From Steve Goddard: Thanks again to Dr. Meier from NSIDC for answering questions, and for offering to do a follow-up.
From Anthony: Responses from Dr. Meier are in italics. I’ve added a poll that you can answer after reading this. Note this poll only allows one vote per IP address. So shared IP systems at offices will only get one vote.
From Dr. Meier: Thank you to Mr. Goddard for presenting this and the previous set of questions. And thank you to Mr. Watts for providing the outlet to publish these. I don’t hope to change the opinion of every climate change skeptic who reads my responses, but hopefully I can provide some useful for information. My answers here and to the previous round of questions are my own and I am speaking for myself, not as a representative of the National Snow and Ice Data Center or the University of Colorado. Thanks to Stephanie Renfrow, Ted Scambos, Mark Serreze, and Oliver Frauenfeld of NSIDC for their input.
One thing I noticed in the comments on my previous answers was a desire for references to peer-reviewed journals. I originally chose not because I didn’t realize there might be an interest and also because a few journal articles doesn’t substantiate human-induced global warming (nor do one or a few articles refute it). It is the preponderance of evidence presented in thousands of articles that provides the foundation for the human-induced global warming theory. Nonetheless, below I provide a few selected references for those that might be interested.
There were lots of good questions from readers, and I have synthesized some of them into a few short ones here for the sake of brevity. There is no question that late-summer Arctic ice extent has declined considerably since the early 1980s, and if the current trend continues linearly – the sea ice will disappear completely at some point in the not too distant future. Most of the questions were along the lines of “how do we know the trend is non-cyclical, and how do we know what is causing it?”
1. Q: The image below shows the general GISS temperature distribution of the previous Arctic warming cycle in the 1920s and 1930s, for stations north of 60N. Turquoise dots had warming similar to the current warming. Red dots are significantly warmer now than they were 70 years ago. Looking at the map, it would be easy to come to the conclusion that the only difference between the current warming and the one 70 years ago, is that the PDO has been in it’s warm phase for the last 30 years – causing warmer temperatures around Alaska and Eastern Siberia. The PDO appears to have recently shifted to its cool phase, and temperatures across Alaska have dropped during the last two years. Why do you believe that the fundamentals of the current warming are so different? Perhaps the warming of the last 30 years was aggravated by a coincidental alignment of the PDO and AMO?
A: The warming of the last 30 years cannot be attributed primarily to the Pacific Decadal Oscillation (PDO) or the Atlantic Multidecadal Oscillation (AMO). The AMO does not have a significant influence on the Arctic. On the Atlantic, side, the North Atlantic Oscillation (NAO)-a regional expression of the Arctic Oscillation (AO)-is the most influential mode of variability in the Arctic. As I’ve mentioned previously, there are natural variations in climate that do indeed affect Arctic temperatures in the Arctic and the sea ice. The NAO/AO is a particularly prominent one and a substantial amount of the decline in the sea ice during the late 1980s and early 1990s could be attributed to a strong positive mode during winters because the positive mode favors the loss of thicker ice that is less likely to melt during summer. However, since about 1995, the AO has mainly been in a neutral or negative state. Under such conditions, the Arctic sea ice should have started to recover. Instead, sea ice extent has not only continued downward, but the decline rate has accelerated. The AO may have been a “trigger” for the precipitous decline, but we wouldn’t have the ongoing decline without the documented warming trend (Lindsay and Zhang, 2005).
The Pacific Decadal Oscillation (PDO) also can play role in temperatures in the Bering Sea region and to some extent in the Pacific side of the Arctic Ocean. The PDO was in a fairly persistent positive mode until the mid-1990s, but it also has shifted to a more neutral state and so cannot explain the decline of the Arctic sea ice since that time. (More details: Overland et al., 2004 and Overland and Wang, 2005).
Another important point is that these climate oscillations can themselves be affected by global warming. There are indications that the positive mode of the AO is more likely to be present under warmer conditions.
2. Q: Given that we don’t really understand what caused the earlier warming period, what evidence is there that the current warming is anthropogenic? How much of your viewpoint about the Arctic future is based on IPCC feedback predictions?
