Guest commentary by Cecilia Bitz, University of Washington
“Polar amplification” usually refers to greater climate change near the pole compared to the rest of the hemisphere or globe in response to a change in global climate forcing, such as the concentration of greenhouse gases (GHGs) or solar output (see e.g. Moritz et al 2002). Polar amplification is thought to result primarily from positive feedbacks from the retreat of ice and snow. There are a host of other lesser reasons that are associated with the atmospheric temperature profile at the poles, temperature dependence of global feedbacks, moisture transport, etc. Observations and models indicate that the equilibrium temperature change poleward of 70N or 70S can be a factor of two or more greater than the global average.
The Arctic Climate Impacts Assessment (ACIA) summarized the evidence for amplification in Arctic surface warming with the statement, “Over the past 100 years, it is possible [33-66% confidence] that there has been polar amplification, however, over the past 50 years it is probable [66-90% confidence]” (ACIA, 2005, p 22). This uncertainty in the evidence of polar amplification should not be confused with the evidence for significant warming in the Arctic. Arctic warming is both highly significant and substantial — it is just not possible to say with very high confidence yet that the Arctic has warmed more than the rest of the hemisphere or globe. The purpose of this posting is to explain why there is sometimes an absence of evidence for polar amplification.
Dramatic changes in ice at the poles are often cited as evidence of recent climate change — changes such as thinning and retreat of the sea ice, collapse of ice shelves along the Antarctic Peninsula and on the north coast of Greenland, melting permafrost, etc. Are these changes evidence of polar amplification? Not really. Because ice is mostly confined to the high latitudes, it is impossible to compare the magnitude of changes in ice across many latitudes. Therefore it seems a mistake to consider changes in ice as prima facie evidence of polar amplification. Instead, I would argue that changes in ice are a consequence of warming, though they may play a role in causing polar amplification. The term “polar amplification” should therefore be reserved to describe the amplification of surface temperature changes.
Fig 1. Latitude-height distribution of the zonal mean difference in annual mean temperature (K) in response to the quadrupling of CO2. [From Manabe and Stouffer (1980)] (click to enlarge)
Manabe and Stouffer (1980) first popularized the phrase “polar amplification” to describe the amplified rate of surface warming at the poles compared to the rest of the globe in their climate model’s response to increasing GHG levels. Their early climate model had a simple ocean component that only represented the mixed layer of the water. Their model had roughly symmetric poleward amplification in the two hemispheres, except over the Antarctic continent, where they argued the ice is too thick and cold to melt back (see Fig 1). Both poles warmed more at the surface than the midlatitudes or equatorial regions. Figure 1 also shows that polar amplification only occurs below about 300mb (ie, only in the troposphere). The vertical profile of warming in the lower atmosphere and cooling in the stratosphere from GHGs is well understood as a function of increased absorption and re-radiation.
Fig 2. Linear surface warming trend in °C per century from NCAR CCSM3 averaged from 9 ensemble members using the SRES A1B scenario. (click to enlarge)
Observed polar climate change from the instrumental record is not symmetric. Except along the Antarctic Peninsula (Vaughan et al., 2003), most evidence of significant warming is from the Arctic. In addition, total sea ice extent in the Southern Ocean has had no significant trend since satellites began taking data in 1979 (Cavalieri et al 2003). Newer climate models generally also have very modest or no polar amplification over the Southern Ocean and Antarctica in hindcasts of the last century. The presence of a deep and circulating ocean component is key because ocean heat uptake increases most in the Southern Ocean as the climate warms (see Gregory 2000). The asymmetry at the poles does not however result from a difference in feedback strength associated with the ice or atmosphere. In fact, when these same climate models are run to equilibrium (in the same way that Manabe and Stouffer ran their model so that ocean heat uptake is not a factor) the hemispheres have nearly equal polar amplification.
Fig 3. Zonal mean surface temperature change at 2080-2099 relative to 1980-1999 for models archived at PCMDI for the IPCC AR4. The temperatures are normalized by the global mean to emphasize the relative polar amplification across models. (click to enlarge)
In addition to the asymmetry from ocean heat uptake, models have been used to attribute a considerable fraction of the warming on the Antarctic Peninsula and the lack of warming elsewhere on Antarctica to a decreasing trend in stratospheric ozone levels in the past few decades (Shindell and Schmidt, 2004). Due to the successful treaty to reduce ozone-depleting chlorofluorocarbons (CFCs) emissions, ozone levels in the stratosphere are expected to recover over Antarctica by about 2040, so eventually Antarctica begins to warm somewhat in climate model predictions of the 21st century (see Fig 2) (WMO, 2002).
It is well established that climate models exhibit Arctic amplification of future climate change (see Fig 3). In addition, averaging over numerous hindcasts from a single model started with differing initial conditions (known as an ensemble average) yields significant Arctic amplification in simulations of the last century. However, single realizations with a climate model do not universally show Arctic amplification in the past [Bitz and Goosse, in prep]. Thus models and observations alike show uncertainty in Arctic amplification in the last century. Nonetheless Arctic amplification in models (and most likely in nature too) is a robust result of forced climate change, provided the forcing is sufficiently large to overcome internal climate variability. Antarctic amplification only occurs if a model is run long enough so ocean heat uptake in the Southern Ocean does not damp the positive feedbacks and if trends in stratospheric ozone do not cause compensatory cooling. Predictions with climate models indicate that Arctic amplification will be significant (above the 95% confidence level) in one to two decades, while significant Antarctic polar amplification will take much longer. A lack of polar amplification over relatively short periods of time is therefore understandable and does not undermine the credibility of climate models or climate theory in any way.
References:
ACIA, 2005. Arctic Climate Impacts Assessment, Cambridge University Press, New York, U.S., 1042pp.
