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Total amount of water vapour in the atmosphere above the oceans 27 October 2024 (kg water vapour per m²). White areas are areas without data. Map source: NOAA, SSM / IS Products. Please use this link if you want to see the original diagram or want to check for a more recent update than shown above.

The upper graph (blue) in the diagram above shows the total amount of water in the atmosphere. The green graph shows the amount of water in the lower troposphere between 1000 and 680 mb, corresponding to altitudes up to about 3 km. The lower red graph shows the amount of water between 680 and 310 mb, corresponding to altitudes from about 3 to 6 km above sea level. The marked annual variation presumably reflects the asymmetrical distribution of land and ocean on planet Earth, with most land areas located in the northern hemisphere. The annual peak in atmospheric water vapour content occur usually around August-September, when northern hemisphere vegetation is at maximum transpiration. The annual moisture peak occurs simultaneously at different levels in the atmosphere, which suggests an efficient transport of water vapour from the planet surface up into the troposphere. The time labels indicate day/month/year. There is a possibility that the step-like change shown 1998-1999 to some degree may be related to changes in the analysis procedure used for producing the data set, according to information from ISCCP.

Water vapour is the single most important greenhouse gas, and climate models forecast an increasing amount of atmospheric water vapour along with global temperature increase, because of enhanced evaporation of water from the planet surface. In addition to its direct greenhouse effect, water vapour is also important for cloud formation. Click here to see a few notes on this.

Most climate models assume that as an increasing amount of atmospheric CO₂ induces slightly increasing atmospheric temperatures, the overall evaporation will increase from the planet surface, and thereby the specific humidity of the lower part of the atmosphere (the Troposphere) will increase as well. As water vapour is the most important greenhouse gas, additional warming will come about, resulting in a much larger temperature increase than that induced from CO₂ alone. Climate models therefore, in general, assume the relative Tropospheric humidity to remain more or less stable, as increasing air temperatures are compensated by increasing specific humidity.

The above diagrams indicate that none of this has been the case since 1948. Only near the planet surface, the relative humidity has remained roughly constant (although with variations), but in the remaining part of the Troposphere below the Tropopause the relative humidity has been decreasing. Even for the specific humidity, this appears to be the case. It has, however, recently been suggested that it that the negative long-term specific humidity trends shown by the above data series are doubtful, and that instead the trend is towards increasing specific humidity (see, e.g., Dessler and Davis 2010).

Average March 2011 surface concentration of CO₂(ppmv). The delayed-mode stream is running several months real-time to make maximum use of satellite and in-situ observations that are currently not provided in real-time. Source: Monitoring Atmospheric Composition and Climate (MACC-II). Click here to se the original diagram or to check for a more recent update.

Please note that the map projection used above is of the type Mercator. This is a useful cylindrical map projection that preserves angles at all locations, but scale varies from place to place, distorting the size of land areas. In particular, areas closer to the poles are more affected, making land areas of similar size looking increasingly oversized towards the poles. To exemplify this effect, the areas of Mexico (1,972,550 km²) and Greenland (2,166,086 km²) are comparable in size. Greenland, however, in the map looks very much bigger than Mexico, even though only the southern half of Greenland is shown. The visual effect of this popular map type is to overstate the importance of temperature variations near the poles, compared to equatorial regions.

Atmospheric CO₂ is measured at several sites distributed across the planet surface. Click on the link below see results from these measurement stations:

Monthly amount of atmospheric CO₂ since March 1958, measured at the Mauna Loa Observatory, Hawaii. Data are reported as a dry mole fraction defined as the number of molecules of carbon dioxide divided by the number of molecules of dry air (water vapour removed), multiplied by one million (ppm). The thin line shows the monthly values, while the thick line is the simple running 37 month average, nearly corresponding to a running 3 yr average. Last month shown: October 2024. Last diagram update: 14 November 2024.