A: There is considerable evidence that the current warming is anthropogenic; this evidence is readily available in thousands of unrelated peer-reviewed scientific journals. You also ask how much of the evidence is “based on” IPCC predictions? In a way, the answer to that question is that none of the evidence is from the IPCC report-and yet all of it is. The reason is that the IPCC report isn’t a source of newly published information, but rather a compilation of evidence from a growing number of articles previously published in scientific journals. All of the information in the IPCC working group reports is referenced to original peer-reviewed journal articles citing researchers from around the world. Thus, the IPCC report is a convenient “one-stop shop” of the latest information, but the ultimate source is the thousands of individual international journal articles that are the basis of the report.
In the first part of your question, you suggest that a lack of understanding of earlier warming periods is a given, and that this casts doubt on our understanding of current warming. From this perspective, it might seem reasonable to assume that because previous change was natural, the current change must be too. Many natural explanations for the current observed warming have been suggested:”it’s just natural variability,” “it’s the sun,” “it’s cosmic rays,” etc. However, these have all been investigated and evidence is simply lacking.
On top of the lack of evidence for natural causes, such suggested explanations ignore the proverbial elephant in the room. Any natural-causes explanation must be accompanied by an argument for why and how human-caused greenhouse gases (GHGs) are not affecting climate in the same way that natural GHGs affect climate. This, again, has not been addressed in a reasonable way.
Here is what we know about greenhouse gases and their influence on climate:
1. Greenhouse gases absorb energy radiated by the earth that otherwise would escape to space, keeping the earth warmer than it would be without GHGs. This is a fact that has been well-known for over 100 years, described in a paper by Arrhenius (1896). GHGs are a necessary part of Earth’s natural “climate control.”
2. GHGs are increasing in the atmosphere. This is known from observations of carbon dioxide dating back to the 1950s from Mauna Loa and other stations, as well as paleo-records of GHG concentrations in ice cores.
3. The GHG increase is due to human-caused emissions. This is clear from the simple fact that we know we’re emitting GHGs through our use of fossil fuels. More scientifically, it is confirmed by a characteristic chemical signature of human-emitted GHGs found in the atmosphere.
4. GHG concentration and surface temperature are closely linked. This is clear from #1, but the relationship is confirmed in ice core records dating back several hundred thousand years. Some of your readers may have heard a suggestion that carbon dioxide lags temperature in the ice core records; that’s not relevant in this case. For more details, see here and here and here
5. The first studies of the effect of GHGs on Earth’s energy budget date back to the1950s (e.g., Revelle and Seuss, 1957). The increasing GHG emissions have already changed Earth’s energy balance. Human and natural changes have increased the radiative forcing (effectively increasing the energy, and thereby the temperature, of the Earth) by about 1.6 Watts per square meter. The largest factor by far is human GHG emissions. Changes in the sun play only a small role. This increased radiative forcing results in a warming of the planet. There is simply not enough uncertainty in these estimates to throw the overall conclusion into doubt: human-induced GHGs have changed Earth’s energy balance and increased temperatures.
FAQ 2.1 Figure 2 from IPCC Working Group I Fourth Assessment Report, 2007.
6. There are feedback mechanisms that can alter the impact of GHG emissions. These include: clouds, water vapor, ice/snow. Ice and snow are clearly positive feedbacks that will reinforce the GHG warming because as they melt, the average albedo (reflectivity) of the earth decreases and more energy is absorbed. The effect of other feedbacks is less certain-and may even counter the effects of GHG warming–but the evidence indicates that they nevertheless do not come close to offsetting the direct effect of GHG emissions.
So, before one can suggest that natural mechanisms explain everything, one has to first demonstrate that something in the above 6 points is wrong. Much of this evidence dates back to at least the 1950s; the theory of anthropogenic global warming is really nothing new. Also note that climate models only play a significant supporting role in the evidence for points 5 and 6. No serious scientific study has yet shown that any of the above 6 points are fundamentally wrong.
