There is an excellent new paper by Bob Knox and David Douglas that provides further insight into the issue of the monitoring of global climate system heat changes. The paper is:

R. S. Knox, David H. Douglass 2010: Recent energy balance of Earth  International Journal of Geosciences, 2010, vol. 1, no. 3 (November) In press doi:10.4236/ijg2010.00000.

The abstract reads:

A recently published estimate of Earth’s global warming trend is 0.63 ± 0.28 W/m2, as calculated from ocean heat content anomaly data spanning 1993–2008. This value is not representative of the recent (2003–2008) warming/cooling rate because of a “flattening” that occurred around 2001–2002. Using only 2003–2008 data from Argo floats, we find by four different algorithms that the recent trend ranges from –0.010 to –0.160 W/m2 with a typical error bar of ±0.2 W/m2. These results fail to support the existence of a frequently-cited large positive computed radiative imbalance.

TROPICAL TROPOSPHERE: The 2006 CCSP report pointed to a mismatch between models and observed trends in the tropical troposphere as a “potentially serious inconsistency.” In short, the climate models need to get the tropical troposphere right, since it’s a vast region where the models all show a relatively enhanced and rapid response to greenhouse gases. If the models and data don’t agree in that region, there might be a deep problem with the way the models represent the climatic system’s response to greenhouse gases. Or at least there is an issue that needs to be sorted out. An important question, therefore, is whether the apparent mismatch between models and observations  is statistically significant, or just random noise. In 2007 Douglass et al. looked at the data and said Yes, the mismatch is significant: if you adjust the models so that they agree at the surface, the resulting profile of tropospheric trends are too high to match the observations. In 2008 Santer et al. said No, the mismatch is not statistically significant. They argued that the Douglass results were biased due to a failure to deal with autocorrelation, and in a model-observation comparison on data ending in 1999 they could not reject a null hypothesis of trend equality. The Santer paper figured prominently in the EPA endangerment finding research and in other places where the validity of climate models is at issue. In a new paper:

* **McKitrick, Ross R., Stephen McIntyre and Chad Herman (2010) “Panel and Multivariate Methods for Tests of Trend Equivalence in Climate Data Series” in press at Atmospheric Science Letters.

we critically examine the common methods used for trend comparisons, and explain some modern econometric methods that provide improved handling of the complex error structures in these data sets. We then apply the methods to the tropical troposphere issue, based on an up to date (1979-2009) time series comprising the full suite of IPCC climate models and 4 observational data series. We conclude that observed trends in the lower troposhere (LT) are significant but those in the mid-troposphere (MT) are not; that on average the balloon and satellite observational data sets agree with each other, though the RSS and UAH satellite series exhibit significant trend differences; that the model-predicted trends are two to four times larger than observed trends and the model-data discrepancy is statistically significant in both the LT and MT layers. See also Supplementary Information; Data/code archive.

See also:

 Climate Audit: McKitrick et al (2010) accepted by Atmos Sci Lett

Jo Nova: The models are wrong (but only by 400%)

The above figure is taken from the Science perspectives paper by Trenberth and Fasullo entitled ‘Tracking Earth’s Energy’

The summary reads:

By measuring the net radiative incoming and outgoing energy at the top of Earth’s atmosphere, it is possible to determine how much energy remains in the Earth system. But where exactly does the energy go? The main energy reservoir is the ocean, which sequesters energy as heat. Because energy is exchanged between the atmosphere and the ocean, this heat can resurface at a later time to affect weather and climate on a global scale. A change in the overall energy balance will thus sooner or later have consequences for the climate. Existing observing systems can measure all the required quantities, but it nevertheless remains a challenge to obtain closure of the energy budget. This inability to properly track energy—due to either inadequate measurement accuracy or inadequate data processing—has implications for understanding and predicting future climate.

The missing heat in  the climate system is discussed at length over at Roger Pielke Sr’s blog  here:

Is There “Missing” Heat In The Climate System? My Comments On This NCAR Press Release

and here:

Further Feedback From Kevin Trenberth And Feedback From Josh Willis On The UCAR Press Release

Roger Pielke Jr also blogs about ‘The Missing Heat’  and concludes:

First, there was ample indication of issues associated with the divergence of model projections and accumulated heat years ago, but for whatever reasons, it was not openly discussed, with the exception of the 2008 NPR story (perhaps I’ve missed others).

