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crandles

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Global warming slowdown 'could last another decade'
« on: August 22, 2014, 01:21:30 AM »
http://www.bbc.co.uk/news/science-environment-28870988

Paper is
Quote
Varying planetary heat sink led to global-warming slowdown and acceleration

http://www.sciencemag.org/content/345/6199/897

abstract
Quote
A vacillating global heat sink at intermediate ocean depths is associated with different climate regimes of surface warming under anthropogenic forcing: The latter part of the 20th century saw rapid global warming as more heat stayed near the surface. In the 21st century, surface warming slowed as more heat moved into deeper oceans. In situ and reanalyzed data are used to trace the pathways of ocean heat uptake. In addition to the shallow La Niña–like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.

Full text pay-walled.

It is in science, so reliable?

More of an ocean cycle and presumably less sensitivity to CO2?


Michael Hauber

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Re: Global warming slowdown 'could last another decade'
« Reply #1 on: August 22, 2014, 03:37:58 AM »
Looks like a good study, but that doesn't make it correct.

The study is primarily based on observations of changes of ocean heat content at various depths.  With the ARGO network in place from 2002, sparse coverage in the important (to this study) deeper sections in the early years there must be some uncertainty of this study's conclusions due to measurement uncertainty.  They do discuss the issue of uncertainty, but the discussion seems a little vague for my tastes.  Perhaps the discussion relies on facts or knowledge that would be well known to researchers in the field.

They find that recent claims of heat being transmitted deeper in the oceans in the Pacific are not supported by the data, with little heat transmitted into the ocean deeper than 300m, and most of the changes in heat content taking place above 300m.  Interesting enough the Pacific ocean down to 1500m seems to not be gaining heat at all since roughly 1998, so perhaps the Pacfic could play a role in the hiatus, but it would not be by transferring heat to the subsurface within the Pacific, but perhaps to other oceans.

They also find that ocean heat accumulation has been reasonably consistent and so there is little role in the slowdown for factors such as volcanic aerosols or increased pollution from China.

The key mechanism that they believe is responsible is the AMO.  An increased Atlantic current moves more warm water into the North Atlantic.  With increased evaporation this increases salinity which results in more water sinking to deeper levels and transfers heat to the 300-1500 metre portion of the Atlantic.  At the same time this increases the melt of Arctic ice which results in more fresh water, which eventually results in a switch to a decreased Atlantic current.  I do find this explanation a little lacking as it doesn't explain why the AMO is maintained in a particular phase for a significant length of time (up to 30 years), or why the fresh water from Arctic melt does not reverse the phase until this length of time has passed.  Does the fresh water build up gradually over time?  They note that the observations are not sufficient to assess whether this mechanism is occurring. 

If this is the mechism it means an interesting link between the global warming pause and the increased Arctic melt.  Could the slow Arctic melt for 2013 and 2014 mean that we are about to see the pause end?  However the last two years seem to show strong melt in the Atlantic side of the Arctic, and there seems to be currently a big build up of heat in the Atlantic just south of the Arctic so perhaps not.

The paper does note that the AMO seems to have a cycle of about 60 years, referring to both the global record (which I think is too short to provide meaningful support for any 60 year cycle), and also to cycles in the much longer Central England Temperature Record.  They seem to believe that the switch occurred in roughly 1998, but do not make any specific prediction for how much longer the pause could go, and simply state that the pause will end whenever the AMO switches phase again.

edit:  also looking at the charts for ocean heat content by basin - there is a large jump in the Antarctic subsurface first, and then a jump up in the Atlantic.  Its hard to say that this is a gradual process with a definite trend and lots of noise on top to make the jumps, or whether the increase is the result of the chance combination of the two large jumps.
« Last Edit: August 22, 2014, 03:44:00 AM by Michael Hauber »
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viddaloo

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Re: Global warming slowdown 'could last another decade'
« Reply #2 on: August 22, 2014, 06:09:14 AM »
Using words like 'pause' and 'warming slowed' in a scientific paper is dangerous, as those half–truths (*) are translated in the tabloids to 'no warming' and in the public mind 'cooling'.

