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mac
Joined: 07 Mar 1999
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mac
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techno900
Joined: 28 Mar 2001
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 Posted: Tue Sep 11, 2018 2:06 pm Post subject: |
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Mac said: | Quote: | | It couldn't possibly have anything to do with the anamolous heating of the oceans could it? |
I guess the water has been warm for quite awhile along the Carolina coast. Nothing new with Florence. A lot more people in the way, so it is a big deal.
| Quote: | These are the major hurricanes to strike the Carolinas since 1879:
• 1996: Hurricane Fran made landfall as a Category 3 storm on September 5 near Cape Fear, North Carolina. Twenty-six people died, including 14 in North Carolina, the hurricane center said. The storm caused about $5 million in damages. Fran's name also was retired.
• 1989: Hurricane Hugo first devastated the Caribbean before striking as a Category 4 storm just north of Charleston, South Carolina, on September 22. Hugo was responsible for 21 deaths in the mainland United States, five more in Puerto Rico and the US Virgin Islands and 24 more elsewhere in the Caribbean. Damages: $9 billion.
• 1959: Hurricane Gracie was a Category 4 storm that made landfall on September 29 near Beaufort, South Carolina, with winds of about 130 mph. Because the storm came ashore at low tide, the impact was lessened, the National Weather Service said. At least 22 people died.
• 1954: Hurricane Hazel wrecked the Caribbean before making landfall on October 15 as a Category 4 hurricane near the North Carolina-South Carolina border. Winds were around 130 mph at landfall. Hazel was responsible for 95 deaths and $281 million in damage in the United States, 100 deaths and $100 million in damage in Canada and an estimated 400 to 1,000 deaths in Haiti, the hurricane center said.
• 1899: An unnamed Category 3 storm came ashore on the Outer Banks of North Carolina with winds of 120 mph, CNN meteorologists said. About 3,000 people were killed by the storm, mostly in Puerto Rico.
• 1893: An unnamed Category 3 storm made landfall north of Charleston, South Carolina, CNN meteorologists said. The death toll was 1,000 to 2,000, though records don't specify where the deaths occurred.
• 1879: An unnamed Category 3 storm with winds of 115 mph made landfall near Morehead City, North Carolina, CNN meteorologists said. A reported 46 people died.
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mac
Joined: 07 Mar 1999
Posts: 17747
Location: Berkeley, California
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| Posted: Tue Sep 11, 2018 2:39 pm Post subject: |
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Didn’t look at the anamoly map did you? Storing heat in the oceans and heating doesn’t cause hurricanes—it makes them more frequent and worse.
But I can tell that Techno didn’t teach science. |
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techno900
Joined: 28 Mar 2001
Posts: 4161
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| Posted: Tue Sep 11, 2018 2:55 pm Post subject: |
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mac said: | Quote: | Didn’t look at the anamoly map did you? Storing heat in the oceans and heating doesn’t cause hurricanes—it makes them more frequent and worse.
But I can tell that Techno didn’t teach science. |
Show me where the hurricanes are "more frequent and worse" in the Carolinas! |
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mac
Joined: 07 Mar 1999
Posts: 17747
Location: Berkeley, California
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| Posted: Tue Sep 11, 2018 3:33 pm Post subject: |
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Hurricanes are fueled by heat in the ocean. More heat means more water in the air and more energy in the storm. The first posting on Florence showed the heat anomaly. This is taken from NOAA's web site:
| Quote: | 2. Global Warming and Atlantic Hurricanes
A. Statistical relationships between SSTs and hurricanes
Observed records of Atlantic hurricane activity show some correlation, on multi-year time-scales, between local tropical Atlantic sea surface temperatures (SSTs) and the Power Dissipation Index (PDI) —see for example Fig. 3 on this EPA Climate Indicators site. PDI is an aggregate measure of Atlantic hurricane activity, combining frequency, intensity, and duration of hurricanes in a single index. Both Atlantic SSTs and PDI have risen sharply since the 1970s, and there is some evidence that PDI levels in recent years are higher than in the previous active Atlantic hurricane era in the 1950s and 60s.
