Greenhouse Gas Emissions
Greenhouse gases encompass a wide range of emissions, as tracked by the IPCC and scientists across the globe for their ability to modify the atmosphere and subsequently the climate. The major GHGs are carbon dioxide (Co2), methane (CH4), and Nitrous Oxide (N20) which together (with land use change, more below) make up over 97% of global GHG emissions by warming potential as of 2019 (US EPA, 2016a).
(US EPA, 2016a)
Major emissions from GHGs globally began with the industrial revolution, and within climate science we typically use around the year 1850 as a starting point. Emissions increased gradually as time passed, and technologies that required emissions, such as electricity and cars, were developed and became mainstream.
By 1900, emissions had increased globally to 1.96 billion tonnes (each tonne is ~2204 pounds). This is equivalent (approximately) to the 37.2x weight of the entire Great Wall of China(How the Great Wall of China Still Defies Scale, Time, and Myth, n.d.; JV, n.d.)
By the end of WW2, emissions had increased globally to 4.29 billion tonnes, and the United States of America continued to be the largest emitter by far, emitting 2.4 billion tonnes alone.
Emissions globally exploded in the second half of the 20th century, with the US remaining the largest emitter until they were surpassed by China in 2006, with each country emitting more than 6 billion tonnes in that year alone.
By 2024, global emissions were 38.6 billion tonnes, and continuing to increase every year, despite progress from individual nations to reduce emissions. The only years with a decrease in global emissions were due to the Covid 19 pandemic, and emissions have since rebounded above prepandemic levels by 2.7%, or 19 additional Great Walls.
It is hard to conceptualize such a large weight, even using the Great Wall of China as a benchmark. If we look at the total weight of just carbon dioxide emissions that have occurred globally (1.77 trillion tons or 1.61 trillion tonnes as of 2022), it is MORE than the total weight of all biomass on Earth (every single living thing), and more than every infrastructure project ever made by man. Every road, building, street sign, and dog house, paid for and then some by carbon emissions. Which, again, are only a portion of the total GHGs.
(Elhacham et al., 2020; Hausfather, 2025)
Emissions over time globally
Emissions over time select countries