A new paper in Nature Climate Change out this week by England and others joins a number of other recent papers seeking to understand the climate dynamics that have led to the so-called “slowdown” in global warming. As we and others have pointed out previously (e.g. here), the fact that global average temperatures can deviate for a decade or longer from the long term trend comes as no surprise. Moreover, it’s not even clear that the deviation has been as large as is commonly assumed (as discussed e.g. in the Cowtan and Way study earlier this year), and has little statistical significance in any case. Nevertheless, it’s still interesting, and there is much to be learned about the climate system from studying the details.
Several studies have shown that much of the excess heating of the planet due to the radiative imbalance from ever-increasing greenhouses gases has gone into the ocean, rather than the atmosphere (see e.g. Foster and Rahmstorf and Balmaseda et al.). In their new paper, England et al. show that this increased ocean heat uptake — which has occurred mostly in the tropical Pacific — is associated with an anomalous strengthening of the trade winds. Stronger trade winds push warm surface water towards the west, and bring cold deeper waters to the surface to replace them. This raises the thermocline (boundary between warm surface water and cold deep water), and increases the amount of heat stored in the upper few hundred meters of the ocean. Indeed, this is what happens every time there is a major La Niña event, which is why it is globally cooler during La Niña years. One could think of the last ~15 years or so as a long term “La-Niña-like” anomaly (punctuated, of course, by actual El Niño (like the exceptionally warm years 1998, 2005) and La Niña events (like the relatively cool 2011).
A very consistent understanding is thus emerging of the coupled ocean and atmosphere dynamics that have caused the recent decadal-scale departure from the longer-term global warming trend. That understanding suggests that the “slowdown” in warming is unlikely to continue, as England explains in his guest post, below. –Eric Steig
Guest commentary by Matthew England (UNSW)
For a long time now climatologists have been tracking the global average air temperature as a measure of planetary climate variability and trends, even though this metric reflects just a tiny fraction of Earth’s net energy or heat content. But it’s used widely because it’s the metric that enjoys the densest array of in situ observations. The problem of course is that this quantity has so many bumps and kinks, pauses and accelerations that predicting its year-to-year path is a big challenge. Over the last century, no single forcing agent is clearer than anthropogenic greenhouse gases, yet zooming into years or decades, modes of variability become the signal, not the noise. Yet despite these basics of climate physics, any slowdown in the overall temperature trend sees lobby groups falsely claim that global warming is over. Never mind that the globe – our planet – spans the oceans, atmosphere, land and ice systems in their entirety.
This was one of the motivations for our study out this week in Nature Climate Change (England et al., 2014) With the global-average surface air temperature (SAT) more-or-less steady since 2001, scientists have been seeking to explain the climate mechanics of the slowdown in warming seen in the observations during 2001-2013. One simple way to address this is to examine what is different about the recent decade compared to the preceding decade when the global-mean SAT metric accelerated. This can be quantified via decade-mean differences, or via multi-decadal trends, which are roughly equivalent if the trends are more-or-less linear, or if the focus is on the low frequency changes.
A first look at multi-decadal trends over the past two decades (see below) shows a dramatic signature in the Pacific Ocean; with sea surface cooling over the east and central Pacific and warming in the west, extending into the subtropics. Sea-level records also reveal a massive trend across the Pacific: with the east declining and the west rising well above the global average. Basic physical oceanography immediately suggests a trade wind trend as the cause: as this helps pile warm water up in the west at the expense of the east. And sure enough, that is exactly what had occurred with the Pacific wind field.