The only one of the 6 points still in play to any scientific extent whatsoever is the last point. There has been some interesting research in this area – Richard Lindzen’s Iris effect (a nice summary here) and more recently Roy Spencer’s “internal radiative forcing.”. Spencer’s work is quite new, and has therefore not yet been properly vetted through the peer-review process. (Some informal discussion: RealClimate.
3. Q: You mention the historical record of the Inuit. What do we know about the older historical record from the Vikings?
A: There is archaeological evidence, oral sagas, and some written records, none of which I’m an expert in. However, I can share with you what I know: The Vikings colonized Greenland during about 700-1300 AD, taking advantage of the medieval warm period (MWP). There was reduced ice cover compared to before and after that period that allowed easier sailing between Europe and Greenland. The warmer climate allowed enough farming and ranching to support the population. As climate cooled, crops failed and transport (trade) with Europe became difficult or impossible. There was clearly less sea ice during the MWP than the cool period that followed. It is not known how sea ice conditions compared to today, but ice extents comparable to the 1980s or 1990s would have been sufficient for the Vikings to have successfully sailed between Greenland, Iceland, and Scandinavia; ice would not have had to be at current low levels.
Greenland and northern Europe were clearly warm during the 700-1300 AD; much of the rest of the globe may have been as well. There is often quibbling about whether we’re warmer now than then-the Mann hockey stick plot, etc. But as I pointed out above, such “debate” is almost beside the point: it ignores the elephant in the room that is the GHG emissions produced by humans. We may not clearly know what caused the MWP, but we have a clear cause for the current warming: human-caused GHGs.
4. Q: Is there any hard data on permafrost losses during the last ten years?
A: There is clear evidence of increasing ground temperatures and thawing permafrost, consistent with the warming surface temperatures. Permafrost will respond more slowly to warming, but it is a potentially significant long-term feedback because large amounts of GHGs, particularly methane, are “locked” in the permafrost. As much GHGs are locked in the permafrost as currently resides in the atmosphere. At least some of these GHGs will be released as the permafrost thaws. There have been several papers discussing permafrost thaw and potential climate impacts (Zimov et al., 2006; Lawrence and Slater, 2005; Lawrence et al., 2008).
5. Q: Has there been a trend of the date of minimum Arctic sea ice coverage? Has there been a trend in the date of maximum Arctic sea ice coverage? If there has been warming over the ice (which is not sampled adequately), there should be an earlier maximum and later minimum.
A: There has been a trend toward later minimum dates, but there is substantial variability from year to year in the freeze-up date. A later freeze-up is not surprising because with lower summer ice extent, there is more ocean area to absorb heat that needs to be dissipated before freeze-up can begin. However, there is high variability because the timing of when the ice stops shrinking and begins growing has a lot to do with short-term weather. A late-season warm spell can extend melt, while a quick, early cold snap can cut melt short.
There is essentially no trend in the date of maximum extent. There is even greater variability from year to year in the maximum date than in the minimum date. This is also not surprising. At the time of maximum extent, the boundary of the ice edge is unconstrained and has extended into the north Atlantic and north Pacific. Ice at the ice edge is also thinner at the maximum. Most of it is less than 50 cm thick, because it is ice that has recently formed. This ice is prone to being broken up by winds, advected into warmer waters where it melts, or pushed northward. On the other hand, cold winds from the north can cool surface waters and allow more ice to form, at least temporarily, and extend the ice edge farther south. So, the ice edge location at the time of the maximum is fairly volatile and subject to sudden change. This variability can be seen in AMSR-E data graph, where you can see the bumpiness of the daily extent during the winter season. This is the ice edge “bouncing around” in response to winds, currents, storms, etc.
6. Q: Looking at the AMSR-E sea ice extent graph, I see an alternative description for recent behavior. Until the first week in August, 2008 extent was equal to or greater than 2005 – and NSIDC was even considering a possible return to normal as late as August 1. However, a series of strong storms broke up the ice and caused 2008 to drop below 2005 for a few weeks. As September ends, 2005 and 2008 appear to be converging again. Average daily ice extent in 2008 has been greater than 2005, and nearly every day in 2008 has been greater than 2007. What is wrong with this description?
