Monday, November 9, 2015

The Ice Age scare

We are often told by sceptics that "alarmist scientists" have swung from predicting an Ice age in the 1970's to later warnings of AGW. It is, of course, not true. Stoat has tracked the myth over the years - paper here.

Recently an old 1978 TV episode has been doing the rounds. But this is of course not a scientific paper, nor even a regular documentary, even if narrated by Leonard Nimoy. It's from a sensationalist "believe it or not" weekly series.

I saw an amusing recurrence a few weeks ago. Lamb 1974 was cited in support. But like many such citations, it turns out to be not a prediction of imminent ice, but rather talking about the progress of the interglacial in future millennia. And it ends up with this summary:
“The question of whether a lasting increase of glaciation and permanent shift of the climatic belts results from any given one of these episodes must depend critically on the radiation available during the recovery phase of the 200-year and other, short-term fluctuations. An influence which may be expected to tip the balance rather more towards warming – and possibly inconveniently rapid warming – in the next few centuries is the increasing output of carbon dioxide and artificially generated heat by Man (MITCHELL 1972).”
That was the general scientific view. I am writing about this now because I see, via SkS, that the AAAS is noting the 50th anniversary of a rather remarkable report to the then President, Lyndon Johnson, of a panel of his Scientific Advisory Committee. You can't get a more authoritative statement of the consensus scientific view of the time than that. LBJ signed it.

A sub-report headed "Atmospheric Carbon Dioxide" was written by big name scientists of the time - Roger Revelle, Wallace Broecker, Charles Keeling, Harmon Craig, and J Smagorisnky. It lists in detail the "other" consequences, as headings -
  • Melting Antarctic Ice Caps
  • Rise of sea level
  • Warming of Sea Water
  • Increased Acidity of fresh waters
  • Increase in photosynthesis
It does not make its own temperature forecasts, but quotes Moller (1963) saying that a 25% increase in CO2 should increase surface temperature by between 0.6°C and 4°C, depending on water vapor response. They did go on to say that because he couldn't do this in enough detail, it may have over-estimated. But clearly, they aren't predicting an ice age. And that is in 1965. To the President.

And so on since - the dominant scientific thinking has focussed on the greenhouse effect. I experienced this myself, in 1976. I had been transferred by CSIRO from Canberra to Perth. CSIRO then, although federal, tended to work closely with the states where it was located, especially in remote WA. The WA government was pondering a scientific issue.

Most of WA is dry, but the Southwest, then, got reliable winter rainfall from the "Roaring Forties" belt of westerlies, which came north at that time, then leaving for a dry summer. This is ideal for wheat farming, and the "Wheat Belt" was very important. It had substantial infrastructure (eg rail) to move the harvest.

Industry economics had changed with automation, and for those with capital, it was viable to plant crops in marginal (mostly North fringe) areas, even if every second crop failed. So there was pressure to spend money on expanded infrastructure, to make that possible. WA had heard about the coming non-Ice Age, and asked CSIRO.

I was a recently arrived junior scientist, and like most of the ags and mining folk there, knew little about such matters. But I did have some contacts at Atmospheric Physics in Victoria, so I was asked to enquire. I did.

The story, unanimously, what that global warming was on the way, and would have particular effects on WA. The Hadley cell which drove those winds would expand, pushing them further south. Dryer times. Bad idea.

That was our recommendation, and the expansion didn't happen. What did happen was three very hot, dry summers, so our recommendation was looking good. And the rainfall never really recovered.

1 comment:

  1. Okay, I will agree to an extent, but I insist what I've heard about ice ages bouncing and rebounding has to be true.