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Carbon Dioxide and Earth's Future: Pursuing the Prudent Path

3. More Frequent and Severe Hurricanes


The claim: CO2-induced global warming will increase the frequency, intensity and duration of hurricanes.

How do hurricanes respond to global warming? A popular book and award-winning film (Gore, 2006) suggest that global warming is leading to "an increased frequency of hurricanes," and that rising temperatures are also linked to "a significant increase in both the duration and intensity of hurricanes."

This view of the subject received significant early support in the scientific literature, especially within the climate modeling community. Free et al. (2004), for example, wrote that "increases in hurricane intensity are expected to result from increases in sea surface temperature and decreases in tropopause-level temperature accompanying greenhouse warming (Emanuel, 1987; Henderson-Sellers et al., 1998; Knutson et al., 1998)." In fact, Knutson and Tuleya (2004) stated that "nearly all combinations of climate model boundary conditions and hurricane model convection schemes show a CO2-induced increase in both storm intensity and near-storm precipitation rates."

To test this climate-model-based hypothesis, we examine the pertinent scientific literature to determine how much more frequent, powerful and longer-lasting hurricanes may -- or may not -- have become over the course of earth's recovery from the cooler temperatures of the Little Ice Age, or how hurricanes of the Medieval Warm Period may have differed from those of the Little Ice Age. An analysis of this subject was presented by Idso and Singer (2009) in Climate Change Reconsidered: The Report of the Nongovernmental International Panel on Climate Change (NIPCC), where in examining the peer-reviewed scientific literature up through 2007 they found "little or no support for these predictions and considerable evidence to support an opposite prediction." Therefore, we confine ourselves here to an analysis of scientific papers published after 2007, in order to see if Idso and Singer's conclusion still holds.

With respect to hurricanes occurring over the Atlantic Ocean, we begin with the study of Chylek and Lesins (2008), who applied simple statistical methods to the NOAA HURDAT record of storm activity in the North Atlantic basin between 1851 and 2007 in order to investigate a possible linear trend, periodicity and other features of interest. Using what they describe as "a hurricane activity index that integrates over hurricane numbers, durations, and strengths," the two researchers reported discovering "a quasi-periodic behavior with a period around 60 years superimposed upon a linearly increasing background." However, they noted that "the linearly increasing background [was] significantly reduced or removed when various corrections were applied for hurricane undercounting in the early portion of the record." And further noting that "the last minimum in hurricane activity occurred around 1980," they stated that in comparing the two 28-year-long periods on either side of this date, they found "a modest increase of minor hurricanes, no change in the number of major hurricanes, and a decrease in cases of rapid hurricane intensification."

As a result of these findings, the two researchers concluded that "if there is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60-year quasi-periodic cycle." Consequently, and in spite of the fact that (1) the hurricane record they analyzed started during the final stages of the Little Ice Age (which was the coldest period of the current interglacial), and that (2) the planet experienced a subsequent warming that has been declared by climate alarmists to have been unprecedented over the past millennium or more, they could still find no convincing real-world evidence that global warming enhances either the frequency or intensity of hurricanes occurring over the Atlantic Ocean.

Contemporaneously, Klotzbach and Gray (2008) employed sea surface temperature (SST) data for the far North Atlantic (50-60°N, 50-10°W) and sea level pressure (SLP) data for the North Atlantic (0-50°N, 70-10°W) to construct an index of the Atlantic Multidecadal Oscillation (AMO), which they defined as the difference between the standardized SST and SLP anomalies (SST-SLP) for the hurricane season of June-November, and which they evaluated for the period 1878-2006, after which they compared their results (to which they applied a 1-2-3-2-1 filter) with a number of hurricane or tropical cyclone (TC) properties. And this work revealed the existence of three positive and two negative AMO phases over the period of their study, as may be seen in the figure below.


North Atlantic AMO Index. Adapted from Klotzbach and Gray (2008).