A: The description is incomplete and lacks relevant context. First, all the recent years in the AMSR-E record have had anomalously low maximum extents compared to the 1980s and 1990s. Even the largest winter extent, in 2002, was 250,000 square kilometers lower than the 1979-2000 average. The years 2005-2008 have been 700,000 to 1,000,000 square kilometers below the average. As described above, there is considerable variability during the time around the maximum extent, so the difference between 2005 and 2008 is within what might be expected from natural variations, but both are lower than maximum extents during the 1980s.
While there is a lot of variability in the timing of when the maximum occurs (as mentioned in #5), the actual maximum extent has relatively low variability. This is because in winter it is cold and dark, and ice grows under those conditions. So you always see ice growth, although there is now a significant downward trend at the maximum. In comparing winter ice conditions, ice thickness is much more relevant than ice extent. Data for thickness is not as complete as it is for extent, but it is quite clear that ice is thinning at a rate even faster than the extent decline. During winter 2008, the Arctic was dominated by seasonal ice (ice that has grown since the previous summer) that is much thinner than multiyear ice (ice that has been around for at least a year). Thus, in 2008 the ice has generally been thinner than 2007, and much thinner than earlier years.
We are now seeing some rapid growth of sea ice in the Arctic as the large expanse of exposed ocean cools, but this will all be thin first-year ice. It will thicken over the winter, but by the end of the winter it will only be a half to a third as thick as the ice used to be.
Sea ice also moves with the winds and currents – it doesn’t just grow and melt in place – and thinner ice is generally more easily pushed around. Last year a lot of ice got pushed by winds across the Arctic and even less of the region was covered by thicker old ice at the end of the winter than at the beginning of the winter.
Finally NSIDC did not say that the Arctic sea ice extent would return to “normal” in 2008. The figure referenced in the question, does show one scenario where ice returns to normal, but as stated in the text, that scenario was for a slower than normal melt through the rest of the summer and was deemed highly unlikely. As we say in our August 1 entry: “Thin ice is much more vulnerable to melting completely during the summer; it seems likely that we will see a faster-than-normal rate of decline through the rest of the summer.”
7. Q: Why does NSIDC say that the 2008 minimum sea ice extent “reinforces” the long-term trend when the 2008 extent was clearly higher than 2007?
A: 2008 is in no way a “recovery” relative to the thirty-year trend-and since GHGs act over long time periods, scientists favor looking at change over a long period to detect the GHG signal. From 1979 through last year, the September monthly average extent was declining at a rate of about 72,000 square kilometers per year based on a linear trend. Calculating a linear trend of the data from 1979 through 2008, the decline is now 78,000 square kilometers per year. This may seem counterintuitive, but what happens to the trend each time you add new data depends on where the new data falls relative to the trend line. If a data point falls below the trend line, it will “pull” the trend line downward; a data point above “pulls” the trend line upward. The September 2008 extent, although a bit higher than 2007, was still well below the trend line, so the downward trend line steepened. This is what I mean when I say the trend has been reinforced. Those who attempt to claim that we’ve seen “global cooling” since 1998 may wish to bear in mind that until scientists see a change over a long period, we are skeptical of claims concerning a trend.
The key thing, whether discussing sea ice, temperatures, or any other environmental measure, is to consider long-term trends, not short-term variability.
September monthly sea ice extent and trends for 1979-2007 and 1979-2008.
References:
Arrhenius, S., 1896. On the influence of carbonic acid in the air upon the temperature of the ground, Philos Mag, 41, 237-276.
Lawrence, D. M., A. G. Slater, 2005. A projection of severe near-surface permafrost degradation during the 21st century, Geophys. Res. Lett., 32, L24401, doi:10.1029/2005GL025080.
Lawrence, D. M., A. G. Slater, R. A. Tomas, M. M. Holland, C. Deser, 2008. Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss, Geophys. Res. Lett., 35, L11506, doi:10.1029/2008GL033985.
