Scepticism means having doubts or questioning something, particularly when there is not enough evidence or proof to support it. It's when you don't readily believe or accept things without careful thought and investigation. Full definition
But if any of his staff were listening, they might have been rather worried to discover than with one exception, every caller expressed some degree of scepticism about global warming. (iaindale.com)
On fellow Conservatives who have expressed scepticism about climate change, he says. (totalpolitics.com)
The proposal met with scepticism from many astronomers, until the Voyager 2 spacecraft flew past the planet in 1986 and confirmed the prediction. (astro-canada.ca)