What do you understand by the statement "differential sharing of responsibility for environmental well being"?the qustion is from tenth class NCERT...

Not having the book, I can not tell you for sure because I do not have the context.  However, here is what this line probably means.  Please look in your book to see if it makes sense in context.

My understanding of this is that different people and different countries have different levels of responsibility for maintaining the environment.  This idea is often expressed by developing countries when they are discussing climate change.  For example, developing countries argue that rich countries like the USA should make more of the sacrifices needed to fight global climate change.  They say this because the US can better afford to do this than developing countries can.

Looking at your book, does this make sense?