Posted on 01/29/2008 11:13:13 AM PST by E. Pluribus Unum
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A Global Temperature History of the Past Two Millennia
Reference
Loehle, C. 2007. A 2000-year global temperature reconstruction based on non-treering proxies. Energy and Environment 18: 1049-1058.
What was done
Using data from eighteen 2000-year-long proxy temperature series from all around the world that were not developed from tree-ring data (which provide significant interpretive challenges), the author (1) smoothed the data in each series with a 30-year running mean, (2) converted the results thereby obtained to anomalies by subtracting the mean of each series from each member of that series, and then (3) derived the final mean temperature anomaly history defined by the eighteen data sets by a simple averaging of the individual anomaly series, a procedure that he rightfully emphasizes is "transparent and simple."
What was learned
The results obtained by this procedure are depicted in the figure below, where it can be seen, in the words of its creator, that "the mean series shows the Medieval Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately 0.3°C warmer than 20th century values."
What it means
Loehle notes that "the 1995-year reconstruction shown here does not match the famous hockey stick shape," which clearly suggests that one of them is a poorer, and the other a better, representation of the truth. Because of its simplicity and transparency, as well as a host of other reasons described in detail by Loehle -- plus what we have learned since initiating our Medieval Warm Period Record-of-the Week feature -- it is our belief that Loehle's curve is by far the superior of the two in terms of the degree to which it likely approximates the truth.
Reviewed 30 January 2008
* The temperature minimum corresponds to the years just after 1883. Can you think of anything notable that could have had a climate effect in 1883?
From 1944 to 1956 there was another drop of 0.4 degrees.
Massive dirty post-WWII industrialization. Look up "killer London fog".
Or what about that huge increase of .7 degrees from 1912 to 1944, long before most of our CO2 was released?
Well, to make you happy, that's been attributed to CO2 + increasing solar activity, the Sun given responsibility for 30-50% of it. I estimate the five-year mean increase at about ~0.5 C, by the way.
Unfortunately we can't separate the mixture because government scientists who do environmental studies are being influenced and their careers threatened by political forces.
The studies can still be critically analyzed, no matter who wrote them.
By the way, I neglected to answer your question about the possibility that objections to the Hockey Stick were motivated by other considerations. Yes. Absolutely. I think it was motivated by concern about grand theft Kyoto.
It's good that you know that. My problem is that attacks purporting to be scientific, but which were not and which would clearly be labeled "bad science", were launched at the Hockey Stick, seriously confusing the issue. Some of the erroneous points made about it eight years ago are still being restated today. Yes, the original Hockey Stick has methodological flaws. But when you look at all the reconstructions in the figure I offered -- from ClimateAudit, created by a colleague of Loehle -- the basic hockey stick picture is still there, with only the amplitude of variability and the phasing (somewhat) being the main things that change.
I could say a lot more. But I still want to stay focused on the science. What we need to know scientifically is how much natural variability is contributing to the current temperature rise. On that topic paleoclimate reconstructions can aid assessment, but they are not the full answer by a long shot. So to compare peak MWP temperatures to now and conclude that because they were about the same we currently don't have a problem is not a conclusion backed by a preponderance of scientific data.
Yes. The point I was making was that the amplitude of the temperature peaks depend on the filtering of high frequency signals by either running averages or, in the case of data before the historical record, by averaging inherent in the proxy technique. Does anyone really know how much?
and 1877-1878 was a period with a big El Nino.
Sure. And El Nino, Solar activity (and probably CO2) fluctuate naturally. So spikes happen naturally.
But when you look at all the reconstructions in the figure I offered -- from ClimateAudit, created by a colleague of Loehle -- the basic hockey stick picture is still there
How much of this reconstruction relies on tree-ring data?
What we need to know scientifically is how much natural variability is contributing to the current temperature rise.
Before we do that we should first determine how much of the temperature rise is real or caused by:
a) Local artifacts like Heat Island Effect
b) Improper siting of temperature stations
c) Errors from aging instruments
d) Mathematical errors or outright fraud
Good science allows transparency so that other scientists can see your data and your methods. Unfortunately that is difficult with much of government science and getting harder all the time. Data sets have been moved to pay-per-view sites or given only grudgingly. NCDC weather site data has been withdrawn entirely citing "privacy" concerns. The formula and algorithms used by computer models are shielded from public scrutiny. This is not good science. This is a medieval priesthood.