Second, it took the released CRU emails to open up a public scientific dialogue on this subject, which suggests that there are some issues with either model projections or observations. Judging from the Pielke-trenberth-Willis exchange, I’d put my money on problems with the models.

Third, none of this should alter how we think about the policy issues, as uncertainties have always been with us and always will. But getting uncertainties out in the open is a new thing for the public face of climate science and undoubtedly some will likely try to reassert the old ways of suppressing uncertainties.

The story of the missing heat does not indicate that climate science is a fraud or that we need not worry about a human influence on the climate system. What it does tell us is that there have been some unhealthy goings on in the climate community and we should all bask in the new found sunshine.

So where is the missing heat? Apparently no one knows, but I hope they find it soon.

The study, published in the journal Science, says a 10 per cent drop in humidity 10 miles above the Earth’s surface explains why global temperatures have been stable since the start of the century, despite the rise in carbon dioxide in the atmosphere.

And a rise in water vapour in the 1980s and 90s may also explain why temperatures shot up so quickly in the previous two decades, they say.

Water vapour has long been recognised as an important greenhouse gas. Like methane and carbon dioxide, it absorbs heat from the sun that would otherwise be reflected back into space, keeping the planet warm.

However, most computer models that predict climate concentrate on the levels of water lower down in the atmosphere.

Dr Susan Solomon, of the US National Oceanic and Atmospheric Administration, said: ‘Current climate models do a remarkable job on water vapour near the surface.

‘But this is different — it’s a thin wedge of the upper atmosphere that packs a wallop from one decade to the next in a way we didn’t expect.’

Observations from weather balloons and satellites show that ‘stratospheric water vapour’ increased in the 1980s and 1990s and dropped after 2000.

The changes took place in a narrow altitude region of the atmosphere where they would have the biggest impact on climate.

The reasons why water vapour rises and falls remain a mystery, the scientists say. However, the study estimates that the drop in water vapour since 2000 caused surface temperatures to rise 25 per cent more slowly than they would have done otherwise.

And the increase in stratospheric water vapour in the 1990s is likely to have accelerated the rate of global warming by around 30 per cent, the scientists say.

The stratosphere is a region of the atmosphere from about eight to 30 miles above the Earth’s surface. Water vapour enters the stratosphere mainly as air rises in the tropics.

Daily Mail: Water vapour a ‘major cause of global warming and cooling’

Published Online January 28, 2010
Science DOI: 10.1126/science.1182488
 
Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming

Susan Solomon,1 Karen Rosenlof,1 Robert Portmann,1 John Daniel,1 Sean Davis,1,2 Todd Sanford,1,2 Gian-Kasper Plattner3

Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here, we show that this acted to slow the rate of increase in global surface temperature over 2000 to 2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% compared to estimates neglecting this change. These findings show that stratospheric water vapor represents an important driver of decadal global surface climate change.

1 NOAA Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO, USA.
2 Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA.
3 Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.

Comment from Junkscience.com:

Pardon us for being less than impressed.

For years the air transport industry has been under assault because aircraft contrails allegedly do damage “wetting the Stratosphere”. Likewise the fossil fuel industry and agriculture because methane was supposed to loft to the Stratosphere where it decomposed to water vapor and carbon dioxide. Again, Stratospheric wetting was supposed to be a major concern and now: “Oops! It’s getting dry up here.”

Well guess what? Here’s another hypothetical means of adjustment in Stratospheric moisture levels: Svensmark Effect.

Undeniably Sol’s magnetic exuberance has been rather subdued of late, allowing more galactic cosmic rays (GCRs) to penetrate the Solar System, increasingly ionizing the atmosphere. Is this causing greater flocculation and droplet formation, causing water vapor to condense and fall out of the Stratosphere? We have no idea… and neither do modelers.

Granted, the addition of yet another item to the enormous list of things poorly understood about the climate and not represented (or wildly misrepresented) in models will make no real difference (unlike things well understood since any addition to such a miniscule list inflates it dramatically). Adding yet another excuse to the list of reasons “expected” warming failed to materialize is hardly cause for celebration though, is it.

This suggests that terrestrial ecosystems and the oceans have a much greater capacity to absorb CO2 than had been previously expected.

