THE COLLE GNIFETTI

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1. Conventional wisdom about the abrupt glacial melt in the Alps at the end the Little Ice Age   [LINK] holds that it was caused by black carbon soot deposition on the glaciers. “At the end of the Little Ice Age in the European Alps glaciers began to retreat abruptly in the mid-19th century, but reconstructions of temperature and precipitation indicate that glaciers should have instead advanced into the 20th century. We observe that industrial black carbon in snow began to increase markedly in the mid-19th century and show with simulations that the associated increases in absorbed sunlight by black carbon in snow and snowmelt were of sufficient magnitude to cause this scale of glacier retreat. This hypothesis offers a physically based explanation for the glacier retreat that maintains consistency with the temperature and precipitation reconstructions.” [Painter, Thomas H., et al. “End of the Little Ice Age in the Alps forced by industrial black carbon.” Proceedings of the national academy of sciences (2013): 201302570.]  [FULL TEXT PDF DOWNLOAD]
2. A more recent paper has pointed out a temporal anomaly in the reasoning in the (Painter etal 2013) paper. It says that “Starting around 1860, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions marking the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. The basis for this hypothesis was model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps. Here we present sub-annually resolved concentration records of refractory black carbon (rBC; using soot photometry) as well as distinctive tracers for mineral dust, biomass burning and industrial pollution from the Colle Gnifetti ice core in the Alps from 1741 to 2015. These records allow precise assessment of a potential relation between the timing of observed acceleration of glacier melt in the mid-19th century with an increase of rBC deposition on the glacier caused by the industrialization of Western Europe. Our study reveals that in 1875, the time when rBC ice-core concentrations started to significantly increase, the majority of Alpine glaciers had already experienced more than 80% of their total 19th century length reduction, casting doubt on a leading role for soot in terminating of the Little Ice Age. Attribution of glacial retreat requires expansion of the spatial network and sampling density of high alpine ice cores to balance potential biasing effects arising from transport, deposition, and snow conservation in individual ice-core records.  [ Sigl, M., Abram, N. J., Gabrieli, J., Jenk, T. M., Osmont, D., and Schwikowski, M.: 19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers, The Cryosphere, 12, 3311-3331, https://doi.org/10.5194/tc-12-3311-2018, 2018.]  [FULL TEXT PDF DOWNLOAD]
3. In other words, by the time the (Painter etal 2013) causation is observed most of the glacial melt had already occurred. These data therefore do not serve as evidence that the end of the Little Ice Age was initiated by the Industrial Economy by way of black carbon soot emissions and later exacerbated by CO2  emissions from the combustion of fossil fuels. This temporal anomaly weakens the AGW argument that the Little Ice Age was ended by the Industrial Revolution and not by nature and that the current warming trend is therefore human caused by way of fossil fuel emissions from the Industrial Economy. The results suggest that if AGW science had studied the same data in the absence of advocacy against fossil fuels, a greater attention may have been paid to natural climate change.

CLIMATE SCIENCE RESPONDS, OCTOBER 2018

1. The data show that industrial soot can hardly be responsible for the melting of the Alpine glaciers at the time, taking place mainly between 1850 and 1875. By 1875, the glacier retreat under way then was already around 80 percent complete, Sigl says. But it was not until 1875 that the amount of industrial soot in central Europe exceeded the levels of black carbon naturally present in the atmosphere. Sigl clarifies: It’s only in the last 20 percent of that episode of glacier retreat in the 19th century that the soot could have had an influence.
2. The first half of the 19th century bore the stamp of several large volcanic eruptions in the tropics; their emissions of sulfur particles led to a temporary global cooling. This was the final phase of the Little Ice Age and it caused Alpine glaciers to advance. Up to now it had been thought that their retreat starting in the 1860s could be traced back to the beginning of industrialization. But now we see that this was incorrect. It’s simply a matter of a retreat to the glaciers’ previous undisturbed extent. 1850 is not suitable as a reference year for climate models.
3. The question of when the human influence on climate begins is still open. This beginning does not give suitable reference values for climate models. We think that the 1750s is a more suitable reference point for what we can call “pre-industrial” if we define that reference point in time as before the last and most extreme cold phase of the Little Ice Age. Previously the IPCC had accepted 1750 as the pre-industrial reference year for comparing data from pre-industrial times with those after the beginning of industrialization. That makes sense, since the climate in the middle of the 19th century was not the primordial one, as we now clearly see in our data. Future climate models could factor in the experimental soot data
4. In model calculations on climate change, the trend in the amount of soot in the atmosphere over time is one of many variables considered. So far, though, the modellers have been using an estimated value for the respective amounts of soot, For the 19th century in particular, estimates of the individual industrial nations have formed the basis for this. Up to now, a linear increase in the amounts of soot in the atmosphere has been assumed for the second half of the 19th century.
5. It can now be proven, thanks to the ice core studies, that this does not correspond to reality. Therefore the researchers are advocating the inclusion of experimental soot data in future model calculations. These models in turn form an important part of the report issued roughly every seven years by the recognized advisory authority on global climate, the IPCC, the Intergovernmental Panel on Climate Change. In the IPCC report, the model calculations that mathematically simulate the climate since 1850 have a central role. 

