The prediction of future climate is, undoubtedly, one of the main challenges of our time, marked by the concern about climatic change and its effects, such as drought and natural disasters, poles thaw, rise of the sea level, diseases, etc.

Climatic change poses different scientific challenges to researchers from all over the world, which must be tackled with new ideas, reliable data and advanced instruments.

Science must provide conclusive answers, for example, about the climatic effects of human pollution, the deforestation of wide regions of the globe or forest fires. Rigorous, fast and conclusive answers are not possible when scientific challenges have planetary dimensions.

As regards atmospheric physics's knowedge ans its possible effects on climatic change, research groups from all Europe have developed the project EARLINET-ASOS (European Aerosol Research Lidar Network: Advanced Sustainable Observation System).

25 laboratories, located in 12 European countries, carry out weekly measures simultaneously to obtain indispensable data for the carrying out of climatic studies: the analysis of the presence in the atmosphere of aerosol's particles and the determination of its origin.

One of these stations is located in Granada (Andalusian Centre for the Environment), directed by Prof Lucas Alados Arboledas.

"Atmospheric aerosol represents one of the main uncertainties in the estimation of the radiative forcing of climate and, therefore, for the prediction of climatic change -says Alados-. Aerosols disturb solar radiation in the atmosphere and influence the properties of clouds and rainfall in a way we are still ignorant of".

A few years ago, research works were focused on getting to know the distribution of aerosol particles on a worldwide scale, as well as the properties of the different types of aerosol.

The advances were very relevant, but measurements from land, planes or satellite could only measure the quantity, but not its vertical distribution at different heights, a key question, for example, to get to know its effect on climate, which is generally opposite due to the increase of greenhouse gases.

This is, whereas global warming is associated with greenhouse gases increase, atmospheric aerosol can contribute to a cooling of the earth's system.

Lidar Network and CALIPSO
"EARLINET (2000) and EARLINET-ASOS (2006) are allowing an improvement in the preparation of a wide quantitative and statistically significant database on aerosol's vertical structure and its temporal development in Europe", says Alados.

Satellite CALIPSO was launched to the space in April 2006, which contained the first space lidar station, able to offer a global vision of the vertical structure of aerosol and the clouds over our planet, necessary to express climatic forecasts.

However, if the 25 European lidar stations allow to offer data on a continental scale, they are also essential to validate CALIPSO's global data. The mission will take place all through three years, and will provide essential information on aerosol's properties.

Together with other satellites of the "A-Train" constellation, CALIPSO will help to increase our knowledge about climatic system and the possible climatic change.

While CALIPSO is being validated, the observations of EARLINET all over Europe are collecting and processing essential data to get to know and assess the climatic impact of the masses of air with mineral dust arriving from Sahara to Europe, of European forest fires, the differences between the pollution produced in highly industrialized regions of Eastern Europe, the anthropogenic pollution in underdeveloped areas, the anthropogenic pollution which reaches Europe from North America, etc.

12 countries, 25 scientific groups
Thousands of yearly observaciones have turned EARLINET into an essential information source for the future of meteorological science, the assessment of climtic change and a better knowledge of our environment.

The stations of the EARLINET consortium can be found from the Mediterranean to the Arctic Polar Circle, from the marine environments of mild climates to Arctic weather, from continental climate to semiarid regions, clean airs of sparsely populated areas to regions highly polluted due to urban concentrations and industry.