I am completely not an expert, but I can intuitively state that it is probably not good practice to evaluate trends based on maximum-to-minimum points when the data has considerable variability. Filtering is useful, but I can't say much more about it.
And El Nino, Solar activity (and probably CO2) fluctuate naturally. So spikes happen naturally.
That's why spikes shouldn't be used to evaluate trends.
How much of this reconstruction relies on tree-ring data?
Can't tell from the graph. Certainly some does. Ask McIntyre! But we're discussing Loehle, which is a tree-ring-free analysis -- and the same basic picture emerges. Most of the question is about the global significance of the MWP temperatures.
a) Local artifacts like Heat Island Effect
b) Improper siting of temperature stations
c) Errors from aging instruments
d) Mathematical errors or outright fraud
Yes, it's always good to evaluate the quality of the data. I've been following the discussions of data quality, and I believe this: if you had "perfect" data, you'd see maybe a 10-25% difference in the trends observed now. Here's a couple of things to think about when you are considering data quality:
Global warming brings earlier spring thaw to Great Lakes
Warming Trend Seen In Late Freeze, Early Thaw Of Northern Waterways, Say Science Researchers
Rising Height of Atmospheric Boundary Points to Human Impact on Climate (I think you'll definitely find this one interesting)
The reason I provide these -- and I could provide others -- is that these "natural" indicators demonstrate clearly that a temperature increase is happening, regardless of cause. What would be confounding would be to have all these natural indicators, yet the instrumental data did not show an increasing trend.
Yeah, but you started it. ("Remember that it's warmed up globally about 0.4 C since 1975. That's a big spike.
I guess it depends on your definition of "spike".
I was thinking about those links you posted (BTW what do they have to do with "data quality?) trying to support global warming theory with anecdotes, when I saw this today, Many in China to greet new year without power Millions struggle to get home amid 'coldest winter in 100 years'
A lot of people are going to die from this little weather spike before it is all over. If China were bound by Kyoto can you imagine how they would cope with cold weather like this if they could no longer heat their homes with fossil fuels but were restricted to wind and solar power.
Cold kills more people than warmer weather. If the Earth cools off it is going to be much worse than a heating trend .
Yes, I agree, my phraseology was unfortunate. A 0.4 C rise in 30 years is not a spike. (It isn't based on a valley-to-peak maximum difference, either.)
I was thinking about those links you posted (BTW what do they have to do with "data quality?) trying to support global warming theory with anecdotes, when I saw this today,
What I posted is not anecdotal. Each of the articles is about an observation of a trend. A spring thaw a month early is an anecdote, as is one bitterly cold winter. A trend of spring thaws a week earlier over a century is a shift of significance BECAUSE it shows a change in one direction of a highly variable occurrence. The tropopause height is a clear indicator of the state of the GLOBAL climate -- it essentially synthesizes everything occurring above and below and reacts.
The reason that this is about data quality is that the natural trends are in the same direction as would be indicated by the data. This means that though it may be necessary to keep refining the error bars on the direct instrumental observations, the data and the trends provide mutual support. Everything "fits".
I was originally responding to this comment:
Before we do that we should first determine how much of the temperature rise is real or caused by: (list of instrumental problems)
In essence I was saying that most of the temperature rise has to be real, or otherwise we would not be seeing the significant shifts in natural indicators.
BTW, the correct term for this is "phenologic". A couple of years back there was a big paper about this. Let me look...
Got it. "Ecological responses to recent climate change", 2002. Google Scholar indicates it has been cited 853 times. That's impressive. What I'm still looking for is a free copy...
Here we go. It's a PDF.
Ecological responses to recent climate change
It's not a hard read. Take a look. When you're done, please answer the following question:
If there was no instrumental data at all, just the observations of the trends in the paper, what would be the logical conclusion regarding the direction of change for global climate?
Thanks.
The link you posted,
http://www.sciencedaily.com/releases/2000/09/000921073656.htm
talks about river and lake freeze cycles but the data he gives ends about 12 years ago. Why do you suppose no one has updated this data series? It seems like it would be an easy thing to do.