*) Granted, the surface warming has slowed, somewhat, yet we still find 2005 and 2010 as the warmest years globally on record. Also, the first decade of the 21st century was .2 degrees warmer than the nineties, and to date in 2014, the Twenty Tens are even warmer than the last decade. In what may also well be the 5th year in a row that has a lower September ice volume than any year of any decade before 2010, it seems unreasonable to talk about a pause or of any cooling at all. Just saying it's 'pausing' or 'cooler' doesn't make it so, IMO. If it was, it would show up in the data.
« Last Edit: August 22, 2014, 06:16:40 AM by viddaloo »
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F.Tnioli

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Re: Global warming slowdown 'could last another decade'
« Reply #3 on: August 22, 2014, 12:36:45 PM »
...
It is in science, so reliable?
...
I doubt. I mean, i don't doubt it's in "science" - but i doubt it's reliable. Because

... In addition to the shallow La Niña–like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.
is not a complete bullshit, but IMHO this is massively insufficient to be "mainly" causing near halt of surface temerature growth in 2000s and till now. In particular,
 - "Shallow La Nina-like patterns" - excuse me, but 2000s had El-Nino years too, and those were not exactly most weak El-ninos on record. Also, the qualification of the person who wrote the continuation of this phraze - i mean "in the Pacific" bit of it, - seems to be unclear to me, for a simple reason: even i know that "La-Nina" term - is, and can only be, about surface layers of water of the Pacific ocean. I mean, anyone here _ever_ heard about "Atlantic La-Nina" or "Arctic La-Nina"? I never had;
 - "mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic". What a jewel... 1st, this assumes that we will buy that such a heat transport "initiated" in relatively small part of the world ocean - namely in "North Atlantic" - can push lots of warmer waters into deeps of the world ocean in MOST locations of the world ocean (because if it's not so, then most of world ocean would remain in the usual mode of "warmer water stays above", wouldn't it). Me, i doubt it. Pacific is - by far - the largest water body of the planet, and whatever salinity "anomalies" happen in North Atlantic - Pacific ocean would be rather well isolated from them, and with its size, would still produce lion's share of the world ocean influence upon Earth climate. Second, it is also difficult to see how said "anomaly" in "North Atlantic" could produce any changes in vertical mixing worth mentioning on a planetary scale in "southern oceans" (which, i assume, are parts of Pacific, Atlantic and Indian to the south from some ~50th latitude?). Why? Simple because the distance between "North Atlantic" and "Southern oceans" is too darn great - we talk some 10000+ kilometers here.

I'd rather see such an abstract as a clear sign of the opposite: good authors subtly indicate that "sorry, this paper, we had to alter and tinker to forge a result we were asked to make for this world-wide famous journal".

Personally, i am concinved that the halt in question is mainly caused by the increase of athropogenic aerosol content of the athmosphere - at least the "unintentional" increase due to growing amount of industrial athmospheric short-lived (days to few years of half-life in the athmosphere) pollution (in terms of the whole world), and on top of that, probably some subtle but significant "intentional" addition to it (welsbach seeding and such, see corresponding US patens from 1990s). Less energy coming in = slower or even stopped warming for the time being, very simple.

One can't talk about this in Science, though. It'd be a... sensation, at very least. Also it is related to geo-politics, and is as such an issue of state security for practically all developed coutnries (perhaps except Canada).

Last but not least, "Science" magazine does not have crystal clear reputation per se. I'd recommend to take a look to this guardian's article for a broader picture - http://www.theguardian.com/commentisfree/2013/dec/09/how-journals-nature-science-cell-damage-science , - and to this particular example of Science's... failure to ensure even basic correctness of the matherial they accept for publication: http://www.michaeleisen.org/blog/?p=1439 .

As said somewhere, nowadays there are indeed signs of "wild west" even within very top insitutions which make or are related to the academic publishing... Se la vi.

