A method for calculating the temperature contribution by CO2 is given by SkS in [6] : Where ‘dF’ is the radiative forcing in Watts per square meter, ‘C’ is the concentration of atmospheric CO2, and ‘Co’ is the reference CO2 concentration. Normally the value of Co is chosen at the pre-industrial concentration of 280 ppmv.
Because the “pre-industrial” CO2 is put at 280ppm [6], and the data points in the above graph before 1800 are all very close to 280ppm, a constant level of 280ppm will be assumed before 1800. The only information still needed is the CO2-caused warming before about 1990.
The net effect of CO2 on IR is therefore given by : Rcy = 5.35 * ln (Cy/C0) – j * ( (T0+Tcy-1)^4 – T0^4) Rc y is the net downward IR from CO2 in year y. C y is the ppm CO2 concentration (C) in year y. C 0 is the pre-industrial CO2 concentration, ie. 280ppm. j is a factor to be determined. T 0 is the base temperature (deg K) associated with C 0.
Rcy = 5.35 * ln (Cy/C0) – j * ( (T0+Tcy-1)^4 – T0^4) Rc y is the net downward IR from CO2 in year y.
The amount of CO2 found in the atmosphere varies over the course of a year. Much of this variation happens because of the role of plants in the carbon cycle. Plants use CO2 from the atmosphere, along with sunlight and water, to make food and other substances that they need to grow.
Each year we put more carbon dioxide into the atmosphere than natural processes can remove, which means the net global amount of carbon dioxide rises. The more we overshoot what natural processes remove, the faster the annual growth rate.
Levels of carbon dioxide in the atmosphere rise and fall each year as plants, through photosynthesis and respiration, take up the gas in spring and summer, and release it in fall and winter. Now the range of that cycle is expanding as more carbon dioxide is emitted from burning fossil fuels and other human activities.
How do CO2 levels vary during the year? CO2 levels are lower during the Northern Hemisphere's summer. CO2 levels are higher during the Northern Hemisphere's winter.
According to the new measurements, atmospheric CO2 changes by 8 to 12 parts per million (2 to 3 percent) from winter through the “spring drawdown” in the northern hemisphere.
Second, as human-driven emissions have increased, the rise in CO2 has accelerated. It took over 200 years to reach a 25% increase by 1986. By 2011 – 25 years later – the increase reached 40%. Now after one more decade it is reaching 50%.
Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2.
There is an overall upward trend since data collection began. Global monthly average concentrations of carbon dioxide have risen steadily from 339 parts per million in 1980 (averaged over the year) to 412 parts per million in 2020, an increase of more than 20% in 40 years.
During the day or in spring and summer, plants take up more carbon dioxide through photosynthesis than they release through respiration [1], and so concentrations of carbon dioxide in the air decrease.
there are ups and downs in the CO2 levels in the northern hemisphere. this is due to the fluctuations in the ability of plants to absorb CO2 . there are low rates of photosynthesis that lead to low rates of CO2 consumption, causing peaks and drops in the atmospheric CO2 levels.
Because photosynthetic activity is the cause of seasonal CO2 swings, regions with more plants will experience larger fluctuations. Photosynthesis also occurs in the oceans, but little of this CO2 actually moves into the atmosphere, which is why only land photosynthesizes drive sea- sonal cycles.
In the spring, leaves return to the trees and photosynthesis increases dramatically, drawing down the CO2 in the atmosphere.