Roy Spencer: ocean warming suggests climate sensitivity of 1.3 degrees

Roy Spencer and his colleague Danny Braswell have a new paper out claiming that climate sensitivity is very, very low: 1.3 degrees Celsius. Remember, the recently published WGI report of AR5 gave a range for Equilibrium Climate Sensitivity (ECS) of 1.5-4.5 and for the first time in its history IPCC did not give a best estimate for ECS. So Spencer’s new estimate lies outside the lower boundary of the IPCC AR5 range.

In the last report in 2007 their best estimate was 3 degrees Celsius. An ECS of 1.3 C by the way is very close to the theoretical radiative effect of a doubling of CO2 so it suggests that the positive feedbacks (mainly water vapor and clouds) that produce the 3 degrees of warming in GCMs are not taking place in the real climate.

Readers of this blog are probably aware that in the past year or so there have been a number of papers claiming that ECS is relatively low (between 1.5 and 2 C) based on observational data (Ring et al, Lewis, Aldrin et al, Otto et al, Masters). These studies use our best observational data for the period 1850-2013 (change in global average temperature, change in total forcing, change in ocean heat content). In doing this in practice they assume almost all the warming since 1850 is due to humans, for the simple reason that available forcing estimates for the sun over this period are very small. Note: these studies do take the recent “extra” heat in the oceans into account and therefore do not conflict with the recently popular hypothesis that try to explain the standstill in warming with heat going into the deep oceans.

Spencer and Braswell use a different period (1955-2010) and a different method than the above mentioned studies. They do use the same numbers for the total forcing though and the main reason their estimate for ECS is even lower is that part of their warming is “explained” by El Niño and La Niña events. They use a very simple 1D model and then look for the best parameter settings to describe the warming of the oceans in the period 1955-2010.

Lees verder…


Xie reacts on Curry

Yesterday I decided to ask Shang-Ping Xie and Yu Kosaka of the widely discussed Nature paper about the slowdown in global temperatures to react on Judith Curry’s blog post. Xie promptly did and with his permission I just post his response here. Curry’s sentences are italic.

Here are some thoughts on her take. I liked Judy’s thoughtful blog about our paper, and agree with her view that natural variability modulates the pace of climate warming over a decade or two.

Compare the temperature increase between 1975-1998 natural internal variability associated accounting for significantly MORE than half of the observed warming.

1975 was a La Nina year, and 1998 followed the strongest El Nino in the instrumental record. My estimate indicates that the El Nino-La Nina difference accounts for 0.2-0.3 C difference of her 0.4 C in POGA-C. So for multi-decadal trend, PDO accounts for only 0.1-0.2 C for the longer period of 1950-2010. El Nino and La Nina are part of the short climate cycle of ENSO, averaged out over several decades. Our paper noted that the warm phase of the tropical Pacific Decadal Oscillation contributed to the fast warming during the 1970s-1990s.

I thought that it might account for at least half of the observed warming, and hence my questioning of the IPCC’s highly confident attribution of ‘most’ to AGW.

I have a different take on this. The IPCC conclusion applies to centennial warming from 1880. Much of the 0.8 C warming since 1900 is indeed due to anthropogenic forcing, because natural variability like PDO and AMO has been averaged out over this long period of time.
Our results concern the effect of tropical Pacific SST on global mean temperature over the past 15 years. It is large enough to offset the anthropogenic warming for this period, but the effect weakens as the period for trend calculation gets longer simply because it is oscillatory and being averaged out.

[Update, short reply by email from Curry on Xie's comments:

Hi Marcel, interesting. You can pick different years than 1975 and 1998 (which were neutral relative to enso), and you still see a strong trend from PDO.With regards to the IPCC statement, the AR4 statement was tied to the latter half of the 20th century, and the 'detection' argument identified the AGW signal since mid 1970's. What the AR5 will eventually say, I don't know (other than what was leaked). Judy [end update]

More comments on her blog:

JC comments:  I’m pleased that Xie has responded to what I have written.  El Nino and La Nino don’t seem to me to be easily separable from the PDO.  Picking ENSO neutral years at the beginning and end of the 30 yr period circa the 1970′s to 2000 still shows a strong increase during the period.

Also, I am interested that Xie seems to refer to the forthcoming attribution statement for the AR5, which apparently refers to the period since 1880.  Which is different from the AR4, which referred to the latter half of the 20th century.


Implicatie nieuwe Nature-studie: helft opwarming ’75-’98 door El Niño?

