## Watt about an analysis of night-time cooling?

There’s a recent post on Watts Up With That (WUWT) called an analysis of night-time cooling. I should start by acknowledging that I don’t really understand what the person who wrote this post was trying to do or what they have actually done. The figures have no labels and I haven’t really understood their explanation of the data. Maybe this is really clever and saying something important and I just don’t get it.

One thing the post says is

What I wanted to look at is how much the temperature went up “today”, and how much does it drop “tonight”. Today’s Rising temp is today’s T-max –today’s T-min. Falling temp is today’s T-max – tomorrows T-min, the drop in temp over night. Difference is Rising – Falling.

I think this is a poor choice of definitions. Why is today’s rising temp today’s Tmax – today’s Tmin while the falling temp is today’s Tmax – tomorrow’s Tmin. Surely the rising temp should be something like today’s Tmax – yesterday’s Tmin or defined by the max and min within some 24 hour period. The way it’s defined here seems to allow the possibility that Tmin could quite often simply be the value at midnight (for example) and would allow the rising temp to be determined by a Tmin that occurred after Tmax.

What the post then seems to do is plot these values to see how the slope has varied with time and hence how the cooling and warming rates have varied with time. This is where I think this indicates someone who maybe can manipulate data, but doesn’t understand the underlying physics.

A rate of energy loss for a blackbody is the flux (W m-2) which is given by
F = σT4.
If I want to know how the flux changes with temperature (which I think is what this post is trying to do) I need to differentiate with respect to T to get
dL = 4σT3dT.
This essentially means that the rate of change of the cooling or warming depends both on the temperature T and on the change in temperature dT. Considering only dT, which I think this post has done, doesn’t really tell you how the cooling or warming rate has changed, unless T has remained (or is) constant.

The post concludes by saying

I would expect a Co2 signal to decrease the cooling slope, which we have, I wouldn’t expect it to decrease the warming slope as well.

What would affect both? A change in Orbit or tilt comes to mind, as does a change in Sea Surface Temps, but would SST’s change both? A change in cloud cover might change both.

Maybe a change in orbit or tilt could produce what you see in the data, but it hasn’t happened. We would know. Maybe Sea Surface Temperatures could do it, but what changed the sea surface temperatures? I’ll grant you that clouds are uncertain.

So as far as I can tell this is a post by someone who has tried to infer changes in cooling and warming rates by plotting something that doesn’t really tell you how the cooling or warming rate has changed. They accept that some of what they see in their analysis might be consistent with warming due to CO2 but are also willing to consider that the Earth’s orbit and tilt might have changed in the last 50 years (no it hasn’t). It’s fine to be skeptical of science but when you really don’t understand the underlying physics properly (as I think is the case here) you should at least be willing to consider the possibility that the reason you think there is a problem with climate models is more because you don’t understand them properly than because they really are wrong.