Graphing Out Loud: ups and downs

A while back, we started looking at a poorly thought-out article from the website C3Headlines. C3 is starting to make a name for itself as a goldmine of climate comedy- their claims have recently been addressed at Tamino and SkepticalScience.

We’re going to keep digging into C3‘s claim that carbon dioxide concentrations have been increasing linearly over the 20th century. They seemed to draw this claim by eyeballing the graph of CO2 concentrations and qualitatively describing them as linear, apparently using the inset in their first figure to compare linear, quadratic, and exponential trends. This is a faulty method: it’s an elementary fact of calculus that ANY smooth curve, when viewed appropriately, will appear linear. The point has already been made but it’s worthwhile to keep looking because there are some interesting graphical follies at play; examining them further might help us understand how and why graphs are misunderstood.

Figure 1: From C3Headlines’ article on “The Left/Liberal Bizarro Anti-Science Hyperbole”, which claims that CO2 concentrations are increasing linearly. Click to read it, if you dare…

C3‘s second graph in this article measures the change in atmospheric CO2 by calculating a month-to-month percentage change. It’s not entirely clear why they are using a percent change, rather than the standard practice of expressing rate of change as concentration change per year (like the source of their data uses). Whereas ppm/year is an absolute measure, each datum generated by the percentage-change method depends strongly upon the value of the previous month. As a measure of long-term rate of change, it is a bit questionable.

My primary concern, though, is with their use of monthly data in the first place. In my last article, we noted that, without explanation, C3 confined their focus to January CO2 concentrations. Were they consistent, they’d also look at January rates of change – of course, doing so might lead to unacceptable conclusions.

 Figure 2. Rates of CO2 accumulation have been calculated for the month of January, consistent with earlier investigation of January CO2 concentration. Over the period of observation, rates have increased at a significant (P~0.0005) acceleration of 0.11 ppm/year^2. Monthly rates throughout this article have been calculated by considering the change in CO2 between adjacent months, and assuming that a month is 1/12 of a year. Interpolated values of CO2 were used to avoid annoying data holes early in the record.

Instead, they look at the rate of change for every single month on record. Why do I find that problematic? Well, let’s look at the full record, with monthly resolution:

Graphing Out Loud: curves and lines

I love graphs – my eyes quickly glaze over at a table of numeric data, but a graph, used correctly, can quickly and easily tell the whole story.

‘Used correctly’ is the key phrase – for all their power, graphs are infamously easy to bungle, and when used incorrectly they can misinform – or lie outright.

I’m going to look at an example that touches on a few graphical and statistical concepts near and dear to my heart, as well as carbon geochemistry.

Fig. 1: An image from C3Headlines; the 3 C's are "Climate, Conservative, Consumer". Oh, and the article is titled "The Left/Liberal Bizarro, Anti-Science Hyperbole Continues". It sure would be tragic if they made obvious n00b mistakes after using such language. Click for link!

Coming from an article on the website C3Headlines, this image claims that carbon dioxide concentrations have ‘Linear, Not Exponential Growth’. thereby ‘expos[ing] the lunacy of typical left/liberal/progressive/Democrat anti-science’, The author has reached this conclusion by graphing January CO2 levels* and fitting a linear trendline to them.

Already this is a warning sign – the comparisons the author makes are entirely qualitative, apparently  based up on eyeballing the graph. However, trend lines are created by a statistical process called a linear regression, which comes with a caveat: it will fit a trend line to ANY data given to it, linear or nonlinear. Fortunately, there are also ways of evaluating how good a trend line is.

CO2 Trouble: Ocean Acidification, Dr. Everett, and Congressional Science Standards

A companion article at ArkFab shares my thoughts on peer review in regards to this project and DIY/community/citizen science in general. 

At long last, the much-anticipated booklet, “CO2 Trouble: Ocean Acidification, Dr. Everett, and Congressional Science Standards” is available and approved for human consumption! Download and share HERE (or at Scribd HERE).

In this document, I have bundled, updated, and expanded my series of essays debunking the congressional testimony of Dr. John Everett regarding the environmental chemistry of carbon dioxide.

It has been designed to be a fairly short (less than 30 pages, including images, appendicies, etc.) and accessible read. It has been challenging but fun to write; I have had to learn a lot about GIMP, Python, Scribus, social networking, and of course ocean acidification to get to this point.

It was also very useful for me as an opportunity to go back through my earlier remarks and double-check my work. For example, I later realized that the documentation which Dr. Everett provides for his CO2 data in part two is ambiguous: Although the citation for the rate data is referred to as “Recent Global CO2”, the URL provided links to the longer record as measured at Mauna Loa Observatory. This confusion had led me in the past to make incorrect claims about some of the figures he presents. Ultimately it was inconsequential to my argument, but it was frustrating to have to deal with such ambiguities. On the other hand, this led me into comparing the Mauna Loa record with the global record (Appendix B) which was an interesting exercise.

In researching this project, I also came across new phenomena I wasn’t previously aware of. For example, while I was calculating historical rates of CO2 change, I ran though the 1000-year Law Dome record and saw this:

John Everett, Part IV.8: Deep Time is Deep.

A part of my John Everett series – read more: 0/I – II.0 – II.5 – II.75 –  III.0 – III.3 – IV.0 – IV.4 – IV.8 – V – VII – VIII – Full Report 

We’ve seen that Dr. Everett’s discussion of paleogeochemistry fails to consider both rates of change and the geological record of ocean acidification. There is one last talking point in this section which requires comment:

“From 50-600 million years ago, atmospheric CO2 levels were usually 2-20 times higher than at present. […] This included the age of the dinosaurs, when life was so prolific that we still use its carbon, limestone and chalk.”

