"Veizer and his co-author Nir Shaviv, from the Hebrew University of Jerusalem, discovered that cosmic rays cause excess clouds. When cosmic rays strike earth in abnormally high concentrations, their highly charged particles cause aerosols in our atmosphere to pick up electrical charges. These energized aerosols then attract water vapor causing low-level cloud cover to increase but when our sun is particularly active, the solar wind it produces "blows" these cosmic ray particles away before they can charge up the atmospheric aerosols, diminishing cloud formation. When the Sun is quiet then the rays can effect the planet. This is significant because clouds in the lower atmosphere shield the Earth from solar radiation. They bounce this "insolation" (incoming solar radiation) back into space before it can cause the planet to warm. Thus when cosmic rays are plentiful, so are clouds, and our planet cools. Scientific Allience - Lorne Gunter 2003
A greatly increased number of cosmic rays are getting through to Earth because our Sun's magnetic poles, instead of reversing completely, have only rotated halfway and are now more or less lying sideways along the Sun's equator. Scientists believe that this is due to the way in which the polarity changed during the last solar maximum. This weaker configuration of the magnetic shield is letting in two to three times more cosmic rays (stardust) than at the end of the 1990s. Moreover, this influx could increase by as much as ten times until the end of the current solar cycle in 2012. Solar cycles are approximately eleven years in length.
European Space Agency's (ESA) Ulysses space probe data is finally making it possible to study how cosmic rays are distributed along the path of the Solar System through the local galactic environment. The space probe is showing us that a flood of dusty particles is heading our way. (this was years ago they are now here?)
Astronomers think the current cosmic ray influx, apart from being favoured by the particular configuration of the Sun's magnetic field, is also enhanced by the thickness of the interstellar clouds into which the Solar System is moving. Currently located at the edge of what astronomers call the local interstellar cloud, our Sun is joining our closest stellar neighbour Alpha Centauri in its dense cosmic ray cloud, which is less hot but denser than where we have been. It takes over 70 thousand years to traverse a typical galactic cloud, interestingly this is about the same period of time earth is usually in a glaciated state before the next interglacial period of 10,000 to 15,000 years of warmth returns. Press release 2003 Source: Artemis Society
The Earth's magnetic field also shields the Earth from cosmic rays , which are radiation produced by astrophysical objects The magnetic field, which extends about 36,000 miles into space, is generated in the Earth's core - a big ball of solid iron about 1,490 miles in diameter, surrounded by a sea of molten iron, 4,350 miles in diameter. The magnetic field is not constant as it's produced by this turbulent flow that's deep in the Earth's core. Magnetism trapped in ancient pottery shows that over the past 4,000 years, the magnetic field has weakened by more than 50%. Since people have been measuring, it has been steadily declining. The first measurements were taken about 150 years ago, since then, it's declined not quite 10 percent. Which shows it is dropping rapidly, as the magnetic field wanes, the protective shield it provides shrinks, thus exposing satellites to damage from cosmic rays and charged particles coming from the sun. Even now satellites can be damaged, if not destroyed, because the protective shield is so weakened. So there will be many more reflective clouds cooling the planet than previously and this explains Earth's cooling trend which has been going on for about 4500 years now. The Earth was much warmer by over 6 degrees 4500 years ago and the polar bears didn't die."
What the above means is more rain which falls as snow at the poles which causes the Earth to go into an rapid ice age change.
All of this has nothing to do with human pollution of course.