TRANSLATION

NOT A PROBLEM. WE CAN TWEAK OUR CLIMATE MODELS TO FIX THAT. 

COLLE GNIFETTI BIBLIOGRAPHY

1. 1988: Wagenbach, D., et al. “The anthropogenic impact on snow chemistry at Colle Gnifetti, Swiss Alps.” Annals of Glaciology10 (1988): 183-187. By chemical analysis of the upper 40 m of a 124 m ice core from a high-altitude Alpine glacier (Colle Gnifetti, Swiss Alps; 4450 m a.s.l.), records of mineral dust, pH, melt-water conductivity, nitrate and sulfate are obtained. The characteristics of the drilling site are discussed, as derived from glacio-meteorological and chemical analysis. As a consequence of high snow-erosion rates (usually during the winter months), annual snow accumulation is dominated by summer precipitation. Clean-air conditions prevail even during summer; however, they are frequently interrupted by polluted air masses or by air masses which are heavily loaded with desert dust.Absolutely dated reference horizons for Saharan dust, together with the position of the broad nuclear-weapon tritium peak, provide the time-scale for the following statements: (1) Since at least the turn of the century the background melt-water conductivity has been rising steadily, as has the mean snow acidity. The trend of increasing background conductivity at Colle Gnifetti (1.9μS/cm around the beginning of this century, and at present 3.4 μS/cm) is found to be comparable with the records of mean melt-water conductivity reported from ice cores from the Canadian High Arctic. (2) Sulfate and nitrate concentrations are higher by a factor of 4–5 than they were at the beginning of the century. This is to be compared with the two- to three-fold rise in the concentrations in south Greenland during about the same time span.
2. 1989: Wagenbach, Dietmar, and Klaus Geis. “The mineral dust record in a high altitude Alpine glacier (Colle Gnifetti, Swiss Alps).” Paleoclimatology and paleometeorology: modern and past patterns of global atmospheric transport. Springer, Dordrecht, 1989. 543-564. Ice-core and snow-pit samples from a non-temperated glacier in the summit range of Monte Rosa, Swiss Alps (4450 m.a.s.l.) has been analyzed for total mineral dust and the size distribution of insoluble particulate matter in the size range 0.63–20 microns. Based on a 50 years-record Saharan dust accounts for two third of the mean mineral dust flux of 60 μgcm^-2yr^-1. Both, background and Saharan dust influenced samples show a distinct mode in the volume size distribution of insoluble particles over the optical active size range with a typical volume mean diameter of 2.5 and 4.5 μm, respectively. These two size distribution categories are attributed to the insoluble fraction of the long lived background aerosol and to the relatively short lived aerosol dominated by soil derived dust (i.e. ground-level aerosol in aride areas).
3. 1999: Lavanchy, V. M. H., et al. “Historical record of carbonaceous particle concentrations from a European high‐alpine glacier (Colle Gnifetti, Switzerland).” Journal of Geophysical Research: Atmospheres 104.D17 (1999): 21227-21236. Historical records of the concentrations of black carbon (BC) and elemental carbon (EC), as well as of water insoluble organic carbon (OC) and total carbon (TC) covering the time period ∼1755–1975 are presented. Concentrations were obtained from an ice core of a European high‐alpine glacier, using an optical and a thermal method. Concentrations were found to vary between 7 and 128 μg L⁻¹ for BC, between 5 and 130 μg L⁻¹ for EC, between 53 and 484 μg L⁻¹ for OC, and between 66 and 614 μg L⁻¹ for TC. From preindustrial (1755–1890) to modern times (1950–1975) BC, EC, OC, and TC concentrations increased by a factor of 3.7, 3.0, 2.5, and 2.6, respectively. The sum of BC emissions of Germany, France, Switzerland, and Italy, calculated from fossil fuel consumption, and the EC concentration record correlate well (R² = 0.56) for the time period from 1890 to 1975; this indicates that the ice core record reflects the emissions of western Europe. High pre‐1860 concentrations indicate that by that time BC emissions to the atmosphere were already significant.
