In chapter 3 of Neukirch's Algebraic Number Theory, an analogue of the classical Riemann-Roch theorem is developed for number fields. To achieve this, notation suggestive of cohomology with sheaves of line bundles/divisors is used, however the exposition does not really further develop this "cohomology". In particular, we have the vector space of global sections,
$H^{0}(\mathcal{O}(D))=\{f\in K^{*}|\text{div}(f)\geq -D\}$
but there are no such analogues for $H^{n}(\mathcal{O}(D))$ for $n>0$.
Was such a cohomology theory ever developed? What is it called, and are there any references?