Model-based climate change detection/attribution studies have linked increasing tropical Atlantic SSTs to increasing greenhouse gases, but proposed links between increasing greenhouse gases and hurricane PDI or frequency has been based on statistical correlations. The statistical linkage of Atlantic hurricane PDI to Atlantic SST suggests at least the possibility of a large anthropogenic influence on Atlantic hurricanes. If this statistical relation between tropical Atlantic SSTs and hurricane activity is used to infer future changes in Atlantic hurricane activity, the implications are sobering: the large increases in tropical Atlantic SSTs projected for the late 21st century would imply very substantial increases in hurricane destructive potential–roughly a 300% increase in the PDI by 2100 (Figure 1a).
Figure 1 (click to enlarge)
On the other hand, Swanson (2008) and others noted that Atlantic hurricane power dissipation is also well-correlated with other SST indices besides tropical Atlantic SST alone, and in particular with indices of Atlantic SST relative to tropical mean SST (e.g., Figure 1b from Vecchi et al. 2008). This is in fact a crucial distinction, because while the statistical relationship between Atlantic hurricanes and local Atlantic SST shown in the upper panel of Figure 1 would imply a very large increases in Atlantic hurricane activity (PDI) due to 21st century greenhouse warming, the alternative statistical relationship between the PDI and the relative SST measure shown in the lower panel of Figure 1 would imply only modest future long-term trends of Atlantic hurricane activity (PDI) with greenhouse warming. In the latter case, the alternative relative SST measure in the lower panel does not change very much over the 21st century, even with substantial Atlantic warming projections from climate models, because, crucially, the warming projected for the tropical Atlantic in the models is not very different from that projected for the tropics as a whole.
A key question then is: Which of the two future Atlantic hurricane scenarios inferred from the statistical relations in Figure 1 is more likely? To try to gain insight on this question, we have first attempted to go beyond the ~50 year historical record of Atlantic hurricanes and SST to examine even longer records of Atlantic tropical storm activity and second to examine dynamical models of Atlantic hurricane activity under global warming conditions. These separate approaches are discussed below.
B. Analysis of century-scale Atlantic tropical storm and hurricane records
Figure 2 (click to enlarge)
To gain more insight on this problem, we have attempted to analyze much longer (> 100 yr) records of Atlantic hurricane activity. If greenhouse warming causes a substantial increase in Atlantic hurricane activity, then the century scale increase in tropical Atlantic SSTs since the late 1800s should have produced a long-term rise in measures of Atlantic hurricanes activity, similar to that seen for global temperature, for example.
Existing records of past Atlantic tropical storm or hurricane numbers (1878 to present) in fact do show a pronounced upward trend, which is also correlated with rising SSTs (e.g., see blue curve in Fig. 4 or Vecchi and Knutson 2008). However, the density of reporting ship traffic over the Atlantic was relatively sparse during the early decades of this record, such that if storms from the modern era (post 1965) had hypothetically occurred during those earlier decades, a substantial number of storms would likely not have been directly observed by the ship-based “observing network of opportunity.” We find that, after adjusting for such an estimated number of missing storms, there remains just a small nominally positive upward trend in tropical storm occurrence from 1878-2006. Statistical tests indicate that this trend is not significantly distinguishable from zero (Figure 2). In addition, Landsea et al. (2010) note that the rising trend in Atlantic tropical storm counts is almost entirely due to increases in short-duration (<2 day) storms alone. Such short-lived storms were particularly likely to have been overlooked in the earlier parts of the record, as they would have had less opportunity for chance encounters with ship traffic.
Figure 3 (click to enlarge)
Figure 4 (click to enlarge)
If we instead consider Atlantic basin hurricanes, rather than all Atlantic tropical storms, the result is similar: the reported numbers of hurricanes were sufficiently high during the 1860s-1880s that again there is no significant positive trend in numbers beginning from that era (Figure 3, black curve, from CCSP 3.3 (2008)). This is without any adjustment for “missing hurricanes”.
