the likelihood of extreme precipitation on any given day rose by about 7 percent over the last half of the 20th century
The article does not address the level of uncertainty in their analysis. Even if there is a 7 percent variability from natural atmospheric variability there is no reason to attribute it to rising CO2.
Judith Curry, a mainstream climate scientist stated: I find this kind of analysis totally unconvincing, and it does not recognize the role of natural internal variability such as the Arctic Oscillation, La Nina, etc in producing floods. None of the recent floods are extreme in historical context.
From Roger Pielke Sr., another leading climate scientist:
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 (Pielke et al.)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:
Have large dams altered extreme precipitation patterns during the last Century? Eos, Vol. 90, No. 48, 453-454. Copyright (2009) American Geophysical Union
pielkeclimatesci.files.wordpress.com
The influence of large dams on surrounding climate and precipitation patterns. Geophys. Res. Lett., 38, doi:10.1029/2010GL046482, in press.
pielkeclimatesci.files.wordpress.com
Dam safety effects due to human alteration of extreme precipitation. Water Resources Research, 46, W03301, doi:10.1029/2009WR007704.
pielkeclimatesci.files.wordpress.com
Excerpts from the 2010 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 promote 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 as well as the role of natural variability in extreme precipitation weather events.
pielkeclimatesci.wordpress.com |
