What is the link between hurricanes and global warming?

Hurricanes aren't linked to global warming

"According to the National Hurricane Center, storms are no more intense or frequent worldwide than they have been since 1850. Constant 24-7 media coverage of every significant storm worldwide just makes it seem that way." (Paul Bedard)

Comments 1 to 14:

1. Will Nitschke (www.capitaloffice.com.au) at 16:09 PM on 19 December, 2007
   A well balanced article. Excellent. Thank you!
   
   "It's important to remember that hurricane activity is just one possible side-effect of global warming. While the empirical evidence linking global warming and hurricane intensity seems robust, it has no bearing on the central question of whether human CO2 emissions are causing global warming."
   
   True, but if human CO2 emissions causing global warming do not have damaging consequences, such as increased storm activity, the 'central question' is no longer central, is it?
   
   Some interesting data on hurricanes:
   
   Fewest Northern Hemisphere Hurricane Days since 1977. 3rd Lowest since 1958 (behind 1977 and 1973). See:
   http://www.coaps.fsu.edu/~maue/tropical/
   Response: If the only consequence of global warming was increased hurricane activity, then you'd have a point. However, they are the tip of the iceberg (pardon the pun). See positives and negatives of global warming for a more comprehensive list.
2. Will Nitschke (www.capitaloffice.com.au) at 22:26 PM on 22 December, 2007
   Your list of potential catastrophes makes interesting reading. But there are no citations, so I wonder how many of these items are speculations and how many have any scientific backing to them. Presumably if the global temperature dropped 2C then we could construct an equally long list of potential catastrophes. It seems that the implications of all this is that somehow, miraculously, the current average global temperature must be perfect.
3. Alan McIntire at 13:20 PM on 26 December, 2007
   http://www.physorg.com/news116687408.html
   
   "Titled "Effect of Remote Sea Surface Temperature Change on Tropical
   Cyclone Potential Intensity," their study found that long-term changes
   in potential intensity are more closely related to the regional
   pattern of warming than to local ocean temperature change. Regions
   that warm more than the tropical average are characterized by
   increased potential intensity, and vice versa. "A surprising result is
   that the current potential intensity for Atlantic hurricanes is about
   average, despite the record high temperatures of the Atlantic Ocean
   over the past decade." Soden said. "This is due to the compensating
   warmth in other ocean basins."
   
   "As we try to understand the future changes in hurricane intensity, we must look beyond changes in Atlantic Ocean temperature. If the Atlantic warms more slowly than the rest of the tropical oceans, we
   would expect a decrease in the upper limit on hurricane intensity,"
   Vecchi added. "This is an interesting piece of the puzzle."
   - A. McIntire
4. Sam Spade at 06:29 AM on 25 October, 2009
   HISTORICAL HURRICANE FREQUENCY
   
   ..........Landsea et al, 2009 (From NYT Aug12, 2009)
   The researchers studied storms that played themselves out at sea, either in a day or two or over a longer period, from 1878 to 2008. By the late 19th century, they estimated meterologists missed perhaps two of the larger storms each year, and by the 1950s they were picking up on average all but one each year.
   Yet the researchers estimate that a century ago, as many as 80 percent of short-lived storms came and went without ever being officially noticed.
   Over all, they conclude, storm counts have not changed in the last century.
   
   ..........Mann et al, 2009 (Ditto)
   ...used a mathematical model of hurricane activity and measurements of sediment to estimate how often major storms struck the Gulf and Atlantic Coasts of the United States in the last 1500 years.
   ...the researchers worked with sediment samples from Puerto Rico, the Gulf Coast and the Atlantic Coast from Florida to New England.
   
   Although current numbers are relatively high, they say, both analytical methods suggest that a period of high storm frequency, possibly even higher than today's, began in the year 900 and lasted until 1200 or so.
   
   
   ..........Lund et al, 2009 September 22, 2009
   Clemson University press release:
   
   Hurrican Frequency Is Up, But Not Their Strength...
   
   In a new study, Clemson University researchers have concluded that the number of hurricanes and tropical storms in the Atlantic Basin is increasing, but there is no evidence that their individual strengths are any greater than storms of the past or that the chances of a U.S. strike are up.
   ...studied changes in the tropical cycle record in the North Atlantic between 1851 and 2008.
   "This is a hot button issue in the argument for global warming," said Lund. "Climatologists reporting to the U.S. Senate as recently as this summer testified to the exact opposite of what we find. Many researchers have maintained that warming waters of the Atlantic are increasing the strength of these storms. We do not see evidence for this at all, however we do find that the number of storms has recently increased."
   The study represents one of the first rigorous statistical assessments of the issue with uncertainty margins calculated in...
   While the study did conclude that more storms are being documented, researchers found no evidence of recent increases in U.S. landfall strike probability of the strongest hurricanes. Lund notes that "because these types of storms are so uncommon, it will take many years of data to reliably assess this issue."
5. Sam Spade at 12:51 PM on 25 October, 2009
   FACTORS INHIBITING HURRICANES
   
