Climate scientists decide expansion of Antarctic sea ice is caused by Global Warming. Modern science is easy. Causation is already decided for you – all weather is caused by Global Warming, everything biological is created by Evolution, hydrocarbons come from decayed vegetation, economic success kills Mother Earth, etc. – so to be a successful “scientist” all you need do is explain your data according to the appropriate scientific dogma using words small enough for journalists to understand. Voila! Nobel Prizes will be yours.