| Most scientists believe that the current | | | | explain if you don't include some other types |
| global warming is caused by man-made | | | | of influence from the Sun. |
| emissions of greenhouse gases and that the | | | | |
| most important of these gases is Carbon | | | | It was not until the Danish scientist Henrik |
| Dioxide or CO2. | | | | Svensmark suggested that cosmic radiation |
| | | | could influence cloud cover that a plausible |
| They also believe that the Sun's influence | | | | explains for this apparent correlation was |
| for this warming is very small. We now know | | | | given. |
| that the irradiance or "heat transfer" from | | | | |
| the Sun to the Earth has varied relative | | | | Here is this theory! |
| little during recent decades. Therefore the | | | | |
| conclusion that most scientists have done is | | | | When the Sun is very active, as it is now, |
| that the resent warming must be man-made, | | | | the solar wind and the solar magnetic field |
| this is because they haven't found any other | | | | are both strong. This in turn shields the |
| reasonable explanation. | | | | Earth from high energy particles coming from |
| | | | the cosmos, usually from particles which were |
| However what we know over how much a specific | | | | once created in supernova explosions. This |
| increase of CO2 has on global temperature is | | | | affects low cloud cover formation as the |
| poor. The reason in that the knowledge of how | | | | radiation create ions which seeds cloud |
| greenhouse gases affect cloud formation is | | | | forming water droplets. During times when |
| mostly down to speculations. Cloud formation | | | | there are many high energy particles reaching |
| physics is quite a complicated process to | | | | low altitudes there are more low cloud cover |
| explain with many factors. | | | | and the Earth cools. When there are few high |
| | | | energy particles penetrating to low altitudes |
| So, rather than having a solid theoretical | | | | then less clouds form and the Earth warms. |
| and measured basis for how much man-made | | | | |
| greenhouse gases affect the climate, the made | | | | Usually clouds higher up in the atmosphere |
| estimation is mostly down to deduction. | | | | are almost always ionized from both low and |
| | | | high energy particles because both those |
| They argue: We know how much the temperature | | | | types of particles penetrate high altitudes |
| has increased so therefore we can calculate | | | | at all time. |
| how much a specific increase in greenhouse | | | | |
| gases will increase the global temperature in | | | | The created variations are only in the low |
| the future. We have done this through | | | | altitude cloud cover which is affected by |
| deduction as we already have attributed the | | | | very high energy cosmic particles. |
| known increase to be greenhouse driven. | | | | |
| | | | Recently an experiment called SKY (Cloud in |
| However scientists who study the Sun have | | | | Danish) was made by Svensmark which |
| long noted similarities between solar | | | | conclusively confirmed this cloud forming |
| activity and terrestrial weather patterns. | | | | mechanism experimentally and that this type |
| | | | of cosmic ionization has an important seed |
| Also the weather changes the last century is | | | | effect on clouds. Links between low cloud |
| not something unique. Given the relative | | | | cover variations and high energy particles |
| small changes in the observed irradiance | | | | intensity have also now been confirmed by |
| "heat emitted from the Sun", those changes in | | | | satellite studies. |
| temperature during past centuries are hard to | | | | |