The media have been awash with considerations of the ramifications from careful, scientific measurements taken in the last few decades showing a steady increase in the concentration of carbondioxide gas in the Earth’s atmosphere. It shows such a clear and steady increase and can be shown to have been rising steadily for a hundred years or so up until around 1970 from which time the increase has accelerated. It now rises by two ppm, parts per million, each year. During the last century the increase has been around one hundred ppm.
Now Carbon dioxide was shown, elegantly, to be a “greenhouse gas” in Victorian times, that is a gas which enables the Earth’s atmosphere to retain heat which would otherwise be lost out into space. More carbon dioxide, more heat is retained. There are other such gases of which water vapour is the most common and so has a proportionately large effect, but methane and several industrially produced gases also have this effect.
Way back in the 1970s, before this science emerged, it was reasonably suggested from records and data we had that the planet was probably going to return to ice age conditions. All the indicators showed that the ice age sequences were cyclical and measurements showed clearly that we’d passed a maximal temperature period. There was, of course, much doubt as to how speedy the descent into such conditions would take. Scaremongers suggested that it could be very sudden and so the nightmare scenario was of waking up one day to an ice storm which would not melt away. We’d all have to move to Africa!
Now we have the opposite offered us – except in the movie”The Day After Tomorrow”, of course – as it is accepted by the mass of the new breed of “climate scientists” that we are embarked on a period of increasing temperatures, with a range of end results suggested as most likely consequences. Simply put, we get global warming which causes sea level rise, increased atmospheric turbulance and more fanciful outcomes like the Brazilian rainforest drying out to desert, mass extinction of marine species, due to pH and temperature changes and strains to terrestrial biodiversity as well – “The Sixth Extinction”, as spelled out early and clearly by archaeologist Richard Leakey.
Of course we need models for this and, of course, it has happened many times before. Climate is always changing and not just seasonally. With increasing sophistication modern archaeologists have built up pictures of layer upon layer of such changes through time and, using radioactive carbon dating and ice-trapped carbon dioxide, can pinpoint dates for these changes.
The last time we saw – our ancestors saw – a gross increase in atmospheric carbon dioxide was when levels increased by around one hundred ppm at the end of the last ice age. It happened suddenly, over a few decades or hundreds of years and at the same time, pretty much, the atmospheric temperature increased. Ice sheets retreated, but slowly, and there were periods of retrenchment when the ice came back cruelly.
We can find clear residues of plant pollens, especially trees, deposited in the deep muds, peat bogs and so on dating back to these times, and can find animal remains, including indications of human activities, from this period. The over-riding fact, though, is the realisation that, as the ice sheets started to melt, twelve to forteen thousand years ago, the sea level was about one hundred and twenty metres below its present height.
This seems fantastic at first, and the implications are shattering. If you’d had a mind to, you could have walked eastwards from Gallway on the west of Ireland all the way to New York and never got your feet wet. It was a continuous land mass. There was no Irish Sea, what we call the North Sea was all open plains, more recently designated “Doggerland” by archaeologists. And then, at the far end of Asia were the Baring plains, a solid land mass leading you into Alaska. OK, a lot of the journey may have been quite cold but preferable to the Icelandic route, I should imagine! This would have been over ice sheets from Scandinavia and then westward, an horrible journey that I doubt anyone could have survived.
As the air and seas warmed, however, the sea levels rose only slowly. It took six thousand years for Doggerland to be inundated and Great Britain to be isolated as an island. Tasmania was similarly cut loose from Australia and the Black Sea [re]united with the Med. The rate of sea level rise was thus around ten metres in a thousand years or one centimetre per annum.
Averaged over the last one hundred years the ongoing rate is about two mm per annum, 200mm in total, although it is suggested that the present rate has increased but that is harder to determine yet. Suffice to say that estimates vary wildly. A maximum of two metres is suggested but 200mm to 500mm seem to be accepted at present as projected sea level rise for the coming one hundred years. There’s enough ice to lead to maybe 65 metres rise eventually but it’s a long process, as was clearly shown the last time the climate warmed so much.
By pooling all the archaeological evidence covering the long period of post glacial sea level rising we can prepare ourselves to deal with whatever might occur over the coming era. Further we can theorise as to how to avoid any of the worst potential outcomes and create a more sustainable environment, maybe even become “climate managers”. This seems predicated on the potential chaos which could be wrought by the worst of the above predictions. So many of our centres of civilisation are close to sea level and two metres increase in sea level will devastate huge areas, from London to Bangladesh, from Beijing to New Orleans with The Seyshelles and others just drowned.
Paulo Petri (or Pavlopetri) is a submerged village just off the coast of Greek Island Laconia, drowned some 5000 years ago. Cantre’r Gwaelod is the long lost land off the Welsh coast, as yet undiscovered but well known in folk legend such as Y Mabinogion, and everyone’s heard of Atlantis – lost city, lost civilisation. There are many more examples and Doggerland is possibly the finest. Vast plains, rich woodlands, roaming herds of now extinct animals (eg Auroch). There must have been a thriving human population.
We have a chance now to reverse the process leading to further drowning of human settlements, but only if we radically readjust our behaviour on a planet-wide basis. Tame carbon combustion, harvest renewable energy, stop wasting energy and learn to fix carbon. Algae are great, they do this but at sea and unharvested the carbon is simply recycled as the algae soon die and rot to release the carbon dioxide once more. Mosses do it and create mires and swamps up in the Steppes and the permafrost – so long as that survives! They are, of course, limited by their speed of metabolism in what is, for them, a very short growing season. Otherwise the sure answer to this set of problems is to embark on a global program to plant FiveTrillion Trees. Give or take a few!
Five Trillion Trees!