The evidence for an upward trend is even weaker if we look at U.S. landfalling hurricanes, which even show a slight negative trend beginning from 1900 or from the late 1800s (Figure 3, blue curve). Hurricane landfalling frequency is much less common than basin-wide occurrence, meaning that the U.S. landfalling hurricane record, while more reliable than the basin-wide record, suffers from degraded signal-to-noise characteristics for assessing trends.
While major hurricanes (Figure 3, red curve) show more evidence of a rising trend from the late 1800s, the major hurricane data are considered even less reliable than the other two records in the early parts of the record. Category 4-5 hurricanes show a pronounced increase since the mid-1940s (Bender et al., 2010) but again, we consider that these data need to be carefully assessed for data inhomogeneity problems before such trends can be accepted as reliable.
The situation for various long-term Atlantic hurricane records and related indices is summarized in Figure 4. While global mean temperature and tropical Atlantic SSTs show pronounced and statistically significant warming trends (green curves), the U.S. landfalling hurricane record (orange curve) shows no significant increase or decrease. The unadjusted hurricane count record (blue curve) shows a significant increase in Atlantic hurricanes since the early 1900s. However, when adjusted with an estimate of storms that stayed at sea and were likely “missed” in the pre-satellite era, there is no longer any significant increase in Atlantic hurricanes since the late 1800s (red curve). While there have been increases in U.S. landfalling hurricanes and basin-wide hurricane counts since the since the early 1970s, Figure 4 shows that these recent increases are not representative of the behavior seen in the century long records. In short, the historical Atlantic hurricane record does not provide compelling evidence for a substantial greenhouse warming-induced long-term increase.
There is medium confidence for a detectable human contribution to past observed increases in heavy precipitation in general over global land regions with adequate coverage for analysis (e.g., IPCC AR5) and over the United States (Easterling et al. 2017), although an anthropogenic influence has not been formally detected for hurricane precipitation alone. Several recent studies (e.g., van Oldenborgh et al. 2017; Risser and Wehner 2017) have concluded that Hurricane Harvey’s (2017) extreme rainfall totals, though primarily due to the storm’s slow movement over eastern Texas, were likely enhanced by anthropogenic warming. Physically, a warmer atmosphere holds more water vapor that can enhance moisture convergence and rainfall rates in storm systems such as hurricanes. The statistical analyses in these Hurricane Harvey studies focused on extreme precipitation in general, to which hurricanes contributed, but were not analyses of extreme rainfall only from hurricanes.
C. Model simulations of greenhouse warming influence on Atlantic hurricanes
Direct model simulations of hurricane activity under climate change scenarios offer another perspective on the problem. We have developed a regional dynamical downscaling model for Atlantic hurricanes and tested it by comparing with observed hurricane activity since 1980. This model, when forced with observed sea surface temperatures and atmospheric conditions, can reproduce the observed rise in hurricane counts between 1980 and 2012, along with much of the interannual variability (Figure 5). Animations showing the development and evolution of hurricane activity in the model are available here.
Figure 5 (click to enlarge)
Turning to future climate projections, current climate models suggest that tropical Atlantic SSTs will warm dramatically during the 21st century, and that upper tropospheric temperatures will warm even more than SSTs. Furthermore, most of the CMIP3 models project increasing levels of vertical wind shear over parts of the western tropical Atlantic (see Vecchi and Soden 2007). Both the increased warming of the upper troposphere relative to the surface and the increased vertical wind shear are detrimental factors for hurricane development and intensification, while warmer SSTs favor development and intensification. To explore which effect of these effects might “win out”, we can run experiments with our regional downscaling model.
Our regional model projects that Atlantic hurricane and tropical storms are substantially reduced in number, for the average 21st century climate change projected by current models, but have higher rainfall rates, particularly near the storm center. The average intensity of the storms that do occur increases by a few percent (Figure 6), in general agreement with previous studies using other relatively high resolution models, as well as with hurricane potential intensity theory (Emanuel 1987).
