What's the biggest source of CO₂ in the world? I was with a friend who argued that it was personal passenger vehicles. I was pretty sure that industry and agriculture produced the lion's share of CO₂, but she was adamant. I thought it sounded like her source was conveniently placing the blame for a warming planet on individuals' inability to conserve when I thought that our individual contributions, while not inconsequential, were not the place that we needed to start, necessarily. When I had a moment, I looked it up and found, lo and behold, she seemed to be right. The article <a href="https://ourworldindata.org/co2-emissions-from-transport" author="" source="Our World in Data">Cars, planes, trains: where do CO2 emissions from transport come from?</a> shows the biggest bar for "Road (passenger)". However, the first sentence of this article states that <iq>Transport accounts for around one-fifth of global CO₂ emissions.</iq>, which makes 45% of 20% = 11% of global emissions. So passenger traffic, while a very high percentage, is not anywhere close to the major contributor. The article <a href="https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data" author="" source="EPA">Global Greenhouse Gas Emissions Data</a> has a sub-head named "Global Emissions by Economic Sector", where we see that industry, agriculture, and Energy Production account for about 70% of CO₂ emissions. Transportation, according to this diagram, is only 14%, of which the aforementioned 45% would be only about about 6% of global emissions. <img src="{att_link}global_emissions_sector_2015.png" href="{att_link}global_emissions_sector_2015.png" align="none" caption="Global Emissions by sector 2015" scale="50%"> The figures are from 2015, but I fairly sure that they've not changed significantly in proportion since then. We can debate about the relative utility of "energy production" vs. "personal transport" but personal vehicles do not seem to be the major culprit. Improving efficiencies in agriculture and industry would seem to be a more efficient use of our time. We can also discuss the amount of other pollution---not just CO₂---produced by these sources, as particulate pollution impacts and destroys many, many lives as well.