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Michael Hauber

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Re: Global warming slowdown 'could last another decade'
« Reply #4 on: August 23, 2014, 12:34:22 AM »
La Nina like patterns have been observed and commented on in other basins such as the Atlantic.

eg Wikiepedia

And the fact that heat transport initiated in the North Atlantic has a large impact on the oceans all around the globe is one of the most basic facts of ocean circulation.  Go read up on the THC

The question is whether this circulation can speed up or slow down.  And the data presented in the report clearly shows an increase in heat in the subsurface for most of the Atlantic, strongly suggesting an increase in heat transported down by the descending water in the north Atlantic.
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Re: Global warming slowdown 'could last another decade'
« Reply #5 on: August 23, 2014, 04:26:49 PM »
We are only talking about a global warming slowdown because of the way we have defined and measure global warming. We measure the surface temperatures of the planet and then make the spurious and illogical claim that this measures the amount of warming that is occurring. The science around the greenhouse effect is simple. As CO2 levels rise, the planet captures an ever larger percent of the sun's energy that enters our atmosphere. I have no doubt, whatsoever, that global warming is accelerating, a simple function of this increased capture of the sun's energy.

The only question is where this energy or warmth is going. To think that this heat will be entirely reflected in the surface temperatures of the planet is simply ridiculous. I think it is relatively easy to identify, in a logical manner, where much of this warmth is going. The only real difficulty would be to quantify this heat transfer or capture by the various heat sinks that exist on the planet. Clearly, a large part of it is being captured by the oceans, subsurface. We measure SST anomalies across the planet and they are huge. These anomalies are driven by the heat transfer between the atmosphere and the ocean surface. Why would we think that these increased surface temperatures are not being transferred to the deep ocean. To suggest this is illogical. No we cannot measure this. Good luck setting up temperature probes across the planet at the depths needed to measure these increases. I do not have much knowledge about the ocean currents but they are mixing the ocean constantly. Biologists are recording massive migrations of ocean dwelling species as this warmth spreads. Atlantic Cod are migrating north, colonizing areas that have never been their normal habitat.

The total mass of the hydrosphere is about 1,400,000,000,000,000,000 metric tons (1.5×1018 short tons) or 1.4×1021 kg. The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. Most of the atmospheric warming  is occurring near the surface. The oceans can and will continue to capture a large part of this atmospheric warmth. This capture is reflected by the differences between surface atmosphere temperatures over land versus the oceans.

viddaloo

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Re: Global warming slowdown 'could last another decade'
« Reply #6 on: August 23, 2014, 05:58:44 PM »
I agree that including biology and measuring how far north the various species go would be a cheaper and probably more efficient way of studying the warming of the oceans. If cod and crab move north, then you can pretty accurately compute how much warmer the seas are at those biome depths.
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Yuha

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Re: Global warming slowdown 'could last another decade'
« Reply #7 on: August 23, 2014, 11:46:22 PM »
We are only talking about a global warming slowdown because of the way we have defined and measure global warming. We measure the surface temperatures of the planet and then make the spurious and illogical claim that this measures the amount of warming that is occurring. The science around the greenhouse effect is simple. As CO2 levels rise, the planet captures an ever larger percent of the sun's energy that enters our atmosphere. I have no doubt, whatsoever, that global warming is accelerating, a simple function of this increased capture of the sun's energy.

I agree but want to clarify:

The global warming results from an imbalance between incoming and outgoing radiation caused by reduced outgoing radiation due to higher CO2 levels. The warming will continue until the atmosphere warms enough to achieve a balance again. In this sense the atmospheric temperature is the key temperature. Deeper ocean temperatures have no direct effect to the radiation balance.

However, reduced atmospheric warming does not necessarily mean reduced global warming. In fact, if the CO2 level goes up but the atmospheric temperature does not, the radiation imbalance increases and the global warming accelerates --- assuming nothing else is affecting the balance.

Logically speaking there are two possibilities for a lack of atmospheric warming despite increasing CO2 levels:
  • Something other than CO2 level and atmospheric temperature is reducing the radiation imbalance.
  • All of the extra heat is going into oceans instead of the atmosphere.
In my understanding the evidence currently points to the latter more than to the former, but I claim no expertise in the matter.

