Climate change causes children to shrink
- 08 Dec 2011, 17:30
- Robin Webster
The climate data analyst Tamino, author of the blog Open Mind,
has posted a clever
deconstruction of a popular climate skeptic argument on his
blog Open Mind.
The blog begins
Suppose, just for argument's sake, that
when your son Johnny turned 2 years old you decided to monitor his
growth. His birthday is Jan. 1, so on the first of every month you
measure his height - you even mount a tape measure permanently on
the wall so you can measure him in the same location each time.
The topic alluded to is temperature rise, and the ways in which
data is misrepresented and manipulated by those who wish to argue
that temperatures are not going up - or '
global warming has stopped'.
We've explained why this argument is statistically and
scientifically flawed here, but
Tamino has a lot more fun with it. In his analogy, parents measure
their son, and in October of his third year, they plot his height
as a function of time:
"?!?!?" says the father. His wife thinks there must be some
mistake...
But you're [you're the dad, by the way]
still worried. So you consult your next-door neighbor, who happens
to work with the
Global Warming Policy Foundation, and show the data to him. He
declares, "Your wife must have some pro-growth political agenda.
The data clearly show that your child is shrinking. You'd better
take him to the doctor immediately."
Your wife staunchly refuses to give in
to your irrationality. But the next day your neighbor knocks on
your door and says, "I can prove that your child is either
shrinking, or at least has stopped growing. Look at this graph of
his height since age 3 years, 2 months. Over the last 8 months your
child has shrunk at a rate of 1.3 cm/yr.
Your wife interrupts, saying "Please
don't be so ridiculous. Obviously the last data point is in error,
this photograph proves it." The neighbor retorts, "Even if I leave
out the last data point, the recent growth rate is not
statistically significant! And the estimated rate is only 1.5
cm/yr, far less than the expected rate of about 7 cm/yr according
to the IPCC." (Intergovernmental Panel on Child Care).
Luckily the mother is a bit more switched on. She realises that
there are some other complications:
She looks over her photo album. That's
when she notices that sometimes when you measured little Johnny's
height, he had his shoes on. Other times he was barefoot.
Fortunately, since she photographed all the measurements she knows
when he was barefoot and when he was shod. She carefully measures
the thickness of the soles of his shoes at 2 cm. This, she says, is
an exogenous factor which has nothing to do with his actual growth,
it just causes random fluctuations in the measurements.
She also enlarges her latest photo (she
has all the digital images) and is able to read the correct height
from the image - those Nikon cameras are awesome!
Take a look at Tamino's blog for the end
of the story . Suffice to say the neighbour isn't impressed
with the end result.
Tamino's commenters have also weighed in with helpful advice for
the parents:
Obv. fake. Has there been any
statistically significant growth in the last four months? Also,
does your measure of statistical significance take into account
that the nature of the noise is red; Johnny grows or shrinks
randomly but from his previous height? In addition, Johnny may
experience cyclic growth and shrinkage.
I just think you're being alarmist.
There's no reason to buy larger clothes for Johnny and I feel you'd
need 10 years more data to say anything about the issue