C.D. Keeling's measurements of the level of carbon dioxide (CO2) in the atmosphere since 1957, tracking a rise that threatens global warming, form one of the most important scienti.c data sets ever created. Yet the relatively small funding Keeling required was rarely secure. He could begin his measurements only because of a one-time injection of funds into geophysics during the International Geophysical Year. The original aim was to take a "snapshot" which could be repeated a few decades later to .nd whether the level of the gas had risen as predicted. Keeling and his sponsors made personal appeals to divert additional funds so he could re.ne and extend his measurements; in consequence, with just two years of data he showed that the level was rising. In the following decades, maintaining fund-ing was problematic. Agencies saw the work as "routine monitoring" rather than cutting-edge research. In the 1970s, the rise of an environmental movement helped reframe climate change and CO2 emissions as a threat. Funding expanded within a context of monitoring atmospheric pollution and government agency empire building. But in the early 1980s, political reaction against environmentalism again threatened Keeling's program. The story re.ects larger trends over the past half-century towards the bureaucratization and politicization of science funding.