In comparing annually-averaged results for TC characteristics between the positive and negative AMO phases indicated in the above graph, it can be calculated from the TC data of the two researchers that the positive AMO phase-to-negative AMO phase ratios of hurricane numbers, hurricane days, major hurricane numbers and major hurricane days were 1.53, 1.89, 2.00 and 2.46, respectively, over the entire period studied, while for the 20 most positive and 20 most negative AMO years the values of the same ratios, in the same order, were 1.73, 2.41, 2.80 and 4.94. Clearly, therefore, the state of the North Atlantic AMO is tremendously important to hurricane genesis and development; and this striking natural variability makes it impossible to determine if there is any long-term trend in the TC data that might possibly be due to 20th-century global warming.

One year later, Zeng et al. (2009), as they describe it, "synthesized field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical tropical cyclones from 1851 to 2000 over the continental U.S." In doing so, they determined "there were more forest impacts and greater biomass loss between 1851 and 1900 than during the 20th century." On average, for example, they found that "147 million trees were affected each year between 1851 and 1900," which led to "a 79-Tg annual biomass loss." Average annual forest impact and biomass loss between 1900 and 2000, on the other hand, "were 72 million trees and 39 Tg, which were only half of the impacts before 1900," which results they say are in "accordance with historical records showing that Atlantic tropical cyclones were more active during the period from 1870 to 1900." In addition, they note that the amount of carbon released from the downed and damaged trees "reached a maximum value in 1896, after which it continuously decreased until 1978," whereupon it leveled off for the remaining two decades of the 20th century.

Taking a longer look at the subject, Chenoweth and Divine (2008) examined newspaper accounts, ships' logbooks, meteorological journals and other documents in order to reconstruct a history of tropical cyclones passing through the 61.5°W meridian between the coast of South America (~9.7°N) and 25.0°N over the period 1690-2007, which they describe as "the longest and most complete record for any area of the world." This work, however, was inconclusive for most of the time period, as the two researchers say they could find "no evidence of statistically significant trend in the number of tropical cyclones passing through the region on any time scale." But they did note that "hurricane frequency is down about 20% in the 20th century compared to earlier centuries," and that "this decline is consistent with the 20th century observed record of decreasing hurricane landfall rates in the U.S. (Landsea et al., 1999; Elsner et al., 2004) and proxy reconstruction of higher tropical cyclone frequency in Puerto Rico before the 20th century (Nyberg et al., 2007), as well as model-simulated small changes in Atlantic basin tropical cyclone numbers in a doubled CO2 environment (Emanuel et al., 2008; Knutson et al., 2008)." They also report that "the period 1968-1977 was probably the most inactive period since the islands were settled in the 1620s and 1630s," which finding "supports the results of Nyberg et al. (2007) of unprecedented low frequency of major hurricanes in the 1970s and 1980s." In addition, it strongly suggests that the subsequent short-term increase in cyclone numbers has had absolutely nothing to do with the supposedly unprecedented concurrent warming of the globe, as it appears to be nothing more than a simple recovery from a short-term dip (within a century-scale lull) that reduced yearly cyclone numbers to their lowest levels of the past three centuries.

Going still further back in time, Wallace and Anderson (2010) collected a total of 37 sediment cores along eight transects within Laguna Madre, an elongate water body located behind the narrow low-elevation barrier that is Texas (USA's) South Padre Island; and based on the vertical distribution and grain size of storm over-wash sediments contained within four of those cores from two transects -- which were most ideally positioned -- they were able to construct a detailed history of intense hurricane strikes from 5300 to 900 years before present (BP). Based on their analyses, the two scientists determined that "there has been no notable variation in intense storm impacts across the northwestern Gulf of Mexico coast during this time interval," i.e., 5300-900 yr BP, "implying no direct link between changing climate conditions and annual hurricane impact probability." In addition, they report that "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 their findings -- as well as the similar results obtained by others for Western Lake, Florida (USA), and Lake Shelby, Alabama (USA) -- the two researchers concluded that current rates of intense hurricane impacts "do not seem unprecedented when compared to intense strikes over the past 5000 years," while noting that "similar probabilities in high-intensity hurricane strikes for the eastern and western Gulf of Mexico do not show any clear-cut out-of-phase relationship that would enlighten us as to climate controls on storm pathways." Thus, they reiterated their conclusion that "in the northern Gulf of Mexico, there have been no significant variations in storm impact probabilities and/or storm steering mechanisms from ca. 5300-900 yr BP."

