From time to time, readers here have something to offer other readers which can’t easily be conveyed in the comment section. And, from time to time, I’m eager to get someone else’ perspective. Long time reader, Hank, as graciously offered to write a few posts for Suyt’s space. I’ve happily agreed.
Today, he’s wrote a post which for many of us is mostly old hat, although towards the end of the post you may have a surprise. It seems we get new readers all the time here. Because of the broad areas of subjects we discuss, many may not be familiar with this information. I should also note, not everyone agrees with some of the information provided. Any formatting difficulties are my doing.
A Guest Post by Hank Hancock.
As a medical / technology researcher with a good educational background in mathematics, the one thing that constantly catches my attention is how graphs are misused in both sides of the climate debate to prove a point. I’m not saying all graphs are wrong, just some graphs are wrongly used in ways that do not accurately represent what the data is saying.
Our natural world is full of rhythms. The climate is no exception. The climate naturally warms and cools regionally and globally in response to a number of short term, multidecadal, multi millennial, and longer term cycles that coincide with periodic changes in our planet’s oceanic thermohaline circulation, orbital variations and inclinations called Milankovitch cycles, solar activity cycles, and even cosmic ray galactic cycles. These cycles intertwine with each other to modulate the temperatures of our planet up and down on various time scales. Here’s a list of natural cycles that are believed to affect the temperature of our planet to varying degrees:
- Solar Cycles:
·11 year Schwabe Cycle
·22 year Hale Cycle
·87 year Gleissberg Cycle
·176 year King Hale solar cycle
·210 year Suess Cycle (aka. de Vries Cycle)
·900 year Bond Event Cycles
·2,300 year Hallstatt cycle
·6,000 year (as of yet unnamed) cycle
- Thermohaline Oceanic Cycles:
·65 year Atlantic Multidecadal Oscillation (AMO)
·80 year Pacific Decadal Oscillation (PDO)
·Variable short timescale El Niño-Southern Oscillation (ENSO)
·Short timescale North Atlantic Oscillation (NAO)
- Milankovitch Orbital Cycles:
·22,000 year procession (wobble)
·41,000 year axial tilt
·110,000 and 400,000 year eccentricity
- Cosmic Ray Cycles:
·Decadal and millenial cosmic ray fluctuations (following solar activity)
·140 million year cycles traversing galaxy spiral arms.
I’m sure I’ve overlooked a few. My purpose is not to quantify the effect of the above cycles but to make the point that they are natural cycles.
Keeping in mind that these are fairly regular cycles, we can neatly represent them as peaks and troughs (increasing and decreasing effects on the climate) as in a sine wave. Consider the following graph of a pure sine wave:
Notice that when we use a measuring stick, shown as the green line, that is exactly one full wave length of the cycle (the length from one peak to the next peak of the cycle) we get a zero trend line (the red line). As long as we keep the appropriate length measuring tick, we can slide it in any direction and no matter where we position it, we will always get a zero trend line. The figure below demonstrates this point. Here I’m shifting the measuring stick to the right and measuring two different points on the sine wave.
Notice that although the measurement points are different, the trend remains zero. This again confirms that the sine wave has a zero trend. You can play around with the measuring stick and confirm that anywhere you slide it, it will always produce a zero trend line. In this case, our measuring stick is of correct length and it is telling us the truth.
What happens when you shorten the measuring stick to, say, 3/4 of the length of the sine wave? Think of this in terms of the second graph you drew earlier. Recall that it too had a shorter timeline (measuring stick). Depending on where you slide the measuring stick to, you will change the slope of the trend being measured. The next two figures demonstrate this rather strikingly:
Above, we are measuring two points that intersect the measuring stick on the sine wave. Notice that the trend is positive. Now, lets slide the measuring stick to the left and take two new measurements.
You can see that it radically changed the slope of the trend to negative. Realize that both trends are false. We know the true trend for the sine wave is zero. Now we’re starting to see the problem. If you attempt to measure the trend using a measuring stick that is too short, the trend will always be a contradiction to what the data is saying.
