{"id":288969,"date":"2023-11-28T11:06:09","date_gmt":"2023-11-28T10:06:09","guid":{"rendered":"https:\/\/climatescience.press\/?p=288969"},"modified":"2023-11-28T11:06:12","modified_gmt":"2023-11-28T10:06:12","slug":"new-study-finds-the-post-1900-co2-rise-has-not-discernibly-altered-the-greenhouse-effect","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=288969","title":{"rendered":"New Study Finds The Post-1900 CO2 Rise Has Not Discernibly Altered The Greenhouse Effect"},"content":{"rendered":"\n
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From NoTricksZone<\/a><\/p>\n\n\n\n

By\u00a0Kenneth Richard<\/a>\u00a0on\u00a0<\/em>27. November 2023<\/p>\n\n\n\n

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Variations in the greenhouse effect are predominantly modulated by water vapor and cloud cover. CO2\u2019s role in the greenhouse effect is so minor it cannot be discerned.<\/strong><\/h4>\n\n\n\n
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For decades scientists have reported that a CO2 concentration of about 300 ppm can only increase the downwelling longwave radiation (DLWR), or greenhouse effect, by about 1.5 W\/m\u00b2 at the surface. See, for example, the complementary studies<\/a><\/strong> by Ramanathan (1981<\/a><\/strong>) and Newell and Dopplick (1979<\/a><\/strong>).<\/p>\n\n\n\n

\u201cThe infrared flux dominated by CO\u2082, as is well known, is only about 10% of that controlled by water vapor. The decrease in infrared flux from the surface to the atmosphere due to the increase in CO\u2082 ranges from 1.0 \u2013 1.6 W\/m\u00b2.\u201d \u2013 <\/em>Newell and Dopplick, 1979<\/strong><\/a><\/p>\n\n\n\n

With the total DLWR value assessed as ~330 W\/m\u00b2 , this means that CO2\u2019s 300 ppm (~1.5 W\/m\u00b2)  impact can only enhance the greenhouse effect by around 0.5%. Nearly all the rest is dominated by water vapor (and cloud).<\/p>\n\n\n\n

\u201cCarbon dioxide\u2026increasing downwelling LW radiation by ~1.5 W\/m\u00b2. It is about 0.5% of the 327 W\/m\u00b2 of overall downwelling radiation that warms the Earth\u2019s surface. The vast majority of that warming is contributed by water vapor. Together with cloud, it accounts for 98% of the greenhouse effect.\u201d<\/em>\u00a0 \u2013\u00a0Physics of the Atmosphere and Climate<\/em><\/strong><\/a>\u00a0(textbook)<\/p>\n\n\n\n

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Image Source:\u00a0Salby, 2012<\/a><\/strong>\u00a0(pg. 249)<\/figcaption><\/figure>\n\n\n\n

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New research (Koutsoyiannis and Vournas, 2023<\/a><\/strong>) published in the Hydrological Sciences Journal <\/em>serves to further affirm the minor, even non-discernible role of CO2 within the greenhouse effect.<\/p>\n\n\n\n

Using DLWR data from 71 globally distributed sites, these scientists assesses the post-1900 increase in the CO2 concentration (from 300 ppm to 420 ppm) \u201chas not altered, in a discernible manner, the greenhouse effect.\u201d<\/p>\n\n\n\n

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If CO2 concentration increases were to enhance the greenhouse effect \u2013 and thus be considered the driver of modern warming \u2013 there should be a change in data point distribution (displacement) in alignment with CO2 increases along the equality line as shown in the DLWR data set chart (Figure 2). This has not occurred.<\/p>\n\n\n\n

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\u201cAn enhancement of the greenhouse effect, due to increasing CO2 concentration, through the years would be seen as a gradual displacement of the points from left to right with the progression of time. However, the alignment of the points of the different data sets does not show a gradual displacement from left to right. This means that the effect of the direct CO2 emission at the surface is smaller than the side effects\u2026causing the variability in Figure 2, and thus it is impossible to discern.\u201d<\/em><\/p>\n\n\n\n

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Image Source:\u00a0Koutsoyiannis and Vournas, 2023<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

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In fact, the opposite of what should happen with an enhanced greenhouse effect has been slightly more discernible in data sets. All-sky (clouds included) DLWR trends at the top of atmosphere (TOA) have actually been shown to be declining in 21st century CERES observations, as they are \u201cslightly negative for all-sky.\u201d In other words, the 2000-present greenhouse effect has been\u00a0weakening<\/em>\u00a0despite increasing CO2 concentrations.<\/p>\n\n\n\n

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Image Source:\u00a0Koutsoyiannis and Vournas, 2023<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

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The declining greenhouse effect observed in recent decades has been reported by many other scientists<\/a><\/strong>.<\/p>\n\n\n\n

\u201c\u2026the negative trend of G [greenhouse effect anomalies] indicates that the atmospheric greenhouse effect is temporarily [1985-1999] decreasing, despite the fact that greenhouse gasses are increasing.\u201d  \u2013 <\/em>Cess and Udelhofen, 2003<\/strong><\/a><\/p>\n\n\n\n

If the greenhouse effect has not been enhanced since the 1980s, it cannot be responsible for modern warming.<\/p>\n\n\n\n

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