Further evidence of important environmental information content in red-to-green ratios as depicted in paintings by great masters

• Main Authors: Zerefos, C.S., Tetsis, P., Kazantzidis, A., Amiridis, V., Zerefos, S.C., Luterbacher, J., Eleftheratos, K., Gerasopoulos, E., Kazadzis, S., Papayannis, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: ice core
• Online Access: https://pergamos.lib.uoa.gr/uoa/dl/object/uoadl:3070050

We examine sunsets painted by famous artists as proxy information for the aerosol optical depth after major volcanic eruptions. Images derived from precision colour protocols applied to the paintings were compared to online images, and found that the latter, previously analysed, provide accurate information. Aerosol optical depths (AODs) at 550 nm, corresponding to Northern Hemisphere middle latitudes, calculated by introducing red-to-green (R / G) ratios from a large number of paintings to a radiative transfer model, were significantly correlated with independent proxies from stratospheric AOD and optical extinction data, the dust veil index, and ice core volcanic indices. AODs calculated from paintings were grouped into 50-year intervals from 1500 to 2000. The year of each eruption and the 3 following years were defined as "volcanic". The remaining "non-volcanic" years were used to provide additional evidence of a multidecadal increase in the atmospheric optical depths during the industrial "revolution". The increase of AOD at 550 nm calculated from the paintings grows from 0.15 in the middle 19th century to about 0.20 by the end of the 20th century. To corroborate our findings, an experiment was designed in which a master painter/colourist painted successive sunsets during and after the passage of Saharan aerosols over the island of Hydra in Greece. Independent solar radiometric measurements confirmed that the master colourist's R / G ratios which were used to model his AODs, matched the AOD values measured in situ by co-located sun photometers during the declining phase of the Saharan aerosol. An independent experiment was performed to understand the difference between R / G ratios calculated from a typical volcanic aerosol and those measured from the mineral aerosol during the Hydra experiment. It was found that the differences in terms of R / G ratios were small, ranging between ĝ̂'2.6% and +1.6%. Also, when analysing different parts of cloudless skies of paintings following major volcanic eruptions, any ...