With respect to hurricanes occurring over the Pacific Ocean, there are a number of recent studies, including that of Chan (2008), who investigated possible causes of the multi-decadal variability in intense TC (category 4 and 5) occurrence in the western North Pacific (WNP), which basin generally has the largest number of TCs every year. And based on data for the period 1960-2005, the Hong Kong researcher determined that decadal variations in intense typhoon activity largely result from a combination of the behavior of the El Niņo-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO).

In discussing this finding, Chan said that "the view that global warming would lead to more intense TCs owing to the enhancement of thermodynamic factors ignores the fact that for TCs to intensify significantly, the dynamic factors must 'cooperate'," and he added that "the latter have not been demonstrated to be enhanced basin wide." Thus, he suggested "the more likely conclusion is that the major low-frequency variations in the frequency of intense TC occurrence is probably a multi-decadal one in response to similar variations in the factors that govern the formation, intensification and movement of TCs," and he noted that "such variations largely result from modifications of the atmospheric and oceanographic conditions in response to ENSO and PDO." Thus, and "at least for the WNP," Chan stated "it is not possible to conclude that the variations in intense typhoon activity are attributable to the effect of global warming."

Defining rapid intensification (RI) of a tropical cyclone as occurring when the maximum wind speed of a TC reaches at least 5 knots in the first 6 hours, 10 knots in the first 12 hours, and 30 knots in 24 hours, Wang and Zhou (2008) determined that "all category 4 and 5 hurricanes in the Atlantic basin and 90% of the equivalent-strength typhoons in the western North Pacific experience at least one RI process in their life cycles." Thus, using best-track TC data obtained from the Joint Typhoon Warning Center for the 40-year period 1965-2004, the two researchers determined the climatic conditions that are most critical for the development of RI in TCs of the Western North Pacific on annual, intra-seasonal, and inter-annual time scales; and this work revealed, as they describe it, that "over the past 40 years, the annual total of RI in the western North Pacific shows pronounced interdecadal variation but no significant trend," and they say that this fact "implies that the super typhoons had likely no upward trend in the last 40 years." In addition, they found that when there was a southward shift in the mean latitude of where the tropical storms form (either seasonally or from year to year), the proportion of super typhoons or major hurricanes would increase; and they state that "this finding contrasts [with] the current notion that higher sea surface temperature leads to more frequent occurrence of category 4 or 5 hurricanes."

Contemporaneously, Englehart et al. (2008) developed a "first cut" data set pertaining to the area immediately adjacent to Mexico's Pacific coast. Although only 54% of Eastern Pacific storms reached TC status within this near-shore area over the period 1967-2005, they report that "near-shore storm activity is fairly well correlated with total basin TC activity, a result which suggests that over the longer period (i.e., 1921-onward), changes in near-shore activity can provide some sense of the broader basin activity." Thus, they proceeded with their analysis, discovering significant decadal variability in annual eastern Pacific near-shore TC frequency of occurrence. Also, they found that "long-term TC frequency exhibits a significant negative trend," which -- as best can be determined from their graph of the data -- declines by approximately 23% over the 85-year period 1921-2005. And this result was driven solely by an approximate 30% drop in TC frequency during the late (August-November) TC season, with essentially no long-term trend in the early (May-July) TC season.

