Guest post by Dr. Don J. Easterbrook
1934 has long been considered the warmest year of the past century. A decade ago, the closest challenger appeared to be 1998, a super-el nino year, but it trailed 1934 by 0.54°C (0.97°F). Since then, NASA GISS has “adjusted” the U.S. data for 1934 downward and 1998 upward (see December 25, 2010 post by Ira Glickstein) in an attempt to make 1998 warmer than 1934 and seemingly erased the original rather large lead of 1934 over 1998. The last phases of the strong 2009-2010 el nino in early 2010 made this year another possible contender for the warmest year of the century. However, December 2010 has been one of the coldest Decembers in a century in many parts of the world, so 2010 probably won’t be warmer than 1998. But does it really matter? Regardless of which year wins the temperature adjustment battle, how significant will that be? To answer that question, we need to look at a much longer time frame‒centuries and millennia.
One of the best ways to look at long-term temperatures is with isotope data from the GISP2 Greenland ice core, from which temperatures for thousands of years can be determined. The ice core isotope data were obtained by Minze Stuiver and Peter Grootes from nuclear accelerator measurements of thousands of oxygen isotope ratios (16O/18O), which are a measure of paleo-temperatures at the time snow fell that was later converted to glacial ice. The age of such temperatures can be accurately measured from annual layers of accumulation of rock debris marking each summer’s melting of ice and concentration of rock debris on the glacier.
The past century
Two episodes of global warming and two episodes of global cooling occurred during the past century:
1880 to 1915 cool period. Atmospheric temperature measurements, glacier fluctuations, and oxygen isotope data from Greenland ice cores all record a cool period from about 1880 to about 1915. Many cold temperature records in North America were set during this period. Glaciers advanced, some nearly to terminal positions reached during the Little Ice Age about 400 years ago. During this period, global temperatures were about 0.9 ° C (1.6 ° F) cooler than at present. From 1880 to 1890, temperatures dropped 0.35 ° C (0.6° F) in only 10 years. The 1880 –1915 cool period shows up well in the oxygen isotope curve of the Greenland Ice Sheet.
1915 to 1945 warm period. Global temperatures rose steadily in the 1920s, 1930s, and early 1940s. By the mid-1940s, global temperatures were about 0.5 °C (0.9° F) warmer than they had been at the turn of the century. More high temperature records for the century were recorded in the 1930s than in any other decade of the 20th century. Glaciers during this warm period retreated, temperatures in the 1930s in Greenland were warmer than at present, and rates of warming were higher (warming 4°C (7° F) in two decades). All of this occurred before CO2 emissions began to soar after 1945, so at least half of the warming of the past century cannot have been caused by manmade CO2.
1945 to 1977 cool period. Global temperatures began to cool in the mid–1940’s at the point when CO2 emissions began to soar. Global temperatures in the Northern Hemisphere dropped about 0.5° C (0.9° F) from the mid-1940s until 1977 and temperatures globally cooled about 0.2° C (0.4° F). Many of the world’s glaciers advanced during this time and recovered a good deal of the ice lost during the 1915–1945 warm period. Many examples of glacial recession cited in the news media show contrasting terminal positions beginning with the maximum extent at the end of the 1880-1915 year cool period and ending with the minimum extent of the recent 20 year warm period (1977-1998). A much better gauge of the effect of climate on glaciers would be to compare glacier terminal positions between the ends of successive cool periods or the ends of successive warm periods.
1977 to 1998 global warming The global cooling that prevailed from ~1945 to 1977 ended abruptly in 1977 when the Pacific Ocean shifted from its cool mode to its warm mode in a single year and global temperatures began to rise, initiating two decades of global warming. This sudden reversal of climate in 1977 has been called the “Great Pacific Climate Shift” because it happened so abruptly. During this warm period, alpine glaciers retreated, Arctic sea ice diminished, melting of the Greenland Ice Sheet occur.
The abruptness of the shift in Pacific sea surface temperatures and corresponding change from global cooling to global warming in 1977 is highly significant and strongly suggests a cause-and-effect relationship. The rise of atmospheric CO2, which accelerated after 1945 shows no sudden change that could account for the “Great Pacific Climate Shift”.
1999 to 2010 global cooling. No global warming has occurred above the 1998 level and temperatures have declined slightly.
