This is just a promotional campaign by Elsevier to get people to sign up for mendeley. From https://www.mendeley.com/campaign/about-climate-change

The articles are available for all existing and new Mendeley users to download and read. It is free to setup a Mendeley account, please click here if you need to setup an account. The articles will be available to download this year (until 31 December 2019). However, researchers will have access to the articles permanently once they have downloaded them.

No, these articles are still subject to their original copyright arrangements and may not be shared unless you are the author or a library that subscribes to ScienceDirect, in which case you may have additional private sharing rights.