Annual (12 month) growth rate (ppm) of atmospheric CO₂ since 1959, calculated as the average amount of atmospheric CO2 during the last 12 months, minus the average for the preceding 12 months. The graph is based on data measured at the Mauna Loa Observatory, Hawaii. Data are reported as a dry mole fraction defined as the number of molecules of carbon dioxide divided by the number of molecules of dry air (water vapour removed), multiplied by one million (ppm). The thin blue line shows the value calculated month by month, while the dotted blue line represents the simple running 3 year average. Last month shown: October 2024. Last diagram update: 14 November 2024.

12-month change of global atmospheric CO₂ concentration (Mauna Loa; green), global sea surface temperature (HadSST4; blue) and global surface air temperature (HadCRUT5; red dotted). Entire data series since 1958 are shown in the upper diagram, and the last 15 years in the lower diagram, to enhance modern dynamics. All graphs are showing monthly values of DIFF12, the difference between the average of the last 12 month and the average for the previous 12 months for each data series. Last month included in analysis: September 2024. Last diagram update: 14 November 2024.

Visual association between Oceanic Niño Index (ONI) and annual growth rate of atmospheric CO₂. Upper panel: Annual (12 month) growth rate (ppm) of atmospheric CO₂ since 1959, calculated as the average amount of atmospheric CO2 during the last 12 months, minus the average for the preceding 12 months (see diagram above). The graph is based on data measured at the Mauna Loa Observatory, Hawaii. Lower panel: Warm (>+0.5^oC) and cold (<0.5^oC) episodes for the Oceanic Niño Index (ONI), defined as 3 month running mean of ERSSTv4 SST anomalies in the Niño 3.4 region (5^oN-5^oS, 120^o-170^oW)]. For historical purposes cold and warm episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons. Anomalies are centred on 30-yr base periods updated every 5 years. See also this diagram. Last diagram update: 14 November 2024.

Visual association since 1958 between (from bottom to top) Sunspot Number, Oceanic Niño Index (ONI) and annual change rate of atmospheric CO₂. and specific humidity at 300 mb (ca. 9 km altitude). Upper two panels: Annual (12 month) change rate of atmospheric CO₂ and specific humidity at 300 mb since 1959, calculated as the average amount of atmospheric CO2/humidity during the last 12 months, minus the average for the preceding 12 months (see diagram above). Niño index panel: Warm (>+0.5^oC) and cold (<0.5^oC) episodes for the Oceanic Niño Index (ONI), defined as 3 month running mean of ERSSTv4 SST anomalies in the Niño 3.4 region (5^oN-5^oS, 120^o-170^oW)]. For historical purposes cold and warm episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons. Anomalies are centred on 30-yr base periods updated every 5 years. Vertical stippled lines indicate the visually estimated timing of sunspot minima. Last diagram update: 14 November 2024.

NOTE: The above diagram is inspired by the work of Leamon et al. 2021: Robert J. Leamon, Scott W. McIntosh, Daniel R. Marsh. Termination of Solar Cycles and Correlated Tropospheric Variability. Earth and Space Science, 2021; 8 (4) DOI: 10.1029/2020EA001223

Superimposed plot of five different global monthly temperature estimates shown individually elsewhere. As the base period differs for these estimates, they have all been normalised by comparing to the average of their initial 120 months (10 years) from January 1979 to December 1988. Click here to go to the associated comparison of these five temperature records. The heavy black line represents the simple running 37 month (c. 3 year) mean of the average of all temperature estimates (before 1979 only the three surface records). The blue graph shows the amount of atmospheric CO₂ (Mauna Loa station, Hawaii, see also above). The heavy blue line represents the simple running 37 month (c. 3 year) mean of the monthly CO₂-values. The scale for atmospheric CO₂ (right) is adjusted to display the CO₂-graph roughly parallel to the 1975-2000 temperature increase. For the first two decades in the 21^st century a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios according to the 2007 IPCC Summary for Policymakers (p.7 and Fig.SPM.5). Last month shown: September 2024. Last diagram update: 14 November 2024.