A consistent picture has now emerged to explain the slowdown in global average SAT since 2001 compared to the rapid warming of the 1980s and 1990s: this includes the link between hiatus decades and the Interdecadal Pacific Oscillation, the enhanced ocean heat uptake in the Pacific (see previous posts) and the role of East Pacific cooling. All of these factors are consistent with a picture of strengthened trade winds, enhanced heat uptake in the western Pacific thermocline, and cooling in the east – as you can see in this schematic:
As our study set out to reconcile the emerging divide between observations and the multi-model mean across CMIP5 and CMIP3 simulations, we took a slightly different approach, although there are obvious parallels to Kosaka and Xie’s study assessing the impact of a cooler East Pacific. In particular, we incorporated the recent 20-year trend in trade winds into both an ocean and a climate model, to quantify its impact. It turns out that with this single perturbation, much of the ‘hiatus’ can be simulated. The slowdown in warming occurs as a combined result of both increased heat uptake in the Western Pacific Ocean, and increased cooling of the east and central Pacific (the latter leads to atmospheric teleconnections of reduced warming in other locations). We find that the heat content change within the ocean accounts for about half of the slowdown, the remaining half comes from the atmospheric teleconnections from the east Pacific.
Unfortunately, however, the hiatus looks likely to be temporary, with projections suggesting that when the trade winds return to normal strength, warming is set to be rapid (see below). This is because the recent accelerated heat uptake in the Pacific Ocean is by no means permanent; this is consistent with the shallow depths at which the excess heat can now be found, at the 100-300m layer just below the surface mixed layer that interacts with the atmosphere. [Ed: though see also Mike’s commentary on this aspect of the paper]
Even if the excess heat fluxed into the ocean were longer-term, burying the heat deep in the ocean would not come without its consequences; ocean thermal expansion translates this directly into sea-level rise, with Western Pacific Island nations already acutely aware of this from the recent trends.
Our study addresses some important topics but also raises several new questions. For example, we find that climate models do not appear to capture the observed scale of multi-decadal variability in the Pacific – for example, none reproduce the magnitude of the observed Pacific trade wind acceleration – the best the models can do is around half this magnitude. This begs the question as to why this is the case: given the positive ocean-atmosphere feedbacks operating to drive these strengthened trade winds, the answer could lie in the ocean, the atmosphere, or both.
The study also discusses the unprecedented nature of the wind trends, and suggests that only around half of the trend can be explained by the IPO. So where does the other half come from? The Indian Ocean is as one possibility, given its recent rapid warming; but models capture this in greenhouse gas forced projections. What else might be accelerating the winds in the Pacific beyond what you’d expect to see from the underlying SST fields alone?
The study also points to the length of the wind trend as being crucial to the hiatus; arguing that anything much shorter, like a decadal wind trend, would not have resulted in nearly as much heat uptake by the ocean. This is related to the time-scale for ocean adjustment to wind forcing in the subtropics: in short it takes time to spin-up the ocean circulation response, and then more time to see this circulation inject a significant amount of heat into the ocean thermocline. Given the ocean inertia to change, what happens when the trade winds next weaken back to average values? Does the subducted heat get mixed away before this can resurface, or does the heat find a way to return to the surface when the winds reverse? Our initial work suggests the latter: as when we forced the wind anomalies to abate, warming out of the hiatus can be rapid, eventually recovering the warming that paused during the hiatus. So this suggests that whenever the current wind trends reverse, warming will resume as projected, and in time the present “pause” will be long forgotten by the climate system. [Ed: see again Mike’s piece for a discussion of an alternative hypothesis–namely, the possibility that a La Niña-like state is part of the response to anthropogenic forcing itself].
Of course, other factors could have also contributed to part of the recent slowdown in the globally averaged air temperature metric: increased aerosols, a solar minimum, and problems with missing data in the Arctic. Summing up all of the documented contributions to the hiatus, spanning ocean heat uptake, reduced radiation reaching Earth’s surface, and data gaps, climate scientists have probably accounted for the hiatus twice over. Of course each effect is not linearly additive, but even so, many experts are now asking why hasn’t the past decade been one of considerable cooling in global mean air-temperatures? Or put another way, why isn’t the model-observed gap even wider? One way to explain this is that the current generation of climate models may be too low in their climate sensitivity – an argument made recently by Sherwood et al in relation to unresolved cloud physics. A perhaps completely unexpected conclusion when analysts first noticed the model-observed divergence progressing over the past decade.