Another thing about ice is that it is supposed to create a positive feedback. Ice melts, lowering albedo and causes more melting. But Antarctic ice extents are at a thirty year high in spite of the warming over that period. Could it be that there is also a negative feedback with ice? Sea surface warms, evaporating water that becomes ice in Antarctica, increasing albedo which lowers temperature.
Well, yes I do. And the data indicate a warming trend over the past 150 years, no matter how much you try to confuse the issue and avoid the question.
The data in the paper: later freeze, earlier thaw. Consistent with global warming. No other additional conflations.
Why do you suppose no one has updated this data series? It seems like it would be an easy thing to do.
Well, two things. The data set is highly variable. 12 more years might not add much information to it. Two: did you look at the first link, the authors, and the date? It's a short article; read the whole thing.
Another thing about ice is that it is supposed to create a positive feedback. Ice melts, lowering albedo and causes more melting. But Antarctic ice extents are at a thirty year high in spite of the warming over that period. Could it be that there is also a negative feedback with ice? Sea surface warms, evaporating water that becomes ice in Antarctica, increasing albedo which lowers temperature.
Did I previously provide the link to the paper by a physicist at U. Washington that shows that increasing Antarctic sea ice is a consequence of global warming. Aw, h*ll, this is so much fun I'll do it again. Don't ask me to support this one with analysis; all I can do is take his word for it.
Ach, I forgot, actually there's two of them.
Warmer Air May Cause Increased Antarctic Sea Ice Cover
Here is the information for the second, which is the one to which I was actually referring:
1) Zhang, Jinlun, 2007. Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions. Journal of Climate Vol. 20, No 11, pp. 2515–2529, June 2007
Abstract
Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by the NCEP–NCAR reanalysis data, the model simulates an increase of 0.20 × 1012 m3 yr−1 (1.0% yr−1) in total Antarctic sea ice volume and 0.084 × 1012 m2 yr−1 (0.6% yr−1) in sea ice extent from 1979 to 2004 when the satellite observations show an increase of 0.027 × 1012 m2 yr−1 (0.2% yr−1) in sea ice extent during the same period. The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979–2004 and the extended period 1948–2004.
Have you noticed that we are getting farther away from the human-caused aspect of the warming trend that is supported (well within past ranges before man’s influence) with each of the denier’s statements.
It is admitted that it isn’t necessary to prove that the current and recent past is warming slightly; what is important to the skeptic is that this is the time for caution, not panic and overreaction.
Rising sea levels over a time frame that outran adaptation by the coastal dwellers could prove to be costly, but so far that isn’t the case.
Sea levels can only rise by melting of trapped land ice or thermal expansion of the sea itself (unless the ground is sinking).
The only loss of ice we have charted remains largely seasonal and has been limited to the northern hemisphere.
While the northern hemispere is much more important to the majority of living creatures it is not the whole globe.
Trying to remove the present carbon-load in the earth’s air would prove to be far more costly and disruptive to industry that any gradual rise in sea levels.
If it were accepted that mankind caused it, we still would have to remember that it took hundreds of years for it to be noticed and get to its current state.
What makes anyone think that we can stop and then reverse the process overnight or even a few generations?
I don't believe anyone can draw any conclusion from that study. I have less respect for ecologists than I do for climate scientists. At least climate scientists make an attempt to prove their theories using scientific methods. An ecosystem is complex and chaotic. There is no proof that warming is causing all the changes he talks about. They can advance a theory and rationalize it but there is no proof. Species change radically for dozens of reasons even when the temperature doesn't change.
Months ago there were people saying that polar bear populations were at risk from global warming. The ice was melting and the bears were drowning. Trouble was, most types of polar bears were increasing in number.
Living things have a lot more to worry about than a slight increase in temperature.
So we used to believe that a runaway positive polar feedback effect was waiting to bite us in the butt and now we discover that the science is not settled. We used to believe that the Sun was a constant, and now we know that it is a huge variable in climate change.
Every few years we are discovering new things that radically alters the picture of things that change the climate. In view of this, maybe we should wait until the science settles down before pressing the panic button.
Maybe for the last 27 years. Steve McIntyre was reviewing the heat island effect and the data paint an interesting picture of the differences between rural and urban stations. There was a cooling period 27 years ago but the trend shows a fairly level trend for 117 years if you leave out the really big cities.
