2011-10-28 16:00:18Critique of the SkS human fingerprints graphic
John Cook


Got this feedback:

Re: Graph of 10 Indicators ... on Climate Change;
I think the intent of the graphics is to indicate why GHGs cause the Earth to warm up.
I think the downward pointing arrow labeled "MORE HEAT returning to Earth" is misleading and perhaps confusing to anyone trying to understand the earth's radiant heat balance science.
After plowing through the laws of energy transfer through radiation, one would have to believe that the GHG atmosphere is warmer than the Earth. And I don't believe that is true.
A more accurate description would be to turn the arrow around and label it "Less heat loss from the Earth".

But that alone may also be harder to understand. By the way, this is not the only graphic that explains the situation this way.
I believe more work needs to be done here. The amount of energy involved in either depiction is the same, only the transfer is not from the cooler atmosphere to the warmer Earth.
Is it? 

Now the way I see it, there is more heat being lost to space than downward longwave radiation returning back to Earth. But I'm not saying "more heat returning to Earth than heat escaping to space". I'm saying "more heat returning to Earth than there was before the increased greenhouse effect". So as far as I can tell, "more heat returning to Earth" is a reasonable summation of the phenomenon and also the most intuitive way to explain it to a lay audience. Welcome alternative views though.

BTW, here's the graphic:

10 Indicators of a Human Fingerprint on Climate Change

2011-10-31 13:06:03
Tom Curtis


This is just Damorbel's second law argument about heat flow in different guise.


The problem is that some physicists have defined "heat flux" to mean the net flux of thermal energy.  In doing so they have defined heat in a way which contradicts the common understanding of heat, and the definition of heat used by the pioneers of thermodynamics.  As such, it is IMO, a bad redefinition in that it adds endless confusion in trying to communicate science.  Presumably the physicists who advocate for and use this redefinition find some advantage in their normal work.


It may be possible to avoid this confusion by changing "heat" to "Infrared energy" on the graphic.  However, what is gained in lack of ambiguity may be lost to less scientifically literate readers in understandability.  It may be better to include a specific disambiguation between technical and popular uses in the graphics description.  Alternatively, the misunderstanding may be sufficiently rare as to not warrant any specific action.

2011-11-01 18:18:02
Glenn Tamblyn


This all depends on the target audience. For a lay audience (ie, most people) the current graphic is fine. For someone slightly literate in thermodynamics, the point is valid (sort of). And for those really literate in thermodynamics the graphic is fine as is.

Really it is about whether you adjust the wording/graphic to suit the armchair themodynamicists (and Oh My God there are a few of them) or retain it to accomodate the majority. Basic point in a democracy. Majority rules.