Comment: It would appear that part of the problem is that these studies are performed with foregone conclusions, and assumptions science knows more than it does; that human activity is the primary cause of changes on our planet, and that we understand the complexities of plant and soil life better than we really do .

Pierre Lescaudron explicates the more likely drivers of global dimming - some that are not factored into the models mentioned above - and their effect globally - not just in the Arctic - in his book with Laura Knight-Jadczyk Earth Changes and the Human-Cosmic Connection:

Global dimming

Global dimming is the reduction in the amount of solar radiation received on Earth's surface during fair weather. One of the main causes of global dimming is atmospheric dust. Numerous scientists have demonstrated that a global dimming trend has been in
process for decades.

There's been some debate as to whether atmospheric dust induces a net warming effect on the planet (because it absorbs more than it reflects radiation), or whether it induces a net cooling effect (because it reflects more than it absorbs radiation). In 2008, atmospheric scientist Richard Hansell tested and measured the net effect of atmospheric dust particles on temperatures and concluded that although atmospheric dust both absorbed and reflected solar radiations, it induced an overall cooling effect:

The analysis showed that over half of dust's cooling effect is compensated for by its warming effect. The finding, published in the Journal of Geophysical Research, Atmospheres, could clarify scientists' understanding of how dust influences moisture fluctuations in the atmosphere and surface temperatures around the planet.

As shown in the diagram below, researchers from the Institute of Soil, Water and Environmental Sciences found a significant reduction, globally averaged 2.7% per decade, in solar radiation reaching the Earth's surface over the last 50 years.

© Stanhill & Cohen
Reduction in solar irradiance over the period 1950-2000.

In the 90's an inversion occurred and our planet experienced a global brightening in some regions. Then, after the year 2000, global dimming restarted in certain areas and became overall more chaotic with different continents experiencing opposite trends.

Now, according to mainstream science, global dimming is man-made, caused by the accumulation of aerosol particles in the atmosphere due to industrialization. The trend inversion noticed in the 90s is attributed to the ban of several types of aerosols and other anti-pollution measures. However, a paper published in 2005 showed that over the period 1986-2000, although a slight dimming was occurring over land, a brightening occurred over the oceans.

© Pinker et al
Irradiance over the period 1982-2002. Land measurements on the left (global dimming), ocean measurements on the right (global brightening).

If human activity was indeed the cause of global dimming, and the reduction in human aerosol use the cause for the brightening observed in the 1990s, a brightening over land should have been observed and, possibly, a delayed brightening over the oceans (due to air circulation), since most industrial sources are located on continents. But the paper referenced here shows exactly the opposite.

Since 2000, dimming has been observed in numerous places, including China, India and the whole southern hemisphere, despite the relatively lower presence of anthropogenic pollution in this less industrialized hemisphere. We can deduce from this that while human pollution might indeed affect the amount of sunlight reaching the surface, it's obviously not the only cause and its effects are probably negligible in the larger context.

Unlike human pollution, cometary activity could, at least partly, explain both the global dimming observed above the oceans during the 1990s and the dimming since 2000.

Between 40 and 400 tons of extraterrestrial material is estimated to enter the Earth's atmosphere daily 214,215 most of it arriving in the form of cometary dust. These estimates calculated years ago do not, however, take into account the recent surge in cometary activity. If we factor in the 655% increase in confirmed fireballs (see AMS statistics above) over the past eight years, the quantity of cometary dust entering Earth's atmosphere should be at least six times higher than that generally estimated; that is, daily incoming dust measuring between 260 and 2,600 tons.

He later goes onto to explicate how a rise in cosmic rays accelerates cloud formation, global dimming and global cooling, and that, while this appears to be a more recent phenomenon, with an increase of 13% in just 3 years, their impact on further cooling the planet will also likely have an affect on tree growth in the Arctic, a factor also not accounted for in the study above.

See also:

• Volcanoes, Earthquakes And The 3,600 Year Comet Cycle
• Professor Valentina Zharkova: "We entered the 'modern' Grand Solar Minimum on June 8, 2020"
• Cloud mystery: Climate change and cosmic rays

And check out SOTT radio's:

• Behind the Headlines: Earth changes in an electric universe: Is climate change really man-made?
• MindMatters: The Holy Grail, Comets, Earth Changes and Randall Carlson
• Adapt 2030 Ice Age Report: Interview with Laura Knight-Jadczyk and Pierre Lescaudron