Thursday 14 January 2021

Clouding the issue. And mud in your eye.

Here's an excellent article by Thayer Watkins explaining that clouds have a huge impact on temperatures and weather, many orders of magnitude greater than that of 'greenhouse gases'.

There is no point me summarising, but here's are the highlights:

The effect of clouds depends upon their type and the time of day. The more interesting and important type is the low thick clouds. At night the reflection [of sunlight] effect is zero so the greenhouse effect and reflection of thermal radiation dominate and the low thick clouds have a warming effect. One can easily see that the reflection of thermal radiation is far more important than the greenhouse effect. The greenhouse effect could at most return 50 percent of the outgoing radiation back to the Earth.

Reflection from the underside of clouds probably returns 90 percent of the radiation. The two effects are not in competition. Clouds could return 90 percent from reflection and half of the unreflected 10 percent. Thus it is easy to see why there is such a difference in temperature between a clear night and a cloudy night in the winter. Since the greenhouse effect from the atmospheric gases would be the same on a clear and a cloudy night one could say that the effect from greenhouse gases is negligible compared to the effect of low thick clouds.


This ties in with my observation that there is no 'missing' or 'blocked' outgoing IR from the Earth's surface. If you extrapolate this to Venus, which is completely blanketed in thick cloud, it goes to explaining why the surface is so hot.
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A lot of stories about melting permafrost have been popping up in the random articles that my mobile 'phone suggests. Here's a typical example:

The etymology of the term “permafrost” comes from the English language, meaning permanent frost. It is a layer that underlies the “active” layer of the soil where life develops and that stays frozen all year round, even in summer. It is made up of different amounts of inorganic material (rocks and sand), mixed with organic compounds and water. Frozen water appears in very variable quantities and is a key element in the consistency and durability of the layer over time. Generally, permafrost has a geological age of more than 15,000 years.
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Other articles say "centuries" or "thousands of years". Do these people not read their own articles to do a sense check? Clearly, all the dead plants in the permafrost must have grown there at a time when it was well above freezing. Fifteen thousand years ago was still in the last Ice Age, so the chances are it all grew (and died) since the last Ice Age ended on July 19, about 11,000 years ago.

Therefore, as warm as it might be nowadays, there have been much warmer times since the last Ice Age ended.

2 comments:

Graeme said...

You could also ask how it is that so many mammoths got caught in the permafrost? They must have been grazing on something, ergo stuff sufficient to feed herds of elephant-sized critters must have been growing there, so the temps must have been warmer

Mark Wadsworth said...

G, ta, that's another good point.