Lindsay, R.W., and J. Zhang, 2005. The thinning of Arctic sea ice, 1988-2003: Have we passed a tipping point, J. Climate, 18(22), 4879-4894, doi:10.1175/JCL13587.1.
Overland, J. E., M. C. Spillane, D. B. Percival, M. Wang, and H. O. Mofjeld, 2004. Seasonal and regional variation of pan-Arctic surface air temperature over the instrumental record, J. Climate, 17, 3263-3282.
Overland, J. E., M. Wang, 2005. The third Arctic climate pattern: 1930s and early 2000s, Geophys. Res. Lett., 32, L23808, doi:10.1029/2005GL024254.
Revelle, R., Seuss H.E., 1957. Carbon dioxide exchange between atmosphere and ocean and the question of an increase of atmospheric CO2 during past decades, Tellus, 9, 18-27.
Zimov, S.A., E.A.G. Schuur, and F.S. Chapin III, 2006. Permafrost and the global carbon budget, Science, 312, 1612-1613, doi:10.1126/science.1128908.
Here are a few links showing current and forecast Arctic autumn temperatures. The rapid freeze this year is of course due to cold temperatures, not warm ones. The AP article is full of spectacularly incorrect information.
http://www.cdc.noaa.gov/map/images/fnl/sfctmp_01.fnl.gif
http://www.crrel.usace.army.mil/sid/IMB/newdata.htm
http://wxmaps.org/pix/temp2.html
An amusing claim from the article was that reindeer herds were declining, when in fact the study said exactly the opposite – that they were at a long term peak.
I have a problem with the Radiative forcing graph? Only 1 natural forcing for the entire climate? If el nino doesn’t have an affect on the climate, then why is there a spike in 1998? Don’t let facts get in the way of a good story.
WarmWilliam (05:56:43) :
Thanks to Dr. Meier for his moderate and polite response to questions. I may not agree with the logic but I appreciate the moderate tone of the replies.
Unfortunately I find that general tenor of the AGW believers is stident, often decending to personal slights to any who have views different from their own.
William, I take it you’ve read the responses in this thread?
Some examples:
Sorry good doctor (Meier), but your comments verge on the disgraceful. I can see you have earned your degree at the IPCC university and read very well from their bible….you all speak the same lingo without backing it with facts.
Dr, Meir is a good salesman, but there is nothing new in this. It is obvious that he is an unconditional believer in AGW, to the point that all facts must bend to the AGW theory or be considered irrelevant because of the “elephant in the room”.
I wonder if Meier has ever thought about the possibility that all those thousands
of peer reviewed studies of AGW were based on flawed data or analysis. He refers to the body of evidence through the thousands of scientists who have found GHG made by man as the prime force for AGW. To me its the Pied Piper effect.
“… this evidence is readily available in thousands of unrelated peer-reviewed scientific journals.”
In light of how the Mann “Hocky Stick” was fabricated and pushed through “Peer-Review” … the statement above means nothing to me anymore.
Do all these “unrelated peer-reviewed” studies simply have the obligatory:
“….Oh, and by the way …. we believe this is all due to Man.” …. pasted to the end?
Sorry Doctor, I am not convinced.
As we at present in the midst of a global financial crises I would like to draw a comparison.
If I went to a Bank that did not know me and asked for a loan of $1,000,000 and the only information I could give them was my approx. age, it looks to me that if you were the manager of that bank I would get my loan, PLEASE Dr. change your vocation.
Hell, there is not one scientific org. that can even estimate the number of active volcano’s under the sea. ( personal experience. ) Sailing a yacht in the lower Pacific we encountered a seawater temp. increase of 12°c. Spending a day in the area we found that the affected area was some 23 miles across sea depth was at an average of 2 miles and the center was visibly higher with gaseous activity.
Now deep down there was one hell of a lot of bubbling, but upon our return to Auckland in New Zealand and inquiring with a NZ government volcanologist, he said thank you for the information, it was an unknown volcano, BUT!!! there were hundreds of active volcano’s in the southern Pacific.