Figure 6 (click to enlarge)
Knutson and Tuleya (2004) estimated the rough order of magnitude of the sensitivity of hurricanes to climate warming to be about 4% per deg C SST warming for maximum intensities and about 12% per deg C for near-storm (100 km radius) rainfall rates (see also Knutson and Tuleya (2008) abstract here). Such sensitivity estimates have considerable uncertainty, as a subsequent assessment of multiple studies (Knutson et al. 2010) projected total increases by 2100 of about 2-11% for tropical cyclone intensity, and roughly 20% for near-storm rainfall rates. Our more recent late 21st century projections of hurricane activity continue to support the notion of increased intensity (~ 4%) and near-storm rainfall rates (~ 10 to 15%) for the Atlantic basin (Knutson et al. 2013) as well as for most other tropical cyclone basins (Knutson et al. 2015). Wright et al. (2015) found model-projected increases in rainfall rates for U.S. landfalling tropical cyclones using this modeling system.
A review of existing studies, including the ones cited above, lead us to conclude that: it is likely that greenhouse warming will cause hurricanes in the coming century to be more intense globally and have higher rainfall rates than present-day hurricanes.
Turning now to the question of the frequency of very intense hurricanes, the regional model of Knutson et al. (2008) has an important limitation in that it does not simulate such very intense hurricanes. For example, the maximum surface wind in the simulated hurricanes from that model is less than 50 m/s (which is borderline category 3 hurricane intensity). Furthermore, the idealized study of Knutson and Tuleya (2004) assumed the existence of hurricanes and then simulated how intense they would become. Thus, that study could not address the important question of the frequency of intense hurricanes.
In a series of Atlantic basin-specific dynamical downscaling studies (Bender et al. 2010; Knutson et al. 2013), we attempted to address both of these limitations by letting the Atlantic basin regional model of Knutson et al. (2008) provide the overall storm frequency information, and then downscaling each individual storm from the regional model study into the GFDL hurricane prediction system. The GFDL hurricane model (with a grid spacing as fine as 9 km) is able to simulate the frequency, intensity, and structure of the more intense hurricanes, such as category 3-5 storms, much more realistically than the regional (18 km grid) model.
Using this additional downscaling step, the GFDL hurricane model reproduces some important historical characteristics of very intense Atlantic hurricanes, including the wind speed distribution and the change of this distribution between active and inactive decadal periods of hurricane activity (Fig. 1 of Bender et al. 2010). The model also supports the notion of a substantial decrease (~25%) in the overall number of Atlantic hurricanes and tropical storms with projected 21st century climate warming. However, using the CMIP3 and CMIP5 multi-model climate projections, the hurricane model also projects that the lifetime maximum intensity of Atlantic hurricanes will increase by about 5% during the 21st century in general agreement with previous studies.
The Bender et al. (2010) study projected a significant increase (+90%) in the frequency of very intense (category 4 and 5) hurricanes using the CMIP3/A1B 18-model average climate change projection. Subsequent downscaled projections using CMIP5 multi-model scenarios (RCP4.5) as input (Knutson et al. 2013) still showed increases in category 4 and 5 storm frequency (Fig. 7). However, these increases were only marginally significant for the early 21st century (+45%) or the late 21st century (+39%) CMIP5 scenarios (based on model versions GFDl and GFDN combined). That study also downscaled ten individual CMIP3 models in addition to the multi-model ensemble, and found that three of ten models produced a significant increase in category 4 and 5 storms, and four of the ten models produced at least a nominal decrease. While multi-model ensemble results are probably more reliable than individual model results, each of the individual model results can be viewed as at least plausible at this time. Based on Knutson et al. (2013) and a survey of subsequent results by other modeling groups, at present we have only low confidence for an increase in category 4 and 5 storms in the Atlantic; confidence in an increase in category 4 and 5 storms is higher at the global scale (see below).