References
- G. Foster, and S. Rahmstorf, "Global temperature evolution 1979–2010", Environmental Research Letters, vol. 6, pp. 044022, 2011. http://dx.doi.org/10.1088/1748-9326/6/4/044022
- M.A. Balmaseda, K.E. Trenberth, and E. Källén, "Distinctive climate signals in reanalysis of global ocean heat content", Geophysical Research Letters, vol. 40, pp. 1754-1759, 2013. http://dx.doi.org/10.1002/grl.50382
- M.H. England, S. McGregor, P. Spence, G.A. Meehl, A. Timmermann, W. Cai, A.S. Gupta, M.J. McPhaden, A. Purich, and A. Santoso, "Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus", Nature Climate Change, vol. 4, pp. 222-227, 2014. http://dx.doi.org/10.1038/nclimate2106
- Y. Kosaka, and S. Xie, "Recent global-warming hiatus tied to equatorial Pacific surface cooling", Nature, vol. 501, pp. 403-407, 2013. http://dx.doi.org/10.1038/nature12534
Pierre-Emmanuel Neuroth,
You may wish to read the paper to which JCH linked in #30. The recent slowdown may just be natural variability. Also, I think your #4 has a typo, unless you are referring to the temperature increase since the end of the last ice age.
Re Climate modeling
Great site!
Have any of the climate experts here looked at the fits
to global temperature at
http://contextearth.com/2014/01/22/projection-training-intervals-for-csalt-model/
He gets very good fits to the temperature even just using data from 1880 to 1950. The sensitivity to CO2 is very steady using data from 1880 to 1950 or the full 1880 to 2013 data set.
The start of his modeling work is here
http://contextearth.com/2013/10/26/csalt-model/
Ken
I can see how these results could be interpretted in many different ways though.
And of course, Dan H is always the first to spin it ‘his’ way, which is clearly the ‘shill’ way.
JCH at 43 – The skepticalsience article, Where is global warming going? – http://www.skepticalscience.com/Where-is-global-warming-going.htm – graphs IPCC data to show that only 2.3 percent of global warming is going into the atmosphere. Ninety-three percent is going into the oceans and there appears to be broad agreement it will take as much as 1000 years for this heat to equilibrate with the atmosphere. The 2012 paper, World Ocean Heat Content and Thermosteric Sea Level change (0-2000 m),1955-2010, by Levitus et al. points to the fact that over the study’s span, to a depth of 2000 meters, the oceans have warmed on average only 0.09 C but if all of that heat was instantaneously transferred to the lower 10 kilometers of the atmosphere, it would warm on average 36 C.
The average depth of the oceans is 4267 meters so the deep has a great capacity to absorb heat that would do us in if if it was in the atmosphere or cause us considerable problems in the upper reaches of the ocean.
The second law of thermodynamics dictates we can generate work by moving heat from the surface into the available cold heat sink.
Is it possible that we can actually predict ENSO based on an old method used for evaluating the wave equation in elliptical coordinate systems?
http://contextearth.com/2014/02/21/soim-and-the-paul-trap/
The behavior may be more deterministic than we believed, which is nice for making long-term predictions.
Somebody:
Much of the “pause” and previous warming could be just internal variablility associated with ocean dynamics.
So one might think, if one had only one article in hand. But there’s so much more to know. It seems some of us begin each day with a fresh start, a viewpoint untrammeled by troublesome information.
In line with what I posted yesterday (#46, tp a Gavin response):
http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/feb/20/accounting-for-global-warming-oceans
Dan H @50.
If you were a bit more thoughtful, you would note that figure 3 of Swanson et al 2009 shows about a third of the post-1980 warming is being attributed by the paper to “natural modes of variability internal to the climate system.” Thus it fits with other works of wigglology. For me. the one word in the paper that jumps out and does a little dance is the word “hidden”. This one word speaks volumes about the world view of the authors.
