Greenhouse Gas Statistics

We explain the complexities involved in producing accurate emission statistics of greenhouse gases like nitrous oxide, methane and CO2, for use by the world’s media. We know the troposphere contains excessively high levels of these gases, but pinpointing their precise source(s) can be next to impossible.
Greenhouse gases are invisible but they remain a serious threat to our climate
Greenhouse gases: invisible but deadly. Photo: Mohammed Tawsif Salam (CC-by-3.0)

Quality of Statistics on Greenhouse Gases Remains Uneven

This article takes a brief look at some of the discrepancies in the statistics on greenhouse gas emissions, that are offered to the world’s media by climate research organizations.

Tracking emissions of greenhouse gases (GHGs) like carbon dioxide (CO2), methane (CH4) and nitous oxide (N2O), is essential in order to establish which human activities are most harmful, and what level of climate change mitigation is possible.

Unfortunately, despite the strenuous efforts of statisticians, researchers and climate scientists around the world, the quality of statistics on GHGs remains very uneven. This is no reflection on the climate science involved, or the well-documented causes of our climate crisis – namely, consumption of fossil fuels and deforestation. It is merely a reflection of the complexities involved in obtaining consistent measurements. Even so, it’s frustrating for everyone. And the advent of COVID-19 is only going to make the situation worse.

Understanding how climate change works (e.g. its causes and effects) and in particular how it is speeding up, requires much more uniform and consistent numbers that those we’re getting from research institutes, and other government bodies.

Interestingly, despite the withdrawal of the United States from the Paris Climate Agreement, the quality of global emissions statistics provided by US government agencies, such as the U.S. Environmental Protection Agency, is probably the best on the Internet. 1 Other good sources of figures about emissions include: the BP Statistical Review of World Energy: CO2 Emissions 2 and Global Carbon Budget (2020) – Summary Highlights. 3

Precise Measurements Are Often Impossible

We have to remember that Planet Earth is an extremely complex entity, whose chemical constituents are constantly reacting with each other as they move through Earth’s compartments (e.g. atmosphere, hydrosphere, lithosphere), changing from solid to liquid to gas, and back again, as they do so.

The planet is also very large, with a biosphere extending from an altitude of 12,200 meters (40,000 ft) above sea level, to 12,200 meters below sea-level (or thereabouts). Its land surface covers 148 million sq. km (57 million sq. mi) and its ocean surface extends for 361 million sq. km (139 million sq. mi). Furthermore, some of its critical areas, such as the Antarctic, are difficult, expensive and time-consuming places in which to conduct research.

Keeping a precise account of the chemical contents of the atmosphere, is difficult even for the latest generation of scientific satellites. And if a spike in the levels of a particular greenhouse gas is detected, it may be impossible to trace its source(s) or other contributing factors. Even fixing a precise average measurement may not be possible.

For example, how on earth is it possible to say, with any certainty, what proportion of methane emissions are naturally occurring rather than man-made, especially since natural gas pipelines and fracking wells have been silent emitters for years? In this regard, two cases stand out.

Satellite photo of methane hotspot over Four Corners, in US southwest
A startling red spot of methane hovering over the U.S. Southwest, burning brighter than any other area in the United States (2014). Photo: © NASA, JPL-Caltech, University of Michigan

In 2014, when overflying the Four Corners region of the southwestern United States, SCIAMACHY – one of ten instruments aboard the European Space Agency’s ENVIronmental SATellite, ENVISAT – detected a methane cloud about the size of the state of Delaware, hovering over the San Juan Basin. It represented the largest methane hot spot ever detected by satellite in North America. The area concerned was known for its coal, oil and gas industries, but until the SCIAMACHY overflight, regulators had no idea that such pollution existed. 4

In February, 2018, according to a scientific report published in the Proceedings of the National Academy of Sciences, a blowout at a fracked gas well in Belmont County, Ohio, owned by ExxonMobil, led to more methane being discharged into the air over a 20-day period than all but three European nations release during an entire year. If the Tropospheric Monitoring Instrument (TROPOMI) had not been passing overhead, this massive release of heat-trapping gas might have gone undetected. 5

