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”.
The issue that I see and hear about is that warming was predicted to increase as CO2 increased. This has not happened. So folks are now left thinking that because the predictions of only the past recent few years are observed to be incorrect (in fact temperatures have gone down) what confidence do I have in predictions of 50-100 years ahead.
You can change your story but the facts remain.
It’s a fair point I think and needs a full public analysis and assessment. Especially as so much is resting on this.
Best
Tim
“I went to the “The Wood for trees” interactive graphs and use HADCRUT3 variance adjusted Global mean data from the time period 1997 to 2009 and it shows a flat trend line from at .4C. Thats over the last 12 and 3/4 years.”
a) no, it doesn’t. A trend of +0.13C for a linear trend from my calculation from the numbers.
And why did you pick those two particular dates?
Why not 15 years, or 25 (a single human generation). You *do* know that the sunspot cycle is about 11 years, don’t you? And that the “D” in “PDO” is *decadal* yes? So when you’ve only selected one cycle, how can you determine the cycle length?
You can’t.
You need *at least* two full cycles to see what the amplitude of such a variation is and likewise at least two cycles to have any hope of guessing the average variation of the process.
So why pick one or less cycles?
On the other hand, I’ve spent quite a bit of time in the high desert, where the temporary disappearance of solar forcing causes the temperature to often drop from the 35C range to the -5C range each and every spring night.
“The issue that I see and hear about is that warming was predicted to increase as CO2 increased. This has not happened.”
Really?
Have a look at this:
http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif
Can you look at that graph and say “temperature has not increased”?
PS Such a decadal difference from monotonic increases in temperature were
a) predicted by the models
b) predicted by the scientists
c) seen in the record several times before
That you missed the last one despite the entire thread explaining that one leaves me baffled.
Phillip,
“May well happen” sounds like something between 20% and 60% to me, but I don’t think this term is defined and I don’t think it is used in IPCC reports. But to me the more egregious error isn’t the probability but the prediction itself and the time table — it is very different to suggest that this coming decade will show cooling with some probability versus saying with some probability there will be some decade during this century that shows cooling, and it seems pretty clear to me that he meant the latter.
dave_p asks: “Surely it’s estimates of Arctic temperatures are educated guesswork. Does guesswork have any validity as evidence?”
Yes, of course it does.
Why would it not?
After all, EVERY SINGLE TIME you take a measurement, you are making an educated guess as to the reading on the scale.
Have you never taken temperature readings in school lab?
Were you never told “you have to guess where the base of the liquid is, not read where the miniscus is on the scale” and how you can read a fraction of an interval if the intervals are wide enough?
They are educated guesses.
That you made them, did this prove that parafin wax doesn’t coagulate and show the phase change causing temperature stasis?
re #47
The effect of solar cycle variation on the surface temperature is around 0.1 oC peak to trough (and vice versa of course) with around a 1 month lag, according, for example, to:
Lean JL Rind DH ((2008) How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006 Geophys. Res. Lett. 35 art. #L18701
With an anthropogenic warming near 0.2 oC per decade, the descending part of the solar cycle should have fully countered the warming since around 2003. Presumably the equilibrium response would be somewhat greater than 0.1 oC, and with an extended solar minimum, the surface response will have tended somewhat further towards the equilibrium response and so we expect to have had a solar contribution somewhat larger than -0.1 oC.
Of course some elements of the climate response to reduced forcing have much slower relaxation times (e.g. the ocean response)…Stefan’s comments refer to the elements of the climate system with faster response times (troposphere and surface).
To me, the decrease in temperatures is natural. Temperatures warmed from 1850 to 1880, decreased to 1920, warmed to 1950, decreased to 1980. warmed to 1998 and have decreased since. What is so strange? That is how our planet seems to work at present though it has been capable of decreasing 5 C in 10 years in the past and the reverse. My question is why state that this is abnormal or frightening?
TimJ @51, you could start by actually reading this post before typing.
Next you could not repeat what has been shown over and over again to be not true (“in fact temperatures have gone down”).
http://www.woodfortrees.org/plot/gistemp/from:1990/plot/gistemp/from:1990/trend/plot/gistemp/from:1999/trend
You can assert your story, but the facts do not support it.
If a layman may ask a question, How much of the current estimated rise in temp (.02 degrees C per year?) is due to the increases in atmospheric CO2, and how much to the other greenhouse gasses?
And if the total heat content of the earth were estimated, would it show a consistent annual increase rather than the variability in the average temperture graph?
