The greens' Keystone Pipeline polemics are entirely based on emotions and hysteria versus objective facts and science - despite the vast left wing funding of climate change/global warming alarmists, the empirical evidence remains irrefutable and unequivocal...CO2 emissions from pipeline activities is figuratively a solitary speck of krill on the Southern Ocean's surface
(click on chart to enlarge - data sources)
Using data from government agency sources, it is possible to construct atmospheric CO2 levels (ppm) and human CO2 emissions going back to 1751.
The adjacent chart is a representation of historical past (1751-1899) in regard to CO2.
Interestingly, during this period the atmospheric levels of CO2 (black) grew at a much faster rate than the growth of human emissions (red). Clearly, nature itself was pumping much more CO2 into the atmosphere than evil humans who are constantly vilified by the hysterical global warming alarmists.
The likely cause of this remarkable CO2 growth was from the Earth's own warming, causing oceans to release ever greater amounts of CO2 - not a surprise after the lengthy freezing conditions of the Little Ice Age (LIA). As the world is still rebounding from the LIA cold, nature will continue to warm the oceans thus releasing ever greater amounts of CO2.
As the debate over the Keystone Pipeline heats up (goes crazy?), the actual worst case of human CO2 emission growth due to the pipeline is miniscule. From a Congressional research study (page #29), the total increase of pipeline activity CO2 emissions ranges from 3 million metric tons to 21 million metric tons annually. In contrast, the U.S. emits some 6.5 gigatons of CO2 emissions each year - indeed, a worst case of an extra 21 million tons is the proverbial krill speck in the ocean, so to speak.
On the above chart, the green line is a plot of Keystone CO2 related emissions if the pipeline was opened in 1751 and lasted until 1899. As can be seen in the context of real world emissions, even prior to the modern industrial/consumer age, the pipeline emissions add up to squat.