Cavalieri, D. J., C. L. Parkinson, and K.Y. Vinnikov, 30-Year satellite record reveals contrasting Arctic and Antarctic decadal sea ice variability. Geophys. Res. Lett., doi:10.1029/2003GL018031, 2003.
Gregory, J.M., Vertical heat transport in the ocean and their effect on time-dependent climate change, Clim. Dyn., 16, 501-515, 2000.
Holland, M.M., and C.M. Bitz, Polar amplification of climate change in the Coupled Model Intercomparison Project, Clim. Dyn., 21, 221–232,2003.
Manabe, S. and R.J. Stouffer, Sensitivity of a global climate model to an increase of CO2 concentration in the atmosphere, J. Geophys. Res., 85, 5529–5554, 1980.
Moritz R.E., C.M. Bitz, and E.J. Steig, Dynamics of recent climate change in the Arctic, Science, 297, 2002.
Shindell, D.T. and G.A. Schmidt, Southern Hemisphere climate response to ozone changes and greenhouse gas increases, Geophys. Res. Lett. doi:10.1029/2004GL020724, 2004.
Vaughan, D. G. et al. Recent rapid regional climate warming on the Antarctic Peninsula. Climatic Change, 60, 243-274 2003.
I’m not commenting re 49. 23. directly, just some general comments I’d like to make, below.
It is clear that many contributors to RC do not understand the links between NOAA and NWS and how those links have changed over time. For example, the Weather Bureau was operational for 3/4 of a century before NOAA was created. NOAA came about round 30 years ago, starting out with little or no direct influence on how NWS functioned.
In Jan 2000, Dr. James Baker head of NOAA, made powerful statements while a guest for 5 straight nights on the CBS Evening News with Dan Rather … about the very serious threat of global warming 5 days in a row in Jan. of 2000
Seeing that convinced me that global warming was serious. At that time, the director of NWS was Gen Jack Kelly, now a NOAA administrator. While Gen Kelly was NWS director there was little or no concern given to global warming.
In 2001, there was a policy change of some kind that resulted in the Bush Administration forcing a change in the leadership at EPA, due to statements made by then EPA director (name slips me), which statements were made publicly about a flipflop in the Bush Administration position on CO2 related to global warming. A new EPA leader was chosen, then the Bush Administration called for more science research and technology as his way of dealing with global warming. Directors of the major departments and agencies (the permanent civil service career positions) are now (since 2001) operatiing under the direction of the Bush Administration agency administrators. For example the current director of NWS may be under heavy influence of the current NOAA Administrators (6-7?) and the Department of Commerce (DOC). I think Mr. Mahoney may be both a NOAA Administration and an Assistant Secretary of DOC, but I may be in error on that… hard to determine. Anyway, it never used to be that NWS directors were influenced much in terms of how their programs were operated (except for money). Now it seems like the Bush Administration has heavy influence on operations withing the agencies, especially regarding global warming. In years before 2001, permanent employee directors were pretty much free to run the agency programs the way they felt the agencies would be most responsible to the public. Now the operations of federal agencies seem to be influenced heavily by whoever has the power of the President and Congress. Thus, there is potential for agencies to have more numerous and larger flip flops in the way programs are run for the public service.
I got a bit more lengthy than I planned. Now little time left to proof read, so if other’s at RC see these things a bit differently than described above please comment.
RE melting glaciers (e.g. in Greenland), scientists sometimes state that the sea would rise by such & such (say, 20 feet) if such & such glaciers melt. Now is this 20 feet projected rise taking into account that the land ususally slopes gently away from the shore. I mean, does this indicate that if we live 19 feet above sea level we can expect the sea to come into our homes, or are they basing their calculations on an image of a huge 90 degree cliff along all shores?
Re: 51:
Pat, you’ve done your homework…more than I am willing to do anyway. My whole point is from an operational perspective, the NWS, with its regional centers and local forecast offices has focused expertise in short-to-medium-range weather forecasting…with some hydrology thrown in there. Go in to a local NWS WFO and you will not find global warming experts there. Not now anyway. So why go after the NWS?
On the other hand, go to the big AMS meeting in Atlanta, and go to the 18th Conference on Climate Change (or whatever it’s called), and among the presenters you will see a number of the heavy hitters; many of their affiliations are with the big (NOAA-related) National Centers.
#47. I do understand that some AGW models call for a warming in the troposphere, especially in the tropics, but perhaps the upper air should be cooler over Antarctica, with most of its surface topography well above sea level, this should not come as a surprise at certain times of the year.
Some basic Upper Air analysis calls for the following examples: If the above surface lapse rate is “warmish” lets say a cooling of 8 C/km over an Antarctic station with a surface temperature to be -20 C, at 1 km ASL, 5 kilometers higher, the temperature would be -60 C. But if you take a “normal” Polar lapse rate of
5 C/km the temperature at this 5 kilometers the temperature would be -45 C, warmer!
The just of this story, is that warming of the Upper Atmosphere (by description many places in Antarctica) may be not found if the lapse rate is of a temperate nature . One must look at lapse rates rather than temperatures in the upper air to find any sign of significant warming. This obsession over Upper Air temperatures should be presented with lapse rate analysis otherwise it may be confusing. Then again most contrarian skeptics adore this ambiguity.
Re #52 (LV): 20 feet (or so) is 20 feet, whether across a slope or up a cliff. If you mean did they take into account the fact that there’s a little extra volume involved with the slopes (as opposed to cliffs), I suspect the volume difference is so small as to not make much difference (maybe an inch or two). If you’re really curious, the calculation would be pretty easy to do to a first approximation. All you would need is the number on total ocean shoreline (inc. bays etc.), assume a number for average slope, say 5 degrees, work out the volume involved up to 20 feet, then see how that stacks up against the 20 feet applied to the existing ocean area.
