With 46 molecules in the current ACE version 5 dataset, more data products than any other satellite instrument, ACE is often used to determine atmospheric composition. Not included in this dataset are the following research products: C2H4 (Dodangodage et al., 2025), HFC-125 (Dodangodage et al., 2025), an updated version of HFC-23 (Dodangodage et al., 2025), and an updated version of line-of-sight winds (Wyatt et al., 2025).
Trends for v5.2 ACE molecules
Global distribution maps and trends for each molecule can be viewed by clicking the molecule name in the table below.
Any use of the v5.2 trend figures or values must reference the following paper:
M. Schmidt, P. Bernath, C. Boone, M. Lecours, and J. Steffen. Trends in atmospheric composition between 2004–2023 using version 5 ACE-FTS data, J. Quant. Spectrosc. Rad. Transfer, 325 (2024) 109088; doi:10.1016/j.jqsrt.2024.109088
Linear trend values of all ACE molecules
Linear trend values of 46 ACE-FTS molecules in %/year and ppt/year from are presented below. The most recent trend is shown, unless anomalous (denoted by *), in which the next most recent trend is used. Errors are reported in parentheses as 1 standard deviation on the last digit.
|
Molecule |
Trend %/year (error) |
Trend ppt/year (error) |
Molecule | Trend %/year (error) |
Trend ppt/year (error) |
|---|---|---|---|---|---|
| C2H2 | -1.4(2) | -1.7(3) | HCFC-141b | -0.6(1) | -0.14(3) |
| C2H6 | 0.7(2) | 7.1(1.7) | HCFC-142b | 0.02(2) | 0.09(9) |
| C3H6O | 2.2(2) | 6.7(6) | HCl | -0.33(1) | -8.6(3) |
| CCl4 | -1.04(2) | -0.88(2) | HCN | -0.2(2) | -0.5(4) |
| CF4 | 1.08(1) | 0.930(9) | HCOOH | -0.8(2) | -0.31(7) |
| CFC-11 | -0.93(3) | -2.12(6) | HF* | 0.80(4) | 15.6(7) |
| CFC-12 | -0.61(1) | -3.16(4) | HFC-23 | 3.24(4) | 0.84(1) |
| CFC-113 | -1.57(5) | -1.03(3) | HFC-32 | 14.1(6) | 2.99(5) |
| CH3Cl | 0.16(4) | 0.8(2) | HFC-134a | 6.00(8) | 5.72(6) |
| CH3CN | -0.5(1) | -1.4(4) | HNO3 | 0.2(2) | 10(10) |
| CH3OH | 0.1(1) | 0.8(7) | HO2NO2 | 0.14(8) | 0.4(2) |
| CH4 | 0.80(5) | 15.1(9)\(\times\)103 | HOCl | -0.07(8) | -0.09(11) |
| ClO | 0.3(3) | 1.1(1.1) | N2 | 0.004(3) | 30(20)\(\times\)106 |
| ClONO2 | -0.47(7) | -4.0(6) | N2O | 0.285(6) | 0.95(2)\(\times\)103 |
| CO | -0.3(1) | -0.20(7)\(\times\)103 | N2O5 | 0.1(1) | 1.2(1.5) |
| CO2 | 0.550(2) | 2.25(1)\(\times\)106 | NO | 0.07(12) | 5.5(8.9) |
| COCl2 | -0.52(9) | -0.06(1) | NO2 | 0.04(8) | 1.9(3.6) |
| COClF | -0.7(1) | -0.36(5) | O2 | 0.038(5) | 80(10)\(\times\)106 |
| COF2 | 0.34(8) | 1.0(2) | O3 | 0.20(4) | 14(2)\(\times\)103 |
| H2CO | 0.1(1) | 0.1(1) | OCS | -0.98(7) | -4.5(3) |
| H2O* | 0.22(2) | 12(1)\(\times\)103 | PAN | -8.4(6) | -3.8(2) |
| H2O2 | 0.4(2) | 0.8(4) | SF6 | 3.67(2) | 0.342(2) |
| HCFC-22 | 0.40(8) | 1.0(2) | SO2 | 0.4(2) | 0.05(2) |
Twenty+ Years of Fluorine and Chlorine Inventories
With over 20 years of measurements, ACE is able to track the evolving inventory of fluorine and chlorine in the atmosphere. Using ACE data (version 5.2 - Fluorine and version 5.3 - Chlorine), some highlighted figures are shown below.
Fluorine Inventories
The following figures are taken from:
Raymond, et al.
Twenty Years of Global Stratospheric Fluorine Inventories From Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) Measurements
Journal of Geophysical Research: Atmospheres, 130, e2024JD042298; 2025; doi: 10.1029/2024JD042298
Volume Mixing Ratios
The mean total fluorine Ftot (red), product fluorine Fp (blue), and source fluorine Fs (green) VMR profiles for 2005(upper panels) and 2023 (lower panels) for each of the five latitude bands, within 0–55 km. Vertical dashed gray lines, at 1, 2,and 3 ppb, are provided as a visual aid. Upper stratospheric differences in Ftot, Fp, and Fs are more readily apparent when using these visual aids. All figures have identical x and y axes. Error bars are 1 standard deviation.