The issue that I see and hear about is that warming was predicted to increase as CO2 increased. This has not happened.
Yes it has. What was never predicted, and is not now and has not at any time in the past century happened, is that CO2 would be the only thing that affected the climate, and that the climate would not swing up or down from year to year due to purely internal cycles like El Nino, but rather would pick a temperature that could be exactly computed from CO2 levels alone and thus would go up a little each year just as CO2 levels have been doing.
Climate can be predicted statistically — you can give an expected value and an expected error, and then your predictions can be validated or falsified statistically, and if you give huge expected errors someone else can show they do a better job. Without CO2, there is no reason to predict the 2000s should be warmer on average than the 1990s, which were warmer than the 1980s. If this decade had been as cool as the 1980-1999 average, while CO2 rose and every other known factor such as solar activity remained basically flat, then it would have been outside the range of model predictions and would have presented some problems, requiring the theory to be modified to have a lower sensitivity or something else we weren’t looking for working to cool the climate. As it has easily been the hottest decade on record, the fact that there are still year-to-year fluctuations does not present a problem for the theory.
So folks are now left thinking that because the predictions of only the past recent few years are observed to be incorrect (in fact temperatures have gone down)
Over the last few years, temperatures have gone up, down, up, down, and up again. This tells us… well, nothing.
Your first question is answered in the IPCC reports:
http://www.ipcc.ch
“And if the total heat content of the earth were estimated, would it show a consistent annual increase rather than the variability in the average temperture graph?”
No, it would only show a consistent annual increase if CO2 was the SOLE AND ONLY cause for temperature globally.
It would likely be a LOT smoother an increase, since things like the PDO et al are movements of heat energy from places we don’t measure it to places we do (and vice versa).
But please, consider how hard it will be to read the temperature of the ocean. How expensive is it to manage to do the temperature of 1/3 the earth’s surface ALONE. Now figure you’d need twice that just to cover one layer and that you won’t have the ocean bulk energy content unless you have several dozen layers to even an order-of-magnitude approximation.
And it’s a lot easier to walk to the stepenson screen than kit up and go to 2 miles under the ocean to read one there.
Eve, only denialists say that this change is significant.
But you’ve lost a lot of information.
It went up, then down a little, then up a lot then down a little, then up a lot then down a little, then up…
Now given that the “down” is on average less than the “up”, do you think you maybe are forgetting something just a *little* important here?
Or do you think Hannibal was a wuss crossing the alps, because it went up, then it went down…?
Marc DeRosa (47) — The variations over a solar cycle are manifested with a lag between 0 and 2 years. A better estimate is 6–12 months. The annual variation is invsible to global temperature product yearly averages, yes?
re #61,
Krog, these two very short articles on skepticalscience.com address
your questions:
This one (see Figure 2 taken from Murphy et al 2009, cited previously on this thread) gives the estimated cumulative forcings from each of the greenhouse gases (CO2, CH4, chlorofluorocarbons, N2O etc.)
http://www.skepticalscience.com/Measuring-Earths-energy-imbalance.html
This one (see Figure 1 from Schuckmann et al. 2009, cited earlier on this thread) shows that during the period that shows relatively litle apparent surface warming, that there has been a steady increase in the heat content of the oceans. If one uses earlier data to extend the ocean heat content measure further back in time, there has been a broadly steady increase in total ocean heat content. Since much of the energy absorbed by the earth under a positive radiative imbalance due to enhanced greenhouse forcing has gone into the oceans (likely >90%), this does indicate that there is a broadly consistent annual increase in total heat content.
http://www.skepticalscience.com/How-we-know-global-warming-is-happening-Part-2.html
Since the surface and troposphere are very small parts of the whole system, and have low heat capacity and generally respond quickly to changes in forcings (and to the variability in ocean surface heat due to ocean current fluctuations), there is much more variability in the year on year surface temperature than there is in the year on year accumulated heat in the oceans….
Just to replicate Stefan’s original graph on WFT so people can play with it:
http://www.woodfortrees.org/plot/gistemp/from:1980/compress:12/plot/gistemp/last:300/trend/plot/gistemp/from:1998/to:2008/trend/plot/gistemp/from:1999/to:2009/trend
Taking the trend from the monthly values rather than the decimated annual ones gives marginally different trends, but still in the range 0.17-0.19 K/decade – check the ‘data’ link for the numbers.
I agree that people reading that statement out of context could be forgiven for misinterpreting it (although I did provide that context in my post).