Limestone and chalk, like corals and coccoliths, are made out of calcium carbonate. Many deposits of calcium carbonate occurred when there was much more carbon dioxide in the air. The Cretaceous is named after chalk deposits like the White Cliffs of Dover; CO2 levels during the Cretaceous were over 1000 ppm, compared to current levels around 390 ppm. If the ocean deposited calcium carbonate en masse during the high-CO2 Cretaceous, why should we expect it to become hostile to carbonates now?

The chalk cliffs of Dover, massive deposits of calcium carbonate from the high-CO2 Cretaceous. Is this a paradox? Not really. Click for sauce.

The answer lies, again, in time scales.

Over short time scales, like those on which acidification is currently occurring, the saturation state of calcium carbonate is determined by pH, which is controlled by CO2. However, on longer time scales, it’s controlled by another factor. As this article explains:

“Hence, the key, but rather counterintuitive result, is that on long time scales, ocean pH and atmospheric CO2 are decoupled from carbonate mineral saturation state, which is dictated primarily by weathering (in conjunction with the major cation [Ca2+, Mg2+] content of the ocean). Actually, saturation is not entirely decoupled geologically from pH and CO2, as all things being equal, at high CO2 (and a warmer climate), enhanced weathering requires higher carbonate burial and hence higher ocean saturation. Thus, the presence of “carbonate factories” with widespread CaCO3 production and burial is entirely consitent with a high CO2, low pH world. […] Only in significant and geologically “rapid” departures from steady-state carbon cycling will both pH and saturation fall together…” (my emphasis)

In other words, over a long timeline, it’s the calcium that determines calcium carbonate favorability. Over short timelines, it’s the pH- and CO2 emissions are altering the pH on a short timeline.

John Everett, part 4.4: Has this happened before?

A part of my John Everett series – read more: 0/I – II.0 – II.5 – II.75 –  III.0 – III.3 – IV.0 – IV.4 – IV.8 – V – VII – VIII – Full Report 

Last time we looked at Dr. Everett’s testimony, we examined his claim that, because carbon dioxide levels have been higher in the past, increasing levels are not alarming now. His argument is flawed, because although CO2 levels have changed, they usually change only very slowly. Now, they’re changing abruptly. Graphs of Deep Time can be intuitively misleading, because they collapse time scales and it can be hard to compare the rates of change from one image to the next. For example, this next graph shows information that we have gathered from looking at  gasses trapped in Antarctic ice. It’s obvious that the climate changes over Deep Time- but is it obvious from this graph how historical rates of change compare to modern rates?

Paleoclimatic and paleogeochemical data gathered from the Vostok ice core. Temperature (red) and carbon dioxide (blue) go up and down on these time scales - but its the rate that really matters. Click for sauce.

John Everett, part IV.0: Things and Things’ Changing, dva

A part of my John Everett series – read more: 0/I – II.0 – II.5 – II.75 –  III.0 – III.3 – IV.0 – IV.4 – IV.8 – V – VII – VIII – Full Report 

People who minimize or deny the threat of climate change (or ocean acidification, as in part IV of Dr. Everett’s testimony) will often demand that the change be “unprecedented” – that nothing like it has ever happened before in Earth history. (eg, here) The reasoning seems to be that if there have been ecological events like anthropogenic climate change in the past, then current events must not be alarming, since life on earth has each time survived and recovered:

“We know that the Earth has seen these conditions before, and that all the same types of animals and plants of the oceans successfully made it through far more extreme conditions. ” – Everertt (part V)

 

This has always seemed to me like it’s setting the bar a bit low: Do we only become alarmed when faced with the possibility of sterilizing the planet? And considering the amount of violence which earth life has withstood over the ages, it doesn’t seem a very strong statement that human impact is unlikely to wipe it out.

John Everett part III.3 : … and they get the last word again!

A part of my John Everett series – read more: 0/I – II.0 – II.5 – II.75 –  III.0 – III.3 – IV.0 – IV.4 – IV.8 – V – VII – VIII – Full Report 

Often, in order to explain why a particular Weird Belief is correct despite being at odds with available evidence, the belief holder will invoke conspiracy theories. Young Earth Creationists often invoke a conspiracy by god and/or satan to make the earth look much older than it actually is. Intelligent Design Creationists allege an academic conspiracy to suppress ID research. Climate change skuptiks see conspiracies to falsify data the way I see faces in clouds. It’s not necessarily that conspiracies don’t exist- but because the point of a conspiracy is to mask its own existence, we have to be very careful in deciding which conspiracy theories are justified and which aren’t.

Dr. Everett doesn’t invoke a conspiracy in the classical sense of a bunch of men in suits, smoking cigars in a dimly lit room. But he does seem to invoke a distributed, systemic conspiracy, in which science as a system has been corrupted, and its results can not be trusted. He does this in order to cast doubt on studies of the effects of acidification on calcifiers:

John Everett, part III.0: If some is good, then more must be better.

A part of my John Everett series – read more: 0/I – II.0 – II.5 – II.75 –  III.0 – III.3 – IV.0 – IV.4 – IV.8 – V – VII – VIII – Full Report 

Coccoliths: microscopic death stars of the ocean. Via Wikimedia Commons

Have you ever gone camping with someone who doesn’t know how to build a fire? It might go something like this: you get a pile of twigs burning, and immediately your friend starts piling on huge logs. The fire dwindles. “Hey,” your friend says, “This fire sucks. It must need more logs.” If some fuel is good, then more must be better. It’s a terrible way to roast marshmallows. And yet it’s the philosophy that Dr. Everett applies to the effects of increased carbon dioxide on life.

Here’s an example from part I of his testimony: