71 comment(s) - last by ekv.. on Dec 31 at 5:23 AM
Models overestimate the number of small cooling particles, potentially reducing CO2's role in heatingThe cooling effect of dust created by desert sand blowing into dirt is significantly overestimated, according to a massive new study. That means that the solar radiation likely had a far greater influence on warming, while greenhouse gases like CO2 likely played a smaller than thought role. (Source: bachmont, Creative Commons) Dust particles can effectively render the planet more or less sensitive to solar warming, based on their size. (Source: UCAR)
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.
This revelation is an indirect conclusion of 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 evidence of the composition of atmospheric dust, dust cooling may be less that previously estimated, which in turn may mean that CO2 emissions have less of a forcing effect than previously estimated. While the study does not specifically discuss this, the conclusions lend some support to the theory that the recent increase in solar activity may have played a much larger role in recent warming than atmospheric carbon increases.
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. Past studies have shown that 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 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 ratio of larger particles to small particles (responsible for heating) was two to eight times higher than originally thought. In other words, dust had less of a cooling effect on the atmosphere and more of a melting effect on glacial ice.
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 could be substantially 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.
How much or how little impact this study has on modeling will rest largely on determining more accurately how much atmospheric dust is present. According to a brief conversation we had with Professor Kok, the levels of atmospheric dust and how they change with time is a poorly "understood" topic. Thus the study could potentially invalidate current warming models, or leave them largely unscathed. But it does indicate that a new round of data collection and verification is necessary to determine which is the case.
Despite the controversy that peripheral effect of the study will bring, 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.
Friday, December 31, 2010
DailyTech - Dust Study Raises Questions Concerning Warming Models
via dailytech.com
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