But the real problem with attributing “misunderstanding” to Latif is that Fred Pearce was there. He was reporting on a conference. He was presumably present for the entire presentation, so context should not have been an issue. He had the presentation and chart in front of him, and presumably could refer back to it, or ask Latif if he wasn’t sure.
I’m an admitted climate science amateur with an undergrad math/comp sci degree. So how is it that I can look at the statements and presentation and easily discern Latif’s meaning in retrospect (i.e. describing a *hypothetical situation*) and Pearce could not? What does that say about the state of popular science journalism?
Great post, RC, and great comments, as always.
While I understand the facts of the situation re: the size of measurement windows, natural variation, etc., and how “our friends” misuse the details to their advantage, this seems like a good excuse to ask about something related to some of the comments here that’s intrigued me for some time.
We know beyond all doubt that the world is losing an immense net amount of polar (+ Greenland) ice every year–easily into the hundreds of billions of metric tons per year. Is there any measurable climate effect from melting all that ice? The extra heat needed to effect the solid-to-liquid phase change (80 cal/g) times such a huge amount of ice seems like it would suck up such an enormous amount of heat that it would slightly decrease the observed, higher-than-the-global-average temperature increase in the Arctic.
Or am I missing something here (like a few orders of magnitude, perhaps)?
Re 57. does he seriously equate missing data with taking measurements on a scale?
Krog 6 October 2009 at 4:25 PM:
A typical breakdown of how much various GHGs are currently altering the climate can be found in the IPCC AR4 WG1 summary for policy makers., on page 4.
No. Variability due to internal weather would be eliminated, greatly reducing the total variability in the graph, but other sources of variability, primarily Total Solar Irradiance would remain.
Krog (#61), ask a simple question and you risk getting a really complicated answer:
https://www.realclimate.org/index.php/archives/2006/10/attribution-of-20th-century-climate-change-to-cosub2sub/
… and a comparison with HADCRUT3 which indeed has lower recent trends, although the long term one is pretty similar:
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/compress:12/plot/hadcrut3vgl/last:300/trend/plot/hadcrut3vgl/from:1998/to:2008/trend/plot/hadcrut3vgl/from:1999/to:2009/trend
… and also with RSS …
http://www.woodfortrees.org/plot/rss/from:1980/compress:12/plot/rss/last:300/trend/plot/rss/from:1998/to:2008/trend/plot/rss/from:1999/to:2009/trend
Does the “missing poles” explanation also apply to satellite?
Why not also use the UAH data series along with GISS and HADCrudley?
Krog,
first question:
here ya go:
http://www.google.com/search?q=ipcc+forcing+co2+“other+gases”
second question:
That estimate would do whatever you want it to; without sensors everywhere, you can’t do an actual measurement of “total heat content” so you pick the numbers you like.
Oops, I always forget the double quotes don’t paste in here properly. Use this search, it’s fairly close. Remember there’s no Wisdom button so consider what you find.
http://www.google.com/search?hl=en&safe=off&q=ipcc+forcing+co2+other+gases
First 2 hits are good:
ESRL Integrating Themes: Radiative Forcing of Climate by non-CO2 … Figure 1. Major climate forcing agents and their forcing from the …
http://www.esrl.noaa.gov/research/themes/forcing/
gases and aerosols, or radiative forcing scenarios, often based …. radiative forcing from carbon dioxide. A carbon dioxide increase by …. Forests and Devegetation of Other Vegetation Types (IPCC, 2003). …
http://www.ipcc.ch/pdf/glossary/ar4-wg1.pdf
Mr. Krug: Re: total heat into the earth
A very nice paper is Murphy et al., J. Geophys. Res., v114, D17107 previously cited by Mr. Houlihan, and Mr. Chris, together with a summary at
http://www.skepticalscience.com/How-we-know-global-warming-is-happening-Part-2.html
The rest of this comment probably belongs in the recent sea level rise post, but that thread seems dead, so I hope the moderators will bear with me.
In para 29 of the Murphy paper, they note an anomaly beginning in the middle 1990’s, and go on to speculate as to the cause. In para 30, they trace the anomaly to a decrease in estimated heat uptake by the ocean. They note that the inconsistency between heat uptake and sea level rise might be resolved by increased melting of land ice, although they mention alternatives such as errors in heat content data, or possibly heat uptake into the deep ocean.
Would someone care to comment?
