Originariamente Scritto da
clayco
Questa ironia non te la lascio passare neanche morto perchè siete stati troppo scorretti in quella discussione..
Nessuno ha mai detto che il ritiro dei ghiacciai dipende solo dalla fuliggine, ma anche dalla fuliggine:
e non lo dico io ma Hansen che ti cito
http://stephenschneider.stanford.edu/Publications/PDF_Papers/HansenNazarenko2004.pdf
James Hansen and Larissa Nazarenko “Soot climate forcing via snow and ice albedos” PNAS _ January 13, 2004 _ vol. 101 _ no. 2 _ 423–428GEOPHYSICS
The soot effect on snow albedo may be responsible for
a quarter of observed global warming.
la fuliggine sull'effetto albedo è responsabile di un quarto del riscaldamento globale,
e qua parla anche di alpi oltre che dei ghiacciai centrasiatici
Melting Ice. We suggest that soot contributes to near worldwide
melting of ice that is usually attributed solely to global warming.
Measurements in the Alps reveal BC concentrations as large as 100
ppbw (34, 35), enough to reduce the visible albedo by ?10% and
double absorption of sunlight (21). However, much smaller BC
amounts perturb snowmelt because of positive feedbacks.
The ultimate flux perturbation at the snow surface due to BC is
larger than the product of incident solar flux and the direct
BC-induced snow albedo change. The BC-caused warming of the
snow speeds snow ‘‘aging,’’ i.e., the growth of grain size. More
important, the warmer air causes the melt season, with its much
lower albedo, to begin earlier and to last longer on sea ice and land
ice. In our climate model, as illustrated in Fig. 5, which is published
as supporting information on the PNAS web site, these feedbacks
more than double the direct soot flux perturbation in permafrost,
sea ice, and ice sheet regions, where there is little or no shielding
of snow by vegetation. This effect may be important on glaciers and
the lower reaches of ice sheets, where the added meltwater not only
reduces the albedo but also lubricates nonlinear dynamic processes
of glacier disintegration (36).
The soot albedo effect operates in concert with regional warming
in most of the world, hindering empirical distinction of climate and
soot contributions. However, there has been little warming in
China, including Tibet, over the past 120 years (Fig. 3), yet glaciers
there are retreating rapidly (37). The brown haze over India (22),
heavy with fossil fuel and biofuel soot, reaches to the Himalayas. If
prevailing winds deposit even a fraction of this soot on glaciers, the
snow BC content could be comparable to that in the Alps. Measurements
of glacial soot are needed.
Sea ice drafts measured by submarines in the Arctic suggest a
thinning of the ice by about a meter during 1958–1997 (38). The
Arctic albedo changes (Table 1 and Fig. 6, which is published as
supporting information on the PNAS web site) suggested by soot
measurements in the 1980s (6) cause surface flux changes (Fig. 5)
that are a substantial part of those needed to account for observed
sea ice thinning (38).
Spring snowmelt on tundra in Siberia, Alaska, Canada, and
Scandinavia has trended earlier, by 2–5 weeks, in recent decades
(32). The magnitude of this shift exceeds that in climate model
simulations with realistic global warming (5), suggesting that other
mechanisms contribute to the early snow disappearance.
Dice che la fuliggine sui ghiacciai alpini è responsabile di un cambio albedo del 10% che determina una raddoppio dell'assorbimento di luce solare.
Re: clamoroso (craccato L'HC)
un pò troppo poco.
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