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Clouds cool…in three simple steps…

Just posted at WUWT

1. Clouds happen in the troposphere (well, apart from some special kinds of clouds)
2. Clouds reflect radiation back to space
3. Radiative (“feedback”) effects are negligible in the troposphere (read raypierre’s book if you don’t believe that)

Hence radiative effects have little or no roles to play wrt clouds, apart from reflection back to space.

Therefore clouds can only cool. Empirically this can be shown in days when the sky is overcast apart from where the sun is. Were clouds to warm the surface, an “oven” effect would soon establish itself. Of course it never happens with any kind of tropospheric cloud: if it did it would violate the finding that radiative effects are negligible in the troposphere.

Therefore clouds can only cool.

8 replies on “Clouds cool…in three simple steps…”

I’ll try to explain myself again. Imagine a region at night, and a contiguous chunk of half of it covered with clouds. Call that “C” e the rest “non-C”.

If the clouds make C warmer, convection will kick into action from non-C e bring back the temperature of C to the temperature of non-C. This is just another way to say that in the troposphere, where the clouds and the surface are, convective effects trump radiative ones.

Therefore the clouds cannot make any area warmer than any other area. I wonder instead if the other way around is true, ie. nights are cloudier because they are warmer.

“Hence radiative effects have little or no roles to play wrt clouds, apart from reflection back to space.”

That statement is 100% incorrect. Clouds can reflect radiation from the sun back into space. However, clouds also act as a blanket to help retain heat below the cloud deck. That is indeed a very important radiative effect. For instance, in higher latitudes like N’rn NY and VT, a cloudy night versus a clear night with no mixing can produce 20-30°F variances in low temperatures. Trust me, I’m a meteorologist. This is freshman level met stuff.

What I like about these “observations” is that even a a non-scientist [as myself] can understand it. Pity about some PhD’s.

and if that doesn’t get thru, maybe pointing out to some of the more amenable water melons that clear nights are always way colder than cloudy ones because the physics are one and the same

Look forward to your explanation – must admit my assumption was that clouds at least partly caused nights to be milder, especially in winter in temperate zones.

David S – the “clouds make nights warmer” mantra is one of those things everybody “knows” about but nobody ever bothered to check. But again, once we assume that the troposphere sees little from radiative effects, the mantra evaporates…if only because every night we would be experiencing winds either coming or going, all ready to compensate differing pressures between cloudy and cloudless areas.

Absolutely correct. An effect that we all know on days with the occasional cloud covering the sun— the temperature falls.

Why the alarmists stated the opposite I have no idea but it shows the standard of their argument.

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