Figure 7 (click to enlarge) Tracks and intensities of all storms reaching Category 4 or 5 intensity (>59 m/sec) in the GFDL hurricane model downscaling experiments. Results are shown for the control climate (upper left); CMIP3/A1B 18-model ensemble late 21st century (lower left); and CMIP5/RCP4.5 18-model ensemble early (upper right) or late (lower right) 21st century. All results shown are based on model version GFDL. Track colors indicate the intensity category during the storm’s lifetime.
Returning to the issue of future projections of aggregate activity (PDI, as in Fig. 1), while there remains a lack of consensus among various studies on how Atlantic hurricane PDI will change, no model we have analyzed shows a sensitivity of Atlantic hurricane PDI to greenhouse warming as large as that implied by the observed Atlantic PDI/local SST relationship shown in Figures 1 (top panel). In other words, there is little evidence from current dynamical models that 21st century climate warming will lead to large (~300%) increases in tropical storm numbers, hurricane numbers, or PDI in the Atlantic. As noted above, there is some indication from high resolution models of substantial increases in the numbers of the most intense hurricanes even if the overall number of tropical storms or hurricanes decreases.
Finally, one can ask when a large increase in Category 4-5 hurricanes, as projected by our earlier Bender et al. (2010) study, would be expected to be detectable in the Atlantic hurricane records, if it occurred in the real world. Owing to the large interannual to decadal variability of SST and hurricane activity in the basin, Bender et al (2010) estimate that detection of an anthropogenic influence on intense hurricanes would not be expected for a number of decades, even assuming a large underlying increasing trend (+10% per decade) occurs. While there is a large rising trend since the mid 1940’s in observed category 4-5 numbers in the Atlantic, our view is that these data are not reliable for trend calculations, until they have been further assessed for data homogeneity problems, such as those due to changing observing practices.
D. Other possible human influences on Atlantic hurricane climate
Apart from greenhouse warming, other human influences conceivably could have contributed to recent observed increases in Atlantic hurricanes. For example, Mann and Emanuel (2006) hypothesize that a reduction in aerosol-induced cooling over the Atlantic in recent decades may have contributed to the enhanced warming of the tropical North Atlantic, relative to global mean temperature. However, the cause or causes of the recent enhanced warming of the Atlantic, relative to other tropical basins, and its effect on Atlantic tropical cyclones, remains highly uncertain (e.g., Booth et al. 2012; Zhang et al. 2013;Dunstone et al. 2013; Villarini and Vecchi 2013). A number of anthropogenic and natural factors (e.g., aerosols, greenhouse gases, volcanic activity, solar variability, and internal climate variability) must be considered as potential contributors, and the science remains highly uncertain in these areas. IPCC AR5 concluded that there is medium confidence that reduced aerosol forcing contributed to the observed increase in Atlantic tropical cyclone activity since the 1970s, but does not state any estimate of the magnitude of contribution. They also conclude that it remains uncertain whether there are any detectable changes in past tropical cyclone activity.
Sea level rise must also be considered as a way in which human-caused climate change can impact Atlantic hurricane climate–or at least the impacts of the hurricanes at the coast. The vulnerability of coastal regions to storm-surge flooding is expected to increase with future sea-level rise and coastal development, although this vulnerability will also depend upon future storm characteristics, as discussed above. All else equal, tropical cyclone surge levels should increase with sea level rise. There are large ranges in the 21st century projections for both Atlantic hurricane characteristics and for the magnitude of regional sea level rise along the U.S. coastlines. However, according to the IPCC AR5, the average rate of global sea level rise over the 21st Century will very likely exceed that observed during 1971-2010 for a range of future emission scenarios.
E. Summary for Atlantic Hurricanes and Global Warming
In summary, neither our model projections for the 21st century nor our analyses of trends in Atlantic hurricane and tropical storm counts over the past 120+ yr support the notion that greenhouse gas-induced warming leads to large increases in either tropical storm or overall hurricane numbers in the Atlantic. While one of our modeling studies projects a large (~100%) increase in Atlantic category 4-5 hurricanes over the 21st century, we estimate that such an increase would not be detectable until the latter half of the century, and we still have only low confidence that such an increase will occur in the Atlantic basin, based on an updated survey of subsequent modeling studies by our and other groups.
