Environmental pollution and greenhouse gas emissions that contribute to climate change have adverse impacts on global health. Somewhat paradoxically, health care systems that aim to prevent and cure disease are themselves major emitters and polluters. In this paper we develop a justification for the claim that solidaristic health care systems should include sustainability as one of the criteria for determining which health interventions are made available or reimbursed - and which not. There is however a complication: most adverse health effects due to climate change do occur elsewhere in the world. If solidarity would commit us to take care of everyone's health, worldwide, it might imply that solidaristic health system cannot justifiably restrict universal access to their own national populations. In response we explain health solidarity is to be considered as a moral ideal. Such an ideal does not specify what societies owe to whom, but it does have moral implications. We argue that ignoring sustainability in political decision making about what health care is to be offered, would amount to betrayal of the ideal of solidarity.