Researchers Find No Evidence That Floods Are Getting Worse

By Paul Homewood 

 

More frequent and more devastating floods are both (1) predicted for the future and (2) claimed to already be occurring by a host of climate alarmists, as a result of climate change that they claim is induced by anthropogenic CO₂ emissions. But are these claims correct?

 

 

In a massive review of the subject conducted by a team of seventeen researchers hailing from eleven different countries, i.e., Kundzewicz et al. (2013), we learn the

(1) "no gauge-based evidence has been found for a climate-driven, globally widespread change in the magnitude/frequency of floods during the last decades,"

(2) "there is low confidence in projections of changes in fluvial floods, due to limited evidence and because the causes of regional changes are complex,"

(3) "considerable uncertainty remains in the projections of changes in flood magnitude and frequency,"

(4) increases in global flood disaster losses reported over the last few decades "may be attributed to improvements in reporting, population increase and urbanization in flood-prone areas, increase of property value and degraded awareness about natural risks (due to less natural lifestyle),"

(5) "the linkages between enhanced greenhouse forcing and flood phenomena are highly complex and, up to the present, it has not been possible to describe the connections well, either by empirical analysis or by the use of models," and

(6) "the problem of flood losses is mostly about what we do on or to the landscape," which they say "will be the case for decades to come."

 

In closing, Kundzewicz et al. write that "the climate change issue is very important to flooding, but we have low confidence about the science," adding that "work towards improvements in GCMs [global climate models] to bring us to a point where all of this is made clear is much needed, and may take much time." And they thoughtfully remind us – in the interim – that "although media reports of both floods and global flood damage are on the increase, there is still no Mauna-Loa-like record (see Vorosmarty, 2002) that shows a global increase in flood frequency or magnitude.”

 

Most authors of this paper were also authors of one of two chapters of the recent IPCC SREX report.

 

They also make this interesting point about the cyclical nature of floods, which highlights the danger of looking at short term trends.

 

Even without a change (such as gradual trend), there are extended departures of flood records from long-term average conditions. Among their possible sources are quasi-periodic unforced oscillations of the ocean–atmosphere system. For instance, the probability of flooding in particular regions is related to El Niño or La Niña phases of the ENSO (El Niño Southern Oscillation) cycle (e.g. Wells 1990) or the AMO (Atlantic Multi-decadal Oscillation) phase (e.g. Bouwer et al. 2008). There is a long-term persistence of flooding that could be viewed in the sense of Hurst (see Koutsoyiannis 2011) and Mandelbrot’s Noah effect, referring to the biblical pharaoh’s dream, and clustering of wet and dry years, creating flood-rich and flood-poor episodes. For instance, on the Danube in Vienna, grouping of five of the six largest floods in the 19th century was observed in the last two decades of the century, illustrating pronounced clustering of extreme events (Blöschl and Montanari 2010). Climate models do not adequately represent long-term persistence that is observed in real data, and the effect is typically ignored in climate studies (Koutsoyiannis and Montanari 2007). The implications are not fully understood or recognized. Acceptance of the long-term persistence hypothesis would lead to a dramatic increase in uncertainty in statistical estimation. This thwarts the trend detection.

 

 And finally, they tackle the question of why there is a perceived increase in flood risk:

 

There are several factors that may explain a perceived increase in flood risk: improved and expanded reporting of disasters, increased exposure of population and assets, and higher frequency and/or intensity of the hazard (Kundzewicz et al. 2012). Media play a role—the news coverage is much better, worldwide, than in the past and tends to be focused on the negative side of things (Kundzewicz 2011). Some call it a “CNN effect.”

 

 

The full paper “Flood risk and climate change: global and regional perspectives” is available below.

http://www.tandfonline.com/doi/full/10.1080/02626667.2013.857411#tabModule