Dr. Roy Spencer sent me a notice of his most recent post in email. He offers an invitation for anyone to help “figure this one out”. The result could be “worse than we thought”. – Anthony
(edited 8/23/09 0710 CDT: Changed plots & revised text to reflect the fact that NCDC, not CRU, is apparently the source of the SST dataset; also add discussion of possible RFI interference in satellite measurements)
(edited 8/22/09 1415 CDT: added plot of trend differences by month at bottom)
By Dr. Roy Spencer
In my previous blog posting I showed the satellite-based global-average monthly sea surface temperature (SST) variations since mid-2002, which was when the NASA Aqua satellite was launched carrying the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). The AMSR-E instrument (which I serve as the U.S. Science Team Leader for) provides nearly all-weather SST measurements.
The plot I showed yesterday agreed with the NOAA announcement that July 2009 was unusually warm…NOAA claims it was even a new record for July based upon their 100+ year record of global SSTs.
But I didn’t know just HOW warm, since our satellite data extend back to only 2002. So, I decided to download the NOAA/NCDC SST data from their website — which do NOT include the AMSR-E measurements — to do a more quantitative comparison.
From the NOAA data, I computed monthly anomalies in exactly the same manner I computed them with the AMSR-E data, that is, relative to the June 2002 through July 2009 period of record. The results (shown below) were so surprising, I had to go to my office this Saturday morning to make sure I didn’t make a mistake in my processing of the AMSR-E data.
As can be seen, the satellite-based temperatures have been steadily rising relative to the conventional SST measurements, with a total linear increase of 0.15 deg C over the 7 year period of record versus the conventional SST measurements.
If the satellite data are correct, then this means that the July 2009 SSTs reached a considerably higher record temperature than NOAA has claimed. The discrepancy is huge in terms of climate measurements; the trend in the difference between the two datasets shown in the above figure is the same size as the anthropogenic global warming signal expected by the IPCC.
I have no idea what is going on here. Frank Wentz and Chelle Gentemann at Remote Sensing Systems have been very careful about tracking the accuracy of the AMSR-E SST retrievals with millions of buoy measurements. I checked their daily statistics they post at their website and I don’t see anything like what is shown in the above figure.
Is it possible that the NCDC SST temperature dataset has been understating recent warming? I don’t know…I’m mystified. Maybe Frank, Chelle, Phil Jones, or some enterprising blogger out there can figure this one out.
UPDATE #1 (8/22/09)
Here’s the trend differences between the satellite and in-situ data, broken out by calendar month. The problem seems to be mainly a Northern Hemisphere warm season phenomenon.
UPDATE#2 (8/23/09)
Anthony Watts has suggested that the radio frequency interference (RFI) that we see in the AMSR-E 6.9 GHz data over land might be gradually invading the ocean as more boats install various kinds of microwave transmitters. While it’s hard for me to believe such an effect could be this strong (we have never seen obvious evidence of oceanic RFI before), this is still an interesting hypothesis, so this week I will examine the daily 1/4 deg. grids of AMSR-E SST and compute a spatial “speckle” statistic to see if there is any evidence of this kind of interference increasing over time. I should note that we HAVE seen more RFI reflected off the ocean from geostationary TV communication satellites in the AMSR-E data in recent years.
UPDATE#3 (8/24/09)
OK, gang, this is what I found out today before having to leave work. I downloaded the monthly grids of SST from NCDC (both their v2 and v3b products), and I computed the monthly anomalies at each gridpoint relative to the June 2002 through July 2009 period (since that is the period we have AMSR-E measurements for).
I then differenced the later part of the period (since 2007) with the earlier part (during and before 2004), separately for the NCDC and AMSR-E products.
Then I differences THOSE differences.
What it shows is that AMSRE has either spuriously warmed, or NCDC has spuriously cooled, by 1 to 2 deg C over all of the ‘warmer’ waters of the globe. The problem seems to diminish and then go away poleward of about 30S latitude, and poleward of 45N latitude.
This does NOT look like an RFI issue…it is too uniform spatially. Someone has made a major boo-boo…and I hope it isn’t me. 🙂
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Re: Bob Tisdale (04:33:53)
I have just written to ICOADS representatives to inquire regarding any influences the various series may have had upon one another due to whatever processing may have been applied to the raw data.
