Climate Sensitivity: the Three Babies Test

Source: http://wallpaperfirm.blogspot.com/2011/02/three-sleeping-babies.html

Regular readers will know that this blog has been focusing on climate sensitivity (CS), since it stands at  the core of the climate change debate. It is the point on which climate sceptics fail, since they have no substantial evidence to back their claim that the climate sensitivity is low, whereas there are a number of separate lines of inquiry that back the climate scientists' figure for CS.

The sceptics do have a hypothesis, and it is refutable.

However, up to now I have failed to engage the attention of the masses.

I suspect that it is because Climate Sensitivity sounds technical.

Which, of course, it is.

So now, I offer the Three Babies Test, to make the topic more approachable:

• Imagine three babies in a room.
• Imagine you poke one until it cries.
• Will that baby be the only one to cry, or will all three babies soon be crying?

Climate science predicts that all three babies will end up crying.
Climate sceptics claim that only one baby will cry.

In terms of climate science, here is the first baby: if we double the amount of CO2 in the air, the temperature of the planet will eventually increase by 1*C.
This is simple textbook physics, and cannot be denied without denying the laws of physics. It is accepted by the handful of AGW sceptics who are also climate scientists.

The science shows that this initial increase of 1*C will cause further increases (the other 2 babies start crying) due to changes in albedo (=reflectivity),  water vapour and clouds, (see note below)  and the scientific evidence points to a value of +3*(+ or - 1.5)*C for these further increases.  That is what is meant by Climate Sensitivity.

Sceptics are at pains to deny these changes, but they are unable to provide solid evidence for their belief that they will not take place, and do not even try to address the mass of evidence that points to a CS of 2*C and more.

So there you have it.
That's climate sensitivity for you.

I hope this helps.

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Expansion on this theme: Refuting the climate contrarians' hypothesis


[Note] Worryingly, there are further expected changes, but these are left out of the calculations because they are difficult to quantify.

• from methane release from permafrost &c, 
• release of carbon dioxide from warming soils.
• Decreased uptake of CO2 by warmer oceans
• Increases in wildfires
• Changes in lapse rate and vegetation will also take place

[this page was updated 11 April 2012]