge National Laboratory, The National Oceanographic Atmospheric Administration, The National Center for Atmospheric Research and the involved Universities are scare mongering?
dhogaza, sorry to violate my inclination right off the bat, but I’m curious. As a general rule does sea ice with an extent of 1,000,000 sq km have less ice (volume) than that with an extent of, say, 800,000 sq km? Or even 990,000 sq km?
317 Patrick said, “Water and snow at the same temperature will emit the same radiant energy – NO wait, I think snow is actually closer to being a perfect blackbody, so snow should emit more radiation.”
I believe the primary difference is convection. Water convects while ice and snow don’t. Thus, open water will lose far more heat to space than water covered by ice. Igloos use the same physics to keep occupants warm.
RichardC (313), interesting sensible assessment. But one anomaly: why does the Arctic sea ice extent retreat? Why not stay constant until the thickness all over and all at once reaches zero, and the extent in turn goes to zero like your lake example?
Karmakaze (316), is that a reasonable facsimile of how Arctic sea ice actually forms?
RodB, various people have pointed you to various resources on the web, for instance NSIDC.
Please quit asking people to do your homework for you.
“As a general rule does sea ice with an extent of 1,000,000 sq km have less ice (volume) than that with an extent of, say, 800,000 sq km? Or even 990,000 sq km?”
Why did the change occur?
If it occurred because of panice breakup, then the extent is greater but the volume smaller.
In the general case.
Rod B says:
12 October 2009 at 10:38 AM
RichardC (313), interesting sensible assessment. But one anomaly: why does the Arctic sea ice extent retreat? Why not stay constant until the thickness all over and all at once reaches zero, and the extent in turn goes to zero like your lake example?
Edges, wind, currents and inhomogeneity of thickness.
Which is the taller man?
one who is 10st 8 and one who is 11st 0.
?
Maybe the problem with sea ice is that people are thinking of the tendency for plastic deformation under weight – any thickness variation in ice will tend to drive flow towards a state of constant thickness, in which case at equilibrium the extent = area = volume/thickness (within a given isolated body of water)… Of course, sea ice is not generally thick enough for flow under it’s own weight to be a big factor, right? – regardless of that, there’s breaking up, variations in ocean currents and wind, precipitation, air temperature, water temperature, and so such an isostatic equilibrium doesn’t play much of a role. As opposed to Snowball Earth conditions where there may have been a general flow to the equator…
Sea ice isn’t given the chance to rest to deform either, Patrick.
@Rod B
“is that a reasonable facsimile of how Arctic sea ice actually forms?”
To be honest, I have no idea. Actually not true – I have an idea but I don’t have complete confidence in it.
What I do know is there is one aspect of say Arctic sea ice that is pretty close to what I’m talking about and that is the breakup of shelves into icebergs. That scenario is essentially the same as my idea of having a 5m x 2m x 10cm sheet of contiguous ice be broken up into smaller bits and spread around the ‘room’. When the sheets break up they don’t just sit there, they cast hundreds or thousands of icebergs adrift on the currents, increasing the extent of THAT ice sheet.
It appears that you are assuming the ice melts in place, and are ignoring the iceberg formation that goes on.
My last comment was poorly written, in that it may have seemed that I was trying to imply that volume and area would vary together instead of area and extent being constant – neither is of course true. It is understandable why a person might expect some correlation and I would expect some tendency – if it is cold enough to get ice to freeze to a certain thickness within a certain time then it seems likely the temperature must be cold enough to freeze sea water within some area surrounding that point, since horizontal temperature gradients are finite, but of course, winds and currents can act to pile up or disperse ice; snow can fall on top of ice and accumulate and if anything this would happen more at warmer temperatures below freezing (even if above freezing for sea ice). And there’s salinity variations, etc. Also I used the term isostatic equilibrium but of course sea ice is just about always in isostatic equilibrium with water (except where shear stresses are supported to spread out variations in pressure), just not in gravitational equilibrium.
“I believe the primary difference is convection. Water convects ”
Yes, especially when there is wind-driven (or other) mixing, the surface temperature is dropping (down to 4 deg C for fresh water, lower for sea water) and phase changes concentrate salinity.
That adds to the heat capacity available to the sea surface to moderate temperatures while heat is added or removed. The extra heat released in winter, up to the point at which ice forms and thickens, is still related to if not the same as the extra heat that was absorbed in summer after the point when the ice thinned and melted.
Richard Steckis (314) — Did you actually read the science article? Did you understand it? Looks to me to be another accelerating feedback.
Another which IPCC AR4 did not, it seems, consider.
341
David B. Benson says:
12 October 2009 at 5:18 PM
“Richard Steckis (314) — Did you actually read the science article? Did you understand it? Looks to me to be another accelerating feedback.
Another which IPCC AR4 did not, it seems, consider.”
David. It seems to me that none of these accelerating feedbacks have actually accelerated into REALITY. That is what I am trying to get at. Scaremongering is scaremongering wherever it is published.
David,
One thing I have to agree with in the study is the need to incorporate human land use change into the climate models. I have always argued that it is in land use changes that the greatest human impacts on climate are to be found. Forget about CO2, it is too minor (and relies on an overwhelming impact of negative compared with positive feedbacks which is a ridiculous concept). It is incorporating areas such as land use change, biotic feedbacks and forcings, geologic and cosmic feedbacks and forcings that will allow the models to more accurately represent the climate system.
[Response: Land use changes are used in climate models and give a negative forcing (i.e slightly cooling the planet) (Hansen et al, 2005;2007). You were saying?- gavin]
Having said that. Once, just once I would like to see when a new parameter is incorporated into a model, it shows a NOT AS BAD AS WE FEARED outcome. That would make them more believable in a real world.
“Sea ice isn’t given the chance to rest to deform either, Patrick.”
That’s what I said :)
“David. It seems to me that none of these accelerating feedbacks have actually accelerated into REALITY.”
Rather like the “we’re on a cooling phase” hasn’t actually accelerated into REALITY.
Can someone tell me what has happened to Gistemp since 2002?
http://woodfortrees.org/plot/gistemp/from:2002/plot/gistemp/from:2002/trend
[Response: Seems to be fixed now. – gavin]
Richard Steckis, you seem to be saying that you will not believe the models until they begin to confirm your wishful thinking.
re:343
“Once, just once I would like to see when a new parameter is incorporated into a model, it shows a NOT AS BAD AS WE FEARED outcome.”
I imagine your counter-part on Rapa Nui saying the same thing.
Me, I fear what happens when the tundra starts to put more carbon into the atmosphere than we’re capable of sequestering. When does that happen? At 2C of total warming? Isn’t that 40 years from now? Do you think we’re capable of acting decisively?
Steve, when you select 2002 to present, that range just happens to start with the 2002 unusually warm year, and end with the 2008 low number plus a few months of 2009. You’ve fooled yourself there. Use a longer time span for meaningful global temperature trends.
http://scienceblogs.com/stoat/2007/05/the_significance_of_5_year_tre.php#
Yeah, despite having said this:
you can bet he won’t like this, by Gavin:
since he fervently believes this:
And I love the chutzpah of this:
There we go. All you climate scientists can go home, now, Richard Steckis has spoken!