Mr. Grinzo: Re: latent heat of melting ice
I did this calculation in a previous post, for 500 gigaton of ice melt
500GT x 1e9(T/GT) x 1e3 (Kg/Tonne) x 1e3 g/Kg x 80 Cal/g x 4.2 J/Cal = 1.7e20 J
this is 1.7% of my estimate of yearly oceanic heat increase (averaged over the last decade) of 1e22J from the Levitus (2008) graf.
Thank you CM. I intend to read that IPCC report as soon as I get done with War & Peace. But truly, I realize that there is no simple answer.
Tharanga says:
“It’s futile, stefan. Any time the current year is not the warmest year on record, somebody will try to pick the previous record high as a starting point and convince themselves that warming stopped at the previous high.”
Very well put. Yhis is it in a nutshell.You’ve stated the essence of what skeptics have done time and time again.If you start with 1998, there may be a slight dip from that takeoff point. Whereas if you start with 1997 or 1999 you’ll get a different,result.
Anyhow shoudn’t all this be moot. There’s much ado about decadal records, whether valid projections can be made, whether this decade is warmer(cooler) that the last. Doesn’t all this mask the fact that decades aren’t representative of long term climate. A lot of this may be of some interest, but it’s just conversation as far as trends are concerned.
Igor (37), thanks for the reply, and I apologize for not be able to read these threads as thoroughly as I can in the summer when I am not teaching. The graphs over the period you selected and Stefan apparently discussed are indeed flat, which doesn’t surprise me — I would assume any decades in the past come in any of three flavors: up, down or flat — and I haven’t asked the question becuase I had thought the topic was the current decade and what it might say about future temperatures. I would understand if that’s not actually what folks here are most interested in. Be careful, though, not to refer to the current decade as flat, because, as we are being told, it is not! More seriously, are you saying that because after the previous flat period it then warmed, that means after this flat period it must therefore warm as well? If you are not saying that, sorry for the wrong inference.
#50 Mark: “Force times time. If you smack a heavy ball hard but briefly it won’t move much. If you push the heavy ball for an hour it will eventually move with alacrity. By the time the earth has noticed the fractional change in insolation, it’s already moved and the insolation is going down. Have a think about how much energy the earth’s temperature needs to rise 1C.”
#65 David B. Benson: “The variations over a solar cycle are manifested with a lag between 0 and 2 years. A better estimate is 6–12 months. The annual variation is invsible to global temperature product yearly averages, yes?”
These two responses seem a bit contradictory. If the climate response timescale due to changes in solar insolation are as fast as 6-12 months (as comment #65 suggests), then wouldn’t the annual variation in insolation due to the ellipticity of the Earth’s orbit be manifested in the global temperature data (in conflict with what is said in comment #50)? Or is it slower than 6-12 months?
I agree, the annual ellipticity variation would obviously not be reflected in annual temperature plots. But I guess I was asking more generally: Is the annual variation in energy incident at Earth from the sun (due to the ellipticity of the Earth’s orbit) visible in, say, monthly or weekly temperature averages? I’m thinking that a 1% variation in insolation is fairly large. If it translates into even 0.1% variation in global temperatures, that should still be visible in the global temperature data, yes?
People are leaving behind fuel drums and other items form Arctic expeditions. How hard would it be to leave behind some temperature stations, with enough batteries to last?
Eve @ 4:21PM
The increases were greater than the decreases, resulting in a long term increase overall; see http://woodfortrees.org/plot/hadcrut3vgl/from:1900/to:2010/trend/plot/hadcrut3vgl/from:1850/to:1880/trend/plot/hadcrut3vgl/from:1880/to:1920/trend/plot/hadcrut3vgl/from:1920/to:1940/trend/plot/hadcrut3vgl/from:1940/to:1980/trend/plot/hadcrut3vgl/from:1980/to:2000/trend/plot/hadcrut3vgl/from:1850/to:2010/mean:3
Note that current temperatures are above the trend from 1900, despite “recent cooling” claims.
Why is this frightening? Because some of the additional energy captured by increasing CO2 is going into melting glaciers on which billions depend for agriculture; see http://www.grid.unep.ch/glaciers/img/5-9.jpg. A lot of those glaciers are in the mountains on the China-Indian-Pakistan borders; if they go to war over dwindling water supplies that their people need to survive, they will fight with nuclear weapons.
Marc DeRosa (82) — The seasonal lag, at least in northern hemisphere summer, is about 7 weeks; mid-August is warmer, on average, than around summer soltice. The ellipticity variation is just which hemisphere happens to be having warmer summer and cooler winters than the other, all other things being equal, which they are not. You could check monthly data for both hemispheres separately to see the variations.
