The sea level is rising twice as fast as previously forecast around parts of New Zealand, according to research published Monday, putting the country’s two largest cities at risk decades earlier than expected. Government-backed data amassed from around the country’s coastline found some areas are already sinking three to four millimetres per year, speeding up a long-expected threat. The projections, labelled “a bit terrifying” by one expert, are the result of an extensive five-year, government-funded research programme — NZ SeaRise — that was the combined work of dozens of local and internat…