Richard (15:26:52) :
Ocean temperatures go up by over 0.35 C in a year and a half? Has there been a supervolcano going off under the sea? Mass die off of marine life? Something not quite right there.
Just to keep this in perspective, I scuba dive in the Vancouver, BC area. Ocean temperatures in that area vary 5 or more degrees between the coldest (5-6 C) and warmest (11 C). A 0.35 C difference isn’t that much.
Notice all the frenzied “tail chasing” going on here? Spencer brings up a very basic dilemma which he keeps repeating, to wit, “What it shows is that AMSRE has either spuriously warmed, or NCDC has spuriously cooled, by 1 to 2 deg C over all of the ‘warmer’ waters of the globe.
A high proportion of the back-and-forth responses I’m reading here have absolutely nothing to do with the puzzle raised. That failure to focus on the question at hand may entertain the participants, but it has to frustrate the questioner. The issue at hand is not why the SST has increased or decreased but rather why the NCDC and satellite records of SST have diverged so dramatically (and in directions counter-intuitive to the general tenor of this particular blog).
It brings back the headaches of a distant past life when I spent two years in a “think tank” as resident Neanderthal.
CH
Volcanic signals in oceans
Georgiy Stenchikov
Division of Mathematical and Computer Sciences and Engineering and Division of Chemical and Life Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
Thomas L. Delworth
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA
V. Ramaswamy
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA
Ronald J. Stouffer
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA
Andrew Wittenberg
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA
Fanrong Zeng
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA
Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean integrates volcanic radiative cooling and responds over a wide range of time scales. The associated processes, especially ocean heat uptake, play a key role in ongoing climate change. However, they are not well constrained by observations, and attempts to simulate them in current climate models used for climate predictions yield a range of uncertainty. Volcanic impacts on the ocean provide an independent means of assessing these processes. This study focuses on quantification of the seasonal to multidecadal time scale response of the ocean to explosive volcanism. It employs the coupled climate model CM2.1, developed recently at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory, to simulate the response to the 1991 Pinatubo and the 1815 Tambora eruptions, which were the largest in the 20th and 19th centuries, respectively. The simulated climate perturbations compare well with available observations for the Pinatubo period. The stronger Tambora forcing produces responses with higher signal-to-noise ratio. Volcanic cooling tends to strengthen the Atlantic meridional overturning circulation. Sea ice extent appears to be sensitive to volcanic forcing, especially during the warm season. Because of the extremely long relaxation time of ocean subsurface temperature and sea level, the perturbations caused by the Tambora eruption could have lasted well into the 20th century.
http://www.agu.org/pubs/crossref/2009/2008JD011673.shtml
Claude Harvey (22:11:37) :
Totally agree with your post. It’s been virtually impossible to pick out and follow comments which are relevant to the ‘problem’ outlined by Roy Spencer.
While I generally welcome the ‘free speech’ policy adopted at WUWT, there may be occasions when certain threads need to be more strictly moderated.
Did anybody see Dr. Spencer’s latest posting about the July SST anomaly being the highest ever?
http://www.drroyspencer.com/
What are odds of the mainsteream media and AGW bloggers reporting this?
REPLY: Just posted it – A
Claude Harvey (22:11:37) : ..Spencer brings up a very basic dilemma which he keeps repeating, to wit, “What it shows is that AMSRE has either spuriously warmed, or NCDC has spuriously cooled, by 1 to 2 deg C over all of the ‘warmer’ waters of the globe… the back-and-forth responses I’m reading here have absolutely nothing to do with the puzzle raised. .. The issue at hand is not why the SST has increased or decreased but rather why the NCDC and satellite records of SST have diverged so dramatically …
John Finn (03:29:24) : … While I generally welcome the ‘free speech’ policy adopted at WUWT, there may be occasions when certain threads need to be more strictly moderated.
I too have been guilty as charged. My initial meandering may have caused a little wandering also as some tried to chase my train of thought. Having re-read the two posts I realised I may have grasped the bull by the tail.
I dont agree with John Finn’s suggestion about curtailment of “free speech”, certainly not by snipping “off point” comments.
I agree this is a serious technical matter with serious implications, but most readers here are climate science novices like me and part of the reason for blogs like this is to educate through free discussion.
