The current consensus is that up to half of the modern atmospheric dust load originates from anthropogenically‐disturbed soils. Here, we estimate the contribution to the atmospheric dust load from agricultural areas by calibrating a dust‐source model with emission indices derived from dust‐storm observations. Our results indicate that dust from agricultural areas contributes <10% to the global dust load. Analyses of future changes in dust emissions under several climate and land‐use scenarios suggest dust emissions may increase or decrease, but either way the effects of climate change will dominate dust emissions.

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International audiencePalaeoclimates across Europe for 6000 y BP were estimated from pollen data using the modern pollen analogue technique constrained with lake-level data. The constraint consists of restricting the set of modern pollen samples considered as analogues of the fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration (P-E) is consistent with the regional change in moisture balance as indicated by lakes. An artificial neural network was used for the spatial interpolation of lake-level changes to the pollen sites, and for mapping palaeoclimate anomalies. The climate variables reconstructed were mean temperature of the coldest month (T-c), growing degree days above 5 degrees C (GDD), moisture availability expressed as the ratio of actual to equilibrium evapotranspiration (alpha), and P-E. The constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies, especially for P-E. The reconstructions indicate clear spatial and seasonal patterns of Holocene climate change, which can provide a quantitative benchmark for the evaluation of palaeoclimate model simulations. Winter temperatures (T-c) were 1-3 K greater than present in the far N and NE of Europe, but 2-4 K less than present in the Mediterranean region. Summer warmth (GDD) was greater than present in NW Europe (by 400-800 K day at the highest elevations) and in the Alps, but >400 K day less than present at lower elevations in S Europe. P-E was 50-250 mm less than present in NW Europe and the Alps, but alpha was 10-15% greater than present in S Europe and P-E was 50-200 mm greater than present in S and E Europe

The metabolism of leucine to isoamyl alcohol in yeast was examined by 13 C nuclear magnetic resonance spectroscopy. The product of leucine transamination, ␣-ketoisocaproate had four potential routes to isoamyl alcohol. The first, via branched-chain ␣-keto acid dehydrogenase to isovaleryl-CoA with subsequent conversion to isovalerate by acyl-CoA hydrolase operates in wild-type cells where isovalerate appears to be an end product. This pathway is not required for the synthesis of isoamyl alcohol because abolition of branched-chain ␣-keto acid dehydrogenase activity in an lpd1 disruption mutant did not prevent the formation of isoamyl alcohol. A second possible route was via pyruvate decarboxylase; however, elimination of pyruvate decarboxylase activity in a pdc1 pdc5 pdc6 triple mutant did not decrease the levels of isoamyl alcohol produced. A third route utilizes ␣-ketoisocaproate reductase (a novel activity in Saccharomyces cerevisiae) but with no role in the formation of isoamyl alcohol from ␣-hydroxyisocaproate because cell homogenates could not convert ␣-hydroxyisocaproate to isoamyl alcohol. The final possibility was that a pyruvate decarboxylase-like enzyme encoded by YDL080c appears to be the major route of decarboxylation of ␣-ketoisocaproate to isoamyl alcohol although disruption of this gene reveals that at least one other unidentified decarboxylase can substitute to a minor extent.In most eukaryotes, the catabolism of the branched-chain amino acids leucine, isoleucine, and valine has been well understood for many years (1). The first step is a transamination in which ␣-ketoglutarate accepts the amino group (from leucine, isoleucine, and valine) producing glutamate and ␣-ketoisocaproic acid, ␣-keto-␤-methylvaleric acid and ␣-ketoisovaleric acid, respectively. Next is oxidative decarboxylation of the keto acids by branched-chain ␣-keto acid dehydrogenase to the corresponding acyl-CoA derivatives. Further steps yield, ultimately, acetyl-CoA and acetoacetate (from leucine), acetyl-CoA and propionyl-CoA (from isoleucine), and succinyl-CoA (from valine). All of these metabolites can enter the tricarboxylic acid (TCA) 1 cycle. It has been known for many years that yeasts do not operate the same metabolic routes because branched-chain amino acids can serve as the sole source of nitrogen but not carbon (2, 3). The predominant view, in a rather sparse literature, is that yeasts first use transamination but that decarboxylation of the keto acids proceeds via a "carboxylase" to an aldehyde that is then reduced in an NADH-linked reaction producing the appropriate "fusel" alcohol (2-4). This scheme is sometimes called the "Ehrlich pathway" to honor the originator of the ideas (5), which were slightly modified later (6). Acceptance of the so-called Ehrlich pathway is problematical for at least four reasons. First, the supposed pathway has never been proven to exist. Simply showing that e.g. radioactively labeled leucine is converted into isoamyl alcohol does not prove that the individual steps are those envisaged in ...