October 17, 2011

No Change in Storminess

As we enter the winter season, we all realize that if a large snow storm forms anywhere on the planet, someone will immediately appear and claim we are witnessing the effect of global warming. However, winter storms (aka extratropical cyclones) are tough to sell to the public given the images of cold, snow, wind, and misery at the low end of the temperature scale. So if winter storms are a hard sell, hurricanes (aka tropical cyclones) are nothing short of ideal – warm water, heavy rain, wind, and misery in already warm parts of the world.

But, it turns out that in either case, new research reported in the scientific literature finds little in the way of changes that are unusual in today’s climate of “global warming.”

The first article appeared in Tellus written by five scientists with Germany’s Hamburg University who were investigating changes in the recent behavior of extratropical cyclones. Sienz et al. (who tend to get a bit technical) begin noting:

“Extratropical cyclones are the major source of intra-annual climate variability in mid-latitudes. Huge damage is caused by intense storms and heavy precipitation associated with extraordinary intense baroclinic vortices [i.e., extratropical storm systems –eds.]. The growth and intensity of these vortices are determined by sea surface temperatures, baroclinicity and large-scale teleconnections (for example the North Atlantic Oscillation, NAO) which might be altered in an anthropogenic climate change”.

With respect to what we might expect to see with storm behavior, they note:

“For the northern hemispheric winter the majority of scenario simulations show a slight decrease of the total number of cyclones, while, on the other hand, there are hints that the number of intense cyclones increases. However, models do not agree with respect to these conclusions, in particular if individual regions are considered.”

In other words, we have no clue what should be happening to cyclonic storms in the Northern Hemisphere as a whole and even less so for particular regions.

To help better understand what has been happening, the team gathered what are called “re-analysis” data from September, 1957 to August, 2002; these data are created by a model but the data are derived from a large collection of observations on a daily basis. Re-analysis data are quite popular now in climate change research, and despite some limitations, they are showing up everywhere in the literature. From the re-analysis data, the team computed four different measures of cyclone intensity including “geopotential height in the centre of a cyclone, mean horizontal gradient of the geopotential height in the neighbourhood, cyclone depth, all measured at 1000 hPa, and relative vorticity in the cyclone centre at 850 hPa.” Let’s not turn this into an advanced class in atmospheric science—so it will suffice to say that these are all very credible measures of the intensity of a storm event. Sienz et al. report “no significant trend could be found in [any] of the cyclones quantities”. In their conclusions section, they note “The absence of a significant trend in the cyclone parameters for the whole North Atlantic is consistent with the findings of” other scientists who have explored the same issue.

You might argue that evaluating storm activity from 1957 to 2002 is hardly a long enough time period for conducting any meaningful, long-term climate analysis. Maybe you’d prefer something a bit longer? Well, then you are in luck. A recent article in Geology allows us to peer back over 5,000 years of storm activity—so let’s have a look.

The research was conducted by a pair of earth scientists from Rice University who were funded by British Petroleum. We suspect that given this fact, their work was held to a higher standard of review compared to other submissions to Geology, and they apparently survived and the work is published in a highly respected outlet.

In some coastal areas, lagoons form and in a few special locations, the topography is just right for capturing overwash sediments from extreme storm events. Given the study area in southern Texas (near spring break paradise South Padre Island), the Wallace and Anderson team could reconstruct extreme hurricane (i.e., tropical cyclone) events going back 5,300 years. The area subsided at about that time producing the right conditions for recording intense storms of the past, but prior to 5,300 years ago, the lagoon was not in a position to record large hurricane events.

Wallace and Anderson collected 37 different cores within the lagoon (Laguna Madre), and they used radiocarbon dating and grain size analysis to detect large events in the past (big storms produce big sediments). When looking at the period 5,300 to 900 BP [before present], they conclude:

“Although high-frequency oscillations between warm and dry and cool and wet climate conditions have occurred in Texas through the late Holocene, there has been no notable variation in intense storm impacts across the northwestern Gulf of Mexico coast during this time interval, implying no direct link between these changing climate conditions and annual hurricane impact probability. In addition, there have been no significant differences in the landfall probabilities of storms between the eastern and western Gulf of Mexico during the late Holocene, suggesting that storm steering mechanisms have not varied during this time.”

In discussing any link between sea surface temperatures in the Atlantic and hurricane activity, the authors are dismissive of the link and suggest that “[r]ather, intervals of frequent intense hurricane impacts (i.e., ca. 4400–3600 yr B.P., 2500–1000 yr B.P., 250 yr B.P. to present) can be correlated with periods of fewer El Niño events and increased precipitation in tropical Africa.” They conclude

“Current rates of intense hurricane impacts for Western Lake, Florida, Lake Shelby, Alabama, and Laguna Madre, Texas, do not seem unprecedented when compared to intense strikes over the past 5000 yr.”

We continue to feature evidence from throughout the scientific literature showing that storm activity around the planet is not increasing in activity, whether we feature extra-tropical or tropical storm events. While the global warming alarmists contend we are impacting these storms, the facts suggest otherwise.

References:

Sienz, F., A. Schneidereit, R. Blender, K. Fraedrich, and F. Lunkeit. 2010. Extreme value statistics for North Atlantic cyclones. Tellus A, 62, 347-360.

Wallace, D.J., and J.B. Anderson. 2010. Evidence of similar probability of intense hurricane strikes for the Gulf of Mexico over the late Holocene. Geology, 38, 511-514.




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