While the denialist fraternity shout with joy at the appearance of such papers (for instance, note the provider of the 2007 paper’s PDF for google scholar), the work is at the end of the day nought but curve-fitting. Swanson & Tsonis (2009) is rightfully written in less definite language “This suggests that a break in the global mean temperature trend from the consistent warming over the 1976/77–2001/02 period may have occurred.”
Despite all the denialist hurrahs, all such studies as this fail to fit their work into climatology proper. They trumpet that they have “solved” the early 20th century warming leaving a nice smooth forcing that they helpfully attribute to anthropogenic causes. But is the anthropogenic forcing going to be such a nice oh-so-smooth curve? These studies write in some magical wiggle and silently airbrush out the likes of sulphur dioxide. This is not new work, yet it cannot get past the ‘first paper’ status. Thus I brand it ‘curve-fitting’ and ‘wigglology’.
Dan H at 50 pointed to Swanson et al. 2009, which says
That’s very bad news, as we know that CO2 matters.
#52 Thanks Ken,
I think England et al are using a fine approach. The characteristic that we should be monitoring is the free energy of the system. That includes heat, kinetic energy (wind, pressure), latent energy, and imparted forcing energy terms including changes in potential energy. The free energy is partitioned between these contributions and these contributions can shift over time, with the sum showing a secular near-monotonic trend once all the fluctuating terms are accounted for and balanced. This approach is often referred to as variational principles in thermodynamics, see recent work by W Muschik, P Ván, C Papenfuss.
England’s work is clearly showing how missing thermal energy can be compensated in excess wind energy. Same goes for pressure in the SOI measurement, think in terms of the ideal gas law.
The CSALT model is a case where I put everything in the hopper and see what pops out. The biggest fault that I have seen skeptics make of the model is that it is overfitting. I have no problem with that — even if it is not doing the factor accounting perfectly, it makes a great heuristic.
33. Deniers point to the recent so called pause in global temperature increases as proof there is no global warming. There are other instances of apparent pauses in the last couple of hundred years. And yet, looking at these periods in hindsight refutes the idea that these periods proved that there has been no warming.
It is simply invalid to be in the midst of a short period of time and then use that current period of time as a proof against global warming given the historical data and ups and downs in temperature that we have.
I don’t think you have to go back 10,000 years to demonstrate how wrong the deniers arguments are. On the other hand, for the vast majority of people you are dealing with, arguments don’t matter, logical or otherwise.
In any event, deniers will you your data to argue that we don’t need CO2 to get the warming you speak of.
The ‘pause’ debate seems to boil down to: ‘it didn’t warm when I/they/it wanted, where I/they/it wanted, or at the rate I/they/it wanted’, followed by pro-pollutionists throwing another raw data grenade (actual or invented) into the middle of the research.
The pro-pollutionists present ENSO and the Flat Temperature Society as:
http://ggweather.com/enso/oni.htm .
The research’s cleanest observation graph (no butterup intended) of ENSO and the Great Warming is:
https://www.realclimate.org/images/climcent_sat_enso.png
The clarity revealed in the RC graph reduces a debate about pause to the nail-head years – ’06, ’08, and ’09. Well, giddyup that. The clarity also reveals the underlying warning about the warming – the climate system is relying on El Nino’s for global cooling – and that influence is failing.
[Response: Relying on La Nina’s you mean. “Flat Temperature Society” — I love it! –eric]
Very interest post, and certainly covers all the likely causes of the flattening of the rise in tropospheric temperatures over the past decade or so. Some thoughts:
At a recent workshop with the APS, Santer strongly suggested (and presented slides to the effect) that the impact of volcanic aerosols over the past 10-15 years might be larger than anyone has thought, owing to a series of moderate volcanic events. There has been a definite measure increase in stratospheric optical depth as a result of these. Santer seemed to suggest a paper on this might be forthcoming.
