Carbon 13 Capital

Carbon 13 is a venture builder based in Cambridge with a single-minded focus: stand up new climate companies and back them through pre-seed and seed. The model is part programme, part fund. Founders are recruited into a structured cohort, formed into teams around climate-impacting problems, and supported through incorporation, prototype, and first cheque. For physician AI founders, the firm is relevant only where the work touches planetary health, biological resilience, climate-driven disease, or the broader intersection of climate and human biology.

The thesis is climate first. Carbon 13 backs companies whose central product directly reduces, removes, or avoids greenhouse gas emissions or builds resilience against climate impacts. Healthcare appears at the edges, in areas like climate-driven infectious disease modelling, AI for environmental health, biosurveillance, and tools that monitor or reduce the environmental footprint of clinical operations. Pure clinical AI tools without a climate thesis are not a fit, and founders should be honest about that fit before engaging.

Cheque sizes are small, generally under two hundred and fifty thousand dollars at pre-seed, deployed as part of the venture-builder programme alongside structured equity for the firm and the cohort infrastructure. The aim is to bridge a newly formed company from idea to first external seed round. Geography is UK-centric, with the cohort run from Cambridge and ties into the wider Cambridge research and engineering ecosystem.

The Carbon 13 team brings a mix of climate, science, engineering, and venture experience, supported by a dense network of academic and industry advisors across climate technology. Programme participants get structured help with team formation, technical validation, customer discovery, and fundraising for the round that follows the programme.

The right way to engage is through the open application process for the cohort, which is the primary entry point. Outside the programme, the firm engages selectively with companies that are already aligned on climate and ready to spin out from a research environment. When you apply, lead with the climate thesis: what is the emissions or resilience impact, what is the underlying scientific or technical insight, and why does this need a new company rather than a research project. Bring an honest view on whether you want to commit to a venture-builder model with the equity dynamics and time commitment that requires. The right time to engage is when you are ready to commit full-time to building a climate-impact company, not when you are exploring the space part-time. Physician AI founders without a clear climate wedge will be a poor fit and should focus on healthcare-specialist seed investors instead.