2025 Global Carbon Budget
The 2025 Global Carbon Budget was just released. The data included in the report goes from 1750 to 2024, since the report was published before the end of 2025. Below "FFI" stands for fossil fuels and industry and "LUC" stands for land use change. I'm not including uncertainties in my graphs below for the sake of keeping the graphs readable, but the uncertainties are discussed in the report linked at the bottom of this post.
.png)
Here's the budget's accounting for cumulative human emissions and sinks + atmospheric growth. Total human emissions are 752 GtC (505 GtC FFI and 248 GtC LUC) and sinks total 400 GtC (210 GtC Ocean and 190 GtC land). Atmospheric growth totaled 312 GtC. This means that human sources totaled 752 GtC and sinks + atmospheric growth totaled 712 GtC, with a budget imbalance of 40 GtC, so the budget nearly balances. Above I put the 40 GtC imbalance in the land/ocean sink category, though it may be split between cumulative emissions and the land/ocean sinks.
.png)
Carbon emissions continue to increase, though rates have mostly flattened over the 15 years or so. The bad news is that 2024 experienced record high emissions, so we haven't yet reversed the trend towards decreasing emissions yet. Here are graphs showing this from 1850 and 1958 (when the Keeling Curve begins).
.png)
Human carbon emissions (FFI + LUC) are mirrored by the land and ocean sinks plus atmospheric growth, such that on average, human emissions equals the growth of carbon in the ocean, land and atmosphere. This can be shown graphically below. I took the atmospheric growth in GtC (blue) and plotted it with the total land/ocean sinks subtracted from human emissions (red). As you can see, sometimes red is higher than blue and sometimes blue is higher than red, but they are both following roughly the same trend. In other words, natural and seasonal variability can affect the balance for any given year, but overall, human emissions is driving the increase in CO2 and is responsible for ~100% of the increase in CO2 above preindustrial levels.
.png)
.png)
And since studies show warming increases linearly with cumulative emissions, I plotted HadCRUT5 with cumulative emissions below and found a slope of 1.77°C per TtC. This is consistent with the IPCC: "the AR6 reports the TCRE likely range as 1.0°C to 2.3°C per 1000 PgC in the underlying report, with a best estimate of 1.65°C."[1] To be clear, 1000 PgC = TtC = 1000 GtC. This implies a warming rate of 0.018°C per 10 GtC, which is just below to our annual emissions. Since we're currently at a long term mean of ~1.36°C above 1850-1900, this means we're on track to hit 1.5°C in about 7 years with continued emissions of 11 GtC/yr. We've emitted between 11 and 12 GtC annually for the last few years, so this may be a conservative estimate.
.png)
When debunking a ridiculous paper published a few years ago, I decided to try to quantify changes in carbon sinks and the airborne fraction as CO2 increases. This is hard to do from the carbon budget data because the data is given annually, and in the early years of the record, CO2 remains the same concentration for multiple years while in recent decades, CO2 increases multiple ppm per year. This added a bias to a graph produced in that paper. To correct for this, I binned CO2 values in 10 ppm increments and plotted the change in those bins. There's probably a better way to do this, but I think it was a good, simple way to show that the land and ocean sinks are becoming less efficient and the airborne fraction is increasing as atmospheric CO2 increases. This is consistent with projections from the IPCC.
References:
[1] Friedlingstein, P., O'Sullivan, M., Jones, M. W., Andrew, R. M., Bakker, D. C. E., Hauck, J., Landschützer, P., Le Quéré, C., Li, H., Luijkx, I. T., Peters, G. P., Peters, W., Pongratz, J., Schwingshackl, C., Sitch, S., Canadell, J. G., Ciais, P., Aas, K., Alin, S. R., Anthoni, P., Barbero, L., Bates, N. R., Bellouin, N., Benoit-Cattin, A., Berghoff, C. F., Bernardello, R., Bopp, L., Brasika, I. B. M., Chamberlain, M. A., Chandra, N., Chevallier, F., Chini, L. P., Collier, N. O., Colligan, T. H., Cronin, M., Djeutchouang, L., Dou, X., Enright, M. P., Enyo, K., Erb, M., Evans, W., Feely, R. A., Feng, L., Ford, D. J., Foster, A., Fransner, F., Gasser, T., Gehlen, M., Gkritzalis, T., Goncalves De Souza, J., Grassi, G., Gregor, L., Gruber, N., Guenet, B., Gürses, Ö., Harrington, K., Harris, I., Heinke, J., Hurtt, G. C., Iida, Y., Ilyina, T., Ito, A., Jacobson, A. R., Jain, A. K., Jarníková, T., Jersild, A., Jiang, F., Jones, S. D., Kato, E., Keeling, R. F., Klein Goldewijk, K., Knauer, J., Kong, Y., Korsbakken, J. I., Koven, C., Kunimitsu, T., Lan, X., Liu, J., Liu, Z., Liu, Z., Lo Monaco, C., Ma, L., Marland, G., McGuire, P. C., McKinley, G. A., Melton, J., Monacci, N., Monier, E., Morgan, E. J., Munro, D. R., Müller, J. D., Nakaoka, S.-I., Nayagam, L. R., Niwa, Y., Nutzel, T., Olsen, A., Omar, A. M., Pan, N., Pandey, S., Pierrot, D., Qin, Z., Regnier, P. A. G., Rehder, G., Resplandy, L., Roobaert, A., Rosan, T. M., Rödenbeck, C., Schwinger, J., Skjelvan, I., Smallman, T. L., Spada, V., Sreeush, M. G., Sun, Q., Sutton, A. J., Sweeney, C., Swingedouw, D., Séférian, R., Takao, S., Tatebe, H., Tian, H., Tian, X., Tilbrook, B., Tsujino, H., Tubiello, F., van Ooijen, E., van der Werf, G., van de Velde, S. J., Walker, A., Wanninkhof, R., Yang, X., Yuan, W., Yue, X., and Zeng, J.: Global Carbon Budget 2025, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2025-659, in review, 2025.
.png){kind=link}
Comments
Post a Comment