Nitrous Oxide: A Statistical Nightmare

The chemical compound nitrous oxide (N2O) is a dangerous greenhouse gas that also damages our protective ozone layer. So, it needs to be watched carefully. Unfortunately, there are numerous processes – natural and man-made – that release N2O into the air throughout the world. They include: nitrification and denitrification processes in uncultivated soils, the use of nitrogen fertilizer in agriculture, decomposition of livestock manure, denitrification in the ocean, permafrost thawing, the oxidation of ammonia in the atmosphere, and fossil fuel combustion or burning biomass. Current statistics state that roughly 38 percent of N2O emissions come from man-made activities, the remainder from natural processes.

Question: Given the obvious difficulties of scale, how does someone know that 38 percent of atmospheric nitrous oxide (N2O) is caused by human activity? Might it be 33 percent? (Or 41 percent?)

Because, if so, this 5 percent represents global emissions of 475,000 metric tons of N2O. And because nitrous oxide has a global warming potential (GWP) of 265 – meaning, it traps 265 times more heat than carbon dioxide 6 – this is the equivalent of nearly 126 million metric tons of CO2.

In addition, some researchers convert nitrous oxide to carbon dioxide at the old rate of 298 rather than 265. 7 This adds an extra 15.6 million tons of carbon dioxide, making our little 5 percent discrepancy worth a whopping 141.6 million metric tons of CO2.

Like methane, nitrous oxide is an exceptionally powerful greenhouse gas which scientists are still trying to understand. For example, until 2019, little was known of its connection with Arctic permafrost, whose thawing was more associated with carbon dioxide and methane. Yet, according to a recent study which surveyed 120 square miles of the permafrost surface, during the month of August, using the airborne eddy-covariance method, nitrous oxide was being emitted at about 12 times the rate previously assumed. 8 Another chance discovery of something that, presumably, has been going on for some time.

Calculating the amount of F-gases being emitted into the atmosphere is no easier. Unfortunately, F-gases have a huge global warming potential, which means that calculations must be even more exact in order to present an accurate picture.

See: How To Reduce Your Carbon Footprint

Imperfections of Climate Models

Climate models are improving all the time, but as yet they cannot scale-up many of their findings with any great precision. The same problem applies to lab work, where clear evidence of a chemical reaction may not accurately reflect global reality. This may not undermine the main conclusions. But it may lead to statistical inconsistencies between small-scale and larger scale studies.

Differences in Data Collection Methods

Different research methods (like top-down or bottom-up approaches) can also cause statistical variations. for example, top-down methods may conflict with bottom-up methods. 9 A good example is the ongoing debate about how much methane is emitted around the world. There’s a massive discrepancy (about 32 percent) between methane emissions calculated using top-down methods (558 million tonnes per annum), compared to those using bottom-up methods (736 million tonnes per annum). 10 See also: Why Are Methane Levels Rising?

Differences in how statistics are compiled also leads to inconsistencies in carbon dioxide emission

Searching for Statistics On Greenhouse Gases

Anyone who spends a lot of time searching for figures about greenhouse gas emissions – needs the patience of Job. Published reports seem to contradict each other. Numbers don’t always add up. Sometimes, even when two sets of statistics do seem to agree, it transpires that one of them doesn’t include the same categories of the other, or the same category is defined differently.

For example, some statistical reports on methane emissions have a separate “permafrost” category, others don’t.

Some statistical surveys of carbon dioxide emissions maintain separate categories for cement manufacture and for natural gas flaring, others don’t. Some include a separate category for ozone emissions in the troposphere, others don’t.

