Report 9; May 8, 2023
Global average temperatures have been steadily increasing since the 1970s as is shown in the first two diagrams. The third diagram breaks down the different heating into two three categories: Atmospheric, Oceanic and Average temperatures.
The fourth diagram shows where increased heat energy has been stored since 1960. Note that the largest storage is above 700 meters in the Ocean.
The fifth chart is a pie chart showing the % of heat in each category. At 93.4 %, the ocean is the largest site of global storage. As I showed in my last report (#8) most of the atmospheric greenhouse gases are from CO2, Methane and Nitrous Oxide.
These gases contribute to global warming of the atmosphere in both their heating power and the length of their life times.
Global warming potential (GWP) is a measure of how much infrared thermal radiation a greenhouse gas added to the atmosphere would absorb over a given time frame, as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO2). GWP is 1 for CO2. As you can see, Methane and Nitrous oxide are more powerful warming gases than CO2 although they have a shorter lifetime than CO2. (Methane emitted today has 84 times the warming potential of CO2 in the next 20 years.) As the small charts to the right of the major chart show, even if no new CO2 were added to the atmosphere, 20 % of existing CO2 emissions would remain after 1000 years after their emission.
In the next chart, you can see a listing of the components of Radiative Forcing. Note also that aerosols, such as carbon particles, mineral dust , clouds and contrails, cool the atmosphere. At the bottom of the diagram, note the increased radiative forcing that has occurred since 1750.
Effective radiative Forcing shows the history of all of the atmospheric gases and land use changes that have contributed to global warming, not simply CO2. The effect of volcanic eruptions is shown by the dotted black line; the total anthropogenic effect by the dotted red line.
Climate forcing is a natural process closely related to Global temperature as is shown in the next two diagrams. The past 400,000 years of alternating ice ages and global warming are indicated. The Vostok temperatures are derived from water isotopes in Antarctic ice. The GHG Forcing is also measured from ice cores. The pattern of GHG Forcing since the end of the peak of the last Ice maximum, instead of decreasing as it has done in last four periods of maximum, had increase dramatically especially since 1750. So has the increase in aerosols resulting in rapidly rising temperatures. (Note the time scale has been greatly enlarged for the last 275 years.)
Since the end of the Holocene, temperatures have been increasing. In the last 200 years, they have accelerated rapidly to the point at which the biosphere has become greatly degraded. At present, unless drastic decreases in the emission of greenhouse gases occurs, planetary heating will reach the point at which intrinsic feedbacks will prevent the stabilization of ecological processes that have allowed the existence of more than 8 billion people, let alone, modern civilization to continue.
Methane and CO2 gases have increased not only in modern times, but also as early as 5000 years ago. As in other glacial maxima, methane and CO2 started declining from a maximum about 10,000 years ago (as shown in the two black arrows in the diagrams below. The blue dotted lines and the range of possible variations are shown in the blue band). However about 5000 years ago the measurements of CH4 and CO2 rose significantly. This rise is probably related to the clearance of land for agricultural and grazing.
The correlation can be seen in the following maps and charts which reflect land use changes with the development of agriculture and associated land clearance.
First the spread of cultivated rice in China and southeast Asia as early as 5,000 years ago.
Then the clearance of forests in Europe and China.
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The dates of the probable domestication of crop plants and the dates of their diffusion as basic agricultural systems is shown on the next map
The spread of domesticated animals and concurrent changes in land cover are shown in the next map.
The study by Ruddiman et al.[1] well illustrates the long lasting impact of human caused emissions of CO2 and methane. The modern period is simply the latest and most profound influence that humans have had in changing the ecology of the Earth.
I will follow these introductory remarks about the increase of GHG and its sources in my next report.
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Ruddiman, W.F., D.Q. Fuller, J.E. Kutzbach, P.C. Tzedakis, J.O. Kaplan, E.C. Ellis, S.J. Vavrus, C.N. Roberts, R. Fyfe, F. He, C. Lemmon and J. Woodbridge: Late Holocene climate: natural or anthropogenic? Rev. Geophys. 54, 93-118, 2016. ↑