Des cyclones plus intenses à cause du réchauffement

Les cyclones comme Irma, qui a touché mercredi les Caraïbes, se nourrissent de l'énergie dégagée par les océans: du coup, les scientifiques prévoient que l'intensité de ces évènements, également appelés ouragans ou typhons, se renforce mais pas leur fréquence à l'échelle du globe.

Faute de données satellitaires à l'échelle planétaire avant 1970, il n'est pas possible de dire comment l'activité cyclonique a évolué au XXe siècle. Avant la mise en place d'une surveillance satellitaire complète, des cyclones même très intenses ont pu passer inaperçus s'ils n'ont pas touché les terres par exemple. Le nombre réduit de cyclones participe aussi à la faiblesse des données statistiques et rend leur exploitation plus difficile.

Dans l'Atlantique nord, depuis une vingtaine d'années, une augmentation de la fréquence des cyclones a été constatée mais c'était l'inverse entre 1970 et 1995, selon Franck Roux, de l'Université Paul-Sabatier de Toulouse.

En fait, les chercheurs se sont aperçus que l'activité cyclonique dans cette région suit des cycles de plusieurs dizaines d'années et estiment qu'il n'est pas encore possible de dire si la hausse dans cette région relève d'une variabilité naturelle ou du changement climatique.

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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOURS RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOURS RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter account of RCI Guadeloupe shows damage on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: Pedro Toledo purchases plywood at The Home Depot as he prepares for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Hurricane Irma at 1200 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  MIAMI, FL - SEPTEMBER 06: Luis Lorenzo and Jairo Ruiz (L-R) purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: Luis Lorenzo and Jairo Ruiz (L-R) purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Hurricane Irma at 1200 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This satellite image obtained from NASA's GOES Project shows Hurricane Irma (C) at 1145 UTC on September 6, 2017, followed by Tropical Storm Jose (R). Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NASA/GOES Project / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NASA/GOES Project" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Huricane Irma at 1145 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Huricane Irma at 1130 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / Jose ROMERO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This image obtained from the National Oceanic and Atmospheric Administration shows Hurricane Irma on September 5, 2017, at 1215UTC. Irma picked up strength and has become an "extremely dangerous" Category Five hurricane as it approached the Caribbean, the Miami-based National Hurricane Center reported. Irma is about 270 miles (440kms) east of the island of Antigua packing maximum sustained winds of 175mph (280kph). / AFP PHOTO / NOAA/RAMMB / Jose ROMERO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS

Dans le Pacifique nord-ouest, il y a eu une légère diminution de l'activité cyclonique entre 1980 et 2010.

Les modèles informatiques simulant le climat font état d'un renforcement de l'intensité des cyclones (vents et pluies) et d'une possible baisse de leur fréquence au niveau du globe à l'avenir.

«Des cyclones d'une intensité plus grande sont l'une des conséquences attendues du changement climatique», explique Valérie Masson-Delmotte, membre du GIEC, groupe de référence au niveau mondial sur le climat.

«Plus la température de l'eau et le taux d'humidité sont élevés, plus le cyclone peut prendre de l'intensité. Or, ces deux éléments sont plus intenses du fait de l'augmentation de l'effet de serre», explique la climatologue. «On considère qu'il y a 7% d'humidité en plus dans l'atmosphère par degré de réchauffement», précise-t-elle.

«Le changement climatique ne crée pas ces tempêtes mais il accentue leurs impacts», résume Anders Levermann du Potsdam Institute for Climate Impact Research.

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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOURS RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOURS RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter accound of RCI Guadeloupe shows a flooded street on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  A handout picture released on September 6, 2017 on the twitter account of RCI Guadeloupe shows damage on the French overseas island of Saint-Martin, after high winds from Hurricane Irma hit the island. Monster Hurricane Irma slammed into Caribbean islands today after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / RCI Guadeloupe AND TWITTER / Rinsy XIENG / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RCI Guadeloupe / Rinsy XIENG" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO INTERNET - NO RESALE - IMAGE AVAILABLE AS PART OF A 48-HOUR RIGHT TO INFORMATION FROM WEDNESDAY 6TH OF SEPTEMBER 2017 8PM GMT /
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  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
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  MIAMI, FL - SEPTEMBER 06: Pedro Toledo purchases plywood at The Home Depot as he prepares for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Hurricane Irma at 1200 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
• AFP

  MIAMI, FL - SEPTEMBER 06: Luis Lorenzo and Jairo Ruiz (L-R) purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: People wait in line to purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  MIAMI, FL - SEPTEMBER 06: Luis Lorenzo and Jairo Ruiz (L-R) purchase plywood at The Home Depot as they prepare for Hurricane Irma on September 6, 2017 in Miami, Florida. It's still too early to know where the direct impact of the hurricane will take place but the state of Florida is in the area of possible landfall. Joe Raedle/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==
• AFP

  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Hurricane Irma at 1200 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This satellite image obtained from NASA's GOES Project shows Hurricane Irma (C) at 1145 UTC on September 6, 2017, followed by Tropical Storm Jose (R). Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NASA/GOES Project / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NASA/GOES Project" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
• AFP

  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Huricane Irma at 1145 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
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  This satellite image obtained from the National Oceanic and Atmospheric Administration (NOAA) shows Huricane Irma at 1130 UTC on September 6, 2017. Irma slammed into the French Caribbean islands on Wednesday after making landfall in Barbuda, packing ferocious winds and causing major flooding in low-lying areas. As the rare Category Five storm barreled its way across the Caribbean, it brought gusting winds of up to 185 miles per hour (294 kilometers per hour), weather experts said. / AFP PHOTO / NOAA/RAMMB / Jose ROMERO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS
• AFP

  This image obtained from the National Oceanic and Atmospheric Administration shows Hurricane Irma on September 5, 2017, at 1215UTC. Irma picked up strength and has become an "extremely dangerous" Category Five hurricane as it approached the Caribbean, the Miami-based National Hurricane Center reported. Irma is about 270 miles (440kms) east of the island of Antigua packing maximum sustained winds of 175mph (280kph). / AFP PHOTO / NOAA/RAMMB / Jose ROMERO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / NOAA/RAMMB" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS

L'augmentation du niveau des océans est l'un des marqueurs du réchauffement de la planète. La hausse, variable selon les régions du globe, a été en moyenne de 20 cm au XXe siècle et pourrait atteindre jusqu'à près d'un mètre à l'horizon 2100.

Or, les cyclones produisent aussi une houle qui génère des «marées de tempête». Les deux effets conjugués contribueront à exposer davantage constructions et populations côtières.

Des travaux montrent, selon Météo France, que «la latitude à laquelle les cyclones ont atteint leur intensité maximale a migré vers les pôles au cours des 35 dernières années dans les deux hémisphères».

Cela pourrait être lié à l'expansion de la ceinture tropicale, c'est-à-dire des zones de part et d'autre de l'Equateur où règne un climat chaud et humide.

«Des endroits qui sont plus habitués et mieux préparés aux cyclones pourraient être moins exposés et d'autres, moins bien préparés, pourraient l'être davantage», renchérit James Kossin de l'Agence américaine océanique et atmosphérique (NOAA).