Your “big (NOAA-related) National Centers” don’t have any local or state contacts in government or media centers. There has been no way for not so “big (NOAA-related) National Centers” people in NASA, NOAA CMDL, NCDC and other not so big agencies to get the word out locally on global warming. The really big agency is NWS (more than 5000 government employees and managers with ties to local and state governments through their “outreach”, but nobody is reaching out to inform the people about the change in climate that happening. It’s obvious that rapid global warming is already upon us and that most of it is due to our emissions from burning fossil fuels, but no one is willing to talk about it or try to explain it to the public at the local level.
The attitude to not take any economic risks toward reducing greenhouse gas emissions has been sickening me for six years already, since Jan. of 2000. I have two young adult daughters who would like to have families. Do you think this world will offer the babies born this year a good chance for a happy life? I don’t. Young people need to think about this now, as part of their decision making process on starting or building on a family. They’re not. They should think about how their babies will feel about all this after they mature.
RE #49
Steve, the reference I gave is written by Carl Mears. Christy and Spencer (UAH) appear to still include the highest latitudes of the SH in their analysis. If you will look at the CCSP Draft SAP 1.1, Chapters 3 and 4, figures 3.5c and 4.3a and 4.3b, you will notice the different coverage. It should be noted that RSS also excludes other mountain areas and maybe Greenland as well (Fig 4.3). You may download the individual chapters as Acrobat files or just the figures from each chapter.
http://www.climatescience.gov/Library/sap/sap1-1/public-review-draft/default.htm
Of course, C & S may be doing something different now, for all I know.
Re: #43 #56
The Arctic’s temperatures exert a major influence on local weather conditions, including weather predictions. Therefore, global warming – and polar amplification in particular – ought be very much of concern to an agency like the NWS, who’s duties include weather prediction and the issuance of storm warmings, flooding alerts and heat wave advisories to the public.
Regarding getting the information out before the public, pat’s right. The NWS has a powerful means of communications with the public through its contacts with local TV, radio and newspaper media meteorologists. It uses them when it issue advisories and warmings, it should have been alerting them about greenhouse gas warming as well. Political interference by the Bush administration prevented that.
The TV and radio personalities who carry the message about “weird” weather, flash flooding and storms, etc., cite the NWS as the source of the predictions in much of what they present over the air. It’s not NOAA who gets the credit for issuing the warnings and alerts – itâ??s the NWS.
The fact that the NWS ignores global warming has a direct bearing on the accuracy of its predictions. The Arctic air that moves into Wisconsin nowadays is not as cold as it once was. The warming has already measurably influenced the timing of snowmelt, when the ground frost can be expected to leave, when ice goes out on its rivers and streams, and even what kind of plants are prevalent.
The seasonal weather we have experienced in the past in Wisconsin is no longer a good indicator of what kind of weather we can anticipate in the future. For example, the cold, numbing weather conditions during the Ice Bowl football game in Green Bay when the Packers beat the Dallas Cowboys in the NFL Championship Game doesn’t visit anymore. It had been the kind of winter weather Wisconsin was once known for. During the 50s and 60s, we annually had several days of 20 below zero (sometimes lower) temperatures. Not anymore.
NWS managers have been given orders not to reality of global warming into public conversations, reports and public presentations. I’ve heard it said on a Wisconsin public radio program that I listened to last fall. A member of the public called in and said they walked into a federal agency staff meeting in Manitowoc Co., WI, and heard the NWS staffers say they had orders not to talk to the public about global warming. They were forced to choose between disciplinary action and the possible loss of job and retirement pay, or being silent about global warming. The public has been deceived by our government into believing global warming is not a problem. This problem needs to be corrected because there are a lot of people in the U.S. who believe global warming is still not really happening (nor is polar amplification), because neither the National Weather Service, their president nor their local TV meteorologist have said it is. That needs to be corrected, now!.
Congress needs to act on this, now! What is needed are Congressional hearing. The issue should also be extensively addressed in the State of the Union speech. It probably won’t be if people who know it should be remain silent though.
http://www.beyondearthday.com
Mike, Pat,
I yield that you are paying more attention to NOAA/NWS than I am, at least administratively. I stress that issuing a severe thunderstorm warning for Taylor county is very different–and requires a different kind of expertise–from informing the public about global warming. Do I think local offices *should* have the capacity to do better AGW outreach? Yes. Do I think they *do* have that capacity currently? No I do not.
I agree with you: throughout the Upper Midwest, winters are not what they used to be; that stopped in 1986. We may indeed have seen an obvious impact up here before much of the rest of the country, where the jury still appears to be out. But for people who are from this region and can make even mediocre observations, it’s a no-brainer. Substantial regional climate change is well underway.
A minor correction. You said that: “The fact that the NWS ignores global warming has a direct bearing on the accuracy of its predictions. The Arctic air that moves into Wisconsin nowadays is not as cold as it once was.”
The second part of the statement is accurate; the first is fallacious. NWS forecast verification scores are not suffering from the effects of GW. The initial conditions on which numerical forecast models are based are already present…so modified conditions are built into the forecasts.
RE: #52. Taken as a whole, the ice sheet in Greenland is not melting, but growing. While receding has occured near the Greenland coast, significant increases have been measured in the interior of
Greenland, resulting in a net total gain of 5.4 ± 0.2 cm/year.
Johannessen et. al. 2005. SCIENCE: http://www.sciencemag.org/cgi/content/abstract/310/5750/1013
[Response: It is not as clear as that. The remote sensing does not give the answer right to the edge, and there is significant melting at lower elevations. See Alley et al 2005 http://www.sciencemag.org/cgi/content/abstract/310/5747/456 from the a few issues before. -gavin]
re 59.