Er is massale belangstelling van de media en de blogosfeer voor de vandaag gepubliceerde Nature-paper van Shang-Ping Xie en Yu Kosaka. De Volkskrant wijdde er vandaag een bericht aan en NRC zal vanmiddag ongetwijfeld volgen. De hoofdconclusie van het artikel is dat het tropische deel van de Pacific (Grote Oceaan, het gebied waar El Niño and La Niña optreden) waarschijnlijk een belangrijke rol heeft gespeeld bij de stagnatie van de mondiale temperatuur in de afgelopen vijftien jaar.

Simpel gezegd komt het erop neer dat er vermoedelijk periodes zijn van enkele decennia waarin El Niño’s domineren gevolgd door een periode waarin La Niña’s de boventoon voeren. Dat laatste zou het geval geweest zijn sinds 1998 met de veelbesproken stagnatie van de mondiale opwarming als gevolg. De auteurs zijn in de paper vrij gedecideerd over hun resultaten: “The simulated global-mean temperature is in excellent agreement with observations, showing that the decadal cooling of the tropical Pacific causes the current hiatus.”

De auteurs haasten vervolgens te zeggen dat deze periode van stagnatie dus weer voorbij zal gaan en gevolgd zal worden door een nieuwe periode van opwarming:

We conclude that the recent cooling of the tropical Pacific and hence the current hiatus are probably due to natural internal variability rather than a forced response. If so, the hiatus is temporary, and global warming will return when the tropical Pacific swings back to a warm state.

Dit is allemaal volstrekt legitiem. De grote zwakte van de paper en vrijwel alle media-aandacht is echter het onbesproken laten van de logische vervolgvraag. Als een periode met blijkbaar grotere La Niña-activiteit de opwarming door broeikasgassen volledig kan platleggen, hoeveel draagt een periode met grotere El Niño-activiteit dan eventueel bij aan opwarming? De paper zwijgt in alle talen over deze toch minstens zo belangrijke vraag. Althans in de tekst. Judith Curry was echter heel alert bij het lezen van de paper, of beter gezegd, bij het bekijken van de figuren en spotte misschien wel de belangrijkste bevinding van de paper in figuur 1b:

Hier is een zogenaamde controle-run te zien. Xie en Kosaka gebruikten een klimaatmodel en legden aan hun model de daadwerkelijk opgetreden temperaturen in de tropische Pacific op. Met die opgelegde oceaantemperaturen en verder de bekende klimaatforceringen (broeikasgassen en aerosolen) kon het model de stagnatie van de laatste vijftien jaar veel beter simuleren (te zien in hun figuur 1a, hier niet getoond). In figuur 1b leggen ze wel de oceaantemperaturen in de Pacific aan het model op maar wordt het model niet gevoed met broeikasgassen en aerosolen. De uitkomst geeft dus een indicatie van de natuurlijke respons van het klimaat. Kijk nu eens goed naar de opwarming in het model (rode lijn) tussen 1975 en 1998, de periode van opwarming die door het IPCC en de meeste klimaatwetenschappers grotendeels aan broeikasgassen wordt toegeschreven. Het opleggen van alleen de zeewatertemperaturen geeft echter al 0,4 graden opwarming in het model!

Met broeikasgassen en aerosolen erbij neemt de opwarming (hun figuur 1a) toe tot ongeveer 0,68 graden in dezelfde periode van 1975 tot 1998. Curry merkt dus terecht op dat de studie suggereert dat meer dan de helft van de opwarming het gevolg van natuurlijke klimaatverandering lijkt te zijn. Dit staat haaks op de belangrijkste conclusie van het vierde en ook het aankomende vijfde IPCC-rapport dat stelt dat tenminste de helft van de opwarming door broeikasgassen komt. Daarom schreef Curry:

Like I said, my mind is blown.  I have long argued that the pause was associated with the climate shift in the Pacific Ocean circulation, characterized by the change to the cool phase of the PDO.  I have further argued that if this is the case, then the warming since 1976 was heavily juiced by the warm phase of the PDO.  I didn’t know how to quantify this, but I thought that it might account for at least half of the observed warming, and hence my questioning of the IPCC’s highly confident attribution of ‘most’ to AGW.

Ik heb Xie en Kosaka gemaild en hen gevraagd te reageren op het blogbericht van Curry. Zodra ik antwoord heb zal ik het hier melden.




A Late 20th Century European Climate Shift: Fingerprint of Regional Brightening?

The shift in the Central Netherlands Temperature in 1987

My first peer reviewed paper is out. The full title is: A Late 20th Century European Climate Shift: Fingerprint of Regional Brightening? First author is Jos de Laat of KNMI. The idea for the paper was mine, but Jos certainly did most of the work. The paper is freely available on the website of the journal Atmospheric and Climate Sciences.