AbruptSLR

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Re: Global warming slowdown 'could last another decade'
« Reply #8 on: August 24, 2014, 12:27:04 AM »
Many recent internet articles have referenced the Chen & Tung (2014) paper (about the possibility that the absorption of heat by the Atlantic Ocean, is primarily responsible for the global warming hiatus) while stating that the world should have about another 15-years of suppressed rates of global warming [see: Chen, X. & Tung, K.-K., (2014), "Varying planetary heat sink led to global-warming slowdown and acceleration", Science, Vol. 345, no. 6199, pp. 897-903, DOI: 10.1126/science.1254937].  This is premised on the assumptions that the AMO has about a 70-year period (so 35-year of heat and 35-years of cooling) and that the 35-year cooling period peaked in 2006, which could leave about 10-years of further cooling, assuming the AMO cycle is the dominate natural oscillation affecting mean global surface warming.

Nevertheless, many prominent scientists (who I agree with) indicate that they believe that the Chen & Tung (2014) conclusions are too simplistic, and that the larger story certainly includes interactions between the Pacific, Atlantic, Indian and Southern Oceans (not to mention aerosols, bio-cycles and numerous other feedback mechanisms).  Indeed, the first linked internet article writes:

Extract: "There is some heat going into the Atlantic, writes Kevin Trenberth, a researcher at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, in an email. But Trenberth—who was not involved in the current study—disagrees with how it's getting there.
Trenberth argues that processes in the Pacific Ocean drive changes in the North Atlantic current. The same basic mechanism that may drive heat into the Pacific—intense trade winds that pile up warm water in the western Pacific—has large ripple effects on the atmosphere.
Those ripples influence jet streams, or currents of air flowing through the atmosphere, across the U.S., and over the North Atlantic Ocean. And those atmospheric currents can drive changes in ocean currents."

http://news.nationalgeographic.com/news/2014/08/140821-global-warming-hiatus-climate-change-ocean-science/

Also the second linked article writes:

Extract: "Richard Alley, a geoscientist at Pennsylvania State University in University Park, says the study is interesting — “but whether it’s a completely different story or part of the same story is something I think is still coming out.”

Alley welcomes the focus on the Atlantic, however. “Those of us who work in palaeoclimate have for a very long time had an idea that the Atlantic matters,” he says. “The evidence from the ice ages is that there were huge North Atlantic changes that show up in climate records all over the world.”"

http://www.nature.com/news/atlantic-ocean-key-to-global-warming-pause-1.15755?utm_source=dlvr.it&utm_medium=tumblr


While Kim et al (2014) indicates that before 2040 CMIP5 models indicate that the amplitude of the ENSO phases will increase, indicating that when the El Nino events return for the next 25-years they are likely to be stronger than previously experienced leading to more abrupt climate change [see: Seon Tae Kim, Wenju Cai, Fei-Fei Jin, Agus Santoso, Lixin Wu, Eric Guilyardi & Soon-Il An, (2014), "Response of El Niño sea surface temperature variability to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2326].

Furthermore, McGregor et al (2014) illustrate the interaction between the Pacific, and Atlantic, Oceans [see: McGregor, S., A. Timmermann, M. F. Stuecker, M. H. England, M. Merrifield, F.-F. Jin and Y. Chikamoto, (2014), "Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming", Nature Climate Change; doi:10.1038/nclimate2330].

Also, Praetorius & Mix (2014) provide paleo-evidence of the importance of the synchronization of the North Pacific, and the North Atlantic, Oceans on Artic amplification: Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

Also the importance of the Pacific Ocean is indicated in: Nicola Maher, Alexander Sen Gupta and Matthew H. England, (2014), "Drivers of decadal hiatus periods in the 20th and 21st Centuries", Geophysical Research Letters, DOI: 10.1002/2014GL060527.

Also, for the important influence of the Indian see: Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423.

Also, the importance of the surface melting of the Greenland Ice Sheet is discussed in: Xu Zhang, Gerrit Lohmann, Gregor Knorr & Conor Purcell, (2014), "Abrupt glacial climate shifts controlled by ice sheet changes", Nature, doi:10.1038/nature13592.

