Scientists from the National Oceanic and Atmospheric Administration have published research into the shrinking levels of sea ice in the Arctic. They wanted to figure out how long it would take before summer sea ice disappeared entirely. Since there's no perfect model for predicting ice levels, they used three different methods. All three predicted the Arctic would be nearly free of summer sea ice by the middle of the century, and one indicated it could happen as early as 2020. Two of the methods were based on observed sea ice trends. If ice loss proceeds as it has in the past decade, we get the 2020 timeframe. If ice loss events are large, like the 2007 and 2012 events, but happen at random some years, the estimate is pushed back to 2030. The third method uses global climate models to 'predict atmosphere, ocean, land, and sea ice conditions over time.' This model pushes the timeframe back to 2040 at the earliest, and around 2060 as the median (abstract). One of the study's authors, James Overland, said, "Rapid Arctic sea ice loss is probably the most visible indicator of global climate change; it leads to shifts in ecosystems and economic access, and potentially impacts weather throughout the northern hemisphere. Increased physical understanding of rapid Arctic climate shifts and improved models are needed that give a more detailed picture and timing of what to expect so we can better prepare and adapt to such changes. Early loss of Arctic sea ice gives immediacy to the issue of climate change."