Updated: Dust Study May Invalidate Most Warming Models

  • Date: 30/12/10

Some of the Earth’s tiniest naturally occurring particles may have just bred a big mess for climatologists.  New findings reveal that models scientists have long used to estimate the causes and effects of global warming may be dramatically flawed due to errors in one of their most important inputs.

These conclusions are found in a new study published in the journal Proceedings of the National Academy of Sciences by Jasper Kok, a climatology researcher with The National Center for Atmospheric Research (NCAR).

I. Recent Warming – Blame it on the Sun?

The study’s key conclusion was to show that the ratio of small soil dust particles (clay), which cool the atmosphere, to large soil dust particles (silt), which yield an indirect heating effect, may be much higher than previous estimated.  This is a critical finding because it shows that the Earth’s climate may be much more sensitive to solar radiation than previous models have indicated, which in turn casts doubt on anthropogenic warming theory — the idea that human carbon dioxide emissions bear the primary warming influence on the climate over the last several decades.

Carbon dioxide, like water vapor, has been shown unquestionably to be a greenhouse gas with some effect on the atmosphere.  And human behavior (direct — via burning fossil fuels, and indirect — via livestock and clearing vegetation) has caused atmospheric CO2 levels to creep upwards over the last half century.  

That said, levels still remain drastically lower than in certain periods of the Earth’s early history.  Furthermore, it is exactly what impact these slightly elevated CO2 levels are having in terms of warming.  While it would be quick to claim causation, due to the correlation in recently rising temperatures, the exact degree of causation — if at all — remains unknown.

Solar activity also climbed over the last few decades as the Earth heated up.  Based on the newly presented events, this may have had a direct forcing effect on the warming, which in turn may mean that CO2 emissions have less of a forcing effect than previously estimated.

II.  Dust in the Wind

Mineral dust blows up into the atmosphere from multiple locations around the globe and plays a critical, but poorly understood role on the Earth’s climate.  The dust is created when sand particles are blown by the wind into soil, shattering it into microparticles.  Major sources of mineral dust include the southwestern United States, northern Africa, Northeast Asia (the Gobi Desert) and Australia.

The smallest microparticles measure a mere 2 microns (2000 nm).  These particles are known as clay.  They tend to stay in the atmosphere for long periods of time, reflecting light and cooling the Earth.  

Large microparticles, known as silt, can reach 50 microns (50,000 nm) — about the width of a human hair).  Their weight causes them to quickly fall out of the atmosphere.  This has both an indirect and direct climate change effect.  The indirect effect, is that they fail to block solar radiation, allowing the sun to heat the atmosphere more readily.  The direct effect is that they tend to accumulate in mountain polar ice, concentrating sunlight, absorbing heat and accelerating melting.

In order to find the true ratio of the particles types, Professor Kok cleverly combined mathematical theory and statistical data.  To determine the breaking method, he used brittle object breaking formulas developed by mathematicians.  Brittle objects, like glass, rocks — or soil — break into a predictable distribution of small, medium, and large particles.  

Using these formulas, the researcher turned to statistical information on arid soil, published in a 1983 study Guillaume d’Almeida and Lothar Schüth from the Institute for Meteorology at the University of Mainz in Germany.  By combining the two, he was able to arrive at what is thought to be the most accurate statistical distribution for particle sizes resulting from soil breaking published to date.

And the results yielded a major surprise.  They showed that the larger particles (responsible for heating) occurred two to eight times more frequently than previously thought.

While this may not seem terribly thrilling, it bears tremendous consequence both to global warming policy makers and to climatology researchers.  It essentially means that one of the most important inputs to climatologists’ carefully crafted computer models is drastically flawed.  In turn this means that major reanalysis of computer-aided climate simulations may be necessary.

III. Back to the Drawing Board

The new findings by no means devalue the idea of using computer modeling to study the Earth’s climate.  But they are an important reminder that climate models are only as good as their inputs, and in many cases those inputs are based on information that’s lacking.

Despite the controversy that this study will likely breed, Professor Kok is more preoccupied by its beauty from a mathematical perspective.  He states, “As small as [the particles] are, conglomerates of dust particles in soils behave the same way on impact as a glass dropped on a kitchen floor.  Knowing this pattern can help us put together a clearer picture of what our future climate will look like.  The idea that all these objects shatter in the same way is a beautiful thing, actually.  It’s nature’s way of creating order in chaos.”

Beautiful indeed.  Professor Kok’s ability to focus on truly objective mathematical and scientific analysis with regard to what is an increasing politicized topic is exemplary as well.  Given recent revelations [1] [2] [3], this kind of objective dedication to scientific truth is not always present in this field, so it’s as refreshing to see that as it is fascinating to observe the symmetry that underlies many laws of our universe.

Daily Tech, 30 December 2010

UpdateDec 31, 2010 11:10 a.m.-

We had a lengthy discussion with Professor Kok to clarify a couple of conclusions that the NSF press release seemed to be pointing at.  Most importantly, Professor Kok explained to us that the levels of small dust was not less than previously expected, rather they were the same and the levels of large dust were higher.

He also explained that solar variance (generally within the range of +/- 0.1 percent of total energy transfered into the atmosphere) and dust’s reflectivity (about +/- 0.3 percent of total energy transfered into the atmosphere) indicate that any correlation between dust and the impact of solar activity would be very weak (around 3 ppm).  At 3000 ppm, dust’s direct effects via atmospheric dust levels are the more important topic to look at, as confirmed by our further discussions with Professor Kok.

That said the key conclusion of this article — that warming models need to be re-run with accurate dust info or risk offering misleading conclusions — still stands, albeit via a different mechanism than we previously thought.  We apologize for the confusion concerning the relationship between solar activity and dust levels.

We’d also like to thank Professor Kok for taking the time to discuss some of this study’s finer points.  We’re looking forward to doing an interview with him on the topic of climate modeling in the near future.

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