As much as political leaders and pundits like to cite scientific consensus as unarguable fact, consensus can change. New classification schemes can emerge. New information can shake loose even the most firmly held beliefs as the scientific method is impartial to politics or patronage. This flexibility and willingness to learn is key to discovery and to human knowledge.
Still, it can be jarring when basic truths seem to abruptly shift. Things like the number of planets or, say, the number of oceans on Earth.