This paper develops an analytical framework for assessing the ecosystems in which climate ventures form and grow in emerging markets and developing economies (EMDEs). It identifies six ecosystem conditions that shape how all new ventures develop, survive, and scale, and applies those conditions against the distinct requirements and challenges of climate ventures in EMDEs. The paper also discusses how different policy and financial mechanisms like carbon pricing and green industrial policy affect these venture ecosystems. This is the first in a two-part series, the second of which will release in early 2027.