The results run contrary to a significant body of recent research which expects that the capacity of terrestrial ecosystems and the oceans to absorb CO2 should start to diminish as CO2 emissions increase, letting greenhouse gas levels skyrocket. Dr Wolfgang Knorr at the University of Bristol found that in fact the trend in the airborne fraction since 1850 has only been 0.7 ± 1.4% per decade, which is essentially zero.

The strength of the new study, published online in Geophysical Research Letters, is that it rests solely on measurements and statistical data, including historical records extracted from Antarctic ice, and does not rely on computations with complex climate models.

This work is extremely important for climate change policy, because emission targets to be negotiated at the United Nations Climate Change Conference in Copenhagen early next month have been based on projections that have a carbon free sink of already factored in. Some researchers have cautioned against this approach, pointing at evidence that suggests the sink has already started to decrease.

So is this good news for climate negotiations in Copenhagen? “Not necessarily”, says Knorr. “Like all studies of this kind, there are uncertainties in the data, so rather than relying on Nature to provide a free service, soaking up our waste carbon, we need to ascertain why the proportion being absorbed has not changed”.

Another result of the study is that emissions from deforestation might have been overestimated by between 18 and 75 per cent. This would agree with results published last week in Nature Geoscience by a team led by Guido van der Werf from VU University Amsterdam. They re-visited deforestation data and concluded that emissions have been overestimated by at least a factor of two.

University of Bristol Press Release, 9th November 2009

The paper: Is the airborne fraction of anthropogenic CO2 emissions increasing? by Wolfgang Knorr. Geophysical Research Letters, VOL. 36, L21710, doi:10.1029/2009GL040613, 2009.

Abstract:

Several recent studies have highlighted the possibility that the oceans and terrestrial ecosystems have started loosing part of their ability to sequester a large proportion of the anthropogenic CO2 emissions. This is an important claim, because so far only about 40% of those emissions have stayed in the atmosphere, which has prevented additional climate change. This study re-examines the available atmospheric CO2 and emissions data including their uncertainties. It is shown that with those uncertainties, the trend in the airborne fraction since 1850 has been 0.7 ± 1.4% per decade, i.e. close to and not significantly different from zero. The analysis further shows that the statistical model of a constant airborne fraction agrees best with the available data if emissions from land use change are scaled down to 82% or less of their original estimates. Despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction can be found.

World Climate Report analysis here.

CRN comment: I ‘like’ the alarmist terminology – negative feedback is described as ‘an amplifying process operating in reverse.’ This sounds rather like Richard Lindzen’s proposed ‘Iris Effect.’

Clouds Appear to Be Big, Bad Player in Global Warming
Richard A. Kerr

Science 24 July 2009:
Vol. 325. no. 5939, p. 376
DOI: 10.1126/science.325_376

Roy Spencer: ‘New Study in Science Magazine: Proof of Positive Cloud Feedback?’

Abstract
Climate feedbacks are estimated from fluctuations in the outgoing radiation budget from the latest version of Earth Radiation Budget Experiment (ERBE) nonscanner data. It appears, for the entire tropics, the observed outgoing radiation fluxes increase with the increase in sea surface temperatures (SSTs). The observed behaviour of radiation fluxes implies negative feedback processes associated with relatively low climate sensitivity. This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs. Therefore, the models display much higher climate sensitivity than is inferred from ERBE, though it is difficult to pin down such high sensitivities with any precision. Results also show, the feedback in ERBE is mostly from shortwave radiation while the feedback in the models is mostly from longwave radiation. Although such a test does not distinguish the mechanisms, this is important since the inconsistency of climate feedbacks constitutes a very fundamental problem in climate prediction.

Introduction
The purpose of the present note is to inquire whether observations of the earth’s radiation imbalance can be used to infer feedbacks and climate sensitivity. Such an approach has, as we will see, some difficulties, but it appears that they can be overcome. This is important since most current estimates of climate sensitivity are based on global climate model (GCM) results, and these obviously need observational testing.

