New Orleans is sinking faster than previously predicted — up to 2in (5cm) each year, according to a new study. And the city is already below sea level.

The data was collected between 2009 and 2012 using radar images taken from an aircraft flying the same route year after year. The study included scientists from Nasa's Jet Propulsion Laboratory, the University of California at Los Angeles and Louisiana State University.

The sinking is caused by a number of factors, not least of which is a rise in sea levels — up to 3in (7.6cm) since 1992 — caused by global warming. Scientists predict that sea levels could rise at least another 3ft (1m) in the next two centuries.

Other key factors include pumping groundwater — and oil and gas — out of the earth, notes the study, published in the Journal of Geophysical Research.

Louisiana has been among the US locations hardest hit by climate change. The government recently set aside $48m (£33m) to move the entire community of the sinking Isle de Jean Charles to drier land. Washington DC is also sinking and could drop at least 6in in the next hundred years, researchers say.

The new data will be employed to plan for a strategy in an effort to mitigate damage and "improve public safety", lead study author Cathleen Jones told Hopefully the information can also be used to improve the "long-term coastal resiliency and sustainability of New Orleans", she added.

Sounding a bit darker, a Nasa scientist warned: "People need to understand that the planet is not only changing, it has changed."