Carbonaceous particles-- which engineers might call "soot"-- have effects on Earth's climate that depend on their chemical, physical, and optical properties. These, in turn, are governed partly by the conditions under which the particles were formed. There are two gaps between available information and the characterizations needed for global climate modeling. First, carbon particles are preferentially emitted from low-technology and failing combustion, rather than the advanced technology typically studied by engineers. Second, studies are often designed to improve understanding of engineering processes with detailed measurements and idealized situations, but understanding total emissions requires information about a wide range of realistic sources. For those reasons, climate models are currently using crude parameterizations of particle properties based on limited information. --During this presentation the speaker will discuss how carbonaceous particles affect climate, how the method of applying atmospheric measurements at combustion sources has changed our understanding of their role in climate, and how further characterizations will improve estimates of past, present and future climate scenarios. Also to be discussed is how the tools at our disposal--combustion source measurements and emission tabulations, atmospheric measurements, and atmospheric chemical and transport models-- can be used to reduce uncertainty and to identify potential mitigation actions.