CO2,? for billions of years, it was no big deal.
Regarding the 800 year lag time,
why 800 years if we can already (apparently) see feedbacks kicking in now within decades?
There is something I’m not understanding.
I wish to add my thanks to Dr. Meier for his answers and for his contributions to this blog’s discussions. I would also like to admonish certain posters to keep the tone respectful.
With that introduction, I am grateful that Dr. Meier confirms my understanding of the AGW position. Yet, I did not find the answers to be persuasive; nor the references – they were not persuasive two or three years ago, and they are even less persuasive now. To avoid repetition of other posts, I will not dive into many details. I am amused by the elephant comment. I do not know of any mainline climate skeptic that ignores the elephant he mentions, but it seems that “global warming pessimists” seem to ignore the rhinoceros, the hippopotamus, and the Apatosaurus in the room.
On point #6, one feedback that Dr. Meier omits is precipitation itself. More than one respected analysts have pointed out that if the models permit slightly more precipitation, then the warming effect negated.
On point #5, I have long been intrigued by this graph. It suggests that the key to climate is radiative forcing with subsequent feedback, and if not for human activities, the radiative forcings would have been essentially flat since 1750. Does that mean that we would still be in the Little Ice Age if the Industrial Revolution had not come along? Somehow the world got into Little Ice Age, but the only significant driver of climate since then has been human induced radiative forcing.
I was delighted to read Dr. Meier’s input. It is very nice to see quiet and rational discussion from the AGW side…even if I disagree…and it was off-putting to see some of the comments here that attack his credentials and him personnaly…thoses comments are uncalled for! Respectfully question his data and conclusions all you want…that is what we are here for..after all, if we can not refute his points, then he just may be RIGHT!
As a biologist, I would, however, like to make an observation. I believe he has mis-identified the species of said elephant. It is not an AGW elephant, it is an unknown species of variable climate elephant. Just becasue we are having trouble identifying it, you can not justify jumping to the conclusion that it must be the AGW variety…unless and until you can conclusively demonstrate that it is inflated by CO2 enhansed hot air.
We do not have to be able to prove that we understand climate changes to disprove AGW. We only need to show that AGW does not adaquately explain what we see happening in the real world. The AGW folks have made some very specific predictions reguarding what we can expect by 2012. Either thier predictions will pan out..or their theory goes into the dust bin.
Expect to hear lots of screaming coming from the dust bin….
cdl
Dr Meier,
you say that
“Many natural explanations for the current observed warming have been suggested:”it’s just natural variability,” “it’s the sun,” “it’s cosmic rays,” etc. However, these have all been investigated and evidence is simply lacking.”
Pardon, but the evidence for e.g. cosmic grays holds just as well as the case for AGW. You should honestly admit that the other possible explanations have not been refuted. Neither have been proven and neither have been refuted.
Alan Chappell (08:46:31) 12 degree centigrade increase in temps from a volcano two miles down, and they try to tell us that the 1999 volcano in the Arctic didn’t effect the ice.
====================================
Frank Lansner wrote:
“We OFTEN still hear that SEA LEVELS are rising. But the truth is, sea levels has not risen one milimeter since 2005 !
See this example, Nasa :
http://climate.jpl.nasa.gov/keyIndicators/index.cfm#SeaLevel“
They specifically write that their graph is updated!
NASA: “Sea Level Last updated 09.16.08″
But they have NOT updated their graph. They stopped updating 2´nd quarter of 2007. Why are they not updating?”
Frank, actually there’s a tiny square in the top corner of the graph. If you hover your mouse over it, it says, “Latest measurement, 39mm August 2008”. No idea why they’ve stopped recording on the graph though – it seems a bizarre way to show a measurement.
So CO2 lags by 800 years in the ice cores, and the current theory is:
1) For Unknown Reason A, the temperature starts to rise.
2) For Unknown Reason B, 800 years later, CO2 starts to rise.