Related to heat going into the oceans, there are many related effects, not just the fact that the tropospheric sensible heat might not rise as fast during such a period. Namely: Increase in the overall size and energy levels of the IPWP, which has effects on overall tropospheric/stratospheric/mesospheric circulation patterns as this additional energy in the IPWP (which has been rising since the 1950’s on a decadal basis) has global effects. Additionally, the rising OHC globally has lead to a greater measured advection of energy toward the north pole via ocean currents, and this has allowed for the decrease in net sea ice. Of course this energy finds its way out of the ocean to cause general tropopshere warming in the polar region and melting of permafrost, etc. Hence, the Cowtan & Way’s approach helps to “recapture” some of this increase in advected energy from the equator to the pole.
“Flat Temperature Society”
Oh my goodness, that’s perfect. I feel like I was around when something was born; this one definitely has legs!
If the wind does not stop blowing, relying on La Nina events won’t be much of a problem for them, will it?
And don’t forget, their AMO is still on the bench begging, “Put me in coach, put me in!”
> Flat Temperature Society
Apt, but polysyllabic.
“Flat Heat Society”?
distinguishing temperature and heat seems one of their issues
Re- Comment by R. Gates — 22 Feb 2014 @ 10:24 AM
“IPWP?” I am concerned that you are so busy that you are unable to type “International Parliamentarians for West Papua,” the most amusing of two meanings for your acronym in acronymfinder.com. People not familiar with climate science come here to learn something. This is one of the goals of this site.
Steve
[Response: Indo-Pacific Warm Pool. Yes, acronyms are overused. It takes me less time to type Indo-Pacific Warm Pool than IPWP because it uses words that my fingers “know”, while IPPW — see there you go, I mis-typed it! — does not. Of course, this doesn’t necessarily help much. Gates’s reference to “Increase in the overall size and energy levels of the IPWP” isn’t really an explanation — it’s more just a description of what has been observed (though I’m not sure what he means by “energy levels”. –eric]
I think there is so much more to discover. I have long held the view that global temperatures have been suppressed by the a nodal rise in atmospheric moisture. Moisture has the effect of absorbing energy at the surface and transporting it vertically. The more intense energy flows are increasing the air circlation in the Hadley cells possibly to the extent that Brian Farrel’s theory is playing out at least in part in the Northern Hemisphere. So the combination of air mass overflow into the Arctic pressure cell coupled with the confusing dynamics of the Atlantic conveyor we are seeing seemingly contradictory weather effects in the upper northern hemisphere.
Another thing that I have noticed is there seems to be some synchronicity between massive weather events in the western European field and Australia. Hard to make an argument to support that until I downloaded a weather app Weer en Verkeer which makes available a lot more global weather information in animated form. A month ago the Australian moisture display appeared to be showing a huge amount of moisture crossing the equator over the Phillipines and moving into the Northern Hemisphere weather systems. If this is what I saw then indeed there is a mechanism to possibly cause seemingly synchronised weather events diagonally opposed in seperate hemispheres.
I think that there is so much that ee don’t know and yet the US is moving the to reduce research funding in many fields of science.
The westerlies, live and in regards to #59 http://earth.nullschool.net/#current/wind/surface/level/orthographic=-183.30,7.72,303 a discussion can be found here http://forum.arctic-sea-ice.net/index.php/topic,730.msg20743.html#msg20743
Speaking of acronym confusion, I was at a meeting the other day where someone talked about performance tuning a big atmospheric model with support in part from the IPCC. No not that one, the Intel Parallel Computing Center.
Dr. Ricky Rood at WU agrees with the general idea of tracking all of the constituent energy factors:
If the oceans is absorbing the heat, then does that therefore cause the oceans to produce more evaporation which in turn should have a greater cooling affect? This apparently occurs with trees. More co2 should also cause a greater increase in all vegetation as CO2 is what plants live on, cooling the planet even more. http://carnegiescience.edu/news/water_evaporated_trees_cools_global_climate.
Has this been factored in?
Mark 5:
“Has this been factored in?”
Mark, in all seriousness, what makes you imagine that basic stuff like this has been ignored by scientists?
England notes that “Even if the excess heat fluxed into the ocean were longer-term, burying the heat deep in the ocean would not come without its consequences; ocean thermal expansion translates this directly into sea-level rise, with Western Pacific Island nations already acutely aware of this from the recent trends.”