The past 500 years
Temperature oscillations recorded in Greenland ice cores over the past 500 years (Fig. 2) are truly remarkable. At least 40 periods of warming and cooling have occurred since 1480 AD, all well before CO2 emissions could have been a factor.
The past 5,000 years
Figure 3 shows oxygen isotope ratios from the GISP2 Greenland ice core for the past 5,000 years. Note that temperatures were significantly warmer than present from 1500 to 5000 years ago.
The past 10,000 years
Most of the past 10,000 have been warmer than the present. Figure 4 shows temperatures from the GISP2 Greenland ice core. With the exception of a brief cool period about 8,200 years ago, the entire period from 1,500 to 10,500 years ago was significantly warmer than present.
Another graph of temperatures from the Greenland ice core for the past 10,000 years is shown in Figure 5. It shows essentially the same temperatures as Cuffy and Clow (1997) but with somewhat greater detail. What both of these temperature curves show is that virtually all of the past 10,000 years has been warmer than the present.
So where do the 1934/1998/2010 warm years rank in the long-term list of warm years? Of the past 10,500 years, 9,100 were warmer than 1934/1998/2010. Thus, regardless of which year ( 1934, 1998, or 2010) turns out to be the warmest of the past century, that year will rank number 9,099 in the long-term list.
The climate has been warming slowly since the Little Ice Age (Fig. 5), but it has quite a ways to go yet before reaching the temperature levels that persisted for nearly all of the past 10,500 years.
It’s really much to do about nothing.
Dang.
I can’t edit my previous post to correct the “bold” tags.
🙁
[Reply: It was a WordPress glitch. I’ve fixed it. ~dbs, mod.]
Old Sea Dog, 12/29/10 @ur momisugly 1:50 AM
I suspect there are a lot of variables in solar brightness, I’m not aware of this type of study.
@Easterbrook
Your graph labels “without CO2 change” and “without CO2 increase” are wrong.
CO2 was on a steady rise during those time periods and because of the logarithmic nature of CO2’s LWIR absorption curve the early period increases, while being smaller in absolute ppm measure, have the same effect as the later period increases of larger absolute magnitude.
That’s an amateurish error, doctor, and reveals a large gap in your knowledge of this subject area.
This is a great post by Dr. Easterbrook.
The pro-AGW’ers hate it when real data is presented. It brings out an emotional reaction in them (see MVB above). They would prefer it if no actual data is presented and that we just continue on perpetuating the myth that today’s temperatures are the warmest ever.
Well, they are not.
No matter how angry that makes one. But that is an emotional reaction versus a factual data-based reaction.
The d018 isotopes are the best temperature proxy we have. It has been proven in hundreds of examples to reasonably reflect the temperature of the time. And this goes back hundred of millions of years. It might not be perfect, but it is the best proxy we have got.
It needs to be properly calibrated to the location however. The isotope change per 1C temperature change varies with the latitude, altitude, and proximity to the ocean. The fact that they also vary with ice volume means it does accurately reflect the general temperature of the time. More ice, the colder Earth has been. Rather straightforward in my opinion versus a reason to question it.
The Greenland GISP2 isotopes, however, have not been calibrated properly to date (including by Richard Alley) to the latitude and altitude they were laid down. Hence, Dr. Easterbrook using just the isotope numbers for the most part versus the temperature implied by them.
[This is a BLOG rather than a science journal. Though some entries may contain errors at least here they are not hidden. … bl57~mod]
Of course I know that this blog is not a science journal. However, the inference is that focusing on a few graphs from journal articles that are presented in a misleading and confusing way somehow trumps the work of hundreds of journal articles.
Note that RB Alley, whose data are cited in this post is a noted and senior “warming” professor at Penn State. No doubt he had something to do with bringing that fast rising star, Michael Mann, to his department. If I were “editor” for this posting by Easterbrook, I would have sent it to Alley to ask for his comments on the interpretation of his data. Recently Alley has testified before the US Congress on the threat of rapid warming caused by human activities. Somehow, I expect that he would be very surprised that his data could be interpreted to show that Greenland has been warmer than present over most of the last 10,000 years. People here should be more skeptical about how Easterbrook has replotted Alley’s data. Since Easterbrook is a professor of geology, he should try to publish these new intrepretations in a scientific journal. If accepted, they would certainly attract a lot of scientific interest and acclaim.
