Hi,
There is yes.
For example, if you leave the description empty in your variants and only fill it in the main product, the system will automatically use the main product description for all the variants on the frontend.
And it's the same with almost all the fields of a product.
Now, if you already have copy/pasted the same description in all the variants of the product, there is no easy way to update all the variants. But I would actually recommend deleting all the descriptions in the variants and only adding the updated one in the main product. You can delete all the descriptions of the variants of a product with a mass action (menu System>Mass actions).