Over a standard solar cycle, it is just barely possible to ascertain a lag between solar minimum/maximum and global temperature variations. This will happen in both hemisphers at the same time. Various attempts to pin down the lag suggest 6–12 months is more likely than 0 months or 24 months.
You say:
” but it does not show in the GISS data, see Figure 1.”
It actually does show in the GISS data from 2001. We must remember that the years between 1998 and 2001 was a period of an intense El-Nino followed by a deep La-Nina. If one examines the monthly data, the warming trend becomes statistically insignificant after 2000.
Eric L #62 says:
“Without CO2, there is no reason to predict the 2000s should be warmer on average than the 1990s, which were warmer than the 1980s.”
Why not? The laws of physics do not preclude a temperature increase in the absence of Greenhouse Gas Forcing.
Mark #63 says”
“No, it would only show a consistent annual increase if CO2 was the SOLE AND ONLY cause for temperature globally.”
Rubbish. This is a toally nonsensical statement. It precludes all the other GHGs and other causes of climate forcing.
Here it is:
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1997/to:2009/plot/hadcrut3vgl/from:1997/to:2009/trend
We know why too. Decreased solar activity has offset the increase in greenhouse gases at the same time.
To prove that:
Solar activity, 1997 to 2009:
http://www.woodfortrees.org/plot/pmod/from:1997/to:2009/plot/pmod/from:1997/to:2009/trend
Note the downward trend line.
The CO2 levels, same period:
http://www.woodfortrees.org/plot/esrl-co2/from:1997/to:2009/plot/esrl-co2/from:1997/to:2009/trend
See the upward trend line.
So, what was Edward’s point?
Stefan,
you are saying that there is a hole in the Hadley and that there is no shortfall in the GISS data. You also state that the missing warming is in this hole.
I had a look at the GISS station data and it seems that there is the same hole in the GISS data. There is only three stations north from 80N (81.6N, 80.6N and 80N) and only about 12 stations between 70N – 80N reporting up to date temperature measurements.
A huge part of the arctic in the GISS data has no temperature measurements at all, the area between 70N-81.6N is covered by about 15 temperature measurement points.
Your animated graph in the spinning globe shows the biggest warming in the area where there is no measured data. Is it true that the arctic temperature anomaly shown in your graph comes from an atmospheric model (re-analysis) data which takes spatial correlation into account through an extrapolating/interpolating in space and not from actual measurements?
In the previous RC post about this issue, Rasmus said “it’s important to note that the NCEP re-analysis and other re-analyses (e.g. ERA40) are not regarded as being appropriate for trend studies”. How come your trend analysis in this post is OK? Rasmus also said that “GISTEMP does not really have a better empirical basis in the Arctic”.
I do understand the need to reassure people that the global warming has not stopped. I have no problems understanding that there are ups and downs in the temperature data when the long term data shows overall warming. However, what really bugs me is the continuous effort to put data in where there is no data.
[Response: See my response to #14. It is a data-sparse region, and the issue is the assumptions that were made to cover this region. -stefan]
David B. Benson #84: “The seasonal lag, at least in northern hemisphere summer, is about 7 weeks; mid-August is warmer, on average, than around summer soltice. The ellipticity variation is just which hemisphere happens to be having warmer summer and cooler winters than the other, all other things being equal, which they are not. You could check monthly data for both hemispheres separately to see the variations.”
I’m not sure I’m being entirely clear. I’m referring to measured global temperatures (not simply just one hemisphere or the other), since the insolation occurs over the entire Earth and not simply one hemisphere. I do understand the hemispheres are heated unevenly throughout the year due to the earth’s axial tilt, and maybe this plays a factor (but I don’t know for sure). Or is the fact that the southern hemisphere is more oceanic than the north more of a factor?
I guess what I’m asking is whether there is a noticeably higher global surface temp, on average, in January (perihelion) + climate response time (whatever that turns out to be) vs the average surface temp in July (aphelion) + the same climate response time.
What started this train of thought in my mind is that in the original blog entry, the unusually low solar irradiance (0.1% lower than at solar max) was called out as a factor in climate, when in fact the orbital ellipticity causes a 1% variation in insolation. Shouldn’t a 1% variation be more easily seen in the climate data? I’m mainly trying to ascertain what effect solar insolation has on climate, and how long it takes for the climate to respond to variations in the insolation.
Marc, you write ‘I’m referring to measured global temperatures’
Do you know of anyone who has measured the global temperature for Earth?