Diagram showing the University of Alabama (UAH) monthly global surface air temperature estimate (blue) and the monthly atmospheric CO₂ content (red) according to the Mauna Loa Observatory, Hawaii. Purple line (running along red CO₂curve) shows theoretical temperature change due to changing atmospheric CO₂. The Mauna Loa data series begins in March 1958, and 1958 has therefore been chosen as starting year for the diagram. Reconstructions of past atmospheric CO₂ concentrations (before 1958) are not incorporated in this diagram, as such past CO₂ values are derived by other means (ice cores, stomata, or older measurements using different methodology), and therefore are not directly comparable with modern atmospheric measurements. Last month shown: September 2024. Last diagram update: 13 October 2024.

Diagram showing the Remote Sensing Systems (RSS) monthly global surface air temperature estimate (blue) and the monthly atmospheric CO₂ content (red) according to the Mauna Loa Observatory, Hawaii. Purple line (running along red CO₂curve) shows theoretical temperature change due to changing atmospheric CO₂. The Mauna Loa data series begins in March 1958, and 1958 has therefore been chosen as starting year for the diagram. Reconstructions of past atmospheric CO₂ concentrations (before 1958) are not incorporated in this diagram, as such past CO₂ values are derived by other means (ice cores, stomata, or older measurements using different methodology), and therefore are not directly comparable with modern atmospheric measurements. Last month shown: September 2024. Last diagram update: 13 October 2024.

Diagram showing the HadCRUT5 monthly global surface air temperature estimate (blue) and the monthly atmospheric CO₂ content (red) according to the Mauna Loa Observatory, Hawaii. Purple line (running along red CO₂curve) shows theoretical temperature change due to changing atmospheric CO₂. The Mauna Loa data series begins in March 1958, and 1958 has therefore been chosen as starting year for the diagram. Reconstructions of past atmospheric CO₂ concentrations (before 1958) are not incorporated in this diagram, as such past CO₂ values are derived by other means (ice cores, stomata, or older measurements using different methodology), and therefore are not directly comparable with modern atmospheric measurements. Last month shown: September 2024. Last diagram update: 17 November 2024.

Diagram showing the NCDC monthly global surface air temperature estimate (blue) and the monthly atmospheric CO₂ content (red) according to the Mauna Loa Observatory, Hawaii. Purple line (running along red CO₂curve) shows theoretical temperature change due to changing atmospheric CO₂. The Mauna Loa data series begins in March 1958, and 1958 has therefore been chosen as starting year for the diagram. Reconstructions of past atmospheric CO₂ concentrations (before 1958) are not incorporated in this diagram, as such past CO₂ values are derived by other means (ice cores, stomata, or older measurements using different methodology, and therefore are not directly comparable with modern atmospheric measurements. Last month shown: October 2024. Last diagram update: 17 November 2024.

Diagram showing the GISS monthly global surface air temperature estimate (blue) and the monthly atmospheric CO₂ content (red) according to the Mauna Loa Observatory, Hawaii. Purple line (running along red CO₂curve) shows theoretical temperature change due to changing atmospheric CO₂. The Mauna Loa data series begins in March 1958, and 1958 has therefore been chosen as starting year for the diagram. Reconstructions of past atmospheric CO₂ concentrations (before 1958) are not incorporated in this diagram, as such past CO₂ values are derived by other means (ice cores, stomata, or older measurements using different methodology), and therefore are not directly comparable with modern atmospheric measurements. Last month shown: October 2024. Last diagram update: 18 November 2024.

It is generally agreed that, from a theoretical point of view, the temperature effect ∆T of increasing atmospheric CO₂ may be expressed as (see, e.g. Myhre et al. 1998 and IPCC Third Assessment Report, section 6.1):

∆T = ∆F * l

where ∆F = 5,35ln(C1/Co) W/m², and where Co and C1 indicates the concentration of atmospheric CO₂ at the beginning and end of the time interval considered. The factor l is a so-called climate sensitivity parameter (expressing the global mean surface temperature response to the imposed radiative CO₂ forcing). This factor has been determined to about 0,26^oCW^-1m². The relation shows that as the concentration of atmospheric CO₂ increases, its theoretical greenhouse effect increases in a logarithmic fashion, not linear. Therefore, for each increase in CO₂ concentration, the effect on temperature is smaller and smaller.