How does the direct effect of thermal expansion due to increased ocean heat storage square with rates of sea-level change over the period of the so-called “hiatus”?
According to satellite data compiled by the CU Sea Level Research Group, sea levels have risen with a tightly linear trend of about 3.2 mm/a since 1992. We know that over that same time period, influx of meltwater from Greenland and the Antarctic has increased in rate, and obviously we also know that atmospheric CO2 forcing has increased steadily, with a slightly concave up curve, over that period as well, thanks to anthropogenic emissions.
My question is, given that influx of meltwater has steadily increased in rate, and given that CO2 forcing has increased (in a warming climate system already out of equilibrium), why has there not been any increase in the rate of sea level rise since the “hiatus” began?
If anything, the facts would seem to logically indicate a slowdown of ocean heat uptake and its concomitant effect of thermal expansion, offsetting in equal proportion the increase in volume due to increased meltwater, resulting in the observed linear sea level trend.
Is this due perhaps to increased reservoir impoundment from new dams such as the massive Three Gorges dam in China? That seems ostensibly plausible, but despite that project, at least according to hydroclimatologist Peter Gleick of the Pacific Insitute global reservoir storage has slowed and leveled off over the the period of time corresponding to the “hiatus”. And we must also consider the fact that humans have been hastily emptying the world’s deep aquifers of fossil water, which ultimately ends up in the oceans.
In a nutshell, how is it possible that all the extra heat from greenhouse warming is going into the oceans, alongside increasing rates of meltwater, yet the rate of global sea level rise has remained essentially constant since 1992, well before the onset of the “hiatus”?
Mark 5 #74, Why should increased evaporation have a greater cooling affect? Water vapor is the strongest greenhouse gas. Also apparently plants do not uniformely grow better with elevated CO2 levels (-> increased rate of climate change), see for instance http://climatestate.com/2013/09/23/plant-productivity-reduction-with-climate-change/ and http://www.skepticalscience.com/co2-plant-food.htm
Nick Manny #76, maybe because the 3.2 figure is an assemble of mean global SLR based on tide gauges?
Here is the estimate for the Pacific Ocean from CU data http://sealevel.colorado.edu/files/current/sl_Pacific_Ocean.txt which implies 6-7 cm SLR since the 90s.
Nick Manny, where are you getting your information that sea-level rise is linear?
http://tamino.wordpress.com/2014/01/23/true-lies/
#74–It ain’t that simple. Just the evaporation piece, for example, has a number of ‘moving parts’, many of which might be in play in the case considered:
http://en.wikipedia.org/wiki/Evaporation#Factors_influencing_the_rate_of_evaporation
Raising SSTs might increase evaporation a bit, but what about wind fields, atmospheric pressure and air temperature (which of course affects relative humidity)? For a trustworthy projection, all of that (and more) would have to be quantified.
And that’s leaving out the fact that the heat going into the ocean is not necessarily raising surface temps. In fact, the process described in the post above “bring[s] cold deeper waters to the surface…”, which is why La Ninas *lower* global mean SST (and indeed global mean temp generally.)
Nick Nanny 76: “How does the direct effect of thermal expansion due to increased ocean heat storage square with rates of sea-level change over the period of the so-called “hiatus”?”
Perhaps my comment at 35 has some relevance to this. Péter Berényi posted a plot of the Volumetric thermal expansion coefficient of ocean water as a function of depth at https://skepticalscience.com/news.php?n=273&p=2 (comment 53). As you point out Greenland and the Antarctic melting has increased since 1992. Heat flows from hot to cold regions, thus from the tropics to the poles aided by tropical storms. Moving surface heat mechanically from the tropical ocean surface into the largest cold sink on the planet (which appears to be happening naturally in any event) enables you to produce power even as you sap the strength of tropical storms and perhaps slow sea level rise?
Nick Manny, rather than relying on logic as you say you are doing:
try looking up the things you’re assuming are facts, to see what information you’re missing.