Ken,
In our posts earlier this month at RC (Naturally trendy) we discussed the NWS hydrologic probabilistic products, which are based on the NWS Advanced Hydrologic Prediction Service, AHPS. http://www.crh.noaa.gov/ahps2/index.php?wfo=mpx
In 93. you said that you “believe large short-term hydrologic events do make it into the probabilistic outlooks also. It’s not perfect, but I do think it is a reasonable product”.
In 94 I replied that although I understand that things can’t be perfect, I believe that professional hydrologists should try to adjust for inadequacies in modeling procedures and forecasts, which currently do not take account of the large amount of evidence showing that hydrologic climate warming has been happening in the Upper Midwest.
A took quite a bit of my time in posting additional links in 94. and 96. on AHPS hydrologic operational products in effect now for many river stations in Minnesota, Wisconsin and Michigan. I’d like it if you could review some of the information at those links and post any comments you may have on that to this thread instead. Although the Upper Midwest isn’t in a polar region, like Mike said, we did used to feel the effects of bitter arctic air much more frequently years ago than in recent decades. After your review (hopefully you can squeeze in some of your time), I’d like to know if you still think it’s OK for NWS to ignore regional hydrologic climate change trends in issuing their 90 day probabilistic guidance for spring flood potential, and at other times of the year for floods and droughts?
Naturally trendy?
https://www.realclimate.org/index.php?p=228
Re: 59:
Long ago, I used to be able to eat and pay bills because of the NWS. Administrative stuff aside, the folk working there do way more with their salary than 99% of professions [data point possibly biased :o) ]. I used to plot Skew-Ts by hand, and the technological revolution should have freed up time spent plotting etc. to think about stuff and to acquire more data – but instead budget cutcutcuts haven’t alleviated stress and there still aren’t enough data in the GulfAK and WPac to do the job the way it should be done.
Just a different perspective.
Best,
D
re 62.
NWS would be serving in the best public interest by helping to educate the public about global warming. Why aren’t they?
Dano,
Thanks for the perspective. I still teach hand-plotted stuves, because, you know, we all had to go through it! (For those of you wondering what Skew-Ts and Stuves are, they are “psuedoadiabatic” diagrams on which weather balloon or “sounding” data are plotted. They have numerous axes: temperature, pressure (height), mixing ratio, dry and wet adiabatic lapse rates. I think they are fun, but most would disagree).
D, I think you were referring to the unusually low pay NWS employees receive, especially if they don’t make their careers there. Or were you saying they engage in an abnormal amount of “extracurricular” activies?
Pat, in answer to your question, I spent a decent amount of time looking at and studying the links you provided. I must admit that I generally am on the other side of hydrology (precipitation production), so I had to stretch my brain a bit.
If the probabilistic forecasts *are* being informed by the traces you showed–which do indicate a one-month shift towards earlier peak flows in recent years–then I think that information should indeed be available to the public, even if burried somewhere in a technical discussion.
I am not sure on which level you mean “…ignore regional hydrologic climate change trends…” If you mean that they don’t even take it into account when making their probabilistics, then I think that is patently dumb, because we have a bonafide trend that I personally feel I can hang my hat on with very good success. If you mean that they aren’t mentioning it as a basis for their reasoning, then, no, I do not think that is okay. I should stress that if it did seem like I disagreed with your position, it was because we were talking about two different things.
RE 58, Here is an example of perverse TV weather reporting. NBC News yesterday (1/12/06) had a segment on really abnormal weather events around the world — way too warm where it’s usually cold, extreme rainfall, etc, including 60 degrees (I assume F) below the norm in Delhi this week, where many many people have died from the cold. They seemed to be leading up to, “Could this be due to GW?” They didn’t even mention GW (if I recall), but came to the conclusion that these events were all quite normal. Typical January weather.
Well, if it’s abnormal, how can it be normal, esp. worldwide? I thought the least they could have done is say, “We can’t attribute any single weather event to GW, since GW is about overall statistics, but these weird events are what we might expect in a global warming world. So let’s do what we can to reduce our GHGs.”
At the very least they should have remained mum about it being normal & typical & usual. We’ll have a new generation who think GW & its effects are typical & normal, so don’t fight them, just live (& die) with them.
Ken (#64), it was the pay even then, how hard you scramble, and the distractions to continuous thought during the time you’re in the office (I wasn’t eating prime rib, for sure). Conditions then (and data paucity) made wx forecasting more difficult than it needed to be. This was before the internets and Wx Channel-type operations, so it was tough to strike out on your own. We sometimes had to plot sfc obs too, and I still have ICAO station identifiers crowding out important information in my head [it’s fun when you don’t have to do it]. BTW, I think if you plot by hand, LIs are much easier to comprehend and appreciate – I suspect some of these young guys in PacNW don’t recognize this…
Say, what was the topic again?
Best,
D
re: 24. Tom Rees wrote … “The pattern of modern warming is
different, however, suggesting a different mechanism is afoot”.
My recently completed plots of annual temperature for 19 climate stations in Alaska (most 1950-2005) are now at:
http://ph.groups.yahoo.com/group/ClimateArchiveDiscussion/photos
Do you see PDO and global warming signatures?
Ken said: …” If you mean that they don’t even take it [G. warming] into account when making their probabilistics, then I think that is patently dumb …”.
