Costas Varotsos Discusses Ozone & Temperature Analyses

Emerging Research Fronts Commentary, August 2011

Costas Varotsos

Article: Long-memory processes in ozone and temperature variations at the region 60 degrees S-60 degrees N

Authors: Varotsos, C;Kirk-Davidoff, D
Journal: ATMOS CHEM PHYS, 6: 4093-4100, SEP 12 2006
Addresses: Univ Athens, Dept Appl Phys, Athens, Greece.
Univ Athens, Dept Appl Phys, Athens, Greece.
Univ Maryland, Dept Atmospher & Ocean Sci, College Pk, MD 20742 USA.

Costas Varotsos talks with and answers a few questions about this month's Emerging Research Front paper in the field of Geosciences.

SW: Why do you think your paper is highly cited?

I think that this particular paper has been highly cited because it was the first to show that the fluctuations of the global total ozone (TOZ) and global tropospheric temperature (TRT) obey power-law dynamics. This paper brings together two fields that are climate system physics on the one side and nonlinear dynamics, complexity theory, chaos, and fractals on the other.

The climate system (which is a subsystem of the global system) consists of five subsystems, the atmosphere, cryosphere, lithosphere, biosphere, and hydrosphere, which are interacting continuously with each other, not only naturally but also through human intervention. The chaotic character of the climate system dynamics limits the reliability of climate projections. Thus the reliable prediction of global climate change or of one of its components (e.g., ozone-sphere) is impossible without consideration of the complexity of all the interactive processes.

In an attempt to shed light on the aforementioned complexity, scaling analysis of atmospheric data certainly is becoming an important approach which can be traced back to Lewis Fry Richardson (Richardson LF, "Atmospheric diffusion shown on a distance-neighbor graph," Proc. Roy. Soc. A 110: 709–37, 1926). This is an exciting field of research with very many active workers being very busy in the field.

In our paper, we have explored the non-linear dynamics of two crucial parameters, the atmospheric TOZ and TRT, which are of considerable climatic and biological importance. The reason that we have chosen these two data sets to explore their memory effects is because these are closely connected with two crucial environmental problems, notably: the ozone depletion and the global warming. The latter, I think is an additional reason that our paper is attractive, because the work described in it resides in an area of great importance to climate, ozone depletion, and modern physics.

SW: Does it describe a new discovery, methodology, or synthesis of knowledge?

This paper synthesized years of research, culminating in a new discovery for scaling dynamics in the area of atmospheric physics. Employing recent methods and tools borrowed from modern statistical physics, complexity theory, chaos, and fractals, we can better understand the climate system operation and visualize errors in the treatment of the intrinsic long-range correlations, the correct modeling of which would greatly enhance confidence in long-term climate and atmospheric physico-chemistry modeling.

Consideration of the decay of correlations in time has often yielded insight into the dynamics of complex systems. A randomly forced first-order linear system should have fluctuations whose autocorrelation decays exponentially with lag time, but a higher-order system will tend to have a different decay pattern.

Log-log plot of the DFA-l versus temporal interval ?t (in months) for detrended and deseasonalized CO2 concentrations, over Mauna Loa Observatory (19.5°N, 155.5°W) during 1959–2004. The slopes for DFA-1, DFA-2, DFA-3, DFA-4, DFA-5 are 1.10 (±0.02), 1.13 (±0.02), 1.09 (±0.02), 1.06 (±0.02), 1.06 (±0.03), respectively (source: C. Varotsos et al. 2007, Atmos. Chem. Phys., 7, 629–634).

This paper introduced the following: the global TOZ and global TRT fluctuations in small time intervals are positively correlated to those in larger time intervals in a power-law fashion. For TRT, the exponent of this dependence is larger in the mid-latitudes than in the tropics at long time scales, while for TOZ, the exponent is larger in tropics than in the mid-latitudes. In general, greater persistence (i.e., stronger memory) could be a result of either stronger positive feedbacks or larger inertia.

The difference in persistence patterns between ozone and temperature could arise because the TOZ distribution is more closely tied to gradients in temperature than to the temperature itself. The increased slope of the power distribution of temperature in mid-latitudes at long time scales compared to the slope in the tropics could be connected to the poleward increase in climate sensitivity predicted by the global climate models.

SW: Would you summarize the significance of your paper in layman's terms?

Ozone is a very minor trace gas in the atmosphere (there are only 3 ozone molecules per 10 million molecules in the atmosphere). Yet its importance for mankind vastly exceeds what might be expected from this very low concentration of ozone. It provides a shield, the ozone layer, which protects us—and the biosphere in general—from the adverse effects of high-energy solar ultraviolet radiation which is a major cause of skin cancers.

The ozone concentration in the atmosphere fluctuates widely from day to day but behind this there is a steady decrease (the ozone depletion) of a few % per decade due to the release of man-made chemicals (primarily CFCs) into the atmosphere. The ozone layer also affects the balance of heat energy between the Earth and the rest of the universe and so knowledge of future ozone concentrations is essential in climate modeling to predict future global warming.

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