Arrhenius first published the theory of electrolytic dissociation in his doctoral thesis of 1884. In 1903 he received the Nobel Prize in chemistry "in recognition of the extraordinary services he has rendered to the advancement of chemistry by his electrolytic theory of dissociation."

(Thanks to Juan Weiss for this reference.)

Arrhenius used basic principles of physical chemistry to estimate the extent to which increases in atmospheric carbon dioxide are responsible for the Earth's increasing surface temperature, the "greenhouse effect."

Arrhenius defined immunochemistry, and laid out its frontiers.

In this work Arrhenius predicted the possibility of man-made global warming. His prediction that significant global warming would take ~3000 years to develop is now recognized as a substantial underestimate due in part to his failure to foresee the rapid increases in fossil fuel use during the twentieth century. Digital facsimile from the Internet Archive at this link.