Cliff Mass puts a brown paper bag on your doorstep … sets it on fire … and rings the doorbell

Cliff Mass has joined the ranks of those who want you to believe that California’s wildfire problem isn’t getting worse.


He starts (his blog post here) by saying that the number of fires in California has decreased over the last several decades, and claiming that any increase in area burned has not been significant. His “analysis” amounts to this:


For the same 30 years (1987-2016), wildfire area has grown slightly, with huge transient peaks and troughs (see below). With such variability, I suspect the trend would not be significant. Final statistics for 2017 are not yet available on the CALFIRE website.


You “suspect”? Did you not do the math? Do you not know how?

Question for you, Cliff: if you didn’t do the math, if you only “suspect,” then why do you later say “area burned has not been increasing”?

I did the math. One thing that’s clear is that the variation doesn’t follow the normal distribution, so a robust trend test is in order. I like the non-parametric Theil-Sen estimate, and it gives a p-value of 0.0497. For the sake of Cliff Mass and other folks who may not know what a p-value is, it’s the chance of seeing that much change just from an accident of randomness. So yes, Cliff, the trend is significant.

But wait, there’s more. That’s only the data through 2016. Cliff notes that data for 2017 aren’t yet final, and of course neither are numbers for 2018. But in fact there is data for 2017. CalFire notes that “Statistics may not include wildfires in State Responsibility Area protected by CAL FIRE’s contract counties.” so the 2017 number may not be the total, but it’s safe to take as a lower limit — the area burned is at least that much. As for 2018, CalFire notes that we’ve had 749,770 acres burned through August 5th of this year, so again we have a lower limit, this year’s burn area will be at least that much. It’s likely to be a lot more, since we’re less than half-way through August but the traditional “fire season” is September-October.

Let’s include those lower-limit numbers in the analysis. It will, of course, bias the result against a significant trend in area burned — but hey, Cliff Mass and his claims need all the help they can get.

Result: the p-value is 0.017. That’s significant at the 98.3% confidence level. And remember, that’s allowing a “cheat” which favors Cliff Mass’s proposition, by using only lower bounds for 2017 and 2018 rather than final numbers.

On a side note: as of yesterday, the Mendocino complex alone had consumed 304,402 acres — more than the whole-state totals for 10 of the 32 years Cliff Mass uses. But don’t worry, Cliff Mass says “area burned has not been increasing”.

Climate scientists say that climate change is a big factor in the increase of California wildfire. The leaders of CalFire say that climate change is a big factor in the increase of California wildfire. The veteran firefighters on the ground, the ones risking their lives, say that climate change is a big factor in the increase of California wildfire. Cliff Mass — the guy who “suspects” there’s no significant trend — tells me “area burned has not been increasing”.

Do drop on by, Cliff. Be sure to mention the number of fires and that paper by Keeley and Syphard; I’d love to discuss them. But first things first: we want to know whether you still think that area burned has not been increasing.


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13 responses to “Cliff Mass puts a brown paper bag on your doorstep … sets it on fire … and rings the doorbell

  1. cliff mass is a total tool

  2. Let’s be kind to Cliff Mass: he recognises he is not competent to do the maths so all we get is his wishful thinking rather than fake maths. On that basis, he is less offensive than Heller/Goddard.

  3. It must be very tough for any college professor who teaches aspects of global warming. There is an optimism bias that can twist communication, After all students are young and innocent. And because most students have heavy bank loans, they want a good future, and nobody WANTS to tell them the harsh realities. Me neither. But all professionals – and even citizens and neighbors- have a Duty to Warn. It didn’t always work that way.. we used to say “to each his own” or ‘let go and let live”. We ignored so much . But now we realize that our space ship is a globe structure. And we have to protect it all – we have a duty to warn anyone who is marching into a future that we may not be able to follow. University faculty has an ethical duty to warn students of the dangers ahead. Just as we would warn our own children.

    Denial, disavowal, discounting, delay, distraction, etc – The biases and excuses may be unconscious, but it is still very important that we stay alert, open and ready to warn others, and ready to act to protect our globe, we all must tend to life support systems. First task – get good information.

    Thanks Tamino, for all that you do

  4. Unsurprisingly, Mass has rejected your criticism, stating “Taminos analysis is very weak, including an inappropriate statistical approach that did not consider the variability of the time series. Also he likes to insult and call folks names”.

    Yep, the statistician supposedly used an inappropriate statistical approach. Much better to use the Mark IV eyeball!

    People who have seen his Twitter account know what to make of his complaint about Tamino insulting other people…

    • What the everlasting fuck?!? Thiel-Sen is nonparametric, and hence quite robust. I suppose that will work for the innumerate dumbasses at WTFUWT, but it just makes him look dumber than owlshit to anyone who knows anything about statistics!

      • Yeah, but that approach gives an answer Cliff Mass doesn’t like, so it must be “weak” and “inappropriate”. His criticism will work for most of his audience, and that sadly does not just include the WUWT fanatics. It has to be said he got quite a bit of pushback on his blog; however, he left most of the subsequent attacks to Jim Steele, and only deigned it ‘worthy’ to respond to the one person who referred to Tamino.

  5. There is a piece by Zeke Hausfather at CarbonBrief that looks at wildfires both across the US and globally.
    It rather confirms my opinion that the AGW-wildfire issue is very complex and of course complexity is not our friend when faced by denialist gobshite.

  6. “The leaders of CalFire say that climate change is a big factor in the increase of California wildfire. The veteran firefighters on the ground, the ones risking their lives, say that climate change is a big factor in the increase of California wildfire.”

    These are climate scientists?

    • No, Dennisa, these are the people who see first hand and deal with the effects of climate change for a living year after year. Get an effing clue.

  7. I don’t do significance estimates by eye (does anyone, except Cliff in this instance?) But there’s another aspect to ‘grown slightly’, which is the trend estimate. And I’ll take a flier that OLS would produce something reasonably close on the order of 25%, which I would not personally call ‘slight.’

    [response: OLS estimates the trend value as of 2016 (the last year of the data used by Cliff Mass) is 2.26 times the trend value in 1987 (the first year of the data used by Cliff Mass). Theil-Sen suggests 2.87 times as high. Maybe a better idea is to log-transform the area burned (so that then the noise becomes roughly Gaussian), in which case the ending trend value is 2.56 times the initial value.]

    • …Which would clearly be a good illustration of the virtues of doing the math…

      Surprised it’s that great an increase, but very, very definitely not anything anyone could reasonably call ‘slight.’

  8. rhymeswithgoalie

    So, if instead of having a lot of little wildfires we have a few widespread conflagrations, that means we have *fewer wildfires*. Fewer is *better*.

    Glad I could clear that up.

  9. What can we do to tempt you to discuss the Keeley paper? :-)