Climate change

Climate change, including climate change, climate change or climate variability, refers to the change of climate on Earth and Earth-like planets, regardless of causes, whether natural or human. The current, caused mainly by the man-made global warming is an example of a climate change. A climate change can mean a cooling or heating for different periods. The term climate variation sometimes referred specifically climate change, the last few decades or cyclical in nature.

The climate state during the last year, hundreds of thousands is essentially the result of the Milankovitch cycles that changed the sunlight during periods of millennia and so brought about the change between ice ages and warm periods. The radiation from the sun determines the energy budget at the earth. A climate change will take place when the radiative forcing is changed. At the moment the Earth emits less long-wave infrared radiation into space, because the radiative forcing was increased by a significant increase in the concentration of greenhouse gases. Abrupt climate change can be caused by asteroids, volcanic eruptions or by feedback processes in the climate system.

• 5.1 Collective portals

Causes of natural climate changes

Climate changes can have many different causes. Numerous cyclic and non - cyclic processes and events affect the Earth's climate and reinforce or neutralize each other. Some of these factors are now scientifically well understood and widely accepted, others are plausible but not yet quantified as fundamental causal relationship, some are obvious due to good correlations of the suspected factors with specific climate data, but their effect relationships are not yet fully understood.

The Earth's orbit around the sun and the tilt of Earth's axis

Both the Earth's orbit around the sun and the tilt of Earth's axis and thus the angle of incidence of solar radiation at different latitudes of the earth are subject to various cycles with a duration of 25,800 to about 100,000 years, which were first studied and calculated by the Serbian astrophysicist and mathematician Milutin Milankovitch and are therefore now known as Milankovitch cycles. The problems caused by the Milankovitch cycles fluctuations of the energy radiation in the atmosphere are often very large and are believed to be responsible for the ice age cycle today.

The sun

The sun and the light emitted from their solar energy are the driving force for the energetic drive of the terrestrial weather and climate. Apparently depend on both long -term climate change as well as our daily weather closely with the activities of our sun.

In addition comes from the sun is a constant solar wind, which consists of a steady stream of electrically charged particles and the strength of which varies greatly. The detection of the interaction between the changing solar activity and the magnetic field of our planet studied the science under the term " space weather ".

The solar variations can be explained by regular changes in the magnetic field of the sun. The magnetic behavior of the Sun is subject to recurring cyclical fluctuations. Such a sunspot cycle, ie the period between a solar maximum and a new solar maximum, lasts about eleven years. On the cycle peak, which was reached in 2001 the last time the solar wind is a veritable solar storm. On the solar surface then happen tremendous eruptions hurl large amounts of high-energy particles into space. The released elemental forces correspond approximately to the explosion of 66 billion Hiroshima bombs. The first observations of sunspots date back to the year 1610. At that time they were made ​​, among others by Galileo with a telescope. Regular censuses there since 1860 from the astronomical observatory in Zurich.

Essentially, the scientists explore three mechanisms that could explain the relationship between solar activity and weather and climate evolution on Earth:

• First, the intensity fluctuations of the votes of the sun's ultraviolet radiation effects on ozone formation in the atmosphere. This leads to changes in the ozone layer and has as feedback to the global circulation of the air mass.
• Second change under the incoming solar wind, the electrical properties of the Earth's outer atmosphere, which affects the lower layers of the atmosphere. The scientists believe that this is influenced by the solar wind, cosmic particles rain favors the formation of clouds to the earth's atmosphere. Although increasing clouds shields on the one hand from the sunlight, but disabled on the other hand, the radiation ( the "greenhouse effect").
• Third, the atmosphere is subjected during sun minimum amplified cosmic radiation. The particles of the solar wind shield during such periods the earth less against the chill of the heavier and very high-energy particles that meet as cosmic radiation from space on our planet.

Yet little is known about the importance of the individual mechanisms. Also, little is known about whether there are interactions between the mechanisms. In addition to the eleven-year cycle already mentioned another were observed. For example, there is the Gleißberg cycle that recurs every 80 to 90 years, or another cycle of about 208 years. Next, the sun can also decades have reduced activity. Edward Maunder examined 1890, the historically observed sunspots and discovered a "pause" in the eleven-year cycle 1695-1720 ( Maunder Minimum ), the strikingly with the " Little Ice Age " coincides.

The Continental Drift

The most important and most recognized explanation for the strong temporal changes in the mean global temperature - in relation to very long time scales - is the continental drift, ie the movement of the land masses on Earth. The arrangement of the continents was not always so, as we know it today. Thus formed the present-day South America, Africa, the Arabian Peninsula, India, Australia and Antarctica until 150 million years ago the supercontinent Gondwana large or Gondwania, which lay at the geographic South Pole. So there was at that time the ice in what is now the Sahara.

The theory that has continental drift as a basis, stating that the precipitation at the poles reinforced has a chance to form ice or snow when there country is because the country much more solar radiation is reflected as water. Due to the increased reflection of light occurs there to a local cooling and there is ice. This ice is more suitable due to its high albedo to reflect solar rays. There will be a positive feedback with decreasing temperatures and an ever progressive ice formation. By the bound in the ice water, however, the sea level drops. This is associated with a smaller water surface and therefore it can from the oceans evaporate less water. This means that the rainfall decline in the global mean and the ice in the consequence also less rapidly growing. If the poles in the contrary case, over the sea, so it is only possible at very low temperatures that sea ice forms. The opposite the sea water higher albedo also leads to a self-reinforcing icing.

The self-reinforcing global cooling only comes to conversion, when the CO ₂ concentration in the atmosphere has risen sharply. This natural greenhouse effect is caused by the fact that the ejected by volcanoes CO ₂ is less strongly bound in rocks and biomass because of the large-scale glaciation and thus affects the climate.

In our time, the geographical South Pole lies on a continent of Antarctica. As before some 25 million years ago an opening between Antarctica and South America, the Antarctic Circumpolar Current and increased glaciation formed began. That's why today there are around 90 per cent of terrestrial ice in the up to 4500 m thick ice of Antarctica.

The volcanism

Large volcanic eruptions can lead to a multi-year cooling of the climate. Gases and ash are then far up into the atmosphere. In particular, the gases can reach (up to 50 km altitude 17) be up in the stratosphere. By photochemical processes in the atmosphere can form tiny particles (aerosols) that reflect the sun's rays, thus preventing the radiation of heat energy from the gases. The result is a cool down.

The volcanic eruption of Laki crater in Iceland in the summer of 1783 has probably led to the extremely cold winter of 1783 /84, Northern Europe and North America and floods in Germany in spring 1784 (see Vasold 2004, under literature). In April 1815, the Tambora volcano on Sumbawa broke, an island which lies today in Indonesia, and apparently caused the " year without a summer " (1816 ).

Other important factors

Other factors that can affect the climate are

• The greenhouse effect,
• Atmospheric particulate matter, known as aerosols,
• Changes in atmospheric circulation, monsoon,
• Changes in ocean currents: global conveyor belt, North Atlantic Oscillation, Southern Oscillation Index, El Niño ( ENSO ),
• The heat content of the oceans,
• The moon through its influence on the tides and thus the major ocean currents.

Man-made climate change

In addition to natural factors also humans can affect the climate. In 2007 came the " Intergovernmental Panel on Climate Change " (Intergovernmental Panel on Climate Change), which summarizes the state of the science on behalf of the United Nations to the conclusion that global warming since the industrial revolution mainly by the accumulation of greenhouse gases humans is caused.