Any doubts about industrial activity changing the atmosphere ought to be answered by this image (below) of ship tracks off the west coast of the US captured by NASA’s Terra satellite on October 5.

These are different in composition, and larger and more enduring than jet contrails.

Although first recognised as being formed by the exhaust plumes of ships in 1965, when they were detected by early cloud cover monitoring satellites, they are now being seen by some researchers as answering one of the many puzzles about the causes of anthropogenic global warming.

And with a twist. Ship tracks cool the atmosphere by blocking incoming solar radiation … good … and inhibit rainfall … bad, very bad.

The theory advanced by the GISS and other atmospheric researchers is that the northern hemisphere, being populated by more shipping and more sulphate emitting industry, shows a lesser rate of warming than the southern hemisphere because of a differential caused by these larger sized reflective particles, which fall out of the atmosphere more rapidly than carbon dioxide.

In short, something new, and sinister, in north/south divides when it comes to the causes and disproportionate effects of global warming.

Ships burn heavy-grade marine diesel fuels that emit sulphur dioxide and have in studies been seen as adding to the load of industrially released sulphate aerosols that characterise the skies over China, India and other areas of major metal smelting and manufacturing activity.

They also liberate fossilised carbon adding to the thermal opacity of the atmosphere, which retards heat radiation back into space through the greenhouse gas affect, and drives global warming.

Jet contrails differ from ship tracks by forming where water vapour traces in the air are able to condense on fine particles of soot ejected from engines after the combustion of kerosene.

These contrails also deflect incoming solar radiation but contaminate the atmosphere with nitrous oxides, which are potent greenhouse gases, as well as liberating fossilised carbon.

Peter Fray

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