NASA: Climate change tipping point close

The US National Aeronautics and Space Administration (NASA) reports that more than 2 trillion tonnes of land ice in Greenland, the Arctic, Antarctica and Alaska has melted since 2003.

Scientists made the alarming discovery using data from new satellite technology.

According to NASA, the melting ice has already raised global sea levels by around half a centimetre.

In addition to melting ice, warming sea temperatures are contributing to the rise in sea level, as water expands when it heats up.

Scientists have also discovered that melting Arctic ice releases the greenhouse gas methane into the atmosphere, which is over 20 times more potent than carbon dioxide.

Temperatures are rising fast, with some parts of the Arctic up to 10 degrees warmer than average this autumn.

NASA now estimates that sea levels will rise by up to a metre by the end of the century - although this could happen faster as the effects and speed of global warming are difficult to predict.

NASA scientists believe the earth is edging extremely close to the tipping point of climate change - when the world warms up so much that there is no way of turning back.