Ben D says:
December 29, 2010 at 5:19 am
I like your reply. I’m pretty much in agreement with it. Near as I can tell there is a steady 0.5C rise in temperature, on average around the world, during the industrial era on top of which rides variations of +- 1.0C. The 0.5C rise correlates well with a calculated rise of 1.1C per CO2 doubling. That is the low end of the IPCC estimate for climate sensitivity to CO2 doubling. The flaw in CAGW ointment isn’t the warming caused by CO2 alone which appears to be well supported in the observations (measured temperatures and CO2 content of the atmosphere) and is consistent with what the basic physics predicts should be observed. The flaw in the CAGW is the so-called “amplification” i.e. a 1 degree rise from CO2 causing an additional 2 degree rise from increased water vapor. That amplification is entirely fictional and not at all supported by observations. This is a fatal flaw for CAGW as it removes the “C” from CAGW turning catastrophic warming essentially into beneficial warming so long as the warming is predominantly at higher latitudes during the nights and winters which in effect merely lengthens the growing seasons where such lengthening is a great boon to the biosphere in general and agriculture in particular.
I’m no AGW skeptic I’m a CAGW skeptic. My position is best described as BAGW – Beneficial Anthropogenic Global Warming. I expect the benefits to continue until there’s no longer enough fossil fuel left to keep it going and therein lies the heart of the problem – what do we do when the fossil fuel reserves are used up? There’s enough to keep going for a century or maybe two at most then the proverbial shit is going to hit the fan. We need a less expensive, abundant, sustainable source of energy in place. The sun is ultimately that source. We need a means to harvest it and I have every confidence that technologic progress will meet that challenge in a timely manner without draconian conservation measures, without massive changes in infrastructure away from liquid hydrocarbon transportation fuels, and in general without great inconvenience or disruption in the way we live. The future is bright and while the landscape might be further defaced by more apartment buildings it won’t be defaced by wind turbines which IMO are a boondoggle only exceeded by diversion of corn meal from food products into ethanol fuel production.
It would be nice if the scientists would remember that in their articles posted to WUWT they are not just writing to their fellow scientists but are helping us layman get up to speed. I am griping about the charts. They are easy to understand unless you don’t understand the the measurements being depicted. It is the little details. For example -31.50c is what, the average temperature of the planet? Triangle O18 o/oo means? The assumption of prior knowledge of the reader often results in a failure to communicate. Usually it would only take a sentence to explain the less than obvious.
[Reply: 0/00 is per mille, or a tenth of a percent; one part in a thousand. O18 is an oxygen isotope. Triangle (∆) means change, and is usually called delta, such as ∆T = change in temperature. –31.5°C refers to the temperature at a location such as Vostok Antarctica, or Greenland. It is not the average planetary temperature, but the changes show whether the planet was in a warming or cooling trend at the time, such as the MWP or LIA. ~dbs, mod.]
The new guest author program, which include myself as one of those new guest authors, appears to have fostered a greater need for internal peer review before the articles are published. Anthony and Willis and guest authors like Spencer and Lindzen didn’t seem to need much in the way of peer review but with this new influx of guest authors the comments are now stuffed with repetitious exposure of errors in the articles.
A call for volunteers to do basic fact checking of article drafts prior to publication might be in order. A great example of what wouldn’t make it into print is the erroneous labels attached to figure 1 claiming no increases in CO2 from 1880-1940. CO2 did indeed increase during those periods according to the best available observations and the logarithmic LWIR absorption curve of CO2 (which is basic physics first demonstrated experimentally 150 years ago) makes those early industrial period increases every bit as effective as the increases from 1940-2010.
When looking at temperature graphs covering thousands of years you must remember the changes in Earth obliquity and eccentricity and the resultant surface insolation differences. My understanding is that currently both obliquity and eccentricity are declining which will take us back into a long glacial period. In that light, shouldn’t we be encouraging anything we may be able to do that will help keep the the planet warmer?
Geoff Sharp says:
December 29, 2010 at 5:11 am
“The sad fact is after continued growth of CO2 output the temperature record is still fixed at 1998. Why is it not climbing as the AGW models predicted?”
