Increased atmospheric carbon dioxide content was concluded to have had an ambiguous climatic influence and may be less important than sometimes considered. Several studies have suggested increased turbidity has produced a recent global cooling trend. An examination of some climatic effects of volcanic eruption was made in relation to the prediction that the effect of 500 supersonic transport aircraft would be comparable over the North Atlantic to the amount of stratospheric injection from the 1963 Mount Agung eruption.
During the last 1800 years there have been eight periods of increased erosion and alluvial sedimentation in New Zealand, which have generally decreased in magnitude towards the present. Throughout New Zealand, alluvium of all erosion periods contains abundant remains of plants as evidence of widespread destruction of vegetation during erosion periods. Indices of the relative magnitude of alluviation, and estimates of the damage to vegetation in the current Waipawa Period (since 1950), are applied to estimate the impact of earlier erosion periods.