In the face of global climate risks, world cities increasingly figure in academic and policy discourse as strategic spaces for harnessing the expertise and governance capacity needed to steer societies toward more sustainable and low-carbon futures. This article reviews existing approaches to the study of urban climate politics, by way of asking what contribution Ulrich Beck’s theory of world risk society – and principles of methodological cosmopolitanism – make to such epochal conversations? Three main analytical frameworks stand out: low-carbon transition literature highlight generic processes of socio-technical ‘greening’ of urban infrastructures; urban policy mobility work documents growing intercity networks around climate and sustainability; and actor–network theory-informed takes on urban controversies engage the localized politics of specific city-based ‘riskscapes’. While each framework makes valuable contributions, this article suggests that all of them remain under-theorized from the point of view of the specific dynamics of local–global interdependencies in urban climate risk politics. In response, the article draws on Beck in outlining the contours of new urban–cosmopolitan risk communities. To this effect, empirical studies into large-scale East Asian and European port cities is used to illustrate how a shared transnational risk imaginary (e.g. of future sea-level rises) may help spur collective action and new forms of trans-boundary solidarity. Reflecting on such research practices, the article ends by pointing to the need for reworking methods of (multi-sited) ethnography and comparison as central parts of realizing Ulrich Beck’s cosmopolitan sociology in the domain of urban climate risks.