Well, I agree; panic stops can sure mess up the contents of the vehicle, but at some point you also start applying the brakes when you see a bumpy road ahead.
The only loss of ice we have charted remains largely seasonal and has been limited to the northern hemisphere.
Have you seen some of the mountain glacier retreats? That's hardly seasonal.
Trying to remove the present carbon-load in the earth’s air would prove to be far more costly and disruptive to industry that any gradual rise in sea levels.
No one's seriously talking about removal. Slowing down the rate of increase is the first issue.
What makes anyone think that we can stop and then reverse the process overnight or even a few generations?
Changing the present trajectory is what should be addressed first.
Every day I wake up I tell myself not to be surprised when what I expect to happen happens, but I keep hoping anyway.
I have less respect for ecologists than I do for climate scientists. At least climate scientists make an attempt to prove their theories using scientific methods.
That's a completely unfair characterization of the science of "ecology", which covers a lot of ground. Much of this comes under the heading of population biology, ornithology, botany, zoology -- do you have problems with those sciences, too?
There is no proof that warming is causing all the changes he talks about.
Wondrous, this emphasis on "proof". Science is about supporting hypothesis/theory with observations and data. In this case, the theory is that warming climate would cause a variety of shifts in a certain direction of many different phenological indicators. Examining the indicators, more than 90% show a shift in the predicted direction. That's solid support.
Months ago there were people saying that polar bear populations were at risk from global warming.
Interesting that I'm pursuing this on another thread. They are at risk. Care to know why? Their main food source is seals. Seals swim in the ocean, and they occasionally get out on the ice to rest. Polar bears hunt seals from sea ice, floating on the ocean. With less sea ice, there are less seals on the ice, and the polar bears have less area to hunt from (polar bears are real good at waiting at seal breathing holes and grabbing them when they come up for air). The data show that when sea ice diminishes significantly, polar bear weights go down and polar bear populations decline.
Drowning polar bears is an anecdote. The above statement is polar bear ecology.
Living things have a lot more to worry about than a slight increase in temperature.
Like what they eat, maybe?
In the figure below, I’ve calculated the average unadjusted temperature for actual cities,
First question that pops into my head reading this is: is there a reason that the "unadjusted" temperatures are preferable to the "adjusted" temperatures? Reading the article, my first impression is that the unadjusted temperatures are preferable to McIntyre because he can find trends in them and then cast aspersions on the adjustments because they remove the trends -- when maybe the reason for the adjustments (left unstated) is to remove spurious trends.
You can try all you want, but nature and the data indicate that it warmed up in the 20th century and its warming up faster now -- globally. You can't "adjust" when a lake thaws in the spring.
“Well, I agree; panic stops can sure mess up the contents of the vehicle, but at some point you also start applying the brakes when you see a bumpy road ahead.”
Getting out of the car and looking at the road doesn’t fix it.
For the past few years CO2 output in the US has stabilized while output in the emerging third world is skyrocketing, all the agreements in the world won’t ensure compliance and can’t promise results.
If we try to solve this with taxes the certain result is that the taxes will be with us even if the problem fixes itself.
One of the spurious trends I've noticed is the practice of climate scientists to cherry-pick data. It's pretty obvious that Peterson choose a very peculiar selection of cities for his heat-island study.
I'll wait for an audit of Magnuson's choice of lakes and rivers before I'll buy it as real.
Yeah, but does the theory come before or after the data is collected? I suspect that, in many cases, the theory is proposed after the fact.
In the interests of your health, I advise you not to hold your breath. Realize that the 2000 study was supported by the 2005 Great Lakes study, both of which I've cited to you. And Magnuson's data is all online. Let McIntyre edit all he wants. It may interest to you to know that the general process of scientific peer-review actually discovered a small error that reduced the reported trends by about a day. I'll leave it to you as an exercise to find out what the error was.
The paper was an analysis of many different types of phenological studies. If you had read it -- I suggested that was something you could try -- you probably could have answered your question. Essentially, the paper says: "Observations indicate a warming climate in most parts of the world. Observations indicate that organisms are recently exhibiting changing behavioral and distributional patterns. Most of the observations of the organisms indicate that the changes the expected adaptations to a warming regime. There are very few observations that don't show such an expected response."
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