Climate change is a potential major driver of future terrorism. It is already recognised by many (if not most) nations as a strategic security threat, though the potential role it can play in igniting, facilitating, or exacerbating terrorist conflict has been relatively unexplored. There are, however, growing signs that climate change—either through direct or indirect impacts—should be considered as a significant macro-level driver of terrorism. It is certainly well established that the causes of terrorism can involve both large-scale geo-political processes and at the same time much more low-key individual level personal factors. Much of the traditional debate around the “root causes” of terrorism has concentrated heavily on macro-level drivers with a particular focus on factors tied to economic, political and historical forces.Footnote1 The relative importance of each factor can vary enormously depending on the perspective taken not only in research terms but also in terms of potential policy interventions. It is critical to acknowledge, however, that not all causes will be present in every case, and those that are present do not always have the same degree of impact. A cause of vital importance in one terrorist conflict might play no detectable role in others. Given the above, it is inevitable that we face considerable challenges in our efforts to better understand the causes and their impacts. Attempts to do so have to be sophisticated in how “causes” are framed. Causes can work at different levels and it is important to take the trouble to distinguish between these. Similarly, we have to be alert to how research defines “terrorism” and the impact this then has on the data used and the conclusions reached. Only limited data is available on many key issues and care is needed in selecting relevant and reliable sources.Footnote2 While there may be obstacles to understanding, this does not mean we should abandon the search to comprehend the causes of terrorism. The issue is a critical one and the progress we have seen in recent decades already shows substantial achievements.Footnote3 Of particular interest to this special issue are how we approach terrorism’s macro-level causes. These can be seen as the big drivers of terrorist conflict and will be the main factors responsible for future terrorism. Macro-level factors normally relate to systemic conditions at the level of society, state, international relations, and/or trans-national developments.Footnote4 Examples that have traditionally been looked at include civil war or deep-rooted conflicts, invasion, and occupation by foreign military forces, bad governance and corruption, rapid modernisation or actions by hostile states. Emerging macro-level causes requiring further attention include population growth, social polarisation, migration patterns, and, of particular concern for this issue, climate change.