Furthermore, the linked Msadek et al (2014) reference confirms that as we return to a warm phase of the Atlantic Meridional Overturning Circulation (AMOC), and similarly the warm phase of the Atlantic Multidecadal Oscillation (AMO) within the next 10-years, that Arctic Sea Ice area will reduce:

Rym Msadek, T. L. Delworth, A. Rosati, W. Anderson, G. A. Vecchi, Y.-S. Chang, K. Dixon, R. G. Gudgel, W. Stern, A. Wittenberg, X. Yang, F. Zeng, R. Zhang, and S. Zhang, (2014), "Predicting a decadal shift in North Atlantic climate variability using the GFDL forecast system", Journal of Climate. DOI: 10.1175/JCLI-D-13-00476.1.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00476.1

Abstract: "Decadal prediction experiments were conducted as part of CMIP5 using the GFDL-CM2.1 forecast system. The abrupt warming of the North Atlantic subpolar gyre (SPG) that was observed in the mid 1990s is considered as a case study to evaluate our forecast capabilities and better understand the reasons for the observed changes. Initializing the CM2.1 coupled system produces high skill in retrospectively predicting the mid-90s shift, which is not captured by the uninitialized forecasts. All the hindcasts initialized in the early 90s show a warming of the SPG, however, only the ensemble mean hindcasts initialized in 1995 and 1996 are able to reproduce the observed abrupt warming and the associated decrease and contraction of the SPG. Examination of the physical mechanisms responsible for the successful retrospective predictions indicates that initializing the ocean is key to predict the mid 90s warming. The successful initialized forecasts show an increased Atlantic Meridional Overturning Circulation and North Atlantic current transport, which drive an increased advection of warm saline subtropical waters northward, leading to a westward shift of the subpolar front and subsequently a warming and spin down of the SPG. Significant seasonal climate impacts are predicted as the SPG warms, including a reduced sea-ice concentration over the Arctic, an enhanced warming over central US during summer and fall, and a northward shift of the mean ITCZ. These climate anomalies are similar to those observed during a warm phase of the Atlantic Multidecadal Oscillation, which is encouraging for future predictions of North Atlantic climate."
« Last Edit: August 24, 2014, 02:41:34 AM by AbruptSLR »
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Michael Hauber

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Re: Global warming slowdown 'could last another decade'
« Reply #9 on: August 25, 2014, 02:43:07 AM »

Extract: "There is some heat going into the Atlantic, writes Kevin Trenberth, a researcher at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, in an email. But Trenberth—who was not involved in the current study—disagrees with how it's getting there.
Trenberth argues that processes in the Pacific Ocean drive changes in the North Atlantic current. The same basic mechanism that may drive heat into the Pacific—intense trade winds that pile up warm water in the western Pacific—has large ripple effects on the atmosphere.
Those ripples influence jet streams, or currents of air flowing through the atmosphere, across the U.S., and over the North Atlantic Ocean. And those atmospheric currents can drive changes in ocean currents."


The Chen and Tung paper start their analysis of the 'pause' around 1997 or 98.  They write because that is the usual date claimed as the start of the pause by the contrarians.  But of course this is also the time of the extreme 97/98 el nino, so not unreasonable to think there may be a connection.  And as I stated previously the paper does not convincingly (to me) explain why the North Atlantic current changed so as to bury heat in that ocean.  Perhaps its a result of stuff happening in the Pacific.

A further thought - this is the first attempt I'm aware of to analyse regional variations in subsurface data and possible implications for AGW.  Imagine that there are 10 scientists that are thinking it might be nice to publish such an analysis now that we have the ARGO network up and going.  Nine of them think that we don't have enough data yet, and the pre-ARGO data is not good enough.  One of them thinks we do have enough good quality data to do an analysis.  Guess which one publishes...
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F.Tnioli

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Re: Global warming slowdown 'could last another decade'
« Reply #10 on: August 25, 2014, 11:39:56 AM »
La Nina like patterns have been observed and commented on in other basins such as the Atlantic.
...
Irrelevant. Their abstract is mentioning La-Nina patterns in the pacific. My point was, if they talk La-nina _and_ Pacific, then mentioning "in the Pacific" is redundant - those 3 words which can safely be removed from that abstract, no harm done. Am i wrong, and if i am - why? If i am right, then person who wrote that abstract wasted space for those 3 words, a fraction of second of every reader who spent time to read the abstract, etc. Sloppy! :D
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Laurent

