Besides the urban heat island effect and rapid global population growth, this could be another major anthropogenic reason for why we observe global warming since the end of the Little Ice Age in the first half of the 19th century!
What about junk climate models!
Do not dismiss the study just because it only reveals two limited geographic regions, i.e. the Southeastern US and the United Kingdom. I bet in Europe and Asia there were probably similar situations.
Something seems dubious about this study when you look at the chart below:
- Apparently, Antarctica was also affected.
- Japan is missing.
- Europe (except the UK) is missing.
- What about China?
- Why is central Africa in blue color?
- What was going on in southeast Asia?
Caveat: This research paper also relies on computer simulations not hard facts!
"Pre-industrial pollution from coal smoke and wood-burning in regions like the southeastern U.S. and UK may have made the air murkier than previously thought. This historical haze could significantly alter our understanding of how clouds formed and reflected sunlight in the past.
Tiny particles in the air can have big climate effects. Each tiny dust or soot grain can seed a water droplet, so more particles mean more, smaller droplets and a brighter, whiter cloud. ...
The vast majority of climate models have assumed that the skies over 19th-century Earth were pristine, meaning that anthropogenic aerosols were much lower than those observed today. "
From the abstract:
"Understanding the preindustrial (PI) to present-day (PD) change in cloud droplet number concentration (ΔNd) is important to constrain the anthropogenic influence on clouds and aid future model projections.
Perturbed parameter ensemble simulations of PI and PD conditions in the Energy Exascale Earth System Model (E3SMv3) reveal two locations with consistent negative ΔNd signal across parameter space–the Southeastern US and the United Kingdom–despite a trend of positive ΔNd globally from increased fossil fuel consumption.
These negative ΔNd signals are driven by higher anthropogenic biofuel emissions in the PI. By varying the PI aerosol mass and/or number emissions across these data sets' uncertainty ranges, we can change the magnitude and sign of ΔNd and the effective radiative forcing from aerosol-cloud interactions (ERFaci) regionally and globally, with near-zero ΔNd leading to near-zero ERFaci.
These results highlight the need to constrain PI emission uncertainty to better understand Earth system responses to aerosol-cloud interactions."
Sensitivity of Anthropogenic Cloud Droplet Number Change to Preindustrial Emission Inventories and Physics Parameterizations (open access)
Fig. 1 (partial, enlarged)
(a) Global ΔNd from the Nephele PPE (default, ensemble mean, and means of the lowest and highest 2.5th percentiles) with the Southeastern US (SEUS) and United Kingdom (UK) denoted by green and blue rectangles, respectively.
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