Englehart et al. additionally presented a graph of the maximum wind speed associated with each TC, which revealed an approximate 20% decline in this intensity-related parameter over the period of their study. Consequently, although their work was acknowledged by them to be but a "first cut" at trying to determine how North Pacific TCs might have varied in frequency of occurrence and intensity over the prior 85 years, it clearly provided no support for the climate-alarmist claim that global warming increases both the frequency and intensity of TCs and/or hurricanes. In fact, the data from this part of the world appear to suggest just the opposite.

Also publishing in the same year, Wang et al. (2008) analyzed climatic characteristics of China-influencing typhoons over the period 1951-2004, finding that "the frequency of affecting typhoons has been declining since 1951 at a rate of 0.9 typhoon per decade, which passes the test of 0.05 significance level," and emphasizing that "the past 10 years is the time that sees the least frequency." In addition, they determined that "super-typhoons have the largest drop in the frequency, showing a tendency of decreasing 0.7 typhoon per decade, which passes the test of 0.001 significance level."

Moving ahead one year, Zhang et al. (2009) examined cyclone-generated economic losses and human casualties in China, as well as their changes in space and time; and in doing so, they determined that "direct economic losses trended upward significantly over the past 24 years," but that "the trend disappears if considering the rapid increase of the annual total gross domestic product of China, suggesting that the upward trend in direct economic losses is a result of Chinese economic development." They also stated that "there is no significant trend in tropical cyclone casualties over the past 24 years," and that it is only because "the Chinese economy has been booming since the early 1980s" that there has been an increasing trend in typhoon-caused economic losses between 1983 and 2006. And they additionally noted that "after adjusting for inflation, wealth, and population," Pielke and Landsea (1998) and Pielke et al. (2008) also "found no significant trend in economic losses caused by landfalling tropical cyclones."

Contemporaneously, Kubota and Chan (2009) created a unique dataset of TLP (tropical cyclone landfall numbers in the Philippines) based on historical observations of TC tracks during the period 1901-1940, which were obtained from Monthly Bulletins of the Philippine Weather Bureau along with TLP data obtained from the Joint Typhoon Warning Center for the period 1945-2005, which they used to investigate the TC-global warming hypothesis. And by these means the two researchers discovered, via the data plotted in the figure below, that "the TLP has an apparent oscillation of about 32 years before 1939 and an oscillation of about 10-22 years after 1945." Most important of all, they reported that "no long-term trend is found." In addition, they determined that "natural variability related to ENSO and PDO phases appears to prevail in the interdecadal variability of TLP."


Philippine tropical cyclone landfall numbers vs. year. Adapted from Kubota and Chan (2009).

Working nearby, Ma and Chen (2009) used NCEP/NCAR reanalysis data to determine the SST distribution over the Western North Pacific (WNP) and to evaluate its temporal variability, while they employed TC frequency data obtained from the Joint Typhoon Warning Center, the Tropical Cyclone Year Book of the China Meteorological Administration, and the Tokyo-Typhoon Center of the Japanese Meteorological Agency to characterize TC frequency over the period 1949-2007. This work indicated, in their words, that "SSTs over the WNP have been gradually increasing during the past 60 years ... with a maximum increment of 1°C around the central equatorial Pacific for the last 10 years," and they found that "the warm pool, which is defined to be enclosed by a critical temperature of 28°C, has expanded eastward and northward in recent years," noting further that "there has been remarkable warming in the last decade, more than 0.8°C in some local areas." Nevertheless, and in spite of this "remarkable warming," they determined that "the frequency of TC against the background of global warming has decreased with time."