You can do it for other planets — because we are far enough away from them to point an infrared telescope at them and capture the entire planet in the image.
You can do it with the Moon, by pointing an infrared thermometer at it and capturing numbers over enough of the surface over enough of the time.
You may be imagining that it’s already been done for Earth. But if it could be, in such a simple straightforward way, there would be no need for most of what’s being discussed here.
Think about it. When someone asks you what your temperature is, how do you measure it, where do you measure it, what number are you reporting — and if you put the thermometer somewhere else, would the number be different?
Remarking on (14), which is a question about different ways to obtain a global
average for non-uniformly distributed data points:
I would look upon this as a mathematical exercise in numerical integration. We have N data points distributed on a 2D space, that we want to integrate. The
simplest rule would be to give all points equal weight (this is probably even
cruder than the Hadley averaging). This relatively unsophisitacted quadrature
rule converges slower (i.e. if we assume stations are say randomly placed the
error norm of the method declines pretty slowly towards zero). More
sophisticated quadratures can be created. To my knowledge all these methods
boil down to fitting some set of 2D functions to the observed data. The most
natural 2d functions to use would be spherical harmonics, although other basis
functions could be choosen. As as result of this process (fully determined
once the set of basis functions is selected) each station would be asigned a
weight value. The global average temperature is the a simple weighted sum. In
the simple case where no stations are added or lost, these weight don’t change
(I suspect with real world data, that things get a bit messier). In any case
an intuitive if mathematically inexact measure of confidence would be if all
weights are non-negative. So here we have the basis of a question that can be
answered, “What do the individual station weights look like?”
(17) The problem with validation, is that it is an inherently mathematical
process. Over 99% of humans are innumerate (using the standard that one
must be able to judge the mathematical correctness of the validation process).
So inevitable, in the political context, it comes down to the persuasiveness
of intuitive handwaving arguments, and the degree of trust the various experts
can create in the target audience. It is all too easy to be completely correct
in the academic sense, but badly lose the public debate.
(47) Actually the sensitivity of the inverse square law means the fraction
difference in distance should be doubled, so your 3% becomes, 6%. But this is
overwhelmed at any given location (or even hemisphere), by the seasonal
effects. And even averaged globally, the average albedo of the two
hemispheres is unequal, as is the nonatmospheric heat storage (more water
in the southern hemisphere, means its seasons are more smoothed out than
in the northern hemispehere).
PS, Marc, this might help:
http://schools-wikipedia.org/wp/m/Milankovitch_cycles.htm
Indeed. All the old records will be broken one day as they were in the past. When that day comes people will remember the claims of “global warming stopped in …” and give the proponents of those claims the credibility they deserve.
Rubbish. Mark (who I dislike) is referring to natural variability, among other things.
Actually, it’s a Steckis own goal … Mark doesn’t claim that CO2 is the only cause for rising temps, and Steckis takes him to the woodshed for suggesting that Mark claims that CO2 is the only cause.
Own goal, Steckis.
This may be a silly question, but why is there an Arctic hole in Hadley’s data? What is the rationale for not including the region which is clearly experiencing the fastest/most extensive warming on Earth?
Any explanation on this would be helpful for future reporting.
Cheers,
-Andrew
August 2009 broke that month’s maximum temperature anomaly record for continental Australia by a whole degree Celsius. Also the highest ever maximum temperature anomaly for any calendar month.
G.
Marc DeRosa #87: I think you have a valid point. Note however that the effect you’re after is in temperatures, not in the more commonly discussed temperature anomalies.
You may like this reference: http://www.sciencemag.org/cgi/content/abstract/268/5207/59 . I have no strong opinion on its correctness.
Marc DeRosa,
Just for a few general points:
The amplitude of the 11-year solar cycle is large compared to long-term trends, but the full temperature response you’d expect at equilibrium doesn’t show up because of the large thermal inertia of the oceans and the short-term oscillatory pattern of the solar behavior.
The amplitude of the solar change at the top-of-atmosphere for the much longer eccentricity cycle is very small, and only corresponds to a fraction of the late 20th century forcing. You also don’t expect it to show up in a decadal to century timescale climate record since the corresponding forcing is negligible compared to the shorter-term solar variations, the internal variability of the climate system, or other external forcings acting on the system on timescales of years to decades. To explain glacial-interglacial cycles you need to also incorporate the latitudinal distribution of sunlight and the ice sheet physics which are responsive to enhanced summer melt. Greenhouse gas feedbacks also play a big role in establishing a global pattern of temperature change.