Peter Wadham, head of the Polar Ocean Physics Group at University of Cambridge, has repeatedly made claims that Arctic sea ice will melt "next year". Eg in 2012 he predicted it would fully melt in sept 2016. Since that didn't happen, he now predicts it will fully melt in 2017/2018. IPCC estimates it will fully melt in the late 2030s.
Articles about him in legitimate media are [1][2]. Climate deniers get to say things like [3].
Other climate scientists think he is alarmist [4], and the 2013 IPCC report mentions his papers but is super dissmissive: See section 11.3.4 of the IPCC AR5, references to Maslwoski.