Contemporaneously, Chan and Xu (2009) studied landfalling tropical cyclones of East Asia, based on TC data obtained from the Joint Typhoon Warning Center for the period 1945-2004 and the Annual Tropical Cyclone Data Book (edited by the Shanghai Typhoon Institute) for the period 1951-2000, conducting a comprehensive study of variations in the annual number of landfalling TCs in three sub-regions of East Asia: South (south China, Vietnam and the Philippines), Middle (east China), and North (Korean Peninsula and Japan). As might have been expected, the two researchers discovered that "wavelet analyses of each time series show that the landfalling frequencies go through large inter-annual (2-8 years), inter-decadal (8-16 years) and even multi-decadal (16-32 years) variations, with the inter-annual being the most dominant, and the multi-decadal explaining most of the rest of the variance." And in what they call "an important finding," they state that "none of the time series shows a significant linear temporal trend, which suggests that global warming has not led to more landfalls in any of the regions in Asia."

Last of all, with respect to the Pacific Ocean, Song et al. (2010) write that "in recent years, there has been increasing interest in whether global warming is enhancing tropical cyclone activity," as has been claimed by Emanuel (2005) and Webster et al. (2005). One of the main sources of contention over this matter has been the fact that Wu et al. (2006) and Yeung (2006) examined best track data from the Regional Specialized Meteorological Center (RSMC), Tokyo, Japan, as well as that of the Hong Kong Observatory of China (HKO), and that "in contrast to Webster et al. (2005)," as Song et al. describe it, they found "there was no increase in category 4-5 typhoon activity in the western North Pacific basin." In addition, they report that "neither RSMC nor HKO best track data suggest an increase in TC destructiveness." And they further state that "other studies also examined the differences in TC data sets from the Joint Typhoon Warning Center (JTWC) of the U.S. Naval Pacific Meteorology Oceanography Center in Hawaii, the RSMC, and the Shanghai Typhoon Institute (STI) of [the] China Meteorological Administration in Shanghai (Lei, 2001; Kamahori et al., 2006; Ott, 2006; Yu et al., 2007)," and they indicate that "so far, the reported trends in TC activity in the WNP basin have been detected mainly in the JTWC best track data set," which anomalous data set was employed by Emanuel (2005) and Webster et al. (2005) in drawing their anomalous conclusions.

To help resolve the discrepancies exhibited by the JTWC typhoon database, Song et al. analyzed differences of track, intensity, frequency and the associated long-term trends of those TCs that were simultaneously recorded and included within the best track data sets of the JTWC, the RSMC and the STI from 1945 to 2007. This work revealed, according to them, that "though the differences in TC tracks among these data sets are negligibly small, the JTWC data set tends to classify TCs of category 2-3 as category 4-5, leading to an upward trend in the annual frequency of category 4-5 TCs and the annual accumulated power dissipation index reported by Webster et al. (2005) and Emanuel (2005)." And they add that "this trend and potential destructiveness over the period 1977-2007 are found only with the JTWC data set," while noting that actual downward trends "are apparent in the RSMC and STI data sets." In light of their findings, therefore, plus those of the other scientists they cite, there would appear to be little doubt that the studies of Emanuel (2005) and Webster et al. (2005) provide no evidence for what climate alarmists long hailed as proof positive of their claim that global warming leads to more intense tropical cyclones or hurricanes.

With respect to hurricanes occurring over the Indian Ocean, there are but two studies to report. In the first, Harper et al. (2008) analyzed several "potential influences on the accuracy of estimating TC intensity over time due to increasing technology, methodology, knowledge and skill" for TCs that occurred off the coast of northwestern Australia, primarily in a band between 5 and 25°S, over the period 1968/69 to 2000/01. This work revealed, in their words, that "a bias towards lower intensities likely exists in earlier (mainly pre-1980) TC central pressure deficit estimates of the order of at least 20 per cent in 1970, reducing to around ten per cent by 1980 and to five per cent in 1985," and they say that "inferred temporal trends in the estimated intensity from the original data-sets are therefore significantly reduced in the objectively reviewed data-set." In fact, when all was said and done, they concluded "there is no prima facie evidence of a potential climate-change induced trend in TC intensity in northwestern Australia over the past 30 years."

