Implications Of A New Paper “Impact Of Polar Ozone Depletion On Subtropical Precipitation” By Kang Et Al 2011

There is a new paper (h/t to Steve Milloy) that further documents that

1. Carbon Dioxide is but one of a diverse range of human climate forcings

and

2. That it is atmospheric and ocean circulation pattern changes that are of much more importance than a long term trend in the global annual average surface temperature.

We reported on these two issues, for example, in

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union.

where we wrote

In addition to greenhouse gas emissions,  other first-order human climate forcings are important to understanding the future behavior of Earth’s climate. These forcings are spatially heterogeneous and include the effect of aerosols on clouds and associated precipitation [e.g., Rosenfeld et al., 2008], the influence of aerosol deposition (e.g., black carbon (soot) [Flanner et al. 2007] and reactive nitrogen [Galloway et al., 2004]), and the role of changes in land use/land cover [e.g., Takata et al., 2009]. Among their effects is their role in altering atmospheric and ocean circulation features away from what they would be in the natural climate system [NRC, 2005].

Ozone depletion in the stratosphere can be added to this list.

The new paper is

S. M. Kang, L. M. Polvani,J. C. Fyfe, M. Sigmond, 2011: Impact of Polar Ozone Depletion on Subtropical Precipitation Scienc Express.org / 21 April 2011

The abstract reads [highlight added]

“Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the Southern subtropics in austral summer increases significantly when climate models are integrated with reduced polar ozone concentrations. Furthermore, the observed patterns of subtropical precipitation change, from 1979 to 2000, are very similar to those in our model integrations, where ozone depletion alone is prescribed. In both climate models and observations, the subtropical moistening is linked to a poleward shift of the extratropical westerly jet. Our results highlight the importance of polar regions on the subtropical hydrological cycle.”

An excerpt from the paper reads

In a broader perspective, the impact of polar ozone depletion on tropical precipitation discussed here provides one more instance of how changes in high latitudes are able to affect the tropics. Other well-known examples are the effect of Arctic sea ice … and of the Atlantic thermohaline circulation … on the position of the Intertropical Convergence Zone (ITCZ). Hence the need to deepen our understanding of polar to tropical linkages in order to accurately predict tropical precipitation.”

In a news article on this paper by Richard Black of the BBC,

Ozone hole has dried Australia, scientists find,

it is written

“This study does illustrate the important point that different mechanisms of global change are contributing to the climate impacts we’re seeing around the world,” observed Professor Myles Allen of Oxford University, a leading UK climate modeller.

“It’s very important to unpack them all rather than assuming that any impact we see is down simply to greenhouse gas-mediated warming.”

Myles Allen has succinctly and accurately summarized the significance of this study in his quote.

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