The strengthening scientific consensus about the connection between climate change and health is not reflected at the relevant organizations of the United Nations (UN). It has been more adequately addressed by the informal Group of Eight (G8). Relative to the G8 with its comprehensive agenda, intermittent UN summits focused on health, environment, or development have lagged in recognizing and responding to the connection. This poorer UN performance is not caused by changes in the scientific consensus, or by severe climate and health shocks, which should spur both summit systems, particularly the UN, to act. It depends more on the comprehensiveness, flexibility, annual occurrence, and compact like-mindedness of the G8 summits compared to the subject-specific, organizationally constrained, intermittent, internally divergent UN ones. This suggests the UN will struggle to transform the Millennium Development Goals into new post-2015 sustainable development goals and define a post-2015 climate change control regime with a closer climate-health connection, unless the G8 and now Group of 20 summits address the connection in a UN-supportive way.