Therefore, we conclude that despite statistical correlations between SST and Atlantic hurricane activity in recent decades, it is premature to conclude that human activity–and particularly greenhouse warming–has already caused a detectable change in Atlantic hurricane activity. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.) However, human activity may have already caused some some changes that are not yet detectable due to the small magnitude of the changes or observation limitations, or are not yet confidently modeled (e.g., aerosol effects on regional climate).
We also conclude that it is likely that climate warming will cause Atlantic hurricanes in the coming century have higher rainfall rates than present-day hurricanes, and medium confidence that they will be more intense (higher peak winds and lower central pressures) on average. In our view, it is uncertain how the annual number of Atlantic tropical storms will change over the 21st century. All else equal, tropical cyclone surge levels should increase with sea level rise as projected for example by IPCC AR5. These assessment statements are intended to apply to climate warming of the type projected for the 21st century by prototype IPCC mid-range warming scenarios, such as A1B or RCP4.5.
The relatively conservative confidence levels attached to our tropical cyclone projections, and the lack of a claim of detectable anthropogenic influence on tropical cyclones at this time contrasts with the situation for other climate metrics, such as global mean temperature. In the case of global mean surface temperature, the IPCC AR5 presents a strong body of scientific evidence that most of the global warming observed over the past half century is very likely due to human-caused greenhouse gas emissions. |
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techno900
Joined: 28 Mar 2001
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| Posted: Wed Sep 12, 2018 8:41 am Post subject: |
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Mac's Sept. 9 post: | Quote: | | Anomolously warm water fuels hurricane aimed at the Carolinas. What could have caused that? |
Then I post contradictory hurricane data that proves mac wrong.
Then Mac resorts to his usual derogatory statements "techno didn't teach science".
Then I ask for mac to: "Show me where the hurricanes are "more frequent and worse" in the Carolinas!"
Then Mac posts an article from NOAA and highlights part:
| Quote: | Therefore, we conclude that despite statistical correlations between SST and Atlantic hurricane activity in recent decades, it is premature to conclude that human activity–and particularly greenhouse warming–has already caused a detectable change in Atlantic hurricane activity. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.) However, human activity may have already caused some some changes that are not yet detectable due to the small magnitude of the changes or observation limitations, or are not yet confidently modeled (e.g., aerosol effects on regional climate).
We also conclude that it is likely that climate warming will cause Atlantic hurricanes in the coming century have higher rainfall rates than present-day hurricanes, and medium confidence that they will be more intense.
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From the one who frequently berates others for a "lack of critical thinking"...………….. Of course, he may just be acknowledging that he was INCORRECT with his first statement, but I seriously doubt it. |
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mac
Joined: 07 Mar 1999
Posts: 17747
Location: Berkeley, California
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| Posted: Wed Sep 12, 2018 9:56 am Post subject: |
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Techno--not only did I read it, I highlighted it for you. There is a statistical correlation--but not yet robust enough to call it a cause. Which is why I used the sardonic terms--could this have anything to do with climate change. I also provided a map of the anomaly.
But what is clear, and the conclusion I can draw, is that more heat means more intensity. Heat drives the engine. Tell me about your science teaching, and your grasp of statistics. Maybe even a reliable source? |
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techno900
Joined: 28 Mar 2001
Posts: 4161
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| Posted: Wed Sep 12, 2018 10:08 am Post subject: |
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Mac said: | Quote: | | Which is why I used the sardonic terms--could this have anything to do with climate change. |
Squirming a bit aren't you. Your initial statement was BS since the current hurricane has NOTHING to do with ocean warming or climate change. You are just digging a deeper hole. |
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techno900
Joined: 28 Mar 2001
Posts: 4161
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| Posted: Wed Sep 12, 2018 10:09 am Post subject: |
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Mac said: | Quote: | | Which is why I used the sardonic terms--could this have anything to do with climate change. |
Squirming a bit aren't you. Your initial statement was BS since the current hurricane has NOTHING to do with ocean warming or climate change. You are just digging a deeper hole. |
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