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    Topic: Lower atmosphere. Basics.
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    • What happens in the air surrounding us?

      What happens in the air surrounding us?

      A thin layer of air surrounds our planet which becomes less and less dense the further we go from the Earth's surface. This layer is known as the atmosphere (atmos is the Greek word for gas or vapour, sphaira means sphere).

      The composition and properties of air not only make it possible for plants and animals to live on Earth, they also control our climate.  If we look up into the sky on a clear day we see only blue sky.  However, there are distinct layers in the atmosphere which have different properties.  The lowest layer, where we live and where weather takes place, goes up to eight kilometers in altitude at the poles, and has an altitude of 15 kilometers in the tropics.  This layer of the atmosphere is known as the troposphere.  This word also has Greek roots, tropo means 'something changes'.

      1. Atmosphere from space
      © NASA visible Earth

      In the troposphere, it is the temperature which changes with altitude.  Temperature decreases with height up until the end of the troposphere, the region of the atmosphere known as the tropopause.  In this unit you will learn about the properties, composition, chemistry and processes in this layer.

      The list below gives you an overview of what we cover in this 'basics' section.  For more detailed information, have a look in the 'read more' section.

      • 1. An introduction to the troposphere

        1. An introduction to the troposphere

        The troposphere is the layer of the atmosphere closest to the ground.  It is where plants and animals live and where our weather takes place.  If we look towards the sky, the air seems to be endless. However, the layer of air surrounding our planet, protecting us and making life possible, is really very thin.

        1. The atmosphere from space - source: NASA

        When we travel by aeroplane, 80% of the air mass is below us.  In this unit we look at how the composition and properties of the air vary with altitude.  We compare the dimensions of the Earth's surface with the dimensions of the troposphere and look at how the properties of the troposphere change depending on where we are on Earth.  Finally, we look at the composition of the air and see how very small amounts of certain chemicals affect our climate.

      • 2. The greenhouse effect, light and the biosphere

        2. The greenhouse effect, light and the biosphere

        When we speak about climate, most people think about global warming. And if we speak about global warming, most of us think about the greenhouse effect.  The greenhouse effect is actually a naturally occurring process which has been affected by human activity.

        1. greenhouse effect

        Without the greenhouse effect, life wouldn't be possible on Earth.


        The energy driving our climate comes from the Sun. In the first part of this unit we look at what happens to the solar energy as it passes through the atmosphere, as it hits clouds and when it reaches the surface of the Earth.  We look at how this energy warms the Earth, how some of the energy is returned back into space and what effect clouds and greenhouse gases have.  In the second part of this unit we look at the impact plant emissions have on our atmosphere, both during their growth and if they are burnt in vegetation fires.


        Humans have enhanced the natural greenhouse effect and have changed the climate of the Earth.

        About this page:

        author: Dr. Elmar Uherek, Max Planck Institute for Chemistry Mainz/Germany
        scientific reviewer: Dr. Pascal Guyon, MPI for Chemistry - Mainz
        last published: 2004-05-12

      • 3. Ozone and nitrogen oxides as key compounds

        3. Ozone and nitrogen oxides as key compounds

        Most chemical processes which occur in the atmosphere are oxidation processes. The key chemical compounds involved are the hydroxyl radical (OH), ozone (O3) and the nitrogen oxides (NO + NO2 = NOx). 

        In  this unit we look at the formation and main characteristics of these compounds.  We look particularly at the role of ozone which is essential in the stratosphere but harmful in the troposphere.

        About this page:

        author: Dr. Elmar Uherek - Max Planck Institute for Chemistry, Mainz, Germany
        scientific reviewer: Dr. Rolf von Kuhlmann - Max Planck Institute for Chemistry, Mainz, Germany
        last published: 2004-04-30