I agree. But I’d go a lot further than just saying “it’s dumb”. I’d also say it’s neglectful and potentially injurious to the public. Look at it this way, the National Weather Service, an agency that most people in the U.S. (and outside the U.S.) have come to trust and rely on, has been knowingly making errorenous predicitons by ignoring regional hydrologic climate change trends in issuing their 90 day probabilistic guidance for spring flood potential, for floods and for droughts. Especially now in light of the polar amplification (which suggests the warming rate is speeding up), this is very serious matter that demands to be exposed. Spring is in fact almost already here in Wisconsin. January temperatures in Madison have been way, way above normal for this time of year. Madison’s lakes and rivers are already beginning to open up (I ride right by two three of them on my way to work everyday). Yet the NWS continues to make its predictions based on political directives from the White House, rather than on well-established scientific principles and facts.
Let’s face it, the only way to right this wrong is for the Congress to conduct hearing, exposes the guilty parties, and correct the policies and procedures as soon as possible before spring flooding begins throughout the Midwest.
I am 56 years of age with 5 grandchildren and I would like to support the views of Pat Neumann in 56..
I feel myself a bit like Lynn Vincentnathan, who with a name like that ought to be three people (sorry), as almost understanding what the major issues are.
From a risk point of view I have always been impressed by the impact of ice sheet melting on the way we live (or die). I have read two articles by Mr Hansen on ice sheet melting and in particular how the process could be catastrophic : it has a certain “feel” about it – sorry not to use scientific terms in a science blog but there it is. I remember Aberfan in Wales way back and the usual avalanches and landslides which are a feature of winter sports and adventure holidays. It is easy to believe that the process of cold to warm has a much shorter cycle than warm to cold.
I would like to disbelieve it please!
Can anyone recommend any good science on ice sheet melting?
Re #67,
Pat, one need to take into account the fact that solar cycles have a huge influence on Alaskan temperatures. From Sheng Hu ea. in Science, 2003 (for the abstract of the article see here):
They used sediments of Arolik lake (SW Alaska) to look for temperature proxies. Several cycles (135, 170, 195, 435, 590, and 950 years) were identified, of which the ~200, 400-500 and 950 year cycles are also identified in solar activity connected 14C and 10Be data. To be sure what part of the current Alaskan warming is due to GHGs and what part is solar related, one need to have more accurate estimates of the influence of current solar activity (which currently is very high, compared to the previous 8,000 years).
re 69.
Eachran, I too “would like to disbelieve it please!” I think you may be interested in the referenced material dealing with ice sheet melting, below.
Bowen’s “Thin Ice” is wonderful clear writing. … The author’s website has many photographs that didn’t fit the book:
http://www.mark-bowen.com/
His collection of links to the labs and publications is here:
http://www.mark-bowen.com/links.html
Excerpt from comment 38. at: https://www.realclimate.org/index.php?p=219
More technical, from Science magazine:
Miller, K.G. et. al (Science, 2005) said: “We propose that the early Eocene peak in global warmth and sea level (Fig. 3) was due not only to slightly higher ocean-crust production but also to a late Paleocene-early Eocene tectonic reorganization. The largest change in ridge length of the past 100 My occurred ~60 to 50 Ma (57), associated with the opening of the Norwegian-Greenland Sea, a significant global reorganization of spreading ridges, and extrusion of 1 to 2 x 10^6 km^3 of basalts or the Brito-Arctic province(58). A late Paleocene to early Eocene sea level rise coincides with this ridge-length increase, suggesting a causal relation. We suggest that this reorganization also increased CO2 outgassing and caused global warming to an early Eocene maximum”. The Phanerozoic Record of Global Sea-Level Change (Miller, K.G. et. al.): 25 Nov 2005 Science.
Excerpts from comment 20. at:
https://www.realclimate.org/index.php?p=236
Re #69 “The Two-Mile Time Machine” by Richard Alley is another book about the last ice collapse, when the temperature in Greenland rose by twenty degrees F within three years! They rose another 15F in the following 1000 years as the remaining northern ice sheets (except Greenland) melted. The initial rapid rise in temperature was almost certainly caused caused by the sudden disappearance of the sea ice in the north Atlantic. This would have altered the albedo and also converted the climate from cold continental type to warm oceanic type. The same rapid warming is likely to occur when the Arctic sea ice goes!
You can see how rapidly the Arctic ice is thinning on my webpage at
http://www.abmcdonald.freeserve.co.uk/north.htm
Each year the winter extent remains high but the concentration decreases because the ice is thinning.
This sudden warming cause by the Arctic sea ice is included in James Lovelocks’s new book ‘The Revenge of Gaia’. He says “To give just a single example out of very many: the ice of the Arctic Ocean is now melting so fast it is likely to be gone in a few decades at most. Concerns are already acute about, for example, what that will mean for polar bears, who need the ice to live and hunt.
But there is more. For when the ice has vanished, there will be a dark ocean that absorbs the sun’s heat, instead of an icy surface that reflects 90 per cent of it back into space; and so the planet will get even hotter still.”
See ‘Why Gaia is wreaking revenge on our abuse of the environment’ By Michael McCarthy
Published: 16 January 2006 © 2006 Independent News and Media Limited
http://news.independent.co.uk/environment/article338879.ece
Thanks for 71 Pat, a bit of light bedtime reading I suspect.
re 70.
Ferdinand,
It is wrong to say that the influence of current solar activity … “currently is very high, compared to the previous 8,000 years”.
See p. 19 in Hansen, J. 2005. Is There Still Time to Avoid “Dangerous Anthropogenic Interference” with Global Climate? A Tribute to Charles David Keeling (5.5 MB PDF). Presentation given Dec. 6, 2005, at the American Geophysical Union, San Francisco.
http://www.giss.nasa.gov/~jhansen/keeling/keeling_talk_and_slides.pdf
#74 how does page 19 of Hansen’s paper show solar activity is not at an 8,000 year high?
