Says Camille Parmesan and others, “The biological world is responding rapidly to a changing climate, but attempts to attribute individual impacts to rising greenhouse gases are ill-advised” (from the first issue of Nature: Climate Change).
With everything after the “but” I heartily agree. However, à la Bill Clinton, the truth of the entire sentence depends on what the meaning of “is” is. More of that in a moment. First, let us celebrate that a few members of the Consensus had the guts to say “Slow down!” in print.
Climate change is made of toads and snails and puppy-dogs’ tails. I mean, if there isn’t already, then there soon will be peer-reviewed papers that threaten plagues of toads, surfeits of poisonous snails, and unexpected shortenings of puppy-dog’s tails, all caused by that great maleficence of our time, climate change. “It is the organiser of half that is evil and nearly all that is undetected in this great [world].” It is the Moriarty of sciences.
All know this. Yet Parmesan was brave and said, “It is rarely possible to attribute specific responses of individual wild species to human-induced climate change.” And then came the Holmesian logic:
This is partly because human forcing of the climate is only detectable on large spatial scales, yet organisms experience local climate. Moreover, in any given region, species’ responses to climate change are idiosyncratic, owing to basic differences in their biology. A further complication is that responses to climate are inextricably intertwined with reactions to other human modifications of the environment. Even where climate is a clear driver of change, little insight is gained by asking what proportion of the overall trend is due to greenhouse gases versus solar activity.
The IPCC, however, cognizant of its role of spiritual leader and grants justifier, insists biologists begin “assessing the extent to which observed biological changes are being driven by greenhouse-gas-induced climate change versus natural climate variability.” The debate is over, warming is caused by humans, now show us how all biological changes are due to human activity! (Only bad changes, please; those changes that are good are in spite of climate change, not because of it.)
But Parmesan counters, “the probability of successfully attributing climatic trends to greenhouse gases declines sharply at spatial scales smaller than 106 km2 and at temporal scales shorter than 50 years”, so “it is inappropriate to attribute single events to anthropogenic climate change.”
In other words (my words), the risk of falsely asserting a biological change is due to human activity is large. Charge people to attribute untoward shifts in biological system to humans guarantees they will discover such attributions, whether they are true or not. Even the diciest “attribution” will find its way to print, because the subject will be deemed too important to ignore and because of the eternal reason, “Just in case.”
What makes it worse is that each time an attribution reaches the press, it will taken as more evidence that climate change is here and out to get us. An organism that changes its behavior (in a statistical sense) is only indirect evidence that climate changed. This is because biological changes, rapid or slow, can be caused by things other than climate.
For example, this statement from Parmesan is false, “As biological impacts provide evidence of climate change independently of temperature measurements, they have successfully bolstered ‘detection’, strengthening the scientific consensus that Earth is warming.”
To determine climate change, all we need is a thermometer and a rain gauge (or their equivalents, etc.). We do not need to examine the spoor of Moose or the chemical composition of prairie grass. The evidence of biological changes is not independent of the evidence we have from thermometers (and satellites, etc.). Further, it is silly to use Moose poop or tree rings when you could have used a thermometer.1
This is widely misunderstood. People hear that arctic thermometers register an increase and then hear that ice near that thermometer melted. There is only one piece of evidence here, not two. Ice melting is an effect of the temperature increase. It is not independent evidence of the increase. If we also measure an increase in abundance of some warmth-loving organism by the thermometer, we have not added independent evidence of temperature increase. Ice melting and organisms thriving are what happens when it gets hot out. We do not have three pieces of evidence, we still have just one.2
Thus, all the reports of fuzzy animals suffering, or of bad animals, bugs, and bacteria thriving, are not independent evidence of climate change. And the chance that changes in these beasties can be put down as caused by human activity is small. But there is little hope that Parmesan’s warning will be heeded. The temptations to “discover” attributions are too large and lucrative.
Update To clarify: if we can only say with low probability a given meteorological event is caused (indirectly) by man through climate change, the uncertainty in asserting that changes to an organism that is influenced by the meteorological event is vastly greater. This uncertainty is like multiplying probabilities: the result must be less than either probability.
1If no thermometer exists, then proxies can be used. However, click the “Stats/Climate” link at the top of the page for where this can and has gone wrong.
2It is an entirely different question what caused the temperature increase. An increase is evidence for man-made global warming; but it is also evidence for other theories of climate change (most of which you have not heard of, the press being as busy as it is). Which is the best theory remains unknown.