Effect of Wildfires on CO2 Emissions

With bushfires of Biblical proportions devastating Australia, the last in a series of wildfires that has ravaged forests across Alaska, Canada, Siberia and California, not to mention the ongoing slash-and-burn deforestation in the Amazon Rainforest, CO2 emissions for 2019 are likely to hold firm (or even rise), despite the growing use of renewable energy and other mitigation measures. Wildfires are one of the most widespread climate change feedbacks – viz: man-made CO2 emissions boost the greenhouse effect and its elevated temperatures, resulting in tinder-dry forest floors, which ignite in an instant, causing huge plumes of carbon dioxide to rise into the air, further boosting the greenhouse effect and so on. Arctic fires are especially dangerous, since they accelerate the thawing of permafrost, leading to a potentially much larger feedback.

Greenhouse Gas Statistics for 2019 – Before Coronavirus

For the record, here are the latest full-year statistics on greenhouse gas emissions before the 2020 COVID-19 pandemic.

Total man-made CO2 fossil fuel emissions were 38.0 GtCO2 (72.6%). In addition, roughly 9.8 GtCO2e (18.7%) of methane, and roughly 2.8 GtCO2e (5.4%) of nitrous oxide were emitted, as well as 1.7 GtCO2e (3.3%) of fluorinated gases. In addition, around 6.8 GtCO2e were released via land use change (LUC). This makes a global greenhouse gas emissions total of 59.1 GtCO2e. 11

Effect of COVID-19 Coronavirus On Greenhouse Gas Statistics

The impact of the COVID-19 pandemic on industrial production and the consumption of fossil fuels like coal and petroleum, has been profound, at least during the first half of 2020. With closed factories and cleaner skies, figures for CO2 emissions are likely to be dramatically lower than normal, which is going to distort and confuse matters even more. Because all of a sudden, many indicators are going to show climate change improving, enabling governments to back-pedal on climate action policies such as decarbonization and farming reforms.

NO2 – Nitrogen dioxide levels drop over China during early stage of Coronavirus
NASA map showing the concentrations of nitrogen dioxide over China between January and February 2020 at the outbreak of the coronavirus. The drop in NO2 levels also coincided with lunar new year celebrations in China and across much of Asia, when businesses and factories generally close. Photo: © NASA

It may take a couple of years for the world to return to normal, and during this time most greenhouse gas statistics – including those on methane and nitrous oxide, as well as carbon dioxide – will vary enormously, according to the precise effects of the virus on a country’s economy. For more, see: Effect of COVID-19 on Climate Change.

Greenhouse Gas Statistics: Conclusion

GHG statistics can be annoyingly inconsistent. This is due largely to the complexity of global warming itself, and to its global scale. And the sudden calamitous appearance of Covid-19 has made everything ten times more confusing. In due course, we are bound to see more statistical uniformity, along with higher quality satellite data. Meantime, we must make do with the climate statistics we are offered, and focus on the big picture rather than the devilish detail’


None of the annoying inconsistencies about greenhouse gas statistics, described above, should be used to imply that climate change denial is anything but complete nonsense.


  1. EPA: Greenhouse Gas (GHG) Emissions []
  2. BP Statistical Review of World Energy – CO2 Emissions []
  3. Global Carbon Budget (2020) – Summary Highlights []
  4. Kort, E.A. et al. (2014, October 9) “Four corners: The largest US methane anomaly viewed from space.” Geophysical Research Letters, 41 (19), 6898-6903. []
  5. Satellite observations reveal extreme methane leakage from a natural gas well blowout.” Sudhanshu Pandey, et al; Proceedings of the National Academy of Sciences. December 26, 2019 116 (52) 26376-26381; first published December 16, 2019. []
  6. IPCC. Fifth Assessment Report (2014) []
  7. IPCC. Fourth Assessment Report. (2007) []
  8. Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method.” Jordan Wilkerson, Ronald Dobosy, David S. Sayres, Claire Healy, Edward Dumas, Bruce Baker and James G. Anderson. Atmospheric Chemistry and Physics, 19, 4257–4268, 2019. []
  9. Temporal variability largely explains top-down/bottom-up difference in methane emission estimates from a natural gas production region.” (November, 2018) Timothy L. Vaughn, et al; PNAS 115 (46) 11712-11717 []
  10. Global Methane Budget: Highlights []
  11. UN Emissions Gap report 2020. []
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