Of course the answer is it doesn’t. One on the aspects of climate science that I can’t seem to reconcile is that regardless of what solar scientists discover about how active the Sun is currently climate scientists still attribute very little forcing to the Sun. This hasn’t changed in the last several years. Hansen’s page 19 is basically the same forcings as shown in the 2001 IPCC TAR, which came out before the discovery that the Sun is at an 8,000 year high.
From 1640 to 1710 there were almost no sunspots recorded and the Sun was very inactive. Recent research has shown that the Sun is now at an 8,000 year high for activity. Does it really make sense that from 1750 to 2000 that solar forcing was only .3 W/m2?
[Response: There is no contradiction between a long term trend and it’s magnitude. However, how one scales the sunspot record to forcing is still uncertain on long time scales, though recent analyses have been arguing for a lower effect than previously suggested (Foukal et al, Lean’s latest papers). The key thing for recent decades is that there is no evidence of any increase since the 1950’s , and so solar is very unlikely to be a factor in the recent accelaration of the warming since the 1970’s – regardless of the scaling. – gavin]
Re #74,
Pat, for current solar activity, see Usoskin ea. for the last millennium, and for the past 11,000 years, see the abstract and the article by Solanki ea.
The presentation of Hansen has a lot of good information, but some of the assumptions are disputable. To name a few:
– Slide 12: Changes during ice ages / deglaciations are calculated as 0.75 K/W/m2. This includes the change in ice sheet albedo, aerosols and GHG changes (no changes in insolation?). But the ratio between those three is not true for the onset of the last glaciation, where ice sheets were again at their maximum, before CO2 started to decline, without much influence on temperature. See here for the temperature/CO2/CH4 graphs of the Eemian. This points to a lower sensitivity for CO2 and a higher sensitivity for ice sheet albedo.
– Slide 19&20: all the aerosol forcings here are assumptions, which are very uncertain and probably overestimated (huge changes in aerosol precursor emissions in Europe and South Asia are not measurable in regional temperatures). GHGs and solar only include direct forcing, but differ in feedbacks, like pole ward propagation of the jet stream, influences on cloud cover, precipitation,…
– Slide 21: The model follows the 1993-2003 ocean heat content change closely. But I don’t believe that the same model with the same parameters can follow the 1980-1990 ocean heat content trends (decreasing with increasing GHG levels…). See Levitus Fig.S2
– Slides 32&33: While I am jealous about the nice picture of the Illulisat/Jacobshavn ice fjord (mine is in cloudy, foggy conditions…), the retreat of the break-up point of the glacier started already before 1850 and was fastest in the period 1929-1953, before GHGs had much of their influence. Moreover, Greenland temperatures after 2000 just reach the temperatures seen in the 1930-1940’s, with a cooler climate in between…
re 70.
For periods when GHGs are at low atmospheric concentrations, slight variations in parameters other than GHGs may result in climate changes – possibly even cyclic.
However, when the concentrations of GHGs are high (like now), effects of slight variations in other parameters (like solar radiation) are washed out – for having a noticeable effect on climate.
re: #75 gavin
Foukal or Lean argue for a lower effect than the IPCC figure that Hansen used of .3 Wm2 for the last 250 years??
Also there are studies showing an increase in tsi since the 1980s. Scafetta and West show an increase as measured by ACRIM. While this is fairly new work and is still being discussed I think it’s a bit strong to say there is no evidence of increased solar forcing.
Re #75: Jim, you array climate scientistis against solar scientists, but I think it’s fair to say that most solar scientists (including one of the RC co-authors) disagree with your cites.
Re #77:
Pat, I think that you underestimate the strength of natural variations. A small (1%) decrease in cloud cover in the (sub)tropics (30S-30N) for the period 1985-1994 results in some 3 W/m2 more loss to space. That is as high as the combined forcing of all GHGs together since the start of the industrial revolution (but with opposite sign!)… The same for the Arctic, where cloud forcing trends actually exceed GHG forcing trends with an order of magnitude (again with opposite sign…)…
Re #75 (Gavin):
Gavin, as already mentioned by JimR, although there is still controversy between the MODIS and ACRIM calculation of TSI, if ACRIM is right, there is a short-term (11-year) increase of TSI of some 0.45 W/m2 TOA between the last two cycles. Based on different methods to deduct the short-term cyclic sensitivity (~0.10 K/Wm-2) for solar forcing (Douglass & Clader, Lean ea., White ea., Scafetta & West) the increase would be responsible for some 7-20% of the recent warming. Based on the 22 year cyclic sensitivity (0.14 or 0.17 K/Wm-2, according to White ea., resp. Scafetta & West), this may increase to 10-30% of the recent warming.
Moreover, even if the TSI plateaued in recent decades, it is higher today than in the 1930-1940’s (based on solar reconstructions). That means that the longer-term sensitivity via ocean heating and ice albedo still is at work. If one should stop GHG emissions today, all models still expect an increase of 0.6 K (and more) in the following century, due to similar feedbacks. Why shouldn’t that be true for solar influences?
I don’t think that one need to exaggerate the controversy between solar scientists and climate modellers, but I have the impression that climate modellers need to listen more carefully to what solar scientists have found (like the correlation between TSI and low cloud cover) and implement that in their models…
re 78.
There is little or no evidence for increased solar forcing but there is overwhelming evidence for increased greenhouse gas accumulation forcing. Trends at NWS cooperative climate stations show warmer overnight lows in January and February in higher latitude regions of the US. Temperature plots for stations with 100 years of record are at: http://groups.yahoo.com/group/ClimateArchiveDiscussion/
Ferdinand, as you are well aware, here’s what the solar scientists have found: http://ams.confex.com/ams/pdfpapers/74103.pdf . Accurate observations of the last quarter century show about .1oC insolation forcing. Also, regarding your proposal for insolation to have effects into the future similar to the GHG warming lag, what mechanism do you propose for this? Are you saying that insolation-driven heating has inertia?
