The world's oceans are already rising faster than projected, according to a new report this week.

The latest report found levels were above projected levels that were released by the UN Intergovernmental Panel on Climate Change (IPCC) in 2007.

Authors Stefan Rahmstorf, Grant Foster and Anny Cazenave found the rate of sea-level rise of the past few decades was greater than projected by the IPCC models.

Their work, published in Environmental Letters this week, concluded that IPCC sea-level projections for the future may also be biased low.

The trio analysed global temperature and sea-level data over the past few decades and compared them to projections published in the third and fourth assessment reports of the IPCC.

They wrote that their concern was supported by the fact that the ice sheets in Greenland and Antarctica were increasingly losing mass.

The study was released in the same week as a United Nations report found 2012 temperatures were the ninth highest on record since 1850, despite the effect of La Niña weather patterns which cool the earth's atmosphere.

The next IPCC report, on the state of the earth's climate and necessary reposnses to climate change, is due out in 2013-2014.