The retreat of the Alpine glaciers is considered to be dramatic and threatening. Wood and peat findings, however, prove that the Alps were generally greener in recent millennia than today. The results of a scientist’s research are tempering the fears about global warming.
Glaciologist Christian Schlüchter was shaken when he first recognized what his own research actually means: “Up to now we were convinced that the Alps always had great ice fields with magnificent glaciers. Now you can see that this picture was wrong.” Switzerland’s glaciers covered less area for at least half the time during the last 10,000 years than they covered in 2005.
Since the 1990s, Schlüchter, a geology professor at the University of Berne, and his research team have been collecting what can be found as Swiss glaciers retreat – pieces of wood, re-leased by retreating ice, peats that were flushed out by glacial melt water. The findings seem unspectacular at first glance, but they are up to 10,000 years old. One can see the traces left on them by the glaciers. The wood pieces, even whole tree trunks, are often heavily scratched and bent. The remains of peat are compressed into dense balls.
Uncovered Trees and forests
Such organic remains were known before, says Schlüchter. They were also found in the lateral moraines of former glaciers. However in the last 20 years they have been found directly at glacier tongues and glacier gates. The reason for this is probably a temporary advance of glaciers in the 1980s. Many advancing glacier tongues then dipped apparently deep in the sediments in front of them and liberated material that was buried there after earlier retreats.
The wood and peat findings prove that in some areas where today only rubble and bare rock or still ice exist, trees used to grow. There must have been even whole forests in some cases because the findings are so frequent in some places that it could not have been only individual trees. It is laborious scientific work to estimate in which places and to which heights the trees used to grow. Based on the flow and movement patterns of individual glaciers Schlüchter and his team reconstruct the way the wood and the peat must have followed, and estimate their original location. Earlier it was believed that the findings had been transported on the surface of the glacier and had fallen down at the end of the glacier tongue, says Christian Schlüchter. But soon it became clear that they were rather dragged along on the ground or been moved within the ice.
Glaciologist Schlüchter knows almost exactly the point in time when the trees were growing and the turf was created because specialist laboratories have determined the age of many of his objects. This is possible by using carbon isotopes contained in the finds. This enables Pro-fessor Schlüchter to determine when and where the organic material originates from.
The statements relate only to individual glaciers, which release such wood and turf remains, for example to the Tschierva glacier in the Grisons, or to the Unteraar glacier in the canton of Berne. However the pattern of each occurrence and findings allows estimates as to how the glaciers of the Swiss Alps as a whole have grown since the end of the last glacial period. Several times in the last 10,000 years the glaciers pulled back and melted down to pitiful remnants – for centuries or even millennia. Some individual trees at these heights grew even over 600 years old.
According to estimates, the so-called equilibrium line, which forms the border between the zones of accumulation and ablation of a glacier, was up to 300 meters higher than today at certain times. For many years glacier research only explored the advances and the maximum extension of the glaciers, says Schlüchter. Why nobody has been interested in how far they were retreating between the advances is a mystery for him.
What exactly led to the sometimes spectacular and rapid glacier melting in recent millennia cannot be said with certainty. Not only the temperature but also the precipitation, the humid-ity and the prevailing winds affect the behaviour of a glacier. According to Schlüchter’s re-search it is nevertheless plausible that rising temperatures were a key cause. “The temperatures were at maximum between 1 and 1.5 degrees higher than today”, he says.
It is striking that times during with little ice in the Alps coincided with periods of great solar activity. This can be shown by the measurement of nuclides (i.e. certain atoms) in the soil which stand in a relation to solar activity. Schlüchter and his team are currently working to determine the past levels of rainfall and temperatures with the help of substances contained in the wood samples. In this way he wants to learn more about the prevailing climate when the corresponding trees were growing.
2000 years ago, in Roman times, the ice in the Alps had also retreated extensively. This is also confirmed by travel reports of the time. In these reports, glaciers or the “white Alps” are hardly ever mentioned even though the Romans often travelled over the mountain passes. “Presumably it was up to one degree warmer than today”, estimates Schlüchter. Whether there has been such a warm period with very little ice in the Middle Ages, he cannot say with certainty.
The findings of Schlüchter expose not only the image of the glacier-covered Alps as a mirage. Rather more, the observed retreat of glaciers today seems perfectly normal. And the current temperature increase seems to be hardly extraordinary. When asked whether his research re-sults qualify the fuss about climate change, Professor Schlüchter hesitates with an answer: “It is simply much controlled by the sun.” How did other scientists react to his findings? Schlüchter does not want to talk about it. He suggests, however, that there were negative reactions.
Wilfried Haeberli, professor of geography and a glaciologist at the University of Zurich, does not answer directly questions regarding the significance of Schlüchter’s findings. However, he apparently does not believe it’s is of great significance. Haeberli stresses that glaciers have developed differently in the last twenty years than at any time in the past millennia. Accord-ing to him, the organic findings from glaciers in Europe and North America have shown that. Moreover, the solar radiation has been slowly declining for thousands of years because of changes in Earth’s orbit, a development which would be supposed to make glaciers grow. That they are melting instead is indicating an exceptional rise in temperature.
Heinz Wanner, scientist at the Oeschger Centre for Climate Research in Bern, raises the same arguments. Due to the declining sun today one would expect a larger ice cover than a few thousand years ago. Today the glaciers are therefore melting because of manmade climate change. Wanner calls Schlüchter’s method “exciting” but he does not think much of it. He argues that one could not say exactly how far back the glaciers had melted at some point be-cause of the localities of wood and turf. Additionally, “modern glaciology” would necessarily involve calculations of energy and mass balance of glaciers, which is missing in Schlüchter’s method of analysing wood findings. Wanner claims that only on the basis of such calculations could one make “accurate statements” for the past and future of glaciers.
Christian Schlüchter doubts, however, that science can accurately predict the future of gla-ciers. One open question, for example, is why the current melting of glaciers started in 1850, long before man-emitted CO2 could have had an impact on the climate. It also bothers him that predictions about the future evolution of glaciers are simply based on linear continuity of the long decline of the last 150 years into the future: “This is nonsense.” No one can know how the glaciers will develop. There have, for example, been advances in the 1980s, which no one had foreseen and no one can explain.
Mainstream climate researchers, however, predict that the Alpine glaciers will have melted altogether leaving just a few remnants by the end of the 21st century. Schlüchter distances himself from such predictions: “The development of glaciers is complex. I regard such pre-dictions as not very scientific.” Melting could happen more slowly, but also more quickly – no one knows.
Only recently, another unscientific prediction was exposed in the latest report by the Intergovernmental Panel on Climate Change. The report claimed that the glaciers in the Himalayas will have melted almost completely by 2035. It took almost three years, however, until ‘modern glaciology’ discovered and recognised that this blatant miscalculation was only supported by a report of an environmental organization and not by a peer reviewed scientific paper. In comparison, Schlüchter’s method of dating empirical wood and turf remains appears soothingly down-to-earth: limited in its explanatory power, but more precisely for that reason and more confidence-inspiring.
© Die Weltwoche, 14 April 2010 / translation by Philipp Mueller