{"73817":{"#nid":"73817","#data":{"type":"news","title":"Hurricanes Are Getting Stronger, Study Says","body":[{"value":"\u003Cp\u003EThe number of Category 4 and 5 hurricanes worldwide has nearly doubled over the past 35 years, even though the total number of hurricanes has dropped since the 1990s, according to a study by researchers at the Georgia Institute of Technology and the National Center for Atmospheric Research (NCAR). The shift occurred as global sea surface temperatures have increased over the same period. The research will appear in the September 16 issue of the journal Science, published by the AAAS, the science society, the world\u0027s largest general scientific organization.\u003C\/p\u003E\n\u003Cp\u003EPeter Webster, professor at Georgia Tech\u0027s School of Earth and Atmospheric Sciences, along with NCAR\u0027s Greg Holland and Tech\u0027s Judith Curry and Hai-Ru Chang, studied the number, duration and intensity of hurricanes (also known as typhoons or tropical cyclones) that have occurred worldwide from 1970 to 2004. The study was supported by the National Science Foundation (NSF).\n\u003C\/p\u003E\n\u003Cp\u003E\u0022What we found was rather astonishing,\u0022 said Webster. \u0022In the 1970\u0027s, there was an average of about 10 Category 4 and 5 hurricanes per year globally. Since 1990, the number of Category 4 and 5 hurricanes has almost doubled, averaging 18 per year globally.\u0022  \n\u003C\/p\u003E\n\u003Cp\u003ECategory 4 hurricanes have sustained winds from 131 to 155 miles per hour; Category 5 systems, such as Hurricane Katrina at its peak over the Gulf of Mexico, feature winds of 156 mph or more.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This long period of sustained intensity change provides an excellent basis for further work to understand and predict the potential responses of tropical cyclones to changing environmental conditions\u0022, said NCAR\u0027s Holland.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Category 4 and 5 storms are also making up a larger share of the total number of hurricanes,\u0022 said Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech and co-author of the study. \u0022Category 4 and 5 hurricanes made up about 20 percent of all hurricanes in the 1970\u0027s, but over the last decade they account for about 35 percent of these storms.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe largest increases in the number of intense hurricanes occurred in the North Pacific, Southwest Pacific and the North and South Indian Oceans, with slightly smaller increases in the North Atlantic Ocean.\n\u003C\/p\u003E\n\u003Cp\u003EAll this is happening as sea-surface temperatures are rising across the globe-anywhere from around one-half to one degree Fahrenheit, depending on the region, for hurricane seasons since the 1970\u0027s.\u003C\/p\u003E\n\u003Cp\u003E\u0022Our work is consistent with the concept that there is a relationship between increasing sea surface temperature and hurricane intensity,\u0022 said Webster. \u0022However, it\u0027s not a simple relationship. In fact, it\u0027s difficult to explain why the total number of hurricanes and their longevity has decreased during the last decade, when sea surface temperatures have risen the most.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u0022NCAR is now embarking on a focused series of computer experiments capable of resolving thunderstorms and the details of tropical cyclones,\u0022 said Holland. \u0022The results will help explain the observed intensity changes and extend them to realistic climate change scenarios.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe only region that is experiencing more hurricanes overall is the North Atlantic, where they have become more numerous and longer-lasting, especially since 1995. The North Atlantic has averaged eight to nine hurricanes per year in the last decade, compared to the six to seven per year before the increase.  Category 4 and 5 hurricanes in the North Atlantic have increased at an even faster clip: from 16 in the period of 1975-89 to 25 in the period of 1990-2004, a rise of 56 percent.\n\u003C\/p\u003E\n\u003Cp\u003EA study published in July in the journal Nature came to a similar conclusion. Focusing on North Atlantic and North Pacific hurricanes, Kerry Emanuel (Massachusetts Institute of Technology) found an increase in their duration and power, although it used a different measurement to determine a storm\u0027s power.