Chlorine Inventories
The following figures are taken from:
Raymond, et al.
Twenty-One Years of Global Atmospheric Chlorine Inventories From Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) Measurements
Journal of Geophysical Research: Atmospheres, 131, e2025JD045176; 2026; doi: 10.1029/2025JD045176
Volume Mixing Ratios
Mean total chlorine Cltot (red, solid), product chlorine Clp (blue, dashed) and source chlorine Cls (green, dotted) VMR profiles for 2005 (upper panels) and2024 (lower panels) for each of the five latitude bands, within 0–61 km. Vertical gray lines, at 1, 2, and 3 ppb, are provided as a visual aid. Upper stratospheric differences in Cltot, Clp, Cls are more readily apparent when using these visual aids. All figures have identical x and y axes. Uncertainty (1σ) is represented by shaded envelopes.
Percent Contribution to Total Fluorine
Percent contribution to Ftot of each fluorine‐containing species for 2005 (upper panel) and 2023 (lower panel) in the latitude band 30°–60°N within 0–55 km. Common groups of species are colored similarly to improve visual clarity. PFCs and SF6 are dark green, HCFCs are blue, HFCs are orange, CFCs are light green and minor species (SO2 F2, NF3, COClF +Halons) are colored gray. A dashed region indicates the tropopause and a blue line indicates the start of the mesosphere.
Percent Contribution to Total Chlorine
Percent contribution to Cltot of each chlorine-containing species for 2005 (upper panel) and 2024 (lower panel) in the latitude band 60–30°N, within 0–61 km. Common groups of species are colored similarly to improve visual clarity. HCFCs are steel-blue, CFCs are lime green, Chlorocarbons are gray, Cl-VSLS are lavender, and Minor species (COClF + Halons) are colored white (in-between Cl-VSLS and ClONO2). A dashed region indicates the tropopause and a blue line indicates the start of the mesosphere.
Total Column Abundance
Stacked area plot showing the relative change in weighted total column abundance (TCA; molecules/cm2) from 2004 to 2023 for five groups of fluorine source species in the 60–30 °N latitude band. The PFC group is defined as CF4, PFC-116, PFC-218, and PFC-318. The “other” group contains SF6, NF3, and SO2F2. The TCA for each species is the vertically integrated product of their volume mixing ratio (VMR) and the corresponding ACE-FTS air density profiles, yielding absolute abundances. Abundances are weighted by the number of fluorine atoms per molecule. The change in abundance for each group is calculated relative to its lowest annual value between 2004 and 2023. Abundances are weighted by the number of fluorine atoms per molecule. The relative change in TCA of Ftot is computed and plotted independently and shows good agreement with the changes in the grouped source species abundances. A clear increase in HFCs and HCFCs is evident, along with a continued decrease in CFCs, consistent with the effects of the Montreal Protocol. [Note: This figure is not included in the paper, but data from the paper used to generate this figure]
Total Column Abundance
Stacked area plot showing the relative change in weighted total column abundance (TCA; molecules/cm2) from 2004 to 2024 for four groups of chlorine source species in the 60–30°N latitude band. The Chlorocarbon group is defined as CCl4, CH3Cl and CH3CCl3. The Cl‐VSLS group contains C2Cl4, CH2Cl2,CHCl3, and 1,2‐DCA. The change in abundance for each group is calculated relative to its lowest annual value between 2004 and 2024. Abundances are weighted by the number of chlorine atoms per molecule. The TCA of Cltot is computed and plotted independently, and shows good agreement with the changes in the grouped source species abundances. A clear increase in Cl‐VSLS and HCFCs is evident in recent years, along with a continued decrease in CFCs, consistent with the effects of the Montreal Protocol.
Radiative Forcing from Fluorine-Containing Molecules
Mean radiative forcing (RF) (mW/m2) between 2004–2023 in the 60–30 °N latitude band. Coloured regions show each species’ RF normalized (i.e. expressed relative) to its minimum value during 2004–2023. The black line represents the total RF (sum of all species), referenced to its 2023 value and shifted upward so that the 2023 point aligns with the upper boundary of the shaded regions. The total RF (black line) increased by ≈ 30 mW/m2 between 2004 and 2023, with relative contributions from CFCs and HFCs changing in opposing directions. Uncertainty, not shown, is 1 standard deviation of the mean RF, approximately 10 mW/m2 for all years and latitudes. Calculations were limited to the altitude range below representative tropopause heights for the latitude region (16 km). [Note: This figure is not included in the paper, but data from the paper used to generate this figure]
Radiative Forcing from Chlorine-Containing Molecules
Mean radiative forcing (RF; mW/m2) between 2004 and 2024 in the 60–30°N latitude band. Colored regions show each species' RF normalized (i.e., expressed relative) to its minimum value during 2004–2024. The black line represents the total RF (sum of all species), referenced to its 2024 value and shifted upward so that the 2024 point aligns with the upper boundary of the shaded regions. The total RF (black line) declined by 21 mW/m2 between 2004 and 2024, with relative contributions from HCFCs and CFCs changing in opposing directions. Uncertainty, not shown, is 1 standard deviation of the mean RF, approximately 10 mW/m2 for all years and latitudes. Calculations were limited to the altitude range below representative tropopause heights for the latitude region (16 km).