Avoiding dangerous climate change by lessening greenhouse gas (GHG) emissions is a policy stance of many governments. In Australia there is bipartisan support to reduce the nation’s GHG emissions. Agriculture contributes around 14 per cent of Australia’s GHG emissions, so lessening agricultural emissions helps fulfil policy goals. The task of cost-effectively reducing agricultural emissions is aided by understanding the sources of those emissions, their temporal trends and spatial spread, as illustrated in this paper. We examined the emission profiles and trajectories of 246 mixed enterprise farms in the south west of Australia over the years 2002 to 2011. The National Inventory 2010 methodology was used to calculate the farms’ emissions profiles during this period. We also categorised farms according to their financial performance and enterprise type and then examined their emission profiles and trajectories. Results show an overall decrease in emissions per hectare during the decade for the farm sample population, with emissions peaking in 2005. The main source of emission reduction is a decline in the stocking rate, due to farms shifting more towards crop production. In addition, drier years in the latter half of the decade, combined with a greater expense of supplementary grain feeding, encouraged farmers to carry fewer sheep. The results also show that farm emissions are strongly influenced by several variables. Larger farms tend to have lower emissions per hectare and farms that are financially weaker tend to have higher emissions per hectare. Significance differences (P<0.05) were observed in the emission profiles of the various farm enterprise categories (crop specialists, livestock specialists and mixed enterprises). The study also estimates the burden that inclusion of agriculture in the carbon tax scheme would have caused. If farm businesses were required to pay for their emissions at current prices then livestock specialists would have the least capacity to pay whilst crop specialists would have the greatest capacity to pay. The mean ratios of the farm aggregate operating surplus (exclusive of emission payments) to the cost of those payments during the decade were significantly different (P<0.05) for the three farm enterprise categories. These ratios were 36 for crop specialists, 13 for mixed enterprise farms and 5 for livestock specialists. The results of this study can be used to evaluate potential responses to GHG reduction policies and to target farming systems and types of farm businesses for effective emissions reduction in the region.