'The null hypothesis says global warming is natural'

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.
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For story: 'The null hypothesis says global warming is natural'3 Comments Post a Comment

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.
by banana republican at 6:33 AM on 21 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.

by JMG3Y at 6:56 AM on 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
by Coby Beck at 11:02 AM on 21 Dec 2006