The Earth is a self regulating organism with extremely complex interactions of millions of processes and variables. Each one interdependent with every other in a system so complex that we don't have the technology to completely understand it.

The atmosphere begins on the sun and reaches all the way to the core of the planet. The complex interaction between the atmosphere, the cycles of water in the lakes, seas and rivers and the life processes (respiration) of every living thing on the planet work together to produce the weather conditions prevalent today and for the foreseeable future:

1. The Earth temperature is always changing.
   

2. Over time there have been periods when it has been colder than it is today.
   

3. For most of the Phanerozoic it has been much warmer than it is today.
   

4. Life has persisted during periods both hot and cold.
   

5. There is no one right temperature.
   

6. Carbon dioxide has always been present in Earth's atmosphere.
   

7. Over time there have been periods when CO2 has increased and decreased naturally.
   

8. For most of the Phanerozoic it has been much higher than it is today.
   

9. Life has persisted during periods with high CO2 and low CO2.
   

10. CO2 levels will change with or without human contributions.
    

11. Over time there have been a number of ice ages. Life has endured multiple ice ages.
    

12. For most of the Phanerozoic there have been no persistent polar ice caps.

Despite all the changes within the Earth system, which have occurred during the past 4.5 billion years in very different spacial magnitudes and time scales, the basic pattern however remained remarkably the same. With the aid of a variety of hierarchical exchange mechanisms and feedback processes, which we currently can't fully comprehend, the system was able to compensate to a certain degree for all sorts of flaws and imperfections. This ability of Planet Earth, to preserve its dynamic balance by way of self regulation, is often compared with the physiological equilibrium tendency of living organisms. (Gaia Hypothesis) The earth is more the sum of all components. Changes in the lithosphere, hydrosphere, atmosphere and biosphere cannot be understood by simply applying linear patterns of explanation. That is the reason why it is so difficult to make concrete statements about its future development and especially about the impact of human intervention in its natural structure.

The thrust and the control of long-term global tectonic developments of the Earth's interior (endogenous dynamics) faces a hydrosphere and atmosphere which is moving and shifting on the outside, kept alive by the radiation of the sun and causing a constant transformation of the earth's surface (exogenous dynamics). The energy and material exchange processes involved are of a much smaller scale and take shorter time than those created by processes rooted in the earth's core.

Today's climate system is composed of innumerable regional subsystems across different spatial and temporal scales, which in turn feed back on the overarching climate. As geological evidence reveals, the geologic past has been caught up in progressive climatic changes and climate disasters, impacting on the rock formation and the livelihoods of animal and plant world at the time. And so the future development of the Earth's climate will not be free from long-term climatic shifts as well as sudden surges.

In order to come up with reliable predictions, it is imperative, apart from gaining the best possible theoretical understanding of the underlying mechanics of such developments and events, to always base the research on sound empirical data, ie. palaeoclimatic knowledge of the actual progress and factors controlling them.

Even the most complex simulation models and most powerful computer systems can't assist to obtain reliable, geologically relevant medium- to long- term predictions, if the results are not verifiable by sufficiently long time series of real climate data measurements.

This uncertainty is particularly evident in the contrast of today's common future scenarios for the Earth's climate. On the one hand, the prediction of a global warming disaster, which lets the polar icecaps melt, the sea level rise and expects wide areas and many smaller islands inundated by the sea. On the the hand and in stark contrast to that the equally disastrous expectation of a new ice age with an extended global glacier cover of land masses even in low latitudes.

Until now the earth gave evidence to be a tough planet. In geologically terms, even if humans in the not very distant future might have disappeared from its surface, the planet will retain its powerful momentum for a long time.

The very cold god of physics is there with the red pen to make sure we all get it right in the end ...

Hierarchical exchange and feedback processes