Reprinted from Newsletter 113, dated 2004 October

Global warming: what is a reliable gauge?

Steve Reed

Recent emotive statements about the impact of human activity on the biosphere include the assertion that there is “a third more CO2 in the atmosphere now than in 1860”.

To estimate the CO2 fraction of the atmosphere with any accuracy requires an immense network of sampling stations at all heights — something we do not yet have. We had nothing of the kind, at all, in 1860.

Also, the CO2 fraction is very small, so that any variation in the estimates registers as a large percentage change. (Always beware of “percentage changes” in statistics!)

A map of the world, with red and blue traces showing path and direction. A blue line runs southwest from the UK, past the Carribbean, and down the east coast of South America. It runs east along Antarctica, at which point it branches in two. One branch runs north, up the east coast of Africa. It turns red as it runs along the south coast of India and then southeast along the west coast of Malaysia. Meanwhile, the other branch runs further East along Antarctica, and south of Australia. It then turns north between Australia and New Zealand and into the northern hemisphere. It runs in a large clockwise loop east of China and west of America, and turns red. It then runs west, along the north of Papua New Guinea, and among the Philippines, Indonesia, and past Thailand. It rejoins the other branch. The current then runs southwest and west, past the south tip of Africa, then northwest. It runs close to the blue current running the other way on the east tip of South America, then runs north and northeast back to the UK.

The graphic is a vastly oversimplified diagram of how warm and cold water circulates (so far) in the Earth’s oceans.

The question of the CO2 fraction is thus plagued by statistical spin and a lack of reliable data — and there is no rule-of-thumb which can compensate for this. If the CO2 fraction were to increase significantly — and enhance the greenhouse-effect — more heat would be retained in the weather-system, leading to faster evaporation from the oceans, heavier rain or snow fall, faster replacement of the icecaps, more rapidly moving glaciers etc. The system would be more vigorous, but the temperature would not rise, because all of these effects involve the transfer of latent heat (owing to the unique phase-change behaviour of water). It’s a thermo-static, water-cooled system.

Worldwide precipitation data would tell us something — and enough might even be available now to give us a rough indication — but do the “climate-change” evangelists refer to it? Not a chance! Anecdotally, one hears that the rains are failing in central Asia and north Africa (and that English country gardens are about to become spiny deserts) — and the doomsters are quick to cry “global warming!” — but, in fact, these effects are the very opposite of those to be expected from more heat in the system.

The only reliable gauge of global temperature, as opposed to heat content, is the level of the sea (owing to the heat-expansion of water). And sea level, despite the dire predictions of some, has obstinately refused to rise at a faster rate than it has been rising for 10,000 years. Indeed, over the last ten millennia, the rate of the rise in sea level has progressively slowed, and it appears to be still slowing.

Certainly there is no justification, in the current furore about “emissions” and “climate-change”, for wrecking our economy, curtailing our personal freedoms or subjecting ourselves to pan-continental or global dictatorships — as some suggest we should.

Local conservation of beauty-spots and general care of our surroundings — which I wholeheartedly support — are another matter entirely.