‘The null hypothesis says warming is natural’—An inappropriate test, and one that would fail anyway 4

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Natural variability is the null hypothesis; there must be compelling evidence of an anthropogenic CO2 warming effect before we take it seriously.

Answer: The null hypothesis is a statistical test, and might be a reasonable approach if we were looking only for statistical correlation between increasing CO2 and increasing temperature. But we're not -- there are known mechanisms involved whose effects can be predicted and measured. These effects are the result of simple laws of physics, even if their interactions are quite complex.

But putting aside inappropriate application of the null hypothesis, we are indeed well outside the realm of natural global variability, as seen over the last 2,000 years and even over the last 12,000 years. We can go back several hundreds of thousands of years and we still see that the temperature swings of the glacial/interglacial cycles were an order of magnitude slower than the warming rate we are now experiencing.

In fact, outside of catastrophic geological events like the Paleocene Eocene Thermal Maximum there are no known precedents for warming this fast on a global scale. I'd say the case for "it's all natural" is the one that needs explaining.

Oh, and by the way, we do in fact have compelling evidence.

Former musician, turned tree planter, turned software engineer. Same old story…

I have been blogging about climate change since 2006 at A Few Things Ill Considered.

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  1. banana republican Posted 11:33 pm
    20 Dec 2006

    isn't the null hypothesis...That global warming isn't occuring?
    And what does it matter what the causes? If the earth was cooling, people in areas that get a lot of snow would be terrified, regardless of the causes. They'd want something done.
    What we're up against isn't the deniers that deny on principle, it's the deniers that deny, because, frankly, they don't think it matters if the earth warms, or that it'll be a good thing.

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  2. JMG3Y Posted 11:56 pm
    20 Dec 2006

    Now wait one minute hereDoes the distinction of human-induced vs. "natural" really matter? Does it change the consequences if the change is human-induced or due to natural variation? No, not in the least.
    Implicit in this distinction is the idea that "nature", when perturbed, will return to a human species friendly optimum, that this intersection of human life enabling conditions exists precisely for humans. That if through our actions we push one or more metastable parameters in this dynamic system we call earth over a threshold to a different human life unfriendly optimum, Gaia or some higher being will come running in to save us from the consequences of our behavior.
    Or, alternatively, that anything we humans do we can undo simply because we did it. This either represents supreme overconfidence in our intelligence to both recognize signals and develop solutions or a failure to understand the implications of lagged positive feedbacks in dynamic systems on timeframes.
    Finally, that nature is so big we puny humans really can't alter its course. Oh, really?
    Nope, all these are flawed ideas based on misperceptions, misunderstandings or outright ignorance.
    </soapbox; start caffeine inflow>

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  3. Coby Beck's avatar

    Coby Beck Posted 4:02 am
    21 Dec 2006

    GW is ongingYour first argument seems to rely on a notion that GW has been triggered so now does it matter why.  GW is onging and will stop once the GHG levels in the atmosphere have been stabilized for a couple of decades.
    That is an oversimplification but it is a reasonable first order approximation of the situation.  This is not an implicit assumption it is a highly reasonable expectation based on well established theories of climate and very sophisticated modeling.
    We may of course be wrong, but any doubts that there are about the models only mean we are incurring greater risks.
    GW is very clearly caused primarily by human actions, it is trivially obvious that is we thing GW is a bad thing we should stop causing it.

    Invent a clever saying, and your name will live forever!



    -- Anonymous

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  4. trickytank Posted 10:49 pm
    14 Jun 2007

    Null hypothesis is subjective.Nice post Beck.
    The null hypothesis is not an objective test. It's construction is subjective. We will get a consistent answer from the same data.
    There are also some who believe the null hypothesis is not a good test in general and underestimates both the benefits and consequences of medicines we use.

