Nature has provided us some stark recent reminders that our climate is changing, often towards the extremes. Super Typhoon Haiyan slammed the Philippines. The ‘polar vortex’ blanketed the United States in snow. While East Coasters in the United States may still feel some of the polar sting, it is the world’s poorest and most vulnerable that feel the sustained harms of climate change. In Maplecroft’s 2013 ranking of its Climate Change Vulnerability Index, the top 10 most vulnerable countries were also low- and lower-middle income. Because of its effects on the poor, actions related to climate change made two of Nancy Birdsall’s (@nancymbirdsall) list of the top ten development priorities for 2014.

Recognising and even prioritising a problem is one thing – and this is a big, complex and multi-causal, cross-border and prone-to-collective-action-failures problem. But right now, what we really lack is the evidence about the best way to help the most affected protect their environment as they can and adapt to changing climate conditions as needed.

Wealthy countries have consistently underprovided funds for addressing climate change, including investing in evidence about what works and why (though there is debate about whether this is a real or artificial scarcity of resources). In the face of resource scarcity, better evidence about works, where and why becomes all the more important, so that we can choose the interventions that are most effective and cost-effective in producing both environmental and human-welfare impacts among the poor and vulnerable at individual, community and national levels.

At present, there is an array of measures for addressing climate change and its harms, as laid out in this 3ie working paper as well as the Stern report on the economics of climate change. But as things stand, we seem to be long on choice but short on evidence.

In response, 3ie has opened a funding window focused on the theme of climate change and disaster risk reduction. Through this, 3ie will support and catalyse the generation of a critical, coherent body of evidence on two key responses to climate change: (1) the suite of activities under the auspices of REDD and REDD+ (Reducing Emissions from Deforestation and Forest Degradation) – which already includes the routine collection of Geographic Information System data and the machinery of Measurement, Recording and Verification systems – and (2) early warning mechanisms to reduce the risk of loss and damage from natural disasters.

Beyond the clear goals of understanding what works, where, when and why, 3ie has additional aims in opening this window. And these goals go beyond trying to answer questions about what works, where and why. First, we anticipate methodological innovations, as proposals for impact evaluations will need to be innovative to establish credible counterfactuals and to tease apart causal impacts in programmeswith many moving parts.

Second, researchers will have to grapple with reasonable expectations about how long is needed to see the impacts of interest in REDD/REDD+ and early warning systems. Since these impacts might show only in the medium-term, or in the face of a disaster, making strong claims about impact will require careful planning and a coherent theory of change to produce convincing evidence on impacts.

And third, a wider variety of outcomes should be considered than just environmental, including those relating to economic, social and physical welfare. We need to better understand if programmes and policies can be designed in such a way to create complementarities between measures that reduce emissions and those that reduce poverty and improve human welfare. Rigorously addressing multiple outcomes and the relationships between them through careful designs funded in this thematic window will help decision-makers better understand what works, where and why for climate change, poverty reduction and improving human welfare.