The climate change blogosphere is polarized, with on one side ‘the climate mainstream’ and on the other side ‘climate sceptics’. While it is difficult to quantify the impact, the climate change blogosphere has played a significant role in scientific, political, media, and public discourse on climate change. The current thesis investigated the precise role of the blogosphere in climate change polarization. A novel theoretical framework was developed to conceptualize climate change polarization, by distinguishing between positional, interactional, and affective climate change polarization. On the basis of six mixed method studies, the results showed how actors in the blogosphere hold extreme opposing climate change positions, have interactions where they either are disengaged or are increasingly contrasting others who hold opposing climate change positions, and emotionally evaluate opposing climate change groupings in a way that reflects hostility. The research contributes to our understanding of climate change polarization dynamics in the online realm.