evidence: Arctic sea-ice plays an important role in controlling the planet's temperature, and any problem with this natural thermostat is a cause for concern. Figures from the US space agency (Nasa) suggest the loss of the minimum Arctic sea-ice extent is in the region of 13.1% per decade, based on the 1981 to 2010 average. [...] The disappearance of the sea-ice in a warming world also contributes to rising average surface temperatures. The sea-ice is estimated to reflect 80% of sunlight back into space, meaning it does not warm the surface.