4. 1999: Schwikowski, M., et al. “Anthropogenic versus natural sources of atmospheric sulphate from an Alpine ice core.” Tellus B: Chemical and Physical Meteorology 51.5 (1999): 938-951. Opposite to greenhouse gases, sulphate aerosol particles are expected to cause climate cooling, but uncertainties exist about source variability and strength. We analysed an ice core from a European glacier to quantify source strengths of aerosol-borne sulphate over a 200-year period. Sulphate from emissions of SO₂increased by more than an order of magnitude during this century. This anthropogenic source is responsible for about 80% of total sulphate in the industrial period, and reflects emissions of west European countries. In the pre-industrial period mineral dust was the dominant contributor, followed by sulphate from SO₂ emissions with volcanoes or biomass burning as possible sources.
5. 1999: Schwikowski, M., et al. “A high‐resolution air chemistry record from an Alpine ice core: Fiescherhorn glacier, Swiss Alps.” Journal of Geophysical Research: Atmospheres 104.D11 (1999): 13709-13719. Glaciochemical studies at midlatitudes promise to contribute significantly to the understanding of the atmospheric cycling of species with short atmospheric lifetimes. Here we present results of chemical analyses of environmentally relevant species performed on an ice core from Fiescherhorn glacier, Swiss Alps (3890 m above sea level). This glacier site is unique since it is located near the high‐alpine research station Jungfraujoch. There long‐term meteorological and air quality measurements exist, which were used to calibrate the paleodata. The 77‐m‐long ice core was dated by annual layer counting using the seasonally varying signals of tritium and δ¹⁸O. It covers the time period 1946–1988 and shows a high net accumulation of water of 1.4 m yr⁻¹ allowing for the reconstruction of high‐resolution environmental records. Chemical composition was dominated by secondary aerosol constituents as well as mineral dust components, characterizing the Fiescherhorn site as a relatively unpolluted continental site. Concentrations of species like ammonium, nitrate, and sulfate showed an increasing trend from 1946 until about 1975, reflecting anthropogenic emission trends in western Europe. For mineral dust tracers, no trends were obvious, whereas chloride and sodium showed slightly higher levels from 1965 until 1988, indicating a change in the strength of sea‐salt transport. Good agreement between the sulfate paleorecord with direct atmospheric measurements was found (correlation coefficient r² = 0.41). Thus a “calibration” of the paleorecord over a significant period of time could be conducted, revealing an average scavenging ratio of 180 for sulfate.
6. 2009: Thevenon, Florian, et al. “Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium.” Journal of Geophysical Research: Atmospheres 114.D17 (2009). Black carbon (BC) and mineral dust aerosols were analyzed in an ice core from the Colle Gnifetti glacier (Monte Rosa, Swiss‐Italian Alps, 45°55′N, 7°52′E, 4455 m above sea level) using chemical and optical methods. The resulting time series obtained from this summer ice record indicate that BC transport was primarily constrained by regional anthropogenic activities, i.e., biomass and fossil fuel combustion. More precisely, the δ¹³C composition of BC suggests that wood combustion was the main source of preindustrial atmospheric BC emissions (C3:C4 ratio of burnt biomass of 75:25). Despite relatively high BC emissions prior to 1570, biomass burning activity and especially C₄ grassland burning abruptly dropped between 1570 and 1750 (C3:C4 ratio of burnt biomass of 90:10), suggesting that agricultural practices strongly decreased in Europe during this cold period of the “Little Ice Age” (LIA). On the other hand, optical analysis revealed that the main source for atmospheric dust transport to the southern parts of the Alps during summer months was driven by large‐scale atmospheric circulation control on the dust export from the northern Saharan desert. This southern aerosol source was probably associated with global‐scale hydrologic changes, at least partially forced by variability in solar irradiance. In fact, periods of enhanced Saharan dust deposition in the ice core (around 1200–1300, 1430–1520, 1570–1690, 1780–1800, and after 1870) likely reflect drier winters in North Africa, stronger North Atlantic southwesterlies, and increased spring/summer precipitation in west‐central Europe. These results, therefore, suggest that the climatic pejorations and the resulting socioeconomic crises, which occurred in Europe during periods of the LIA, could have been indirectly triggered by large‐scale meridional advection of air masses and wetter summer climatic conditions.

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