3) For Unknown Reason C, that initial 800 year temperature rise stops dead, and CO2 takes over the warming, which produces more CO2 (See Unknown Reason B) which strangely continues warming with the same trend rather than an increased trend (can trends increase?) even with the extra CO2.
4) For Unknown Reason D, the temperature starts to drop, even while CO2 is high.
5) For Unknown Reason E, the CO2 finally catches up with the dropping temperature, and begins dropping itself.
And this is considered the ‘proof’ that CO2 is responsible for Global Warming?
Dr. Meier states that “the elephant in the room that is the GHG emissions produced by humans”. I respectfully disagree. The “greenhouse gas” elephant in the room is water.
The anthropomorphic CO2 contribution to a trace atmospheric gas is the mouse in the room with the AGW lady up on the chair screaming. I thank Dr. Meier for his efforts but it just reinforces my impression that the AGW faction no real reply to the questions of the so called “skeptics”. There also seems to be an implication that the onus is the skeptics to present an alternate theory in order to discredit AGW. No, one just needs to show the flaws in AGW to discredit it.
Another great thread from Anthony by inviting Dr Meier. Thank you both of you. May we have lots of these! Of course, I disagree with Dr Meier pretty radically – from the very first sentence in fact, saying AMO has no effect on the Arctic, which I see as contradicted quite clearly by the graphic evidence here: http://www.intellicast.com/Community/Content.aspx?a=128
I would like to see a Climate Audit of the IPCC chart which gives CO2 such a big share of the pie.
I wonder how much Dr Meier reads of the posts here, how much gets filed under “classic skeptic issues” without too much examination. It is VERY easy to do this IMO.
I agree with Phil about courtesy levels – although when one disagrees radically about something that seems this important, it can take time to learn to be courteous. More real debate would help with this.
Seems strange to me that seemingly all the warming is taking place in the Northern Hemisphere, while the Southern half of the planet seems to be going in the other direction. Temps in Antarctica are cooler and ice mass is growing. Could it be that since the majority of the population lives in the NH, and most of the industrial pollution orginates in the NH, that warming is indeed man-made, but is not global? Since CO2 is assumed to be homogenous in the atmosphere, wouldn’t this rule it out as a cause? I think we may be barking up the wrong tree.
Jamie and Frank:
Yes, Jamie, there may be a reason, but bizaare is the appearance of the NASA graph on http://climate.jpl.nasa.gov/keyIndicators/index.cfm#SeaLevel“
They do cite U of C, and without doubt, here is the graph with the missing data points.
http://sealevel.colorado.edu/current/sl_noib_global_sm.jpg
Strangely, the NASA graph omits all the data points well below the trend line in the last couple of years. Meanwhile some people may object to the comparison of two graphs on the NASA site. The first runs for 100 years based on estimates from 23 tidal gauges, then a few years are skipped, and the next graph picks up with satellite measurements. Many researches would cry “Foul!”
edwardturner (16:03:24) :
[Meier]:However, since about 1995, the AO has mainly been in a neutral or negative state. Under such conditions, the Arctic sea ice should have started to recover. Instead, sea ice extent has not only continued downward, but the decline rate has accelerated.
“But the NAO has been extremely positive over this period.”
http://upload.wikimedia.org/wikipedia/commons/a/a3/Winter-NAO-Index.png
Although be careful to notice your ref claims to represent only winter indexes.
http://www.cpc.noaa.gov/data/teledoc/nao_ts.shtml
An Inquirer (11:36:30) :
on http://climate.jpl.nasa.gov/keyIndicators/index.cfm#SeaLevel“
Hover over the little square and it says August 2008, 39
http://sealevel.colorado.edu/current/sl_noib_global_sm.jpg
The 2008 points on this plot seems to be down around 20
The two plots differ in that “inverse barometer” is applied for one but not for the other one. What does that mean?
I’m confused. I thought Dr Meier was referring to the winter index?
a substantial amount of the decline in the sea ice during the late 1980s and early 1990s could be attributed to a strong positive mode during winters because the positive mode favors the loss of thicker ice that is less likely to melt during summer. However, since about 1995, the AO has mainly been in a neutral or negative state.* Under such conditions, the Arctic sea ice should have started to recover. Instead, sea ice extent has not only continued downward, but the decline rate has accelerated.