To see what one particular difficulty is, consider the following conceptual situation:

We instantaneously double CO2. This will cause the characteristic emission level to rise to a colder level with an associated diminution of outgoing longwave radiation (OLR). The resulting radiative imbalance is what is generally referred to as radiative forcing. However, the resulting warming will eventually eliminate the radiative imbalance as the system approaches equilibrium. The actual amount of warming associated with
equilibration as well as the response time will depend on the climate feedbacks in the system. These feedbacks arise from the dependence of radiatively important substances like water vapor (which is a powerful greenhouse gas) and clouds (which are important for both infrared and visible radiation) on the temperature. If the feedbacks are positive, then both the equilibrium warming and the response time will increase; if they are negative, both will decrease. Simple calculations as well as GCM results suggest response times on the order of decades for positive feedbacks and years or less for negative feedbacks [Lindzen and Giannitsis, 1998, and references therein].

The main point of this example is to illustrate that the climate system tends to eliminate radiative imbalances with characteristic response times.

Now, in 2002–2004 several papers noted that there was interdecadal change in the top-of-atmosphere (TOA) radiative balance associated with a warming between the 1980’s and 1990’s [Chen et al., 2002; Wang et al., 2002; Wielicki et al., 2002a, b; Cess and Udelhofen, 2003; Hatzidimitriou et al., 2004; Lin et al., 2004]. Chou and Lindzen [2005] inferred from the interdecadal changes in OLR and temperature that there was a strong negative feedback. However, this result was internally inconsistent since the
persistence of the imbalance over a decade implied a positive feedback. A subsequent correction to the satellite data eliminated much of the decadal variation in the radiative balance [Wong et al., 2006].
However, it also made clear that one could not readily use decadal variability in surface temperature to infer feedbacks from ERBE data. Rather one needs to look at temperature variations that are long compared to the time scales associated with the feedback processes, but short compared to the response time over which the system equilibrates. This is also important so as to unambiguously observe changes in the radiative budget that are responses to fluctuations in SST as opposed to changes in SST resulting from changes in the radiative budget; the latter will occur on the response time of the system. The primary feedbacks involving water vapor and clouds occur on time scales of days [Lindzen et al., 2001; Rodwell and Palmer, 2007], while response times for relatively strong negative feedbacks remain on the order of a year [Lindzen and Giannitsis, 1998, and references therein]. That said, it is evident that, because the system attempts to restore equilibrium, there will be a tendency to underestimate negative feedbacks relative to positive feedbacks that are associated with longer response times.

Concluding Remarks

In Figure 3, we show 3 panels. We see that ERBE and model results differ
substantially. In panels a and b, we evaluate Equation (3) using ΔFlux for only OLR and only SWR. The curves are for the condition assuming no SW feedback and assuming no LW feedback in panels a and b, respectively. In panel a, model results fall on the curve given by Equation (3), because the model average of SW feedbacks is almost zero. In panel b, models with smaller LW feedbacks are closer to the curve for no LW feedback; the model results would lie on the curve assuming positive LW feedback. When in panel c we consider the total flux (i.e., LW + SW), model results do lie on the theoretically expected curve.

Looking at Figure 3, we note several important features:

1) The models display much higher climate sensitivity than is inferred from ERBE.

2) The (negative) feedback in ERBE is mostly from SW while the (positive) feedback in
the models is mostly from OLR.

3) The theoretical relation between ΔF/ΔT and sensitivity is very flat for sensitivities
greater than 2°C. Thus, the data does not readily pin down such sensitivities. This was
the basis for the assertion by Roe and Baker [2007] that determination of climate
sensitivity was almost impossible [Allen and Frame, 2007]. However, this assertion
assumes a large positive feedback.

Indeed, Fig. 3c suggests that models should have a range of sensitivities extending from about 1.5°C to infinite sensitivity (rather than 5°C as commonly asserted), given the presence of spurious positive feedback. However, response time increases with increasing sensitivity [Lindzen and Giannitsis,1998], and models were probably not run sufficiently long to realize their full sensitivity. For sensitivities less than 2°C, the data readily distinguish different sensitivities, and ERBE data appear to demonstrate a climate sensitivity of about 0.5°C which is easily distinguished from sensitivities given by models.

Note that while TOA flux data from ERBE are sufficient to determine feedback factors, this data do not specifically identify mechanisms. Thus, the small OLR feedback from ERBE might represent the absence of any OLR feedback; it might also result from the cancellation of a possible positive water vapor feedback due to increased water vapor
in the upper troposphere [Soden et al., 2005] and a possible negative iris cloud feedback involving reduced upper level cirrus clouds [Lindzen et al., 2001]. With respect to SW feedbacks, it is currently claimed that model SW feedbacks are largely associated with the behavior of low level clouds [Bony et al., 2006, and references therein]. Whether this is the case in nature cannot be determined from ERBE TOA observations.

