Scientific elements for a tentative of climate evolution forecast.

The Sun is the the Earth energy provider.
Sunspots are the springs of Sun irradiance ( energy) variation.
The number of spots varies like cycles of 11 years called Schwabe cycles.
The solar energy emission depends on the sun activity related to the sunspots size and their number.

The very question:

HOW slight irradiance changes could influence the Earth's atmosphere average temperature?

This irradiance variation is indeed low itself as of 1 to 5 W/m2, compared to the irradiace flux value of 1367 W/m2 !

However it was possible empirically to put in evidence a clear relationship between the Sun activity ( sunspots) and its irradiance.

When the Sun activity increases its irradiance increases, then its solar winds are carrying a stronger magnetic field to the Earth vicinity.
The protective effect of solar magnetism against the low energy radiation coming from the cosmos on Earth is thus strengthened.
This strengthening reduces the intensity of cosmic on rays Earth.

Accordingly the cosmic radiation produces less ions initiators of clouds water condensation (less condensation nucleus for water droplets).

The consequence is less low altitude clouds then the Earth albedo is reduced and therefore more heat reaches the ground.
The albedo is defined as the reflectivity factor of energy received by a planet.

When the albedo is high, less energy is absorb by the Earth ground then the average temperature is decreasing.

Following this mechanism  the Earth average temperature should be linked directly to the duration and intensity of solar cycles.

Cosmic radiations should actually ionized gases and atmospheric aerosols in an efficient way and produce clouds droplets nucleus.
The Danish scientist Dr. Svensmark's team confirmed this when reproducing in laboratory what happens within our atmosphere.
"Proceedings of the Royal Society A", 3 October Titre: "Experimental Evidence for the role of Ions in Particle Nucleation under Atmospheric Conditions". Auteurs: Henrik Svensmark, Jens Olaf Pepke Pedersen, Nigel Marsh, Martin Enghoff and Ulrik Uggerhoj.

The thermal consequences of albedo variations are much greater than the thermal variation of the solar irradiance energy received on Earth.
The albedo change following the duration and intensity of solar cycles. Logically it has a fast temperature influence on the planet.

Possible explanation for the 20th century climate:

During the 20th century the Earth was always under the solar magnetic field protection due to a high solar activity.

• Fewer cosmic rays was received on Earth which induces fewer clouds.
• The consequence is an increasing average temperature trend.

Currently and since 2001, the contrary is happening on Earth:

• Less solar activity with consequence of more radiations from the cosmos.
• So we measure a decrease of low atmosphere temperature.
  

This induces more clouds and the registred temperature trend is now : Earth cooling.
Today and since 2007 the Sun is extremely quiet, this is unusual.

• Almost no sunspots.
• Maximum of cosmic radiation on Earth.

What will be the Sun activity and the evolution of the average temperature during the 21st century?

The S.I.M. (Solar Inertial Motion) is an hypothesis because it is not verified by experience but only by statistical observations: The moving positions of Jupiter and Saturn in their orbits around the Sun should be at the origin of changes in the sunspots number ... and variations of the average temperature of Earth, following the Rhodes Fairbridge and Theodor Landsheidt  SIM model.

The curve below is a result of their calculations for the years 1700 to 2030!
It shows a less active cycle forecast for cycles N°24 and 25 which are comming after the current N°23 cycle.

The here above figure is a result of the actual sunspots count for years 1600 to 2000.
The correlation appears good with SIM calculation.

Conclusion: This is a forecast for global climate cooling.

Other climate forecasting:

The Russian scientists of the Arctic and Antarctic Research Institute (AARI) of St. Petersburg have shown that variations of the Arctic temperatures have a natural origin.Anomaly of mean annual air surface temperature 1900-2006 in the zone of 70-90 N and its predicted trend (I.E.Frolov et al. Scientific research in Arctic. Vol. 2. Climatic changes in the ice cover of the Eurasian shelf seas. -SPb.: "Nauka", 2007,158 p).
The curve below illustrates their conclusions.

They forecast a similar cooling trend as the SIM theory.

"This suggest  that the Earth atmospheric temperature should decrease by more than 1°C up to year 2030".

Conclusion:

Since year 2001 the Earth planet should be entering a phase of climate cooling !

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