By Danielle Bochove, Bloomberg Even in a best-case scenario, the Arctic will begin to experience summer months with no sea ice sometime around the middle of the century — sooner than leading climate scientists had predicted, new research finds. The United Nations-sponsored Intergovernmental Panel on Climate Change suggested in its most recent landmark report that the region would start to see Septembers without sea ice around 2050 if humans continue to emit greenhouse gases at high or moderate levels.