Yeah, it’s a travesty alright. The problem is that the CO2 driven surface warming is only ~1.0C per CO2 doubling and it’s lost in the noise of much larger non-anthropogenic variations. It’s no travesty at all if the CAGW boffins would simply admit that water-vapor amplification of CO2-driven warming is a narrative fiction that does not exist in the real world.
Looks like someone has been very bold!
Here are two charts calibrating the GISP2 data in the proper manner.
In central Greenland, the formula is 0.7‰ per 1C (don’t ask me why Richard Alley used 0.35‰).
So, here are the temperature anomalies compared to today. First, where the X-axis (time) is in text so you can see all the datapoints better. This is from 1987 AD to 110,000 BC.
http://img827.imageshack.us/img827/4488/gisp2temperature.png
And then, with the X-axis on the proper timescale.
http://img802.imageshack.us/img802/7913/gisp2temperaturexaxispr.png
I took a look at the RB Alley paper that is the basis of important conclusions of this posting. The article is about rapid changes in climate in Greenland during the Dryas warming, that occured over 10,000 years ago. Evidently, Easterbrook some how plotted data from this study and spliced on what he considers comparable data for recent times.
In order for anyone to assess the appropriateness of his analysis, he would need to provide much more information on his methods. Since his conclusions are seemingly completely unrelated to those of the author of the study, it is really important that Easterbrook provide enough of his methods so that they could be repeated. The fact this his reasults disagree with all of the published record makes this more important. In a scientific analysis it is also important to cite contrary data and to explain why the current analysis is more valid.
The paper being cited is from 2000. Surely, if this paper by a prominant scientist with a “pro warming” record is contrary to other more recent studies, climate scientists would have resolved the issue by now. The author’s main conclusions focus on the potential for “rapid climate change” and have no direct comparisons with recent climate.
In my view, this posting by Easterbrook completely lacks credibility and transparency. The main characteristic of a skeptical scientist is that he or she considers the data carefully, whether the conclusions agree or disagree with his or her world view. As a scientist, I am just as likely to call for the rejection of a paper that generally supports my own view as I am to call for the rejection of a paper contrary to my view of the evidence. The credibility of the support of conclusions by the presented data is the main criterion for assessing a scientific analysis.
Geoff Sharp says:
December 29, 2010 at 5:22 am
A strange comment….looking at the shift in the PDO at 1945 (which was during high solar activity) we can see a gradual decline in temperatures that deepened towards the late 70′s.
Do you have any evidence that the decline in temperatures “deepened towards the late 1970s”? I’m sorry if the “cooling 1970s” fits with your theory but the fact remains that there was very little cooling after the mid-1950s. The 1970s were marginally – though not significantly – warmer than the 1960s. The 1955-80 trend is flat, i.e. neither warming nor cooling.
Hey Bill Illis (of ludicrous claim “The pro-AGW’ers hate it when real data is presented. It brings out an emotional reaction in them (see MVB above). They would prefer it if no actual data is presented and that we just continue on perpetuating the myth that today’s temperatures are the warmest ever.”), I suggest you actually read my comments. I’ve mode not one pro-AGW statement. I don’t even comment on AGW blogs, as they appear not interested in facts, precision, nuance, appropriate graphs, or ever admitting any mistake, no matter what is discovered or going on outside. So why throwing such nonsense at me?
To educate folks I often recommend these two documents (one by Easterbrook, one by Svensmark):
http://scienceandpublicpolicy.org/images/stories/papers/reprint/multidecadal_tendencies.pdf
http://www.scribd.com/doc/338170/svensmark-2007cosmoclimatology
As well as WUWT’s science postings. But the one I’m critiquing (above) just wouldn’t hold up to basic ‘peer-review’ (and I do not mean review by club members by that) and if the low standard continues, I simply won’t feel good about recommending WUWT to warmistas anymore.
Currently enjoying the view of a RAGING snow storm. 😉
People here really lap up anything they agree with, totally uncritically lap it up.
I guess some people above do not know that Richard Alley published his numbers and Dr. Easterbrook is just using them. (Yes, that means an apology is in order).
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt
Now, as I said above, Richard Alley in his (peer-reviewed) publication used an improper formula in converting the do18 isotope data to temperature. As BillD noted above, that was done so that everyone would properly scared by the scary Younger Dryas event (even though it was only one-half to one-quarter as big as Alley said it was and it was just one of about 30 such events in the Greenland ice cores – ie a normal periodic decline in temperatures on top of the 3 km high Greenland glacier).
