I must be perverse. I always seem to end up thinking what nobody – or hardly anybody – else thinks.
For example, when a fireball exploded over Chelyabinsk on 15 February 2013, on the same day that asteroid 2012 DA14 made a close approach to the Earth, I was puzzled that NASA declared on the same day that the two bodies were not companions. They’d come from completely different directions. But I wondered if they might have been. And because I had a computer orbital simulation model (which I’d written myself), I spent the next few years exploring ways in which the Chelyabinsk rock might have been a companion of DA14. And I ended up concluding that it had been following 25 million km behind DA14, as part of an extended rock cloud of the kind that forms when asteroids disintegrate like Schumacher-Levy 9. It had been following DA14 for a long time, slowly drifting away from it. And because the orbit of DA14 crosses the Earth’s orbit, on 15 February 2009 the Chelyabinsk rock passed very close to the Earth, and was thrown into a new Earth-crossing orbit – one which eventually resulted in it arriving over Chelyabinsk on 15 February 2013, from a different direction than DA14. It had been a companion of DA14 for countless ages, just not for the last 4 years of its life. And what that meant was that there was a large cloud of rocks which intersected the orbit of the Earth on 15 February every year, and we should expect lots more of them in coming years.
But nobody else in the astronomical community thinks any such thing. And I’m not part of the astronomical community anyway.
This year I’ve been building a new computer simulation model, this time of heat flows from the Earth to and from outer space. It’s a very simple model of conductive heat flow from the hot centre of the Earth to one point on the surface at some latitude. It’s a bit more complex at the surface, with radiative heat transfers from the Sun to the Earth’s surface, and from the Earth’s surface into the atmosphere.
And it works quite well, producing fairly plausible surface temperatures at different latitudes, cold at the poles, warmer at the equator.
No doubt climate scientists have similar and far more elaborate models, although as far as I can see they confine their attention almost entirely to the atmosphere above the surface, on the grounds that the 60 milliWatts/m² heat flow from the Earth is so small, by comparison with the 340 Watts/m² heat gain from the Sun, as to be negligible.
And one of the big puzzles of the Earth’s climate is: How did the ice melt at the end of the last ice age some 12,000 years ago? For it’s very difficult to melt ice. A lot of heat needs to be added to turn ice to water. And although the Sun has the power to do this, brilliant white sheets of snow-covered ice reflect 80-90% of the Sun’s radiation back into space. So when the Earth gets covered in ice, it gets much colder. And I can see this happening in my own little model: add a highly reflective block of ice to the surface, and the air temperatures in the atmosphere above it drop considerably (up to 70º C in my model). In my model, these highly reflective ice sheets simply never melt.
Of course, if the ice sheets get covered in dust, they cease to be quite so reflective, and more solar radiation is absorbed by them, and they’ll start melting. And this is what happens in my model. And recently climatologist Judith Curry had an article exploring the dust hypothesis. But if the planet gets covered in ice, where does the dust come from? And even if the ice does get covered in dust, and starts to melt, won’t the surface meltwater carry away most of the dust that has accumulated on the surface of the ice? And if there is still some dust remaining, won’t it rapidly get covered with new depositions of brilliant white snow? There are good reasons to suppose that the ice sheets continue to remain covered in fresh highly-reflective snow.
And it may be considerations such as these that drove the climate scientists to look for some other cause for the melting of the ice sheets. And their new suspect was: carbon dioxide. Carbon dioxide absorbs long wave radiation from the warm surface of the Earth. So the addition of carbon dioxide to the atmosphere in sufficient quantities would cause the atmosphere to warm. The warming would be small (maybe only 2 – 3º C), but it might be enough to melt some ice, and thereby add water vapour to the dry atmosphere. And water vapour is also a good absorber of long wave radiation. So the atmosphere would absorb more heat radiated by the warm surface planet surface. And so a feedback loop would be set up which would result in a rapid warming of the atmosphere, and the melting of the ice beneath it.
My simple model isn’t able to reproduce this warming, because there’s no carbon dioxide or water vapour in my model (yet). All I can do is replicate the initial warming, by increasing the absorptivity of air.
But there are doubts about this proposed carbon-dioxide warming process. At the end of the last ice age, the Vostok and EPICA ice cores showed that the concentration of carbon dioxide in the atmosphere did rise. But they rose after the ice had melted. And they probably rose because the newly warmed oceans released carbon dioxide stored in them.
But it seems that the carbon dioxide hypothesis had gained many adherents within the climate science community. How else could the ice have ended at the end of the ice age? There was no other plausible explanation. If the ice cores showed that carbon dioxide had increased after the melt, it was probably because the gas bubbles trapped in the ice had risen inside it, giving a false date.
But I’ve been exploring another hypothesis for the melting of the ice. It’s one that the climate scientists don’t appear to have considered. And it is that the ice was melted not from above, by carbon dioxide in the atmosphere, or dust on the ice sheets, or variations in the heat gained from the Sun, but from below by the warming of the rock beneath the ice sheets. And this warming happened because the ice acted as a layer of insulation on the surface of the Earth, slowing the tiny flow of heat from within it, and causing the subglacial rock temperatures to slowly rise over many tens of thousands of years.
I had some difficulties getting this hypothesis working. But when I exchanged the ice with snow, which is a much better insulator, it worked very well. At latitude 45ª N, 200 m of snow would melt in about 50,000 years, with the surface rocks beneath the snow rising 30º C over that period. And this was without any variation in solar radiation or air absorptivity or dust deposition: the snow was entirely melted from below.
There are all sorts of possible variations on this model, but one principal advantage it would seem to have is that if ice ages start once the temperature of surface rock has fallen below some critical level, then there would be a delay of a few thousand years after the snow had melted while the rock cooled, and long ice ages would alternate with short interglacial periods with almost metronomic regularity. And according to the ice core evidence, the last few ice ages have all lasted 100,000 years.
And this surface rock heating hypothesis would also explain why ice ages are getting longer. For as the interior of the Earth slowly cools, the surface rocks will heat up more slowly, and take longer to melt the same volume of snow. And in the remote past, hundreds of millions of years ago, periods of glaciation would have been relatively short, and warm interglacial periods relatively long. And both of these behaviours seem to be what the available records show.
But, as with DA14 and the astronomical community, nobody in the climate science community seems to be exploring this hypothesis. Instead we are in the grip of what seems to be an ever-mounting hysteria about carbon dioxide.