* Between 1995 – 1999 it was mostly negative. This chart shows the AO has, since 1999, been more positive than negative (except the notable winters of 2001 and 2003 which were very negative).
In light of evidence of a positive NAO over this period (during the important winter months) this paragraph of Dr. Meier’s doesn’t stack. Conditions were not especially favourable for ice recovery since 1995.
Let me add my thanks to Anthony and Dr Meier for enabling this exchange.
A few responses …
David Hagen, (also Frank Lansner) – The most important greenhouse has H2O is commonly assumed to increase with increasing temperature due to CO2. I do not recall having seen quantitative evidence that H2O is increasing.
Try this – Attribution of observed surface humidity changes to human influence
from the conclusion The results presented here add to an increasing body of evidence that atmospheric water vapour has exhibited a significant upward trend over recent decades. Although such a moistening has long been predicted as a response to warming induced by greenhouse gases, this study demonstrates that the observed increase in surface specific humidity is directly attributable to anthropogenic influence and is distinct from the predicted response to natural forcing..
BernardP Should we understand that scientists can ascertain that one carbon dioxide or methane molecule is natural and another is man-made?
LawofNature The ‘characteristic chemical signature’ is the same for all CO2, you are wrong with your statement under point 3.
Dr Meier is right. The ratio of carbon isotopes is different in CO2 that is the result of fossil fuel combustion than that from natural sources, so yes we can distinguish between natural and anthrpogenic CO2. This is named the Suess Effect after the Austrian Chemist who first observed it. A similar analyis is possible for methane.
Gary – Assuming Dr. Meier will do this again, please ask him to address Dr. Stephen Schwartz’s (of BNL) ‘Heat Capacity’ report, published last December, which essentially says that doubling CO2 from current levels would likely increase global temps 1.5 Deg K.
Annan et al comment on Schwartz here . In this more recent paper Schwartz estimates climate sensitivity as 1.9 +-1K, which overlaps with the IPCC’s estimated range, once uncertainties are considered.
Ed Scott There more than 31,000 American scientists who disagree with this conclusion. Assuming this is a reference to the Petition Project, there are actually 31,000 scientists, engineers, doctors, dentists and chiropractors who disagree, a tiny, tiny fraction of the total.
Saying that GHG increase is due to human-caused emissions does not make it true.
Apart from the isotopic signature, simple carbon accounting does it. In a sentence, we know with sufficient accuracy how much CO2 has been produced by fossil fuel combustion and deforestation, and the actual increase in concentrations is less than this would produce, so we can confidently attribute all the increase to human activity. See Takahashi, Science, Vol 305, Issue 5682, 352-353.
He totally didn’t answer question #1 at all not one bit. I won’t even read the rest till he does…
Anybody know what the ‘seasonal signals removed’ on the NASA graph means?
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It’s pretty cute the way we are referred to Real Climate for discussion of Roy Spencer’s latest feedback work. He does admit that feedback to the initial forcing of CO2 is problematic, but really minimizes the amount of uncertainty in that key factor.
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Hey Professor, Real Climate is not an honest forum. Hasn’t anyone ever told you that?
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“We may not clearly know what caused the MWP, but we have a clear cause for the current warming: human-caused GHGs.”
What a lack of humility in science! I think AGW theory ticks off staticians and mathematicians the most. Hey, I lost 5 lbs last month; that means in another 40 months I will weigh zero! Alarmist scientists should know you can match many equations to any squiggly line with a ton of factors to fudge, that doesn’t mean your model predicts the future. Be very careful when you extrapolate empirical data. Be very careful when you use proxies to supposedly fill in your empirical data. Never assume that just because your model is as good as you can get it, that is actually any good at all.
The only cure for this AGW theory ailment is time in the real world. However the worst part is that alarmists are destroying the base ACTUAL environmental problems to be solved. What a collossal waste of time and effort.