I encourage anyone to use the actual GISP2 isotope data and make their own charts.
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gispd18o.txt
Easterbrook continues to hide the incline then?
http://hot-topic.co.nz/cooling-gate-the-100-years-of-warming-easterbrook-wants-you-to-ignore/
Shameless.
JohnWho says:
Wow, now who is “cherry picking”?
Err – you are. Every year since 2001 has been warmer than every other year in whatever record you choose – apart from the hugely anomalous 1998. Even using 1998 as the start peiod and using the correct method (Least Squares fit) to calculate the trend we get a positive slope. Don Easterbrook for some reason specified the 1999-2010 period in his post. You, somewhat charitably, decided to overlook this and decided to interpret his statement in the best light possible. However you inerpret it, the fact is there is no cooling. The last 10 years have been ~0.2 deg warmer than the previous 10 years. Even if you (incorrectly) decide to use ranking as your criteria, Roy Spencer has said there is not a statistically significant difference between 1998 and 2010. In other words they are, to all intents and purposes, equal.
jakers says:
December 29, 2010 at 9:12 am
“People here really lap up anything they agree with, totally uncritically lap it up.”
In some cases it appears that agreement with the conclusion automatically means uncritical agreement with any argument leading to it. That shouldn’t be surprising. I dare say it’s a more prevalent thing in the climate disruption camp.
If you draw a line from Minoan peak to Roman peak to MWP peak to now …. we are screwed. The interglacial is coming to an end.
BillD says:
December 29, 2010 at 8:25 am (Edit)
I took a look at the RB Alley paper that is the basis of important conclusions of this posting. The article is about rapid changes in climate in Greenland during the Dryas warming, that occured over 10,000 years ago. Evidently, Easterbrook some how plotted data from this study and spliced on what he considers comparable data for recent times.
########
made all the more mysterious when you actually look at greenland temperatures over the last 100 years.
#
#
JohnWho says:
December 29, 2010 at 5:25 am (Edit)
Steven Mosher says:
December 28, 2010 at 10:46 pm
http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.gif
hmm.
If your “hmm” means that even NOAA shows that it was much warmer than it is now many times in the past 10,000 years, then “hmm” indeed!
#######
no my hmm had to do with the easterbrook chartmanship, and the fact that the record stops 100 years ago. and the cold temps.. -31C.. and looking at actual temps in greenland.. and wondering what alley has done and what easterbrook has done.
Fact is, its been warmer in the past. That’s not the question.
I wonder if all the climateheads could agree to an experiment. An idea about building three or more identical greenhouses, side by side, but far enough apart not to affect each other in any way. Humidity the same with thermometers calibrated and locations the same. One greenhouse has low ppm CO2, the next has high ppm CO2 and a third with smoke. More could be made for other gasses, such as methane. Wouldn’t the data solve the debate? Or is getting together not possible?
Tom in frozen Florida says:
December 29, 2010 at 7:32 am
“When looking at temperature graphs covering thousands of years you must remember the changes in Earth obliquity and eccentricity and the resultant surface insolation differences. My understanding is that currently both obliquity and eccentricity are declining which will take us back into a long glacial period. In that light, shouldn’t we be encouraging anything we may be able to do that will help keep the the planet warmer?”
No kidding. We’re standing on the edge of a cliff looking at a sign that says “Holocene Interglacial Ends Here” and people are worried about backing away from the edge. Incredible.
Just to point out how close to the cliff we are the axial tilt change that begins and ends interglacial periods doesn’t change total solar insolation to the planet at all, per se. The only thing it does is increases the difference between average winter/summer temperatures as the tilt angle increases and decreases the difference when the angle is decreasing. Cooler summers with milder winters when angle is smaller and hotter summers plus colder winters when angle is larger. And we’re only talking a small change from 24 degrees tilt to 21 degrees and back again.
That small change in the seasons is enough for more snow to accumulate on northern hemisphere land masses when summers are cool and winters are mild. That ends up extending the range of year-round snow cover which in turn lowers the amount of sunlight absorbed by the surface helping the snow persist through the cooler summer season. This becomes a vicious cycle that doesn’t end until there’s a mile of ice covering every land mass north of Kentucky.
With the current arrangement of the continents this favors snow accumulation in the northern hemisphere