The Earth and Mars figures

Methodology

We calculate the Earth and Mars figures on our homepage in two steps: estimate the amount of atmospheric CO2 counted below, then calculate the energy in the methanol it could make. We assume every carbon atom becomes methanol, with enough hydrogen for the reaction.

We report the fuel's heating value before deducting production energy. CO2 supplies the carbon; producing the hydrogen takes energy.

What we count

• Earth: the increase in atmospheric CO2 above the 1750 reference level, projected forward from NOAA's latest available global monthly mean (note A).
• Mars: a seasonal estimate scaled to NASA's approximate atmospheric mass, using a published Viking pressure model (note C).

Earth

Global monthly mean, July 2026 ¹

426.10 ppm

1750 reference concentration ²

278.3 ppm

Difference from 1750

147.8 ppm

Mass per ppm: 2.124 GtC × 3.664 ³

7.782 Gt CO2

Estimated atmospheric excess

≈ 1,150 Gt CO2

A gigatonne (Gt) is a billion metric tonnes. We convert concentration to mass using the standard approximation that atmospheric CO2 is well mixed ³. Between monthly releases, we project forward using NOAA's recent annual trend (note B).

Mars

Approximate atmospheric mass ⁴

2.5 × 10¹⁶ kg

CO2 mole fraction ⁴

0.951

CO2 mass fraction: 0.951 × 44.0095 / 43.49

≈ 0.962

Reference atmospheric CO2

≈ 24,000 Gt

We use the molecular-weight ratio to convert NASA's composition by volume to a mass fraction. We then estimate seasonal changes as CO2 moves between the atmosphere and the polar caps, using a model based on Viking pressure measurements ¹². The counter follows this model through the Martian year. It is currently northern spring on Mars.

From CO2 to methanol

CO2 + 3 H2 → CH3OH + H2O

Methanol per tonne of CO2: 32.0419 / 44.0095 ¹⁰

≈ 0.728 t

Methanol lower heating value ⁵

19.9 GJ/t

Fuel energy per tonne of CO2

≈ 14.5 GJ = 4.02 MWh

We multiply each CO2 inventory by this conversion factor. The lower heating value measures heat released when methanol burns and the resulting water remains as vapor. Engines and generators convert a share of that heat into useful work; the rest is lost.

Energy needed to make the fuel

Making methanol stores part of the energy input in a liquid fuel. Some energy is lost during production. The fuel can then be stored, transported and used in applications such as long-distance shipping, where direct electrification can be difficult ¹¹.

The reaction requires about 137 kg of hydrogen per tonne of CO2. To estimate the electricity needed to produce that hydrogen, we use DOE's 2024 analysis of PEM electrolysis: 55.2 kWh/kg at the beginning of equipment life and 57.5 kWh/kg on average over its modeled life ⁶.

Electricity for that hydrogen

≈ 7.6–7.9 MWh

Chemical energy in the methanol

≈ 4.02 MWh

Fuel energy / electrolysis electricity

≈ 51–53%

The 51–53% ratio compares the energy stored in the fuel with the electricity needed to produce its hydrogen. We leave the additional energy for CO2 capture, compression, methanol synthesis, purification and transport out of this calculation.

We also leave emissions out of the energy figures. Those depend on the electricity supply, carbon source and production process. Burning methanol releases its carbon again, including carbon captured from fossil industrial emissions, so reuse in fuel provides temporary storage. A lifecycle assessment accounts for emissions from production through use ⁷.

In proportion

At the July 2026 reference concentration, Earth's inventory corresponds to about 4.63 million TWh of methanol heating value (16,700 EJ). The Mars reference corresponds to about 97 million TWh (350,000 EJ). World total energy supply in 2024 was 592 EJ ⁸, so the two inventories equal roughly 28 and 590 times that annual supply. We include this comparison to give a sense of scale. It assumes conversion of the full carbon inventory; producing that much fuel would require a larger energy input than the fuel contains.

Notes

A. What the 1750 baseline means

We use the IPCC's 278.3 ppm reference to count the increase in atmospheric concentration since 1750 ². Carbon from natural and human sources mixes in the atmosphere. Removing CO2 from the air would also change exchanges with the land and ocean, partly offsetting the removal. Our figures count the carbon in the air before that response ⁹.

B. Earth's live estimate

NOAA publishes a global monthly mean from marine surface sites after a reporting delay. Recent values are preliminary and subject to revision ¹. We check for updates daily and keep the last valid data if a refresh fails.

Between releases, we project from the monthly mean using the change in NOAA's seasonally adjusted trend over the preceding twelve months. The current starting point is July 2026, with a growth rate of 2.01 ppm/year. We multiply that rate by the elapsed fraction of a year, counting from the 16th at 00:00 UTC. That date is our mid-month convention. The projection excludes subsequent seasonal swings and changes in emissions, so its uncertainty grows with time.

We update both counters using your device's clock and show six decimal places so small changes in the models are visible. The uncertainty in the underlying estimates is much larger than the last displayed digit. We update the inputs as new source data become available.

C. Mars's live seasonal estimate

The seasonal curve comes from Tillman and colleagues' five-component Viking 1 pressure model. We use their first selected year, which was free of global dust storms ¹². NASA's Mars24 equations locate today's date in the Martian year ¹³.

We divide modeled pressure by its fitted mean and use the ratio to estimate changes in global atmospheric mass. We attribute the changing mass to CO2 exchanged with the polar caps and use NASA's approximate atmospheric mass as the cycle's mean. That choice of mean is our assumption.

Local pressure also depends on weather and circulation. We repeat a historical seasonal pattern, leaving current weather, dust storms and year-to-year changes outside the model. The margin of error for this global estimate is unknown.

Sources

1. NOAA Global Monitoring Laboratory, global monthly CO2 and its monthly data file.
2. IPCC AR6 WGI, Annex III, Table AIII.1a, p. 2141: 1750 CO2 concentration.
3. Friedlingstein et al. (2026), Global Carbon Budget 2025, Table 1 and §2.4: concentration-to-mass conversion and its limitations.
4. NASA NSSDCA, Mars Fact Sheet (updated May 2025): approximate mass, composition, mean molecular weight and seasonal pressure range.
5. IRENA and Methanol Institute (2021), Innovation Outlook: Renewable Methanol, Table 10, p. 57: 19.9 MJ/kg lower heating value.
6. U.S. DOE Hydrogen Program, Record 24005 (2024), p. 8: beginning-of-life and average PEM system electricity use.
7. IEA (2024), GHG emissions of hydrogen and its derivatives: electricity, carbon sources and lifecycle accounting.
8. Energy Institute (2025), Statistical Review of World Energy 2025: 592 EJ of total energy supply in 2024.
9. IPCC AR6 WGI, Chapter 5: carbon-cycle response to CO2 removal.
10. NIST Chemistry WebBook: molecular weights of methanol, CO2 and hydrogen.
11. IEA (2023), The Role of E-fuels in Decarbonising Transport: potential uses in sectors that are difficult to electrify.
12. Tillman et al. (1993), annual pressure-cycle model and Table 1 coefficients, author-hosted manuscript; also reproduced in Taylor et al. (2010), Table 1.
13. NASA GISS, Mars24 algorithm and worked examples: solar longitude and time conversion.