Natural factors that affect the climate
The climate that prevails on earth today is determined by a number of factors that affect the climate differently in time and space. The basic factors are radiation from the sun, circulation in the atmosphere and the sea as well as topography on land and in the sea.
The basic energy comes from the sun. Circulation in the atmosphere and in the oceans distributes energy over the earth depending on the appearance of the topography. Another factor affecting the climate is human activity.
Radiation from the sun
The energy from the sun is the fundamental factor for the climate. All bodies (solid, liquid and gaseous) that have a temperature above the absolute zero point emit radiation. The higher the temperature, the more short-wave radiation is emitted.
The radiation from the sun is short-wave, that is, less than 4 microns. The solar radiation that reaches the ground surface at a certain point on earth varies throughout the day and throughout the year. This affects the daily and annual cycles of many climate variables. The most obvious is the temperature and its variation.
Outgoing radiation
Some of the radiation from the sun is reflected back into space when it hits the ground surface, especially light surfaces such as light clouds or snow and ice on the ground. Another part of the sun’s energy is absorbed by the earth’s surface, clouds and atmosphere. Thus, a heating occurs. The solar energy absorbed by the sea or earth surface heats the air closest to the surface or contributes to the evaporation of water.
Some of the energy is emitted as radiation. At the temperatures normally prevailing on the earth, most of the radiation will be of wavelengths between 4 to 100 micrometers, which is considered long-wave radiation.
Radiation balance
The energy per unit area that falls towards the Earth’s surface from the sun depends strongly on the latitude. Somewhat simplified, there is a lot of energy near the equator and less towards the poles. The outgoing long-wave radiation, on the other hand, is only weakly dependent on the latitude.
Therefore, there is an excess of energy near the equator and a deficit in the polar regions. This means that the temperature is higher in the tropics than in the polar regions. The temperature difference would be even greater if there were no processes that efficiently move energy.
Greenhouse gases
The atmosphere may seem transparent to radiation, but the radiation we do not see with the naked eye is largely absorbed. Above all, it is the so-called greenhouse gases that absorb long-wave radiation.
The trapped energy gives rise to a temperature rise in the air. Hot air emits more radiation than cold. The amount of these gases and how they are distributed vertically affects the climate. The most significant greenhouse gases are water vapor, carbon dioxide, methane and nitrous oxide. But also ozone and halogenated hydrocarbons are important.
A large part of the human impact on the climate is caused by greenhouse gas emissions.
Aerosols
Particles in the air (aerosols) also affect the radiation balance. The solar radiation is both spread and absorbed by aerosols. If a larger amount of aerosols is present in the atmosphere, solar radiation at the Earth’s surface decreases noticeably, resulting in a decrease in temperature at the Earth’s surface.
There are various sources of aerosols. Mechanically (wind) swollen dust from deserts is a significant source. Winds and waves over the world ocean bring up small drops of saltwater in the air. The water in the droplets evaporates and remains salt particles.
Fires form gases and soot particles. They can be natural or anthropogenic (created by man). There are also biological sources of aerosols which can be pollen, parts of leaves and insects that noticeably affect the solar radiation. Here you can read more about anthropogenic aerosols.
One of the most spectacular sources of climate-impacting aerosols is explosive volcanic eruptions, which push up dust and sulfur dioxide into the stratosphere.
Can volcanic eruptions affect the climate?
The climatic effects of particles are complex and are therefore not as well known in comparison with the greenhouse gases. The climate effects of particles also vary from cooling effect (sulfate particles reflect away solar radiation) to heating effect (soot particles absorb solar radiation which heats the air). The variation of the aerosols over time as well as their spread in horizontal and vertical directions is also important for their effect on the climate.
Clouds
Clouds are today one of the most problematic factors when describing the physics of the atmosphere. Cloud observations have been made for a long time but are often mostly of a qualitative nature. The clouds are three-dimensional and vary rapidly over time. Clouds may consist of water and / or ice particles.
Quantity and altitude distribution have been studied using satellites and ground-based observations for several decades. However, there are only samples of the number and size distribution of cloud droplets. When clouds are described in climate models, all aspects of distribution and conditions must be included.
Winds
The energy coming from the sun largely penetrates the atmosphere and is absorbed into the earth’s surface. The heated soil surface, in turn, warms the atmosphere or is used to evaporate water.
In essence, there is significant warming of the earth at lower latitudes. This surplus energy is transported to higher latitudes by ocean currents and winds.
These flows of energy can be described by the laws of physics. However, the system is very complex. Where on earth the clouds appear and where precipitation falls is part of our local climate.
Ocean currents
Just as the circulation of the atmosphere affects the climate in a certain place, so do the ocean currents. Of course, the most significant influece in some of the northern parts of the world is the Gulf Stream and its northern foothills the North Atlantic Current. Without this heat transport, there would have been very colder winters in Europe.
Deep Water Formation
The sun warms the top layers of the sea. The surface currents of the oceans are driven by the winds and are therefore intimately connected to the circulation of the atmosphere. The oceans have an average depth of around 4000 meters. In the depths, there is darkness and cold. But here too there are ocean currents. They are driven by differences in salinity and temperature (thermohaline circulation).
The surface water is naturally warmest in the tropics and coldest in the ice ocean. More unknown is that the temperature under the sunlit and heated top layer with a power of 500-1000 m is only 1-4 degrees. The average temperature in the oceans is thus low.
Because hot water is lighter than cold, the solar heated surface water is like a lid on the deep water. This would prevent oxygen-rich surface water from reaching deep and aerobic life (oxygen-dependent processes and organisms) would not be there.
However, there is a rich wildlife and therefore there must be a transport of surface water to the deeper parts of the sea. The important process that performs this is called the conveyer belt in English. If you sketch the flow it looks like a huge conveyor belt that winds around the ocean.
Altitude
The climate in a region can vary rapidly over short geographical distances if the altitude changes. Examples of this are the climate in and around the Alps. At high altitude there are glaciers while at lower altitudes there are forests and fields. This reflects that the average temperature in the atmosphere decreases with height.
Distance from the sea
They sometimes talk about maritime and continental climate. Sea temperatures change slowly compared to land surfaces. Therefore, temperature variations over the year and day are compensated for, for example, at coastal resorts.
More extreme differences are seen when comparing Ireland’s maritime climate with the continental climate in, for example, Novosibirsk, Russia. These locations are approximately at the same latitude.
Erosion and vegetation
Viewed over geological ages, not only does plate tectonics change the earth’s surface. Wind, flowing water and biogeochemical processes also cause changes. Old mountain ranges are worn down. Water brings sludge deposited on the lake and seabed. Generations of dead plants and animals accumulate and form layer after layer.
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