   ...while water temperature is the most important factor in tropical cyclone dynamics, many other environmental factors affect these storms. These include: the deep warm water; moisture availibility; weak wind shear; a source of rotation, and no land interaction/landfall. Only when all these factors exist can a hurricane reach its maximum potential intensity for a given water temperature. In fact, few hurricanes reach their potential because some inhibiting factor exists. Furthermore, global warming could enhance some negative influences regionally; an ensemble of 18 global climate models show that wind shear and dry air will increase in the Atlantic, while in contrast the opposite occurs in the west Pacific where environmental factors favor more hurricanes. Therefore, anthropogenic warmer oceans do not necessarily correlate to increased tropical cyclone activity or stronger hurricanes globally. Climate models give mixed results on whether the average storm intensities will change, but most show evidence for some increase in intensity.
   Pat Fitzpatrick, Hurricanes and Climate...~2007
   
   One inhibiting factor is the El Nino, a body of relatively warm equatorial water in the eastern Pacific. Absent for the past few years, it is expected to bring weak to moderately warm water to the South American west coast. A characteristic of El Nino is westerly winds in the upper troposphere that act to shear the tops off Atlantic easterly waves coming off the African Coast, preventing them from growing into named storms or hurricanes...
   However, this (weak to moderate) El Nino will fall well short of the one that occurred in 2007, limiting the season's total named storms to seven.
   From William Gray's 2001 hurricane forecast
   
   Working in a strategically located lagoon off Puerto Rico, Donelly and Woodruff compiled the long record (cores, 2007) of strong hurricanes in the Atlantic region. The 5,000 year record identified two factors that appeared to heighten Atlantic activity: weak El Ninos in the tropical Pacific and strong monsoons in West Africa.
   Scientists have established that strong El Ninos can stunt hurricane activity by causing strong high-altitude winds that inhibit hurricane formation.
   Other reseaqrchers have identified that storms over western Africa generate atmospheric waves that move into the Atlantic and provide "seedlings" for hurricane development...
   Oceanus Feb 13, 2009
6. Mizimi at 05:59 AM on 2 November, 2009
   The formation of Atlantic hurricanes also appears to be strongly influenced by Saharan dust. The dust from the Sahara tracks westwards into the ocean and causes local cooling, depressing the temp. below thresholds needed for hurricanes to form.
   
   ntrs.nasa.gov/archive/nasa/casi.../20080039568_2008038939.pdf - summarises the work by Lau & Kim.
7. oracle2world at 12:53 PM on 8 March, 2010
   Glad the consensus has determined hurricane frequency should be retired to the ash heap of arguments. So how did this one slip through the consensus?
   
   ----
   Global warming is causing more frequent hurricanes in the North Atlantic and Gulf of Mexico, according to a study from the National Center for Atmospheric Research.
   
   The increased frequency of tropical cyclones ``is largely a response'' to a 1 degree Celsius rise in sea water temperatures since 1905 that was caused by greenhouse gases, the study found. Since 1995, the North Atlantic has experienced an average of 15 tropical storms a year, of which eight became strong enough to be called hurricanes. That compares with 10 tropical storms and five hurricanes per year from 1930 to 1994, the report says.
   
   ``There is an 80 percent chance that the majority of the current increases have been impacted by global warming,'' said Greg Holland, director of the research center in Boulder, Colorado, and co-author of the study. ``The bad news is that we've gone up in numbers overall, and in the proportion of major hurricanes as well.''
   
   -- http://www.climateark.org/shared/reader/welcome.aspx?linkid=81144
8. apeescape at 19:08 PM on 14 May, 2010
   Will,
   
   Human civ., which started ~10000 years ago was largely established thanks to the climate. I think a 2C decrease would also cause a lot of problems.
   
   Here's a nice graph, although I'm having the hardest time pinpointing the source. Maybe Fig. 1.3 of Climate change and human health : risks and responses. Editors : A. J. McMichael et al. WHO. 2003.
   
   
9. Berényi Péter at 18:40 PM on 19 August, 2010
   Sorry guys. Neither hurricane frequency nor intensity is related to AGW. If anything, there is a slight century scale decrease in hurricane activity over the Atlantic (with huge swings up & down). Click on image for explanation
   
   
   
   One thing is sure. To choose 1972 for a starting point of the analysis (as in Fig. 2 above) is utterly misleading.
10. kdkd at 20:08 PM on 19 August, 2010
    BP #9
    
    You're overstating your conclusions again with "Neither hurricane frequency nor intensity is related to AGW"
    
    Given that we can date the current global warming period starts in around 1975 it's a valid hypotheis to ask whether that has an influence on hurricane frequency and intensity.
    