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Re: Global warming slowdown 'could last another decade'
« Reply #11 on: August 25, 2014, 06:04:01 PM »
Unpacking unpaused global warming – climate models got it right
http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/aug/25/unpacking-unpaused-global-warming-climate-models-right

Quote
All of the available evidence indicates that the global surface warming slowdown is temporary, and will only last as long as solar activity keeps falling, volcanic emissions keep rising, and until ocean cycles switch phases.

It’s only a matter of time until global surface warming once again accelerates. And until we get our carbon pollution under control, we’ll remain on a path towards highly dangerous and costly climate changes.
« Last Edit: August 25, 2014, 06:11:18 PM by Laurent »

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Re: Global warming slowdown 'could last another decade'
« Reply #13 on: August 27, 2014, 01:02:22 AM »
The linked reference indicates that if the hiatus were to continue into the near future (such as due to the AMO phase), then the ENSO would play a larger influence on mean global surface temperature.  As we are likely entering a phase of increasing El Nino frequency and strength, we can expect mean global warming to accelerate:

 
Umberto Triacca, Antonello Pasini, Alessandro Attanasio, Alessandro Giovannelli, Marco Lippi, (2014), "Clarifying the Roles of Greenhouse Gases and ENSO in Recent Global Warming through Their Prediction Performance", Journal of Climate 2014 ; e-View doi: http://dx.doi.org/10.1175/JCLI-D-13-00784.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00784.1?af=R


Abstract: "It is well known that natural external forcings and decadal to millennial variability drove changes in the climate system throughout the Holocene. Regarding recent times, attribution studies have shown that greenhouse gases (GHGs) determined the trend of temperature (T) in the last half century, while circulation patterns contributed to modify its inter-annual, decadal or multi-decadal behavior over this period. Here temperature predictions based on vector autoregressive models (VARs) have been used to study the influence of GHGs and El Niño Southern Oscillation (ENSO) on recent temperature behavior. We find that in the last decades of steep temperature increase, ENSO shows just a very short-range influence on T, while GHGs are dominant for each forecast horizon. Conversely and quite surprisingly, in the previous quasi-stationary period the influences of GHGs and ENSO are comparable, even at longer range. Therefore, if the recent hiatus in global temperatures should persist into the near future, we can expect an enhancement of the role of ENSO. Finally, the predictive ability of GHGs is more evident in the Southern hemisphere, where the temperature series is smoother."
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F.Tnioli

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Re: Global warming slowdown 'could last another decade'
« Reply #14 on: August 27, 2014, 10:42:41 AM »
... Finally, the predictive ability of GHGs is more evident in the Southern hemisphere, where the temperature series is smoother."
Not suprising, considering that southern hemisphere has way less persistent brown clouds than northern one. I mean industrial air pollution, which is said to mask significant part of GHG forcing, mainly not so far from their point of entry - http://en.wikipedia.org/wiki/Asian_brown_cloud#Global_warming_and_dimming and such.
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Re: Global warming slowdown 'could last another decade'
« Reply #15 on: August 31, 2014, 02:48:51 AM »
I posted this on Robert Scribbler's blog.  I can’t read the paper (link below to Wiley paywall), but I was able to access some of the key figures from the paper. The paper suggests that hiatus periods very unlikely after 2030, even with volcanoes the size/influence of pinatubo.  This, no surprise, due to overwhelming GHG forcing. This is assuming an RCP 8.5 emissions pathway.

Either way I have been getting the impression that “hiatus periods” after 2020 are very unlikely considering that we still have surface warming in the current “hiatus”.  If anyone has access to this paper, I think it would be a great contribution to this discussion if you could share your assessments of it.  Thanks in advance.  Here is the information below.