This is not a polar story, but I thought it may be useful information, which really corresponds with what the IPCC is saying:
“‘Balmy’ Winnipeg weather breaks 134-year record”:
http://www.cbc.ca/story/canada/national/2006/01/17/winnipeg-weather060117.html
Re #83:
Steve, the 0.1 K you mention is about 25% of the recent warming, and is identical for what was deduced from empirical evidence, based on the 11/22-year cycle (thus not including longer-term responses). That is twice as high as what the direct change in radiance should have induced theoretically in the same period, which points to amplification mechanisms (where several are described in the article). About the past century, the article mentions:
This means that solar is good for (at least) 0.3 K of the 0.7 K increase 1910-2005. But please note that this is based on GCM’s, including the constraints in the models like the uncertain influence of aerosols, cloud feedbacks and indeed… solar sensitivity.
Further about longer-term solar influences:
Moreover, the strength of the response also may be influenced by the initial conditions…
Strong short term to longer term climate fluctuations may result from small solar changes on the THC:
and
This even may happen today…
And I fully agree with next statement:
I havent yet read the reading list from Pat post 71 but I shall.
In the meantime Mr Connelly has recommended that I read the IPCC report on ice sheets. Well I have now and I understand a bit better the representation of the issues : all sensible and logical.
There are two points which immediately stand out :
1. Do I need to worry about the collection and accuracy of data? Does it matter that data has been collected in the 1960s compared with the 1990s?
[Response: You’d need to be a bit more precise about exactly what data you mean to get an answer – William]
2. What impact does the sea have on the ice sheets in two respects : temperature and mechanical through tempests?
[Response: Mechanical: negligible I think. Thermal: ocean-melting under ice shelves is a major source of ablation, at least in some areas (http://www.grida.no/climate/ipcc_tar/wg1/416.htm) – William]
I am still wrestling with the shorter cycle from cold to warm.
William – Post 86. There are two issues attached to my first question and all refs are to IPCC TAR:
a)Are there critical “things” we are measuring today that weren’t measured in the 1960s for the Bauer study on the Greenland Ice Sheet in Table 11.5, for example?
b)Are our measuring techniques and methodology so improved that doubt is cast on measurements taken in the 1920s, say, for sea temperatures in Table 11.1?
For a non-expert like myself, comments like “relatively well documented past 20,000 years” in 8.5.5 are frankly breathtaking.
Thanks very much for firstly pointing me in the right direction and secondly for your response above. I am not at this stage expecting a response to a) and b) above because I have started to look at the issues more closely for myself. I am now well and truly hooked. If I get stuck I shall return to posting. Thanks again.
I’ve heard that the arctic sea-ice hasn’t reached Spitsbergen yet, but can’t find with a search on google whether this is particularly unusual. There do seem to be unusually high temperatures in the far north Atlantic this winter, following on from the record minimum sea-ice extent in September. Are we headed for a record low maximum sea-ice extent in March? Are there any polar/sea-ice experts out there with an opinion?
Thanks
This week in Nature:
Low sea level rise projections from mountain glaciers and icecaps under global warming
re 38. (Ferdinand)
People can now view my temperature plots for 19 stations in Alaska (1931-2005), below.
I don’t see it the way Ferdinand said it (in 38). – Explain?
To view station temperature plots for Alaska:
go to:
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos
click on – AK Climate…Stations – Annual Mean Temperature(F)
19 stations, data for 1950-2005 years of record, excl. 4 stations below:
Anchorage 1931-2005
Homer 1939-2005
King Salmon 1957-2005
McGrath 1942-2005
Coast stations:
Anchorage Annette Barrow Bethal
Cold Bay Homer Juneau King Salmon
Kotzebue Nome St Paul Island Yukatat
Inland stations:
Bettles Big Delta Fairbanks Gulkana
McGrath Northway Talkeetna
—-
I HAVE A SIMPLE Question about global temperature.
If the wind patterns were to change such that the wind blew more from each pole towards the lower latitudes, would that be detected as global cooling? And vice versa. If the wind patterns changed so that more air moved from the equator to higher latitudes, would that result in global warming?
If so, how do you know that temperature changes are not simply due to which way the wind blows? After all, weather patterns in general are mainly due to which way the wind blows.
Is there any data on global wind direction?
re 91 90
Some NOAA NWS 1st order climate stations have prevailing wind direction information (I suggest a goggle to NCDC, and a little surfing around).
Did you review the Annual Mean Temperature plots for 19 stations in Alaska (1931-2005)?
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos
I can see the beginnings of a rapid turn upward in temperature at all stations, especially sharp at stations inland (e.g. Talkeetna AK).
91:
Joel, poleward heat transport (winds blowing from the equator) alone could not warm the globe; it would only even things out, since more of the sensible heat would be transported to higher latitudes, leaving less at the tropics. Of course there could be feedbacks from these processes.
Looking at wind data is not easy; winds are often erratic, and they repsond as much to local topographic features as they do to prevailing meteorological conditions (e.g., the pressure gradient). Also, good, high-quality, longstanding wind data are hard to come by…and wind is almost impossible to proxy.
In the Upper Midwest, where the recent upturn in annual average temperatures has been strongly weighted by increases in wintertime temperatures (especially overnight lows), the winds have not changed much. We haven’t had, to my knowledge, a statistically significant increase in southerly winds. Instead, as other posters have pointed out, northerly winds result in warmer temperatures than they once did, and westerly winds yield slightly warmer temps than before etc.