    In fact, despite some suggestion that both have increased since the early 1970s, it seems from the data that the effect size is small, and because hurricanes are a complex phenomenon, it will take quite a while to have enough data to determine the relationship. Pretending that this hypothesis is somehow disproven is massively overstating your case, and shows that the work you do on this topic is tainted by your preconceptions.
11. Berényi Péter at 01:14 AM on 20 August, 2010
    #10 kdkd at 20:08 PM on 19 August, 2010
    despite some suggestion that both have increased since the early 1970s
    
    Of course they did. However, if one is trying to do valid climate science, the first question to ask is why hurricane intensity has dropped dramatically between 1959 and 1972?
    
    Until we have an answer to that question, there is no point in making fancy theories about the partial recovery after 1990 which still have not reached the levels once seen during the 1940s. Not even those in the 1880s when temperature is supposed to be way lower than today.
12. muoncounter at 05:51 AM on 20 August, 2010
    #11: "why hurricane intensity has dropped dramatically between 1959 and 1972?"
    The question is based on a still-questionable statistic of cumulative SSn by year.
    
    There are many problems with this statistic. Is a year with 3 cat 2 storms 20% worse than a year with 1 cat 5? There are many residents of the Gulf Coast and Florida who would vehemently disagree. The SSn given is at landfall (so that Katrina is a cat 3); it was cat 5 just offshore when it was piling up the storm surge that destroyed lower New Orleans.
    
    And why does the graph shown stop in 1995, when it is labeled as representing 1851-2009? Surely a trailing average could include those more recent (and more active) years.
    
    As I pointed out in the prior thread, total number of named storms seems to increase over the period. Yet this met with the skeptical "In earlier times there must have been a lot that would have deserved a name but never got one, because went unnoticed." Pardon me, but does that seem to be an appeal to disregard a published graph because it doesn't reflect some non-existent data points? Hardly a scientific argument.
    
    'Dropped dramatically' seems to stem from the trend of -0.43 per century. Is there any statistical significance to such a small number? Especially when we routinely hear challenges to a temperature trend of 0.15 degC/decade, nearly 4x as large.
    
    And then there's this point about the 2005 season:
    
    In terms of accumulated cyclone energy (ACE; the sum of the squares of the maximum wind speed at 6-h intervals for all tropical and subtropical cyclones with intensities of 34 kt or greater; Bell et al. 2000), the 2005 season had a record value of about 256% of the longterm (1944–2003) mean. The previous record was about 249% of the long-term mean set in 1950. [emphasis added]
    
    So let's not claim that hurricane intensity is dropping over the long term.
13. kdkd at 08:01 AM on 20 August, 2010
    BP #11
    
    Why [has] hurricane intensity dropped dramatically between 1959 and 1972?
    
    Nope, again, that's a hypothesis (over an even shorter time time span than the early 70s to the present day where we have an increase). This hypothesis will be difficult to test due to low statistical power, and because it's unclear what should be measured to test it (or if the measurements are available).
    
    Again you're overstating your case. In this example you appear to be cherry picking to suit your preconceptions.
14. CBDunkerson at 00:40 AM on 31 August, 2010
    I was playing around with some North Atlantic hurricane data and got a chart very similar to figure 1 above (except up through 2009 and without the 'major hurricanes' distinction) when something occurred to me.
    
    How can Landsea make the 'better detection' argument when there is no evidence of a change in values when the detection methods changed? If you look at the 'tropical storms' section from the end of the 'ships with radio' period through 'aircraft', 'radar', and the start of 'satellite' tracking there is very little change... just some minor up/down variation. If Landsea's claim that storms were systematically missed by the older methodologies were true there should be one or more significant jumps in there. Instead, we see storm levels holding fairly steady until ~20 years into the satellite tracking era... and then climbing steadily for the 20 years since then.
    
    Granted, the period of sharply increasing storm activity is fairly short and difficult to draw definitive conclusions from... but that doesn't change the fact that the data doesn't show any evidence of the measurement bias Landsea suggests is behind the increase.
    
    Also note that there was an earlier increase in frequency up until leveling off around 1950... that corresponds to the early 20th century warming period and the leveling off to a period of more level temperatures... all within the 'ships with radios' measuring period. Again, it is a short timeframe, but again there seems to be a correlation to temperatures rather than measurement methodology.
    
    All of these trends are present, but less distinct, on the 'hurricanes' and 'major hurricanes' subsets of the data as well. Obviously the temperature to storm/hurricane count correlation is not a perfect match... but there is NO correlation between the changing methodologies and increasing storm/hurricane count. Doesn't that invalidate Landsea's argument?

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