For some years I noticed just by visual inspection that in the eighties there seems to be a jump  in the Dutch temperature time series. I asked Jos to have a look at it. He spent some time selecting the ‘best’ method to determine whether this shift is ‘real’. This so called change-point analysis procedure concluded that indeed there is a very significant step change of about 1 degree Celsius in the Central Netherlands Temperature time series in 1987. Lees verder…


Cook’s survey not only meaningless but also misleading

The new Cook et al. survey of the scientific literature is attracting worldwide media attention and even the American president tweeted (“Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous.”) about it. Yesterday my own first reaction on twitter was: “All this talking about consensus … doesn’t improve our understanding of climate even a tiny bit” And I added that “it shows again how meaningless this kind of consensus analysis is”.

Now I still support the label “meaningless” but today I will add “misleading” to the list.

So what’s all the fuzz about? Cook et al. selected around 12,000 scientific abstracts that contained the words “global warming” or “global climate change” published in the period 1991-2011. With a large group of volunteers they then rated the papers using 7 categories. Around 8000 of the abstracts (2/3) take no clear position on Anthropogenic Global Warming (AGW). Of the remaining ~4000 abstracts more than 97% “endorse AGW” according to the paper. Only a tiny amount (78 papers) “reject AGW”. Hence they claim again that there is a consensus, that the debate is over and also that there is a gap between scientists and the public (see graph above). A much larger percentage of the scientists “endorses AGW” than the public at large.

Now here comes the misleading part. If an abstract/paper “endorses AGW”, what would this mean for most people? Let’s look again at the tweet of Obama: “#climate change is real, man-made and dangerous”. If this is what it means for the president of the US, it probably means the same for many citizens who heard the news in the media. However, can this be sustantiated by the survey results? In no way.

To the credit of the researchers they made all their results available in a searchable database. Their rating system is online as well. There are 7 levels of endorsement, going from quantified endorsement of AGW all the way down to a quantified rejection of AGW. Seems fair enough. But here  is the issue. Only the first category can be regarded as a real or strong endorsement of AGW. Here is the description of category 1:

1. Explicit Endorsement of AGW with quantification
1.1 Mention that human activity is a dominant influence or has caused most of recent climate change (>50%).
1.2 Endorsing the IPCC without explicitly quantifying doesnt count as explicit endorsement – that would be implicit.

Now specifically look at 1.1. This comes close to the iconic statement from the IPCC AR4 report which said that “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” Now if 97% of the abstracts would repeat in slightly varying terms this major conclusion, than at least the conclusion of the survey would be more or less fair. However the survey doesn’t come even close.

Brandon Shollenberger, who is guest blogger at The Blackboard, was the first who reported that actually only 65 papers have been rated “category 1″. Yes that’s right, only 65 abstracts clearly “mention that human activity is a dominant influence or has caused most of recent climate change (>50%)”. 65 on a total of 12,000 is 0.5%. So a completely fair conclusion from their survey is that only 1 in 200 abstracts explicitly mentioned that humans are dominating climate. If you ignore the 8000 papers that were labelled category 4 (neutral, meaning having no position on AGW) the 65 would be 1.6%. The paper reported that only 78 papers (1.9% if you ignore the 8000 neutral abstracts) rejected AGW. (to be fair, as you can see in the table below only 10 papers fall in category 7 and therefore (7.1) “explicitly reject or minimise anthropogenic warming with a specific figure”.)

Now where is the 97% endorsement of AGW coming from? What the authors did is to add up the numbers of category 1 to 3 and of the category 5 to 7 which I show below*:

Category 1: 65
Category 2: 934
Category 3: 2933
Category 4: 8261
Category 5: 53
Category 6: 15
Category 7: 10
Total:         12271

As you can see the 78 “rejection of AGW” abstracts are the added number of category 5-7. Category 1-3 together adds up to 3932 papers. This 3932 divided by 4010 (the total of category 1-3 + 5-7) gives their impressive 97% (with the above numbers it is even 98%, see * for more explanation about how these numbers were found). However of these 3932 abstracts 2933 (75%) fall in category 3. Now how strong is the endorsement of AGW in this category? Here is the description:

3. Implicit Endorsement of AGW
3.1 Mitigation papers that examine GHG emission reduction or carbon sequestration, linking it to climate change
3.2 Climate modelling papers that talks about emission scenarios and subsequent warming or other climate impacts from increased CO2 in the abstract implicitly endorse that GHGs cause warming
3.3 Paleoclimate papers that link CO2 to climate change
3.4 Papers about climate policy (specifically mitigation of GHG emissions) unless they restrict their focus to non-GHG issues like CFC emissions in which case neutral
3.5 Modelling of increased CO2 effect on regional temperature – not explicitly saying global warming but implying warming from CO2
3.6 Endorsement of IPCC findings is usually an implicit endorsement. (updated this so it is more than just reference to IPCC but actual endorsement of IPCC)

I like 3.2: “endorse that GHG’s cause warming”. I also strongly agree with this part of 3.5: “implying warming from CO2″. The meaningless result of their whole exercise is that 75% of the abstracts that say something about AGW at all “link CO2 to climate change” or “imply warming from CO2″.