However,more recent data from CALIOP do offer height resolution, and we are currently studying such data to resolve the issue of what, in fact, is determining SW feedbacks. Finally, it should be noted that our analysis has only considered the tropics. Following Lindzen et al. [2001], allowing for sharing this tropical feedback with neutral higher latitudes could reduce the negative feedback factor by about a factor of two. This would lead to an
equilibrium sensitivity that is 2/3 rather than 1/2 of the non-feedback value. This, of course, is still a small sensitivity.

See the full paper here (PDF)

Watts Up With That: ‘New paper from Lindzen demonstrates low climate sensitivity with observational data’

There is a Quadrant article aimed at a wider audience here by Richard Lindzen: ‘Resisting climate hysteria’

See also this post on The Reference Frame blog.

This is what an engineering study would do – identify the most critical areas of uncertainty and closely examine all the issues related to the critical uncertainty. Unfortunately, that’s not how IPCC does things. Instead, clouds are treated in one subsection of chapter 8 and boundary layer clouds in one paragraph.

Interestingly, the language in IPCC AR4 is (using the terminology of climate science) “remarkably similar” to Bony et al (J Clim 2006) url , with the differences as interesting as the similarities. It seems to me that each language change from Bony to IPCC had the effect of papering over or softening the appearance of problems or contradictions, rather than clearly drawing the issues to the attention of the public. (Note – Bony was a lead author of the chapter – another instance of IPCC authors reviewing their own work.)

Read the entire Climate Audit post: ‘Boundary Layer Clouds: IPCC Bowdlerizes Bony’

CRN comment: Reviewer Richard Allen made sensible scientific comments only to see them rejected by the lead authors.

The study, which appears in Nature Geoscience, found that climate models explain only about half of the heating that occurred during a well-documented period of rapid global warming in Earth’s ancient past. The study, which was published online today, contains an analysis of published records from a period of rapid climatic warming about 55 million years ago known as the Palaeocene-Eocene thermal maximum, or PETM.

“In a nutshell, theoretical models cannot explain what we observe in the geological record,” said oceanographer Gerald Dickens, a co-author of the study and professor of Earth science at Rice University. “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”

During the PETM, for reasons that are still unknown, the amount of carbon in Earth’s atmosphere rose rapidly. For this reason, the PETM, which has been identified in hundreds of sediment core samples worldwide, is probably the best ancient climate analogue for present-day Earth.

In addition to rapidly rising levels of atmospheric carbon, global surface temperatures rose dramatically during the PETM. Average temperatures worldwide rose by about 7 degrees Celsius — about 13 degrees Fahrenheit — in the relatively short geological span of about 10,000 years.

Many of the findings come from studies of core samples drilled from the deep seafloor over the past two decades. When oceanographers study these samples, they can see changes in the carbon cycle during the PETM.

“You go along a core and everything’s the same, the same, the same, and then suddenly you pass this time line and the carbon chemistry is completely different,” Dickens said. “This has been documented time and again at sites all over the world.”

Based on findings related to oceanic acidity levels during the PETM and on calculations about the cycling of carbon among the oceans, air, plants and soil, Dickens and co-authors Richard Zeebe of the University of Hawaii and James Zachos of the University of California-Santa Cruz determined that the level of carbon dioxide in the atmosphere increased by about 70 percent during the PETM.

That’s significant because it does not represent a doubling of atmospheric carbon dioxide. Since the start of the industrial revolution, carbon dioxide levels are believed to have risen by about one-third, largely due to the burning of fossil fuels. If present rates of fossil-fuel consumption continue, the doubling of carbon dioxide from fossil fuels will occur sometime within the next century or two.

Doubling of atmospheric carbon dioxide is an oft-talked-about threshold, and today’s climate models include accepted values for the climate’s sensitivity to doubling. Using these accepted values and the PETM carbon data, the researchers found that the models could only explain about half of the warming that Earth experienced 55 million years ago.

The conclusion, Dickens said, is that something other than carbon dioxide caused much of the heating during the PETM. “Some feedback loop or other processes that aren’t accounted for in these models — the same ones used by the IPCC for current best estimates of 21st Century warming — caused a substantial portion of the warming that occurred during the PETM.”

