[pdonis]

The key document given in this article is the Robinson report of 1968. Looking at the excerpts given, this report made a prediction for CO2 level rise that can be tested: it predicted about 400 ppm by the year 2000 (from a value of about 320 in 1968). This was an overestimate: the actual level in 2000 (using the Mauna Loa measurements, which seem to be the key reference relied on in the report) was about 375.

This enables us to test a second prediction made by the report: the temperature increase caused by C02 level rise. The report gives a very wide range for this: 1.1 to 7 degrees Fahrenheit, depending on the humidity change. The usual baseline assumption about humidity is that relative humidity will remain constant, and the report notes that that assumption leads to the larger prediction--7 degrees F--for temperature rise by the year 2000. That is about 4 degrees Celsius.

Even if we correct for the actual CO2 level rise vs. predicted--about a 20% increase vs. 25% predicted--that still gives about a 3 degree Celsius predicted temperature rise by the year 2000, as compared to 1968. The actual rise was about 0.5 degrees Celsius.

The report does say that the estimating method it uses likely overestimates temperature rise; but it does not, as far as I can see, consider the possibility that it might overestimate temperature rise by so much. So as far as I can see, the oil industry's decision to treat this information as much more uncertain than its authors claimed was reasonable.

[btilly]

It seems that you're cherry-picking items in a deliberately deceptive way.

The CO2 level rise clearly must have been an estimate based on, "If we project current usage trends forward, here is how much fossil fuel gets burned. Here is what that does to CO2." That usage model would have been thrown off by the first OPEC price shock of the 1970s, which induced a lot of conservation efforts and resulted in significantly less emissions.

I'd be shocked if they had the basic "fossil fuel to CO2" relationship wrong. There is no way that they could have predicted the economic shocks that slowed consumption.

Now let's talk about their environmental model. They gave a range from about 1 F to 7 F. The actual rise is about 1 F. I'd call that a success! (And why did you switch between F and C? Was it just to make the actual rise seem smaller.)

Moving on, you argue for which model should apply, then argue that they got it wrong. Your behavior already doesn't make me trust you, but let's assume you are right. What mistake likely explains it?

My best guess is that they simply did a long-term steady state model for what temperature things would stabilize at. That is a relatively simple calculation, and would have been fairly accurate if the atmosphere were mostly separate from the ocean. However we've learned since that heat exchanges with the oceans are much larger than we knew. (I remember circa 1990 learning in fluid mechanics that there was a big question THEN about how much global warming would slow down.) So the long-term temperature picture in the model is relatively accurate, but we get there more slowly than predicted.

This is the kind of detail of our system that we COULD NOT have predicted with 1960s science. They knew that they were overestimated and knew that they would be right in the end, but had no way to know how long it would take to get there.

[andrewla]

From this reply it is clear that the GP read, at least, the portions of the Robinson paper excerpted in the article. Unfortunately, the particular critiques that you have made indicate that you have not read them.

For example, the switch from F to C is because the underlying paper is written using F, as that was the style of the time; but the GP presented in C as that is the current preferred unit.

Robinson admits that the model is crude, as he was using an older model of Moller (from 1964), and that he expected that more sophisticated models would improve forecast accuracy. Nonetheless, the numbers presented in the paper are reflected accurately in the GP's post, including uncertainty ranges, and the comparisons seen valid at a glance.

In this case, the GP is not cherry-picking, at least not in the usual sense, as they are using the "cherry-picked" portions of the paper to produce verifiable predictions.

Admitting that early models of climate change make some inaccurate predictions does not necessarily undermine the correctness of the directionality, especially as newer research has come to light, but it does present a less sinister explanation as to why the results were not taken as seriously modern observers feel they should have been.

[btilly]

The article had failed to load for me, so I was basing what I said on what was excerpted and what I read elsewhere.

That said, now that I find it, it is easy to dig in for details. Moller's model from 1964 can be read in http://onlinelibrary.wiley.com/doi/10.1029/JZ068i013p03877/a... and says up front that a 1% increase in cloudiness is sufficient to counteract the warming effects of 30 ppm in CO2. I'm sure it leaves out ocean heat sink effects. According to https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapt... it seems that cloudiness HAS increased several percent. Which means that the top end of the projection (which the GP thinks it the right model) would have been the wrong projection to use.

From whence did the GP draw the incorrect claim that humidity has remained the same? Shouldn't he have done the same Google searches that I just did and come to the same conclusion??

[pdonis]

> I'd be shocked if they had the basic "fossil fuel to CO2" relationship wrong.

I would too, and I wasn't claiming that they did. The CO2 rise prediction in the Robinson 1968 paper was actually reasonable; but the fact remains that to compare their temperature prediction with what actually happened, we have to first adjust it based on what actually happened with CO2 compared to what they predicted.

> They gave a range from about 1 F to 7 F. The actual rise is about 1 F. I'd call that a success!

They gave a range based on different assumptions about how humidity would change. Their prediction of 1 F was based on no change in absolute humidity--i.e., the same absolute water vapor content in the air despite a rise in temperature. That corresponds to a significant reduction in relative humidity, which clearly did not occur. In fact, the actual data on relative humidity change suggests, if anything, a slight increase in RH from 1968 to 2000. The Robinson 1968 paper prediction corresponding to that assumption is 7 F, as I said. So their prediction was not a success.

> why did you switch between F and C?

Current temperature projections, such as the IPCC reports, routinely use C, so that's what most recent figures are quoted in, including the data on temperature rise over the late 20th century. Feel free to convert back to F if you're more comfortable with that.

> the top end of the projection (which the GP thinks it the right model)

I didn't say I personally thought it was the "right" model; I said it's the model that appears to be most consistent with the position taken by the Robinson 1968 paper. Remember that the topic of discussion here is not how the climate actually changed from 1968 to 2000; the topic is whether the oil companies, in 1968, were remiss in not accepting the predictions made in the Robinson 1968 paper and acting accordingly--since that's the argument the article is making.

> From whence did the GP draw the incorrect claim that humidity has remained the same?

I said the usual assumption in making climate predictions is that relative humidity remains constant. (The data seems to bear out this assumption, as I noted above; but I don't see any data on RH in the excerpts of the Robinson 1968 paper.) Relative humidity is not the same as "cloudiness", so I don't see how your findings say anything about how, if at all, RH actually changed from 1968 to 2000.

Also, the Robinson 1968 paper, as far as I can tell from the excerpts, does not mention "cloudiness". This might simply be because that paper misunderstood Moller's model. But in any case, that would mean the Robinson 1968 paper did not take into account an additional factor that would clearly reduce the predicted temperature rise based on a given CO2 rise. So if you are correct that the actual increase in cloudiness was significant in reducing the temperature rise over the last half century, you are agreeing with me that the Robinson 1968 paper was overpredicting temperature rise, and therefore the oil companies, in 1968, were not remiss in treating that paper as they did.