\n\u003C\/p\u003E\n\u003Cp\u003EBut whether all of this is due to human-induced global warming is still uncertain, said Webster. \u0022We need a longer data record of hurricane statistics, and we need to understand more about the role hurricanes play in regulating the heat balance and circulation in the atmosphere and oceans.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Basic physical reasoning and climate model simulations and projections motivated this study,\u0022 said Jay Fein, director of NSF\u0027s climate and large scale dynamics program, which funded the research.  \u0022These results will stimulate further research into the complex natural and anthropogenic processes influencing these tropical cyclone trends and characteristics.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EWebster is currently attempting to determine the basic role of hurricanes in the climate of the planet. \u0022The thing they do more than anything is cool the oceans by evaporating the water and then redistributing the oceans\u0027 tropical heat to higher latitudes,\u0022 he said.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022But we don\u0027t know a lot about how evaporation from the oceans\u0027 surface works when the winds get up to around 100 miles per hour, as they do in hurricanes,\u0022 said Webster, who adds that this physical understanding will be crucial to connecting trends in hurricane intensity to overall climate change.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022If we can understand why the world sees about 85 named storms a year and not, for example, 200 or 25, then we might be able to say that what we\u0027re seeing is consistent with what we\u0027d expect in a global warming scenario. Without this understanding, a forecast of the number and intensity of tropical storms in a future warmer world would be merely statistical extrapolation.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EAddtional Contacts:\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003EAnatta, Media Relations\u003Cbr \/\u003E\n\u003Ca href=\u0022mailto:anatta@ucar.edu\u0022\u003Eanatta@ucar.edu\u003C\/a\u003E\u003Cbr \/\u003E\n303-497-8604\u003Cbr \/\u003E\nNational Center for Atmospheric Research\/University Corporation for Atmospheric Research\n\u003C\/p\u003E\n\u003Cp\u003ECheryl Dybas, Public Affairs\u003Cbr \/\u003E\n\u003Ca href=\u0022mailto:cdybas@nsf.gov\u0022\u003Ecdybas@nsf.gov\u003C\/a\u003E\u003Cbr \/\u003E\n703-292-7734\u003Cbr \/\u003E\nNational Science Foundation \u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"The number of Category 4 and 5 hurricanes worldwide has nearly doubled over the past 35 years as global sea surface temperatures have risen.","format":"limited_html"}],"field_summary_sentence":[{"value":"Storm severity rises along with sea surface temps"}],"uid":"27310","created_gmt":"2005-09-15 00:00:00","changed_gmt":"2016-10-08 03:00:59","author":"David Terraso","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2005-09-15T00:00:00-04:00","iso_date":"2005-09-15T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"73818":{"id":"73818","type":"image","title":"Intensity Graph","body":null,"created":"1449178020","gmt_created":"2015-12-03 21:27:00","changed":"1475894678","gmt_changed":"2016-10-08 02:44:38"},"73819":{"id":"73819","type":"image","title":"Hurricane Katrina","body":null,"created":"1449178020","gmt_created":"2015-12-03 21:27:00","changed":"1475894678","gmt_changed":"2016-10-08 02:44:38"}},"media_ids":["73818","73819"],"related_links":[{"url":"http:\/\/curry.eas.gatech.edu\/","title":"Judy Curry"},{"url":"http:\/\/webster.eas.gatech.edu\/","title":"Peter Webster"}],"groups":[{"id":"1214","name":"News Room"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EGeorgia Tech Media Relations\u003C\/strong\u003E\u003Cbr \/\u003ELaura Diamond\u003Cbr \/\u003E\u003Ca href=\u0022mailto:laura.diamond@comm.gatech.edu\u0022\u003Elaura.diamond@comm.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-894-6016\u003Cbr \/\u003EJason Maderer\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-660-2926\u003C\/p\u003E","format":"limited_html"}],"email":["david.terraso@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}