How trees cool down towns in summer

Introduction

In the temperate zone during a clear sunny day the income of solar irradiance is about 1000 W m-2, which means that an area of 1ha gets up to 10 MW of solar energy. What happens with this energy depends on the availability of water and the type of land cover (2, 5). Most of the solar energy on dry surfaces is converted into sensible heat, which warms up the ground and the air above it (3). In summer, temperatures of such surfaces can exceed 50°C. However, if the surface is covered by functional vegetation (and well stocked with water) 70 – 80 % of the energy can be dissipated through water evapotranspiration (the sum of transpiration and evaporation), which means conversion into latent heat, responsible for landscape cooling (2, 6). As a consequence of the cooling effect of evapotranspiration, the vegetation cover well supplied with water is substantially cooler than adjacent dry surfaces. This can be conveniently documented by means of thermo-vision (4).

The aim of this poster is to demonstrate how trees may work as a perfect air-conditioning system driven by the solar energy and using water. We present several IR photographs of towns with adjacent tree stands in South Bohemia (Czech Republic), which clearly illustrate how vegetation cover in urban areas have a substantial effect on the local climate.

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Dams, energy and climate change

 

coalition climat 21

Round table organized by the European Water Movement
during Climate Forum in Montreuil,
December 5th, 2015 from 16:30 to 18:30

Moderation
Daniela Del Bene, Xarxa per la Sobirania Energetica

Barrages et centrales nucléaires du Rhône
Thierry Uso, Eau Secours 34

Barrages et centrales nucléaires de la Durance
Bernard Mounier, Coordination EBC PACA

Damming the Ebro river
Annelies Broekman, Xarxa Nova Cultura de l'Aigua

The global challenge of dam removal
Ercan Ayboga, Keep Hasankeyf Alive

Análisis y propuestas desde la perspectiva de la soberanía energética
Alfons Pérez, Observatori del Deute en la Globalitzaciò + Xarxa per la Sobirania Energetica

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Floods, urbanization and climate change in Europe

 

coalition climat 21

Round table organized by the European Water Movement
during Climate Forum in Montreuil,
December 5th, 2015 from 14:00 to 16:00

Introduction
Thierry Uso, Aquattac

Evaporation, a new paradigm in urban rainwater management - The case of Berlin
Marco Schmidt, Technische Universität Berlin

Inondations, urbanisation et changement climatique dans l’Hérault
Thierry Uso, Eau Secours 34

Inondations, urbanisation et changement climatique dans le Gard
Ghislaine Soulet, Collectif lanceur d'alertes de l'agglomération d'Alès

Inondations, urbanisation et changement climatique dans les Alpes Maritimes
Monique Touzeau, Collectif Associatif Pour des Réalisations Ecologiques 06

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A blue and just future is possible

Keynote speech from the International Conference on Water, Megacities and Global Change, UNESCO Headquarters, Paris, December 1, 2015

The challenge is stark. Peri-urban slums ring most of the developing world’s megacities where climate and food refugees are arriving in relentless numbers. Unable to access their traditional sources of water because they have been poisoned, overexploited or priced beyond reach, many must pay exorbitant prices to local water dealers or rely on drinking water contaminated with their own waste.

UN-Habitat reports that by 2030, more than half the populations of large urban centres will be slum dwellers and the US National Academy of Scientists says that by 2050, more than one billion of these urban slum dwellers will only have daily access to enough water to fill a small bathtub.

Hardest hit cities will include Beijing, New Delhi, Mumbai, Kolkata, Manila, Mexico City, Caracas, Lagos, Abidjan, Tehran, and Johannesburg. Today, greater Sao Paulo, with a population of almost 20 million people, is literally running out of water.

Read more on the website of Council of Canadians