Also working out of Australia, but only partly in the Indian Ocean, Hassim and Walsh (2008) analyzed tropical cyclone best track data pertaining to severe storms of the Australian region (5-30°S) forming off Western Australia and the Northern Territory (the western sector: 90-135°E, Indian Ocean) and off Queensland and the Gulf of Carpentaria (the eastern sector: 135-160°E, Pacific Ocean) for the presence of systematic intensity and duration trends over the cyclone season periods running from 1969/1970 through 2004/2005; and in doing so, in the words of the two Australian researchers, "substantial differences in trends [were] found between the two sub-regions, with the number, average maximum intensity, and duration at the severe category intensities of tropical cyclones increasing since 1980 in the west but decreasing (in number) or exhibiting no trend (in intensity, severe category duration) in the east."

As Hassim and Walsh concluded, however, more study of Australian-region TCs will be required "to unravel the causes of the clear differences between cyclone trends in the eastern and western portions of the Australian basin." Until then, it will remain unclear what the overall data really suggest, and, of course, why. And even when these questions are answered, the temporal length of the underlying database will still be far too short to differentiate between a long-term trend that might possibly be tied to the warming that produced the Little Ice Age-to-Current Warm Period transition and a shorter-term cyclical regime shift. However, it is worth noting that in reporting results described at the International Summit on Hurricanes and Climate Change that was held on the Greek island of Crete in May of 2007, Elsner (2008) indicates that what he calls paleotempestology -- which he defines as the study of prehistoric storms based on geological and biological evidence -- indicates that "sedimentary ridges in Australia left behind by ancient tropical cyclones indicate that activity from the last century under-represents the continent's stormy past."

With respect to hurricanes occurring over multiple ocean basins, Fan and Liu (2008), who also focused on paleotempestology, conducted a brief review and synthesis of major research advances and findings in this emerging field of work, which they describe as "a young science" that "studies past typhoon activity spanning several centuries to millennia before the instrumental era through the use of geological proxies and historical documentary records." And this analysis indicated, as they describe it, that "there does not exist a simple linear relationship between typhoon frequency and Holocene climate (temperature) change," especially of the type suggested by climate alarmists. They report, for example, that "typhoon frequency seemed to have increased at least regionally during the coldest phases of the Little Ice Age," and they also note that there are typically "more frequent typhoon landfalls during La Niņa years than during El Niņo years."

In the realm of theoretical modeling, Nolan and Rappin (2008) extended the methodology of Nolan et al. (2007) to include a prescribed wind as a function of height that remains approximately constant during the genesis of tropical cyclones in environments of radiative-convective equilibrium that are partially defined by sea surface temperature, which they then employed to explore what happens when SSTs rise. And when subsequently running the adjusted model, they report that "an unexpected result has been obtained, that increasing sea surface temperature does not allow TC genesis to overcome greater shear." In fact, they say that "the opposite trend is found," and that "the new and surprising result of this study is that the effect of shear in suppressing TC genesis actually increases as the SST of the radiative-convective equilibrium environment is increased."

This new model-based result is eerily analogous to the recent observation-based result of Vecchi and Knutson (2008), who found that as the SST of the main development region of North Atlantic TCs had increased over the past 125 years, certain aspects of climate changed in ways that may have made the North Atlantic, in their words, "more favorable to cyclogenesis, while at the same time making the overall environment less favorable to TC maintenance." Hence, it is doubly interesting that Nolan and Rappin conclude their paper with the intriguing question: "Do these results explain recent general circulation modeling studies predicting fewer tropical cyclones in a global warming world," citing the work of Bengtsson et al. (2007)."