The misleading part is that they didn’t specify this result in their paper. Nowhere in their paper or in the supplementary material they even mentioned the total numbers in the different categories like I did in the simple table above. They only showed the total of category 1-3 in their figure 1(a):


Even the other >24% of AGW endorsement (based on the 4010) in category 2 is pretty meaningless:

2. Explicit Endorsement of AGW without quantification
2.1 Mention of anthropogenic global warming or anthropogenic climate change as a given fact.
2.2 Mention of increased CO2 leading to higher temperatures without including anthropogenic or reference to human influence/activity relegates to implicit endorsement.

In a comment under his post Shollenberger nicely explains who the different categories skew the result towards “endorsement of AGW”:

To give an example, if we say, “Humans are responsible for 40% of global warming,” that puts us in the bottom category. Change the number to 60%, and suddenly we’re in the top category. But what if we don’t give a number at all? If we just say “Humans cause some global warming,” we could be supporting a value 20% or 90%. Despite being able to support either position, we’d land in the top categories. That means the results will automatically be skewed toward the top.


Self confirming
Now for anyone who reads climate papers frequently this is totally obvious. Climate scientists have to frame their research in the abstract and there wouldn’t be so much climate papers if there was no concern for CO2.

So the whole result of this survey is completely self confirming. Because there is a concern for CO2 there is a lot of funding of climate science. This then generates a lot of climate science papers (they surveyed 12,000 but mention there are many more). In the abstracts scientists refer to the concern about CO2. The abstract then falls into category 2 or 3 and therefore almost all the papers “endorse AGW”.


* This is how you can replicate the numbers. Go to and type just a single letter in the search term box (I used “a”). This generates the total of 12,271 abstracts. Then select the whole period 1991-2011 and just search the 7 different categories. This generates the table from the blog post above.



New paper cuts recent anthropogenic warming trend in half

An interesting new paper (behind paywall) has been accepted for publication in the Journal of the Atmospheric Sciences. The paper by Jiansong Zhou and Ka-Kit Tung of the University of Washington, Seattle is titled “Deducing Multi-decadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis”. This paper will add fuel to the recent discussions about the nature of the global warming trend and whether it recently has stabilized or not. The authors by the way conclude it has not. Their main conclusions however is:

When the AMO is included, in addition to the other explanatory variables such as ENSO, volcano and solar influences commonly included in the multiple linear regression analysis, the recent 50-year and 32-year anthropogenic warming trends are reduced by a factor of at least two. There is no statistical evidence of a recent slow-down of global warming, nor is there evidence of accelerated warming since the mid-20th century.

Lees verder…


Still no sign of water vapor increase

Roger Pielke sr. has an important blog article showing the latest results of NASA’s Water Vapor Project (NVAP). The graph above is the key figure in a new paper by Tom Vonder Haar, one of the principal investigators of NVAP. Now maybe the graph looks pretty dull to you, but the potential consequences of it are profound. This graph is showing the best measurements we have today of the total amount of water vapor in the global atmosphere (TPW = Total Precipitable Water vapor). As you can see, there is not much of a trend. Now this is not what is expected. Lees verder…


Opwarming door nachtelijke onrust

Er is een belangrijke paper verschenen die meer licht werpt op hoe we temperatuurmetingen moeten interpreteren. Eerste auteur Richard McNider blogde over het artikel op de blog van Roger Pielke sr. en ook Anthony Watts pikte het op. Coauteurs van de paper zijn Bert Holtslag en Gert-Jan Steeneveld van Wageningen Universiteit.

De grafiek hierboven is afkomstig uit de paper en zegt meer dan de spreekwoordelijke duizend woorden. Linksboven is te zien dat de minimum temperaturen (Tmin) boven land veel sterker zijn gestegen dan de maximum temperaturen (Tmax). Rechtsboven is te zien dat klimaatmodellen de verschillen in trends tussen Tmin en Tmax niet goed simuleren. In klimaatmodellen is er nauwelijks verschil tussen Tmin en Tmax.

De paper van McNider en collega’s onderzoekt nu wat de oorzaak kan zijn van die snellere opwarming in de nacht. Een van de belangrijkste conclusies van het artikel is: Lees verder…




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