Comment On The Nature Paper “Human Contribution To More-Intense Precipitation” By Min Et Al 2011

There has been quite a bit of discussion on weblogs of the Nature paper [h/t to Marcel Crok for alerting me to the paper]

Seung-Ki Min, Xuebin Zhang, Francis W. Zwiers and Gabriele C. Hegerl: 2011: Human contribution to more-intense precipitation extremes. Nature. 17 February 2011.

Weblog posts include

On Storms, Warming, Caveats and the Front Page

Attribution of Extreme Events: Part II

Flood Disasters and Human-Caused Climate Change

The Nature paper as well as media coverage is selective on attributing reasons for an increase in extreme precipitation even if this is a robust finding.  Of  concern is the incomplete reasoning that they provide for explaining the increase in extreme precipitation, where Min et al write

“Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas.”

We have published recently on the role of land use change, by itself, as a possible explanation of an increase in extreme precipitation in certain regions. The model study reported in Nature ignored this possibility.

Our papers on this subject, under the leadership of Faisal Hossain, include

Hossain, F., I. Jeyachandran, and R.A. Pielke Sr., 2009: Have large dams altered extreme precipitation patterns during the last Century? Eos, Vol. 90, No. 48, 453-454. Copyright (2009) American Geophysical Union.

Degu, A. M., F. Hossain, D. Niyogi, R. Pielke Sr., J. M. Shepherd, N. Voisin, and T. Chronis, 2011: The influence of large dams on surrounding climate and precipitation patterns. Geophys. Res. Lett., 38, doi:10.1029/2010GL046482, in press.

Hossain, F., I. Jeyachandran, and R.A. Pielke Sr., 2010: Dam safety effects due to human alteration of extreme precipitation. Water Resources Research, 46, W03301, doi:10.1029/2009WR007704.

Excerpts from the Hoassin et al 20010 paper read

“For southern Africa and southern Europe, dams [and the associated landscape changes that result in its vicinity] appeared to have increased extreme precipitation (P99 events) by as much as 20% during the last century. Stations in southern India are found to have experienced a modest increase in the P99 value (Figure 3). In the U.S., the P50 (mean) and P99 values are found similarly sensitive to the effect of dams.”

“Our study seems to indicate that the impact of large dams on extreme precipitation is clearly a function of surrounding mesoscale and land use conditions [e.g., see Pielke et al., 2007; Douglas et al., 2009], and that more research is necessary to gain insights on the physical mechanisms of extreme precipitation alteration by dams. The changes in land use, for example from added irrigation, add a significant amount of water vapor into the atmosphere in the growing season, thereby fueling showers and thunderstorms [e.g., see Pielke and Zeng, 1989; Pielke et al., 1997; Pielke, 2001].”

It appears that the focus of much of the media and in Nature is to prompte a narrowly confined explanation for increases in extreme precipitation (as being due primarily to added CO2 and a few other greenhouse gases).

They have ignored other explanations due to human forcings; e.g. see

Inadvertant Weather Modification – An Informational Statement of the American Meteorological Society (Adopted by the AMS Councul on 2 November 2010)

as well as the role of natural variability in extreme precipitation weather events, as discucssed very effectively in the posts by Judy Curry

Attribution of Extreme Events: Part I

Attribution of Extreme Events: Part II.



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