données historiques

CONT: [...] la concentration en sulfate, en aluminium et en manganèse augmente tandis que le pH et l'alcalinité diminuent. Il est donc possible en étudiant l'évolution de la qualité de l'eau d'identifier les lacs en voie d'acidification ou acidifiés. Malheureusement, les données historiques sont souvent incomplètes ou imprécises.
OBS: Selon M. Richard Adams de la section de traduction de Statistique Canada, on emploie maintenant données historiques au lieu de données chronologiques.

CONT: The causal relationship between certain detrimental effects and acid precipitation, including its accompanying pollutants, can usually be proven by means of comparisons using historical or chronological data or by means of experiments in laboratories.
CONT: ... scientists are using models based on fragmentary historical data or paleolimnology. ... One has to be careful in using historical data. First, methods of measurement may have been different, or even imperfect, so as to give deviating results. And even if chronological data show increasing acidification, this might be a natural process for the region involved, although this is not very likely.