Focusing on five ocean basins -- the Atlantic (1960-2007), the Western North Pacific (1960-2007), the Eastern North Pacific (1960-2007), the South Indian Ocean (1981-2007), and the South Pacific (1981-2007) -- Chan (2009) examined (1) the relationship between the seasonally averaged maximum potential intensity (MPI, an index of thermodynamic forcing) over each basin where TCs typically form and (2) the seasonal frequency of occurrence of intense TCs. In doing so, he determined that "only in the Atlantic does the MPI have a statistically significant relationship with the number of intense TCs, explaining about 40% of the variance," while "in other ocean basins, there is either no correlation or the correlation is not significant." The People's Republic of China's researcher thus states that "even in the Atlantic, where a significant correlation between the thermodynamic factors and the frequency of intense TCs exists, it is not clear whether global warming will produce a net increase in such a frequency, because model projections suggest an increase in vertical wind shear associated with an increase in sea surface temperature," which phenomenon tends to work against intense TC development. As a result, Chan concludes that "it remains uncertain whether the frequency of occurrence of intense TCs will increase under a global warming scenario."

In a concomitant two-ocean-basin study, Wang and Lee (2009) noted that in the Western Hemisphere, tropical cyclones "can form and develop in both the tropical North Atlantic (NA) and eastern North Pacific (ENP) Oceans, which are separated by the narrow landmass of Central America," and that "in comparison with TCs in the NA, TCs in the ENP have received less attention although TC activity is generally greater in the ENP than in the NA (e.g., Maloney and Hartmann, 2000; Romero-Vadillo et al., 2007)." So, in exploring how the TC activities of the NA and ENP basins might be related to each other over the period 1949-2007, as well as over the shorter period of 1979-2007, Wang and Lee employed a number of different datasets to calculate the index of accumulated cyclone energy (ACE), which accounts for the number, strength and duration of all TCs in a given season.

The results of this exercise led the two U.S. scientists to state that "TC activity in the NA varies out-of-phase with that in the ENP on both interannual and multidecadal timescales," so that "when TC activity in the NA increases (decreases), TC activity in the ENP decreases (increases)." And they found that "the out-of-phase relationship seems to [have] become stronger in the recent decades," as evidenced by the fact that the interannual and multidecadal correlations between the NA and ENP ACE indices were -0.70 and -0.43, respectively, for the period 1949-2007, but -0.79 and -0.59, respectively, for the period 1979-2007. In terms of the combined TC activity over the NA and ENP ocean basins as a whole, however, there was little variability on either interannual or multidecadal timescales; and real-world empirical data suggest that the variability that does exist over the conglomerate of the two basins has grown slightly weaker as the earth has warmed over the past six decades, which runs counter to climate-alarmist claims that earth's hurricanes or tropical cyclones should become more numerous, stronger and longer-lasting as temperatures rise.

Most recently, Wang et al. (2010) examined cross-basin spatial-temporal variations of TC storm days for the Western North Pacific (WNP), the Eastern North Pacific (ENP), the North Atlantic (NAT), the North Indian Ocean (NIO), and the Southern Hemisphere Ocean (SHO) over the period 1965-2008, for which time interval pertinent satellite data were obtained from the U.S. Navy's Joint Typhoon Warning Center for the WNP, NIO and SHO, and from NASA's (USA) National Hurricane Center for the NAT and ENP. And as a result of their efforts, they were able to report that "over the period of 1965-2008, the global TC activity, as measured by storm days, shows a large amplitude fluctuation regulated by the El Niņo-Southern Oscillation and the Pacific Decadal Oscillation, but has no trend, suggesting that the rising temperature so far has not yet [had] an impact on the global total number of storm days."

So what does the future hold for us in terms of hurricanes? Based on the numerous empirical observations from the ocean basins described above, it is clear that there is no support for the climate-alarmist claim that global warming increases both the frequency and intensity of hurricanes. In fact, the data seem to suggest just the opposite. Thus, if the world warms any further in the future, for whatever reason (anthropogenic or natural), we would expect to see fewer and less intense hurricanes than have occurred recently.

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