Re #90,
Pat, if you look at what Tom Rees has done, he substracted the influence of the PDO from the temperature line (because the PDO shift resulted in a distinct, probably non-GHG related temperature jump in 1976), and the residual increase in temperature after 1976 is equal to the global increase in temperature for Nome, Fairbanks and Anchorage. For Barrow, the residual increase is 1.5 times the global increase. Thus while there is global warming in Alaska, only Barrow (at the Arctic coast) is warming faster than global average and seems to be vulnerable to polar amplification.
And as already said, linear trends have little meaning where there is cyclic behaviour. There are several Alaskan stations with longer trends, which show warm peaks in the 1930-1940’s. See e.g. Anchorage, Tanana, Fairbanks (and university), Homer, Cordova,… at the GISS stations database
re 94. (Ferdinand)
Ferdinand,
The annual mean temperature plots at stations(19) which I created and show at my link below extend from 1931 all the way through Dec 2005.
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos
My temperature plots in AK are based on data that I downloaded from the Western Regional Climate Center (WRCC) website, updated for Dec 2005 based on NOAA NWS Climate Prediction Center Dec avg mean daily temperature data.
The WRCC station location map for AK stations is at:
http://www.wrcc.dri.edu/summary/climsmak.html
Your interpretation of work by Tom Rees and the attempts to subtracted out influences due to the Pacific Decadal Oscillation(PDO) on the AK upward trends in temperatures has overestimated the PDO effects and downplayed the stronger global warming effects in background. I.E based on my analysis of the 19 station temperature plots, your assumptions exaggerate PDO effects in relation to stronger global warming influences which now appear to be on the way to acceleration in 2006, and beyond. Although I can see there have been PDO shifts and influences on station temperatures from time to time, the magnitude of PDO shifts has been relatively minor and short lived. Some people may be perceiving the shifts to be longer lasting than they are in reality, because global warming is not allowing the temperatures to drop back down to pre-shift levels, and in so doing, the next to come PDO shift starts at higher and higher plateaus of station temperature starting conditions.
Tom does not account for the sharp upward turn to higher temperatures in recent years which is evident at the majority of my 19 stations in AK, especially the stations located inland from the ocean waters.
The station temperature data shows jumps to higher and higher levels, not “cycles” at all. The upward jumps (a few years or couple decades at most) and the overall upward trends (periods of record for the stations) in observed temperature data shown on my station plots are consistent with rapid greenhouse warming. I have the Excel data sheets and my analysis here at home (if you or anyone else would like to discuss the detailed input data used in my station temperature plots.
Joel, poleward heat transport (winds blowing from the equator) alone could not warm the globe; it would only even things out, since more of the sensible heat would be transported to higher latitudes, leaving less at the tropics. Of course there could be feedbacks from these processes.
This I don’t quite believe. There are plenty of heat sinks at the equator and the poles. The heat is not just in the air. So, as warm air moved nothward from the equator, as cooler air took its place, that cooler air would be warmed by the ocean.
Also, there are a lot more thermometers in N.A than there are over the middle of the Pacific or the middle of Antarctica. So, temperature deviation in N.A. would be registered, but the temperature deviation, if any, over the North Pole, equator, or the South Pole, might not be noticed.
Joel:
1. Heat sinks. Basically we’re talking about the oceans here. Whilst cold air would be warmed at the equators, warm air would also be cooled at the poles. Also we can measure the heat in the oceans, and that is also rising. There has to be extra energy coming from outside the Earth system.
2. Thermometers. There is a problem with lack of measurements in some areas [interior of Africa and South America most notably]. Suffice it to say, however, that a lot of work is done examining these measurements to remove biases, etc, such that we can make meaningful statements about long-term global trends.
Climate Station Temperature Summary Update,
for public view at:
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos
Summary: Temperature plots, selected climate stations by state:
AK
19 stations: Annual mean air temperature data 1931-2005
OR_WA
4 stations: Annual mean air temperature data 1928-2005, Oregon in prog.
SD_ND
3 stations: Jan Avg Low Temp., Feb Avg Low Temp., 1896-2005
MN_WI
5 stations: Jan Avg Low Temp., Feb Avg Low Temp., 1890-2005
MI_IND
3 stations: Jan Avg Low Temp., Feb Avg Low Temp.,1890-2005,IND in prog
ANNUAL_MEAN Air Temperature plotted, states excluding AK:
Leech Lake Federal Dam, MN, 1898-2005
Forestburg, SD, 1896-2005
Minneapolis, MN, 1820-2005 1.
1. MINNEAPOLIS-ST. PAUL AREA DAILY CLIMATOLOGICAL HISTORY OF TEMPERATURE, PRECIPITATION, AND SNOWFALL, A YEAR-BY-YEAR GRAPHICAL PORTRAYAL (1820-PRESENT)
By Charles Fisk, Member, American Meteorological Society
http://home.att.net/~minn_climo/
Data (other than 1820-1890 at Minneapolis/St.Paul) was downloaded from the Western Regional Climate Center (WRCC) and Midwest Regional Climate Center (MWRC) websites. Preminary Dec 2005 data, from NOAA NWS websites) were used for annual 2005 data at AK climate stations.
Climate station location map for stations in AK, see WRCC website at:
http://www.wrcc.dri.edu/summary/climsmak.html
A summary of the exceptionally warm winter this year from the Grand Forks, North Dakota, National Weather Service (NWS) office:
http://www.crh.noaa.gov/crnews/display_story.php?wfo=fgf&storyid=1109&source=0
The winter is not even an El Niño, but a weak La Niña, which should theoretically bring cooler-than-normal and snowier-than-normal conditions to the region.
Mods, #99 should read “El Nino” and “La Nina”. I guess the accent won’t work on this board.
[Response: Use ‘& ntilde ;’ rather than trusting to the non-basic ASCII. -gavin]