I admit I am out of my depth here. The more knowledgeable could share their ideas as Dr Spencer and his team try and figure out whats wrong.
In the meantime some of us could discuss variations in sea temperature, radiative imbalances, undersea volcanoes geothermal heat and stuff like that which have some relevance maybe not for this topic but for the general scheme of things.
I hope Dr Spencer wont get too frustrated looking for some illumination among the clutter.
Some novice observations: “The problem seems to be mainly a Northern Hemisphere warm season phenomenon.” The graph clearly shows that it is a warm season phenomenon. But why NORTHERN HEMISPHERE? Dr Spencer has some other knowledge which is obvious to him that he has not stated or shared with us.
I was puzzled by the fact that absolute average global temperatures were not even but showed a sinusoidal pattern with a peak in July and minimum in January. Because the Earth is actually closer to the sun in January furthest in July this further mystified me. I wrote to Dr Roy Spencer and he was kind enough to write back and explain very simply and elegantly “It’s because most of the land is in the Northern Hemisphere, and land reaches a higher temperature than ocean under the same amount of sunlight.” On doing a very superficial examination of insolation, assuming similar cloud covers over the years, I found match was extremely good.
Now I notice that the curve above also has a bulge in the summer months. The difference is that this curve is not a sinusoid but rather like a bell curve skewed to the left. The other difference is that these are not differences in absolute temperatures but the differences in trends. To get to the bottom of this Dr Spencer has meticulously separated the two products NCDC and AMSR-E and computed the difference in trends grid-wise.
He has found that the difference in trends are (as I understand it) majorly around the equator diminishing and then vanishing at latitudes 45 N and 30 S.
These differences are spatially uniform. There is a difference and someone has blundered.
Dr Spencer said that “…Frank Wentz and Chelle Gentemann at Remote Sensing Systems have been very careful about tracking the accuracy of the AMSR-E SST retrievals with millions of buoy measurements…” Is that a cross checking of the Satellite measurements? The Satellite data computes the Sea temperature as X, what does the buoy say, do they match? If this be so then the fault may not be with the satellite data / algorithms.
Does this mystery have anything to do with the relative areas of land and sea in the two hemispheres? Not only is there a difference in the lower latitudes but the difference of the trends increases in the summer months, falling off in December. Herein lie the clues dear Watson. They maybe elementary but I am mystified dear Holmes.
Separate from who is right and who wrong and where the mistake lies are the implications of this. This is big and this is the part I absolutely do not understand. Is NCDC wrong in computing the data they have and the Seas are actually much warmer than what they say? This implies their data is correct but computation wrong?
Or are they right and Dr Spencer has got things wrong? What would that imply? Do satellites are take part of their measurement from the actual sea measurements? Does it mean that his temperatures should actually be higher? Do satellite temperatures only show the anomalies and not the absolute temperatures? Do they have to rely on this for actual measurements of sea temperatures which are taken by NCDC and they have based this on the NCDC figures?
Dr Spencer is clear about this, but could someone explain.
Oops didnt see Antony’s / Roy Spencers post above
Ok the consequences of Dr Spencer being right would be that NCDC have overstated the current warming.
This is big. More than big – this is colossal.
One would even wonder, if NCDC have made a mistake, if their mistake is a genuine one or deliberate?
Re: Claude Harvey (22:11:37) & John Finn (03:29:24)
I suspect the discussion would have taken a different tack if direct links had been provided to plain-text monthly-summaries of all raw & anomaly series being discussed. (I base this comment largely on my experience running online stats courses.)
I agree that there are some comments upthread that suggest misunderstanding, but what I take from such comments is that people are interested and supportive of Dr. Spencer’s efforts. Excluding such gestures of good will would alienate supporters.
As for tolerance of fruitful side-themes: Contrast WUWT with Tamino for some perspective. Tamino engages in shameless quantitative distortion and strictly forbids competing views. It’s a slippery slope in that direction. In sharp contrast, Anthony applies the surefooted approach of wisely sticking to common sense.
Bob Tisdale & Others,
2 last notes:
1) AMO seems relevant in your Southern Ocean mystery.
2) An ICOADS representative has informed me that the cloud “estimate procedure is not related to measurements of SST”.