Spain: Cooling trend in Almería by its greenhouses surface
This is an update of the research on albedo or reflectance, which, 12 years ago, meant the characterization of a buffer effect of global warming by urban settlements, specifically in the horticultural area of Almería.
Albedo is the cooling effect produced in the temperatures of an area by the increase of solar reflectance due to changes in the surface cover, more intense, the greater the surface is covered with light colors or bleached, as the case of greenhouse building or whitewashing of building roofs or urban pavements is.
Greenhouse horticulture has experienced in recent decades a dramatic spatial expansion in the semiarid province of Almería, in southeastern Spain, reaching a continuous area of about 30,000 ha, the widest greenhouse area in the world.
- The discovery, made by researchers led by Pablo Campra, from Almería’s University, was first published in 2008 https://www.researchgate.net/publication/39499812_Surface_temperature_cooling_trends_and_negative_radiative_forcing_due_to_land_use_change_toward_greenhouse_farming_in_southeastern_Spain
It had a great impact on the media and especially on scientists investigating, through climatic simulations, different viable options for adaptation to expected global warming, mainly in urban areas.
- In this article and later articles, they demonstrated that the average temperature in the greenhouse Almería area had not only not followed the global warming trend in this region (+0.5°C per decade), but had a slight trend towards cooling (about -0.3°C per decade). In total a buffering effect of -0.8°C per decade https://www.researchgate.net/publication/303687902_Trend_analysis_by_a_piecewise_linear_regression_model_applied_to_surface_air_temperatures_in_Southeastern_Spain_1973-2014,
- Once the temperature trend was characterized, the next step was to present and demonstrate a hypothesis about the cause of this phenomenon. To this end, Prof. Campra visited the Lawrence Berkeley National Laboratory where he was able to demonstrate that the cooling cause in the area of Almería was the generalized increase in albedo, enhanced by the summer bleaching of greenhouses. This was published in 2013 https://www.researchgate.net/publication/257202462_Mesoscale_Climatic_Simulation_of_Surface_Air_Temperature_Cooling_by_Highly_Reflective_Greenhouses_in_SE_Spain
- In order to supplement the study, he conducted a comprehensive carbon footprint work using Life Cycle Analysis Methodology published in 2011 https://www.researchgate.net/publication/226490855_Including_CO2-emission_equivalence_of_changes_in_land_surface_albedo_in_life_cycle_assessment_Methodology_and_case_study_on_greenhouse_agriculture
The results showed that 45% of the total carbon footprint of the greenhouse horticulture could be considered offset by albedo. It can therefore concluded that the Almería greenhouse covers have two complementary positive effects on climate change: one local, neutralizing global warming in the area, and another on a planetary scale, partially offsetting of the total carbon footprint.
- Apart from that, another carbon footprint offsetting effect, not yet sufficiently understood or valuated, was published in the paper https://www.researchgate.net/publication/221915607_Global_and_Local_Effect_of_Increasing_Land_Surface_Albedo_as_a_Geo-Engineering_AdaptationMitigation_Option_A_Study_Case_of_Mediterranean_Greenhouse_Farming
This indirect effect is called high yield conservation. In Almería, only 30,000 ha, 3% of the provincial surface is covered by greenhouse irrigated farming. 3.5 billion tons of fruit and vegetables worth €2.5 billion come out of it, a huge source of food and income. Thanks to this alternative income (along with the marble sector and tourism) hundreds of thousands of hectares of traditional agriculture, with high erosive and superficial impact, were abandoned and now constitute a green lung, where the Mediterranean scrub in spontaneous expansion is fixing million tons of CO2.
- In 2018, this group’s latest research assessed the effect of implementing modifications comparable to those occurred in Almería albedo but in other types of settlements like Madrid https://www.researchgate.net/publication/330978199_Numerical_Simulation_of_the_Effects_of_Increasing_Urban_Albedo_on_Air_Temperatures_and_Quality_over_Madrid_City_Spain_by_Coupled_WRFCMAQ_Atmospheric_Chemistry_Model
- They currently consider that this research line is closed, although they remain open to establishing collaboration with anyone whose interest would be applying albedo as the only geo-engineering strategy, feasible today, which has proven its effectiveness in urban adaptation to global warming.