Drivers of decadal hiatus periods in the 20th and 21st centuries
Nicola Maher, Alexander Sen Gupta and Matthew H. England
Article first published online: 20 AUG 2014 | DOI: 10.1002/2014GL060527

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060527/abstract

Laurent

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Re: Global warming slowdown 'could last another decade'
« Reply #16 on: September 01, 2014, 12:04:09 AM »
No more pause: Warming will be non-stop from now on
http://www.newscientist.com/article/dn26122-no-more-pause-warming-will-be-nonstop-from-now-on.html?cmpid=RSS|NSNS|2012-GLOBAL|environment#.VAOafFFJzlc

F.Tnioli

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Re: Global warming slowdown 'could last another decade'
« Reply #17 on: September 01, 2014, 03:55:06 PM »
I doubt that.

Reasons.

1. With geo-engineering actively discussed in the White House (USA) for at least a decade, we can't be completely sure that some solution which will provide a further halt won't be implemented. After all, USA is 1) one of countries which have the highest potential (scientifically, politically, even militarily) to implement planetary-scale geo-engineering, and 2) one of countries which will suffer the most if surface temperatures of Earth are to be increased any much further. Once again, i allow myself to note http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5003186.PN.&OS=PN/5003186&RS=PN/5003186 , which was filed 23 years ago. Without doubt, this and similar technologies were developed much further since then.

2. It is difficult to take seriously any article, very 2nd sentense of which contains incorrect statement. As far as i know, this is the case here. I mean this sentense, quote: "Once temperatures start rising again, it looks like they will keep going up without a break for the rest of the century, unless we cut our greenhouse gas emissions". The incorrect statement here is its last 7 words. Truth is (again, as far as i know): cutting down mankind's greenhouse emissions will not prevent further growth of temperatures. Because:
 - last time this planet had ~400ppm, which was some ~6 millions of years ago if memory serves, - average surface temperature was some ~5...6 degrees C higher than pre-industrial (19th century) - we know this from geologists and paleontologists;
 - cutting down all (or, any significant part of) greenhouse emissions will automatically also cut all (or, much of) industrial aerosol pollution. IPCC quantifies man-made aerosols to be significant negative forcing on climate. Differense between aerosols and CO2 is that aerosols settle down rather fast (weeks to few years), while CO2 stays in the athmosphere for centuries. That's why any big reduction of greenhouse emissions will most likely result in rapid and significant growth of surface temperatures. Similar effect (but to a less extent, of course - "neighbours" influence is also significant) happens regionally when some nation or union implements big measures to remove much of industrial air pollution. In particular, this happened in Europe in early 2000s, when Europe removed some of air pollution (by the combination of "exporting" dirty smoke stacks to other remote countries, using cleaner vehicle fuels and filtering industrial output of remaining industrial enterprises). Famous heat wave of 2003 killed dozens thousands in Western Europe;
 - Powerful positive feedback processes (in terms of increasing surface temperature) are already in action, "triggered" by already happened AGW. Among most improtant ones are those: extra water vapour (itself strong greenhouse gas) caused by higher temperatures (the warmer it is, the more water vapour can be, in absolute mass nubmers, per unit of air volume with a given relative humidity); the reduction of Albedo (thawing and darkening of sea ice and glaciers, annual average); massively increased (and further growing) methane emissions in polar regions (from both land permafrosts and seabed clathrates); increasing size and frequency of forest fires (which throw out extra greenhouse gases, adding to global greenhouse effect in medium term - 3...40 years); ocean acidification - which reduces its ability to be a carbon sink (normally, some ~57% of extra CO2 added to the athmosphere - is absorbed by the world ocean);
 - Thermal inertia. Extra CO2 in the athmosphere will remain for centuries, and extra positive forcing on climate (extra energy-per-second within the athmopshere) will remain with it. World ocean is the main "thermal capacitor" of the planet - its thermal capacity is huge. Papers on it exist, are well known and relatively simple. Different authors define the time which is needed to overcome this thermal inertia differently, i've seen results as short as 21...25 years to as long as 40-50 years. In any case, it is obvious that adding some large amount of lasting greenhouse gases into the athmosphere does not result in immediate increase of the Earth surface temperature. Instead, the act of adding such an amount of greenhouse gases starts the gradual process of temperature icnrease, which ends after several decades in a new equilibrium. Because of this, (record high) greenhouse gases emissions of last few decades - are largely not realized yet in the form of increased surface temperatures. EVen if we stop all greenhouse emissions right now, next few decades "naturally" we'd be bound to live with the consequence of the last few decades of greenhouse emissions - namely, propotionally large increase of surface temperatures.