There is a raging debate in the blogosphere regarding what time scale differentiates weather from climate. Most climatologists agree that the smallest unit of climate measurement is 30 years. I think it’s fine to average weather over 30 years to arrive at the climate for that period but it’s not fine to use 30 years as the timeline to represent climate history as is commonly done because it is misleading. The current climate and climate history must be taken into proper context for graphs with trend lines to have any real meaning.
Our present interglacial period, called the Holocene Epoch, started approximately 12,000 to 14,000 years ago. We’re very near the end of our present interglacial period and on the doorstep to the next ice age if mother nature keeps on schedule as depicted below.
Above, I drew in a horizontal blue / red bar towards the bottom of the graph. The blue depicts each glacial period (ice age) and the red depicts each interglacial period (warm age) across the 450,000 year timeline. As you can see, the warm period we presently live in is of similar length to the others. Also notice that the temperatures we’ve experienced in our current interglacial period are cooler than previous interglacial periods.
Now, lets zoom in on just our current Holocene interglacial period with the graph below. It represents the last 12,000 years of our climate history, starting with our climbing out of the last glacial (ice age).
You can see that even in our interglacial, our temperatures follow roughly an 900 to 1200 year cycle of heating and cooling. This overall cycle is formed by the additive and subtractive effect of the various solar and thermohaline cycles enumerated above coming together but, for the most part, there is good correlation to the Bond Event cycles. Notice how the above graph looks a lot like the sine wave we played around with earlier.
At the very bottom right corner of the timeline, I drew in a purple and green horizontal bar. It’s kind of small. The green portion of the bar, which is barely even noticeable represents 30 years – the smallest measure of climate by today’s standards. The purple portion of the bar represents our entire instrument record – the period of time in which man has been measuring and recording temperatures. What do you notice about the temperature trend across the timeline covered by the combined purple and green portion of the bar? The climate is most definitely warming.
Now, draw a straight line from the top peak of the first Holocene Climate Optimum (HCO) to the peak of our current warm period at the far right of the graph. What do you get? That’s right, our climate has been gradually cooling since the HCO.
Funny how, depending on how long the measuring stick is, it tells us something very different. So, are we warming or cooling? Well, both actually. We are in an intermediate short term warming phase of an intermediate cycle superimposed on a climate that is gradually cooling towards the next ice age.
The 30 year measuring stick that is so often used in portraying global climate is entirely too short to say anything about the bigger climate picture. All it can tell us is if we are warming or cooling across the 30 year measurement period, nothing more. That’s about as useful as knowing that we’ve warmed since last night. Yea, we expect that but on the grander scale of climate history, how do today’s temperature changes compare?
Here’s an example of a graph I pulled from the Internet that shows global warming:
Do you see the measuring stick fallacy? The graph is meaningless to speak to global warming because the measuring stick is only 140 years long.
I extracted the trend line from the graph and overlaid in red on top of a 30 proxy temperature reconstruction by Dr. Ljungqvist  below. [editorial: This is not the recent dendro post at WUWT] There is some divergence between the the proxy record and the adjusted instrument record but that’s not my point of interest. Look at the length of time the Wikipedia graph covers. It’s too short to tell the full story of the current climate cycle we’re in.
When we talk about global warming, it has been been drummed into our heads that the globe is warming at unprecedented rates. Unprecedented implies “like never before.” Well, how do the slope and extent in today’s temperature compare to, say, the Medieval Warm Period? Using a little Photoshop magic, lets move today’s instrument record back a thousand years. What do we see? Proof of global warming a thousand years ago!
My point is global warming is almost always presented using graphs that, yep, show global warming but they’re showing only a small part of a cyclical temperature history that omits the history so that we don’t have a sense of the true context of what is shown. When we lengthen the measuring stick to place it into context, what we see is quite revealing.
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Update: Thanks to astute observation and keen eyes of commenter “thallstd“, this post has been updated to address his concerns. The graphs have been updated. The current warming graph has changed to reflect the Northern Hemisphere warming. The Ljungqvist have been updated with this overlay and the time resolution issue fixed. Our thanks to thallstd. —— James