Opinion A group of Swedish scientists at the University of Gothenburg have published a paper in which they argue that spreading peatlands are inexorably driving planet Earth into its next ice age, and the only thing holding back catastrophe is humanity's hotly debated atmospheric carbon emissions.
"We are probably entering a new ice age right now. However, we're not noticing it due to the effects of carbon dioxide," says Professor of Physical Geography Lars Franzén, from the Department of Earth Sciences at Gothenburg uni.
Franzén and his colleagues have examined various scenarios for the peatlands of Sweden, which are a continually expanding "dynamic landscape element". According to the scientists:
Peatlands grow in height and spread across their surroundings by waterlogging woodlands. They are also one of the biggest terrestrial sinks of atmospheric carbon dioxide. Each year, around 20 grams of carbon are absorbed by every square metre of peatland.
The scientists have calculated that the potential is there for Swedish peatlands to triple in extent, enormously increasing their carbon sink effect. By extrapolating to include the rest of the world's high-latitude temperate areas - the parts of the globe where peatland can expand as it does in Sweden - they project the creation of an extremely powerful carbon sink. They theorise that this is the mechanism which tends to force the Earth back into prolonged ice ages after each relatively brief "interglacial" warm period.
"Carbon sequestration in peatland may be one of the main reasons why ice age conditions have occurred time after time," says Franzén.
With no other factors in play, the time is about right for the present interglacial to end and the next ice age to come on. Indeed, Franzén and his crew think it has barely been staved off by human activity:
The researchers believe that the Little Ice Age of the 16th to 18th centuries may have been halted as a result of human activity. Increased felling of woodlands and growing areas of agricultural land, combined with the early stages of industrialisation, resulted in increased emissions of carbon dioxide which probably slowed down, or even reversed, the cooling trend.
Other scientists have attributed the Little Ice Age to a quiet period in the Sun's activity: others say it was purely a local effect in Europe, though that theory has lately been disproved by research in Antarctica.
In any case, the scientists assess that if it weren't for human activity such as carbon emissions, we could expect a new ice era in short order. They write:
Thus, on a global scale, carbon sequestration in peatlands may have had important climate cooling effects towards the ends of previous interglacials ... It cannot be ruled out that similar effects would be seen in a hypothetical Holocene lacking human presence.
It's probably worth noting that the great physicist Freeman Dyson long ago suggested that only relatively small amounts of new peatland would be enough to sequestrate colossal amounts of CO2 from the air. Other scientists have noted in recent times that brief warming spells like that observed at the end of the 20th century appear to have occurred towards the end of previous interglacial periods - just before the glaciers returned.
If Franzén and his team are right, the big chill is now under way, and is only just being held off by increasing human carbon emissions - perhaps explaining why temperatures have been merely flat for the last 15 years or so, rather than descending.
The Swedish scientists' paper is published in the peer-reviewed journal Mires and Peat, and can be read here in pdf.
Naturally this theory runs counter to the global warming scenario as presented by many other scientists and most of the media. That stance has lately been boosted by wildly unjustifiable assertions that global warming caused Hurricane Sandy. Unfortunately if you believe that isolated events prove theories, you would pretty much have to accept that global warming has stopped: ten to fifteen years of flat temperatures, or even a few very cold winters - both of which have just happened - are a lot more significant than one storm (and they still aren't significant enough to mean anything much in a climate context). ®