I must say, i am getting very tired of this "unless we cut down our greenhouse emissions" thing. So many authors and articles actually think that this is "the solution" - and so many others probably intentionally lying about it? - that i am getting sick. It is not "the solution". At best, it's merely a part of "the solution", and frankly, not even most important part. Because greenhouse gases is just one of many critical problems caused by present industrial global civilization. Even if we'd "solve" greenhouse gases, we'd still face others. To me, the most important part of the solution is how to solve "tragedy of commons". It needs to be done, if humans would like to hope to survive any much longer (more than some ~100 years). And it needs to be done on all levels - from personal relations and family, to relations of largest international blocks and unions. How to do it in a most reliable, prompt and least-damaging (to both humans and the rest of the Gaia) manner - this is what i consider to be the most important part of any complex of actions which pretends to be "the solution to the human condition of present day".


P.S. Oh, yes, i know, all i write is probably "calling of the prophet in the desert"; i know that probably noone will hear what i have to say. But "Hope dies last", plus, one can't really know how and why some piece of information here will affect some minds in relatively remote future. I still hope at least some few things written, i do not write in vain...
« Last Edit: September 01, 2014, 04:00:31 PM by F.Tnioli »
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bassman

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Re: Global warming slowdown 'could last another decade'
« Reply #18 on: September 01, 2014, 07:40:36 PM »
Here are the figures from Nature on the 2nd paper mentioned in the news release by Laurent.  This was just published yesterday and is a really fascinating way to look at natural variation vs GHG forcing. 

http://www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate2355_ft.html


Laurent

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Re: Global warming slowdown 'could last another decade'
« Reply #19 on: September 09, 2014, 09:21:20 AM »
Research shows surprise global warming 'hiatus' could have been forecast
http://www.theguardian.com/environment/2014/sep/09/research-global-warming-hiatus

Laurent

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Re: Global warming slowdown 'could last another decade'
« Reply #20 on: October 06, 2014, 12:11:49 AM »
Different depths reveal ocean warming trends
http://www.bbc.com/news/science-environment-29474646

The world is warming faster than we thought
http://www.newscientist.com/article/dn26317-the-world-is-warming-faster-than-we-thought.html?cmpid=RSS|NSNS|2012-GLOBAL|environment#.VDG_HVFJzlc
« Last Edit: October 06, 2014, 12:21:10 AM by Laurent »

bassman

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Re: Global warming slowdown 'could last another decade'
« Reply #21 on: October 06, 2014, 01:04:01 AM »
A really BFD, you beat me to it.   Gavin Schmidt seems to agree.

"@ClimateOfGavin: @SJvatn ...but since it changes estimates of the recent ocean heat uptake, it pushes estimates of sensitivity higher. Esp. for L&C."

bassman

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Re: Global warming slowdown 'could last another decade'
« Reply #22 on: October 06, 2014, 01:28:03 AM »


Here is some of the data from the study linked by Gavin Schmidt,

http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/

jai mitchell

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Re: Global warming slowdown 'could last another decade'
« Reply #23 on: October 06, 2014, 07:28:49 PM »
More critically,

This throws Trenberth's "missing heat" energy balance calculus off by significantly more.  Indicating that Chinese aerosols had a much greater cooling effect than has been previously asserted.

if this is the case than we are currently experiencing an analogous warming spike similar to the post clean air act warming of the mid 1970's as China is aggressively reducing sulfate emissions.
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bassman

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Re: Global warming slowdown 'could last another decade'
« Reply #24 on: October 07, 2014, 09:52:42 PM »
Great post about ocean heat content in reference the 2 studies from Nature.  The deniers already ran with this one but it's really worrisome that more heat isn't going into the abyss. 

http://scienceblogs.com/gregladen/