Knowledge claim: Mr Moussay's grandfather says that the fruits on his trees are ripening earlier and earlier in the year and that this must be due to global warming. 

Topic: Effects of Global Warming

Not a knowledge issue: How do fruits grow?

A weak knowledge issue: Does global warming affect the environment?

A medium knowledge issue: How can we be certain that global warming affects plant growth?

A strong knowledge issue:  How far is it true to say that global warming affects the normal development of nature?