“Pristine” environments are those places  and/or times where and when we hope the environmental influence of humans is minimal. In the modern world, the polar regions, although the Arctic is increasingly threatened, represent perhaps the most obvious such environments. In the past, the pre-industrial era is often referred to as having pristine aerosol. These past and present “pristine” environments motivate several gedanken experiments wherein we can examine the potential of human activities to tilt the balance in ways that affect aerosol, clouds and climate. Here I present two ongoing research activities related to human influence on pristine environments.

I. Contextualizing air quality metrics given our understanding of natural background aerosol.

II. The potential of ship emissions to influence cloud properties.