Rice Unviersity Media Release:

Global warming: Our best guess is likely wrong
Unknown processes account for much of warming in ancient hot spell
14th July 2009

CONTACT: Jade Boyd
PHONE: 713-348-6778
E-MAIL: jadeboyd@rice.edu

Letter abstract

Nature Geoscience
Published online: 13 July 2009 | doi:10.1038/ngeo578

Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming by Richard E. Zeebe1, James C. Zachos2 & Gerald R. Dickens3

The Palaeocene–Eocene Thermal Maximum (about 55 Myr ago) represents a possible analogue for the future and thus may provide insight into climate system sensitivity and feedbacks1, 2. The key feature of this event is the release of a large mass of 13C-depleted carbon into the carbon reservoirs at the Earth’s surface, although the source remains an open issue3, 4. Concurrently, global surface temperatures rose by 5–9 °C within a few thousand years5, 6, 7, 8, 9. Here we use published palaeorecords of deep-sea carbonate dissolution10, 11, 12, 13, 14 and stable carbon isotope composition10, 15, 16, 17 along with a carbon cycle model to constrain the initial carbon pulse to a magnitude of 3,000 Pg C or less, with an isotopic composition lighter than -50. As a result, atmospheric carbon dioxide concentrations increased during the main event by less than about 70% compared with pre-event levels. At accepted values for the climate sensitivity to a doubling of the atmospheric CO2 concentration1, this rise in CO2 can explain only between 1 and 3.5 °C of the warming inferred from proxy records. We conclude that in addition to direct CO2 forcing, other processes and/or feedbacks that are hitherto unknown must have caused a substantial portion of the warming during the Palaeocene–Eocene Thermal Maximum. Once these processes have been identified, their potential effect on future climate change needs to be taken into account.

Nature: Vol 459 | 11 June 2009 | doi:10.1038/nature08047

The proportionality of global warming to cumulative carbon emissions p829

Climate sensitivity models may inaccurately characterize the full Earth system response, as they ignore changes in the carbon cycle, aerosols, land use and land cover. A combination of a simplified climate model, a range of simulations from a recent model intercomparison and historical constraints now show that, independent of the timing of emissions or the atmospheric concentration of CO2, emitting a trillion tonnes of carbon will cause global warming of 1.0 to 2.1 degrees Celsius.

H. Damon Matthews, Nathan P. Gillett, Peter A. Stott & Kirsten Zickfeld

Meanwhile, in the real world we’re +0.04C for 1979 to May 2009 in the lower atmosphere.

Bob Tisdale observes:

Paul, in the press release for Matthew et al (2009)…
http://news.concordia.ca/main_story/014941.shtml?referID=fs_tab_sidebar

they state, “These findings mean that we can now say: if you emit that tonne of carbon dioxide, it will lead to 0.0000000000015 degrees of global temperature change.”

I ran some quick calculations, and the “Matthews Multiplier” indicates that co2 accounts for a little more than half (54%) of the global temperature rise (based on linear trends) since 1979, which is the start year of the MSU TLT data.

But CO2, according to the NOAA ANNUAL GREENHOUSE GAS INDEX, represents approximately 63% of the AGGI.
http://www.esrl.noaa.gov/gmd/aggi/

If the “Matthews Multiplier” was correct, which it’s not, then all AGG would be responsible for 85% of the warming since 1979 and that’s a bit difficult to fathom.

Why?

By removing the impacts of Atlantic Meridional Overturning Circulation and Volcanic Aerosols from global SST anomaly data (1981 to present), the trend in global SST anomalies since 1981 drops by 62%.
Refer to:
http://bobtisdale.blogspot.com/2009/02/impact-of-north-atlantic-and-volcanic.html

For confirmation of the impact of the AMO on global temperatures, they should’ve checked with the Team at RealClimate who write about the AMO, “This pattern is believed to describe…SOME, BUT NOT ALL, of the high-latitude warming observed in the late 20th century.”

If they were to add the immediate impacts of ENSO, that would tweak the trend more. And if they’d studied the process of reemergence, they’d have discovered that global oceans integrate the effects of ENSO. Removing that would lower the global SST rise since 1981 yet again.

I think Matthews et al need to fix their climate models.