Just as an example:
https://www2.ucar.edu/atmosnews/news/10090/global-sea-level-rise-dampened-australia-floods
Mr. Manny: Re: Change in thermosteric component of SLR
Please see my comments on the Unforced variations thread at
19 Feb 2014 11:39 PM
https://www.realclimate.org/?comments_popup=16811#comment-461476
21 Feb 2014 4:21 PM
https://www.realclimate.org/?comments_popup=16811#comment-462130
21 Feb 2014 4:29 PM
https://www.realclimate.org/?comments_popup=16811#comment-462132
and ensuing discussion. Briefly: I suspect that heat is lately being subducted to deeper ocean, resulting in less thermosteric SLR since expansion coefficients are smaller for colder water; this decrease is masked by increased melt from ice sheets.
sidd
Just a little call out on the third figure above (which is based on Figure 5a in the paper). The figure is constructed by tying all the AR4+AR5 projections to the GISTEMP 5-year running mean for 2000. Because the year 2000 5-year mean was on the high side of the noise band* (it includes 1998), that naturally makes the subsequent projections appear to run high.
A fairer chart maker might have attached the model projections to a trend estimate for 2000. The choice made appears to exaggerate the premise of the paper.
(* Of course, one person’s noise is another’s signal. I guess Prof England would say that the 2000 5-year mean is mostly signal.)
To be clear, a fairer rendering of the figure would be like this (apologies for the kludged graphics):
http://gergs.net/wp-content/uploads/2014/02/England-adjusted.png
The “Adjusted GCMs” are left tied to year 2000 trailing 5-year mean (because they are intended to track oceanic effects), while the IPCC models are tied to the long term linear trend at 2000 (because they cannot know about the year 2000 positive “oceanic” offset).
thanks for a nice post in a non inflammatory tone; I for one greatly appreciate it
Nick Manny – “In a nutshell, how is it possible that all the extra heat from greenhouse warming is going into the oceans, alongside increasing rates of meltwater, yet the rate of global sea level rise has remained essentially constant since 1992, well before the onset of the “hiatus”?”
Recent sea level rise (SLR) hasn’t been constant, there was a large increase in ocean heat uptake (the thermal expansion component of SLR) in the early 2000’s followed by a slower rate thereafter. This probably the most obvious feature of the recent trend in ocean heat uptake shown in the Hiroshima widget. This has been briefly covered in a handful of recent papers of sea level rise – see for instance: Ablain et al (2009) – A new assessment of the error budget of global mean sea level rate estimated by satellite altimetry over 1993–2008, who state:
“These new calculations highlight a reduction in the rate of sea level rise since 2005, by ∼2 mm/yr. This represents a 60%reduction compared to the 3.3 mm/yr sea level rise (glacial isostatic adjustment correction applied) measured between 1993 and 2005. Since November 2005, MSL is accurately measured by a single satellite, Jason-1. However the error analysis performed here indicates that the recent reduction in MSL rate is real.”
Some complicating factors are the multi-decadal variation in continental water storage – the land stores more water during La Nina-dominant (negative IPO) periods, water impoundment on land, water extraction on land, and cabbelling. Cabbelling is the reduction in volume when two parts of water become well-mixed. So if you imagine a large fish tank with warm water at the top and cooler water below, the two layers become stratified (separated). If you physically mix these two layers, the total volume they occupy actually decreases.
I’ve yet to see a research paper on the topic, but cabbelling in tandem with the greenhouse gas-forced warming of the oceans and the IPO phase might be part of the solution to closing the sea level budget. The anomalously strong trade wind-forcing means stronger vertical and horizontal (Ekman)transport in the ocean. By removing warm water from the surface of the tropics and mixing it down into the (cooler) deeper ocean, the spin-up of the wind-driven ocean circulation may be providing a (probably small) counter-acting response to global sea level rise.
