Wildfires on peatlands can nearly double global fire-driven carbon emissions, requiring centuries to re-sequester carbon (C) losses. Peatland fires require sufficiently hot, dry conditions and/or drainage for the peat to burn. Although these conditions have historically been infrequent, the warming and drying climate could increase the potential for wildfires and subsequent emissions. Here, we evaluate how climate change impacts peatland fire emissions by using the United Kingdom as a case study—where peatlands store an estimated 3.2 PgC. We use a fire emission model to quantify fire-driven C emissions using high-resolution land-surface data and fire-weather indices. Between 2001 and 2021, we estimate 0.8 TgC has been emitted from fires on peatlands, which can contribute up to 90% of total annual UK fire-driven C emissions. Consequently, protecting peatlands from fires in the UK would be a cost-effective way to slow climate change by avoiding future emissions. Peatland emissions spike during prominent dry years, implicating the inter-annual climate as a dominant driver of year-to-year variability. Integrating future climate projections suggests that a 2°C global warming level could increase fire-driven C emissions in peatlands by over 60% solely via increased burn depths. Our findings are likely a bellwether for other temperate peatlands where climate change is leading to drier conditions, which increase burn depths and C emissions.