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Series Intro
'There is no evidence' -- Yes, there is 59
'Mauna Loa is a volcano' -- CO2 rise is measured on top of a volcano! 8
'Warming is due to the Urban Heat Island effect' -- No, it isn't 25
'One hundred years is not enough'--Yes it is 18
'The scientists aren't even sure' -- No scientist ever is 33
'One record year is not global warming'--Luckily, there are plenty more years to consider 19
'Glaciers have always grown and receded'--A few glaciers melting does not mean global warming 14
'The temperature record is unreliable'--But temperature trends are clear and widely corroborated 8
'It's cold today in Wagga Wagga'--Weather and climate are different 2
'The satellites show cooling'--No, they don't 15
'What about mid-century cooling?'--No one said CO2 is the only climate influence 11
'Antarctic ice is growing'--Well, probably not, but even if it were, we are not off the hook 8
'Global warming stopped in 1998'--Only if you flagrantly cherry pick 170
'But the glaciers are not melting'--Except ... they are! 3
'Antarctic sea ice is increasing'--Yes, but ... 14
'Sea level in the Arctic is falling'--Sea level is a surprisingly complicated thing 11
'Climate sensitivity is not very high'--Thermal inertia of the oceans means the jury is still out 2
'Some sites show cooling'--But you can't draw global conclusions from individual sites 0
'Global warming is a hoax'--I wish James Inhofe were just a hoax ... 12
'There is no consensus'--If this is not consensus, what would consensus look like? 109
'Position statements hide debate'--True enough, but that is not the whole picture 5
'Consensus is collusion'--Is climate science maturing, or should we reach for our tinfoil hats? 8
'Peiser refuted Oreskes'--In a poor piece of work that has been retracted by its author 4
'Models don't account for clouds'--Clouds are complex and uncertain, but unlikely to stop warming 6
'Climate models are unproven'--Actually, GCM's have many confirmed successes under their belts 13
'Aerosols should mean more warming in the south'--More North. Hemisphere warming is well-understood 1
'We can't even predict the weather next week'--But weather is not climate 11
'Chaotic systems are not predictable'--Sure, but who says climate is chaotic? 13
Understanding what is happening right under our noses does not require paleoclimate perfection 1
'They predicted global cooling in the 70s'--But that didn't even remotely resemble today's consensus 29
'Hansen has been wrong before'--Maybe, but not about the climate! 13
'It was warmer during the Holocene Climatic Optimum'--This period was not global and not like today 4
'The Medieval Warm Period was just as warm as today'--Repeating this point does not make it true 216
'Greenland used to be green'--Don't judge a book by its cover, much less a land by its name 23
Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago 5
'The hockey stick is broken'--Well, no ... but who's playing hockey anyway? 6
'Vineland was full of grapes'--Or was it an early advertising campaign? 4
'Global warming is part of a natural cycle'--This idea is one short step above appealing to magic 39
'Mars and Pluto are warming too'--No they aren't -- and what if they were? 24
'Volcanoes emit more CO2 than humans'--Not even close ... 31
'The null hypothesis says warming is natural'--An inappropriate test, and one that would fail anyway 4
'Climate is always changing'--That doesn't mean it isn't different today 5
'Natural emissions dwarf human emissions'--But emissions are only one side of the equation 5
'The CO2 rise is natural'--No skeptical argument has been more definitively disproven 12
'We are just recovering from the LIA'--Why should we expect this to happen? 4
'Climate scientists dodge the subject of water vapor'--No, they really don't 4
Water vapor is indeed a powerful greenhouse gas, but there is plenty of room for CO2 to play a role 29
There is no proof in science, but there are mountains of evidence 78
'CO2 doesn't lead, it lags'--Turns out CO2 rise is both a cause and an effect of warming 43
'Geological history does not support CO2's importance'--Just not true 0
'Historically, CO2 never caused temperature change'--Not so 19
'It's the sun, stupid'--Very bright, yes, but not getting brighter 18
The problem is not how high the temperature may go, but how fast it is changing 14
'Kyoto is a big effort for almost nothing'--Kyoto is only in its first phase 16
China and India have joined Kyoto, they just have different obligations, as is morally appropriate 3
'Climate change mitigation would lead to disaster'--Not really, but this may be lesser of two evils 6
Only if you ignore fossil fuel emissions 10
In 2008, did temperatures drop as much as they rose over the whole 20th century? 71
Is the IPCC so wrong their theories contradict a basic laws of physics? 23
Is the American Physical Society a crack in the climate change consensus? 3
Summer ice in the Arctic has recovered--Was the Arctic ice retreat a climate anomaly? 7
'Global warming comes from within'--Is heat at the Earth's core the real cause of global warming? 10
Was there another breathless announcement of another phony record, and another quiet retraction? 1
Hansen wants the skeptics thrown in jail--Did James Hansen really want to try the climate skeptics? 6
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