Using pristine Southern Ocean air to estimate pre-industrial pollution - Ars Technica

To improve and cross-check estimates of past aerosol levels, researchers have gotten creative.

A new study led by Isabel McCoy at the University of Washington uses the fact that the skies around Antarctica are close to free from human-caused aerosol pollution to set a new pre-industrial baseline.

In this case, the researchers are looking at the latter by using satellite cloud data.

While aerosol pollution from coal-burning and other combustion activities tends to be present throughout the Northern Hemisphere, Antarctica’s atmospheric isolation keeps those aerosols at bay.

Using the Antarctic as an indicator of pre-industrial aerosol levels, the researchers apply the satellite data to a number of climate models?

First, they compare how well the models match modern cloud-droplet concentrations around the world, and then they calculate the impact of aerosol pollution over time.

While the models show only a modest increase in summer, the satellite data revealed that Antarctic droplet concentrations actually get as high as the polluted Northern Hemisphere—an eyebrow-raising result.

If models are essentially overestimating the effect of human-caused aerosols on clouds and underestimating the effect of natural aerosols, then the calculated effect of human aerosol pollution will be too large.

The impact of aerosols has been studied using multiple lines of evidence beyond just the models, and the newly calculated value supports the current best estimate derived using the full body of evidence, although it’s a slightly tighter range.

So the study’s takeaways relate more to the climate models, which the researchers say could use this information to work on improving the models’ cloud-aerosol connection.