If all other effects in the real world are ignored, the above relation shows that any doubling of atmospheric CO₂ concentration produces a temperature increase of nearly 1^oC (0.96^oC), no matter how high the initial concentration of CO₂.

The purple line in the above diagrams is calculated using the observed concentration of atmospheric CO₂ since March 1958. The axis for CO₂ is adjusted to show overlap between CO₂ (red) and the calculated accumulated temperature effect (purple). In all graphs, the temperature axis has been adjusted to position the initial calculated effect of CO₂ roughly at the average for the beginning of the observed temperature graph (blue). This is done to make it possible to compare the theoretical CO₂ temperature development (purple) with the observed development (blue).

All these diagrams show the observed temperature development to be much more complicated than the theoretical development from atmospheric CO₂ alone. With exception of the UAH diagram, the overall observed temperature increases since 1958 is much larger than calculated from CO₂ alone. In addition, the observed temperature development is characterised by recurrent intervals characterised by increasing and decreasing temperatures, respectively, a development extremely different from the calculated temperature (purple graph). Clearly many other factors than only CO₂ is in control of the real-world atmospheric temperature.

In contrast to this real-world observation, climate models are programmed to give the greenhouse gas carbon dioxide CO₂ a leading role on control on the global air temperature. The fact that the observed real-world temperature has been changing much more than expected just from CO₂, is usually ascribed to an added greenhouse effect of atmospheric water vapour in the upper Troposphere, the concentration of which by the models is expected to increase along with CO₂ (see, e.g. Schneider et. al. 1999).

However, measurements of water vapour in the upper Troposphere apparently show this assumption to be mistaken (see, e.g., diagram on p.46). Therefore, the quite substantial difference between modelled and observed atmospheric temperature must be caused by other factors. In addition, the very dynamic change pattern displayed by the observed temperature also needs to be explained, before a firm understanding of global climate dynamics can be claimed.

All temperature-CO₂ diagrams above shows both atmospheric temperature and atmospheric CO₂ to be increasing since 1959. However, this fact does not demonstrate that temperature is controlled by CO₂. In fact, it might just as well demonstrate the opposite relation (temperature controlling CO₂), or, that both temperature and CO₂ is controlled by a third factor.

Myhre, G., E. Highwood, K. Shine, and F. Stordal 1998. New estimates of radiative forcing due to well mixed greenhouse gases, Geophys. Res. Lett., 25(14), 2715–2718, doi:10.1029/98GL0190

Schneider, E.K., Kirtman, B.P., and Lindzen, R.S. 1999. Tropospheric Water Vapor and Climate Sensitivity. Journal of the Atmospheric Sciences, 56, 1649-1658.

Click here to read a few reflections on the relation between global temperature and the amount of atmospheric CO₂.

Average December 2010 methane emissions per day (mg CH₄/m²). The delayed-mode stream is running several months behind real-time to make maximum use of satellite and in-situ observations that are currently not provided in real-time. Source: Monitoring Atmospheric Composition and Climate (MACC-II). Click here to se the original diagram or to check for a more recent update.

Plot showing showing the growth of atmospheric methane (in the marine boundary layer), the seasonal variations and the difference between northern and southern hemispheres (NOAA, GLOBALVIEW), from 1993 to 2002.

Diagram showing monthly of atmospheric CH₄ since April 1984 at Cape Grim, Tasmania, Australia. Last month shown: December 2015. Last diagram update: 5 October 2016.

Diagram showing variations of atmospheric CH₄ since May 1983 at Mauna Loa, Hawaii. No smoothing has been attempted, as data points are not equidistant. A number of apparent observation outliers have been removed. Last day shown: 29 December 2015. Last diagram update: 5 October 2016.

Atmospheric methane (CH₄) is measured at several sites distributed across the planet surface. Click on the link below see results from different measurement stations: