Search

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 structural differences seen in the paintings had not altered the results discussed above. However, a detailed study on all possible sources of uncertainties involved (such as the impact of clouds on R / G ratios) still needs to be studied. Because of the large number of paintings studied, we tentatively propose the conclusion that regardless of the school, red-to-green ratios from great masters can provide independent proxy AODs that correlate with widely accepted proxies and with independent measurements. © Author(s) 2014. CC Attribution 3.0 License.

Air temperatures in urban areas continue to increase because of the heat island phenomenon (UHI) and the undeniable warming of the lower atmosphere during the past few decades. The observed high ambient air temperatures intensify the energy demand in cities, deteriorate urban comfort conditions, endanger the vulnerable population and amplify pollution problems especially in regions with hot climatic conditions. The present paper analyses 40 years of hourly data series from nine meteorological stations in Greece in order to understand the impact of air temperature and relative humidity trends on the energy consumption of buildings. Using a typical office building, the analysis showed that for the period in question the heating load in the Greek building sector has decreased by about 1 kWh/m2 per decade, while the cooling load increased by about 5 kWh/m2 per decade. This phenomenon has major environmental, economic and social consequences, which will be amplified in the upcoming decades in view of the expected man-made climatic changes in this geographic area. © 2013 Elsevier Ltd. All rights reserved.

Heat island which is the most documented phenomenon of climatic change is related to the increase of urban temperatures compared to the suburban. Among the various urban heat island mitigation techniques, green and cool roofs are the most promising since they simultaneously contribute to buildings' energy efficiency. The aim of the present paper is to study the mitigation potential of green and cool roofs by performing a comparative analysis under diverse boundary conditions defining their climatic, optical, thermal and hydrological conditions. The impact of cool roof's thermal mass, insulation level and solar reflectance as well as the effect of green roofs' irrigation rate and vegetation are examined. The parametric study is based on detailed simulation techniques coupled with a comparative presentation of the released integrated sensible heat for both technologies versus a conventional roof under various climatic conditions. © 2013 Elsevier Ltd.

This research focuses on projecting the energy demand of the building sector in Greece by calculating energy consumption, using output data from regional climate models up to 2100. More specifically, Greece was subdivided into 13 climatic zones after assessing climate model data taking into account climate change estimates for the period 2010-2100. These zones allow a detailed estimation of the effects of climate change in specific regions of the country, thus creating a database which is used to model the energy demand of the building sector in each zone. Through the use of building data from Eurostat and the European Centre for Environment, a set of three building typologies was created in relation to the building envelope, which corresponds to 85% of the building stock in Greece. These typologies were later appended to each of the 13 climatic zones and a simulation for their energy demand was calculated using climatic data from 3 distinct climatic scenarios. Results show that the energy demand for heating the building sector in Greece could decrease by about 50%, while the respective energy demand for cooling could increase by as much as 248% until 2100. These effects are more evident in the Southern part of the country. © 2012 Elsevier B.V. All rights reserved.