If this is in fact a real consideration, then we may see a larger-than-expected rise in global sea level when the IPO moves back to its positive phase. When the trade winds weaken, the wind-driven export of near-surface water out of the tropical ocean will slow down, as will the vertical transport of warm surface water down into the ocean interior. The surface ocean should warm quickly and, with greater thermal expansion in the warmer surface layers of the tropics, we could see a greater contribution from thermal expansion in positive IPO phases moving forward in time – assuming the large-scale ocean and atmospheric circulation themselves don’t undergo any significant changes.
There are lots of theories about the apparent pause in temperature increase. From the article, the theories in total add up to more than the discrepancies between the models and actual temperatures.
.
How will we determine which theory is right, and how long will that take?
AndyL,
What theory? There are a few possibilities. You can sift through the research and draw some conclusions, you can observe and add things up ie if averaged peak temperatures stay stable but oceans continue to heat, glaciers continue to retreat, polar caps continue to recede, atmospheric moisture continues to increase, weather intensity continues to rise, etc…then obviously there is more energy in the environment, or you can just sit back and wait for thirty years. In the end it will be obvious, one way or another, and you can then muse to yourself “why didn’t I see that sooner!”.
#74 Mark 5 says:
“More co2 should also cause a greater increase in all vegetation as CO2 is what plants live on, cooling the planet even more”
That possible negative feedback has been overestimated by many people, even by some scientists.
Plants also need nutrients from soil, and WATER. Those limit yield in many, many places.
To save water, that evaporates at stomata, these usually partialy close if CO2 concentration increases. They don´t need to be so open to get the CO2 they actually need …
#76 Nick Manny wonders:
“…how is it possible that all the extra heat from greenhouse warming is going into the oceans, alongside increasing rates of meltwater, yet the rate of global sea level rise has remained essentially constant since 1992, well before the onset of the “hiatus”?”
Many people think the hiatus is many years “old”. Two decade, or at least 15 year old …
Not at all … It is actually only three years old, too short a period to produce what you mention it should.
Following list, taken from NASA, shows “sliding” decades, and corresponding temperature changes:
1991-2001: +0.12ºC
1992-2002: +0.43ºC
1993-2003: +0.42ºC
1994-2004: +0.25ºC
1995-2005: +0.26ºC
1996-2006: +0.26ºC
1997-2007: +0.19ºC
1998-2008: -0.12ºC
1999-2009: +0.25ºC
2000-2010: +0.30ºC
2001-2011: +0.02ºC
2002-2012: -0.04ºC
2003-2013: +0.02ºC
Apart from the decade starting in the exceptional year of 1998, ONLY last thee ending in 2011, 2012 and 2013 show no clear warming.
I am thinking that the increased wind energy is more of a compensating factor than the claim of increased volcanic activity as proposed by Santer and others recently.
If there is really an increase that large, will Sato at GISS release a stratospheric aerosol optical thickness update to reflect this turn of events?
http://data.giss.nasa.gov/modelforce/strataer/
Or is it that the volcanic fraction of the compensation is actually fairly small and it is reported on just for the sake of completeness?
Rafael,
Be careful with your statistics. Whenever you started with a cold year (1997, 2000, 2001), your trend was high, and when you started with a warm year (1998, 2002, 2003), your trend was low. Similar results occur when you end with a warm (2010) or cold (2012) year. Over short timeframes, the trends can be heavily influences by one or two datapoints, especially if they occur at the endpoints. If you are adament about usign 10-year timeframes, it would be best to plot 10-year averages, and examine that trend.
Naive question perhaps: could the pause be similar to the way the temp of ice doesn’t move while it is melting? It is still absorbing heat as before, but the phase transition leaves temperature constant until the water is fully liquid.
The polar ice seems to be melting a good deal faster than anticipated over about the period of the “pause”. Could the extra heat absorption from faster melting account for the slower overall rise in average global temperatures?
Hi all. Question: What does it mean to say that the pause or slowdown is not significant? What if we flipped it and said there has been no significant warming, as we often see. Are those statements equivalent? I’m struggling with what it means to say a non-change is not significant, ascribing significance to a null.