(the following math you can easily follow with only secondary school (högstadie) math in your head. I have only that)
"Based on a climate sensitivity of 3 degrees for a doubling of atmospheric CO2 levels, at 550 ppm CO2 which is twice the pre-industrial level of 280 ppm CO2, mean global temperatures will rise to about 3 degrees Celsius."
If we can trust this data, this means that the equilibrium temperature for a doubling of atmospheric C02 is about 3 degrees.
But it's not that simple. The amount of methane and many of the the other greenhouse gases counts even more than carbon dioxide. Many of them are namely stronger greenhouse gases than carbon dioxide. For example methane is, during the first 20 years (and this is what counts here), an over 80 times more potent greenhouse gas than carbon dioxide. The concentration of methane in the atmosphere is currently around two-and-a-half times greater than its pre-industrial levels (see
this IEA article for more information).
Nitrous oxide is about 300 times more potent than carbon. According to
this article from 2017, nitrous oxide had increased by 23 % since preindustrial times at the time of the writing of the article. Now it is perhaps about 24 % or more.
The levels of both methane and nitrous oxide are rising exponentially in the atmosphere.
Therefore it is more fruitful to count the CO2e (
CO2 equivalent) of all the greenhouse gases together, so we can do justice to the rise of methane and the other gases. Otherwise we cannot do that.
So, what is the CO2e today?
This NOAA site (NOAA's Annual Greenhouse Gas Index. An Introduction) says the following:
"In terms of CO2 equivalents, the atmosphere in 2022 contained 523 ppm, of which 417 is CO2 alone. The rest comes from other gases." (1)
The carbon dioxide level in the atmosphere rises with about 2,1 ppm annually nowadays. So how long do we have until we have reached 550 ppm CO2e?
There is very little information on the internet about CO2e, so I have to do some own calculations.
If 417 ppm is 137 ppm over the 280 ppm preindustrial benchmark, and the other greenhouse gases have added 106 ppm to this equation during the same time, then for every ppm of carbon dioxide halt in the atmosphere, we can add about 0,77 ppm of other gases (106 is 77 % of 137).
Lets then do the math. Every year of 2,1 ppm rise of carbon dioxide, we have to add about 1,6 ppm (1,6 is 77 % of 2,1) to get to the CO2e. 2,1 ppm + 1,6 ppm is 3,7 ppm CO2e.
So how many years of 3,7 ppm CO2e do we have before we reach 550 ppm CO2e? We have about 526,7 ppm CO2e in the atmosphere right now. And we have 23,3 ppm CO2e to consume before we reach 550 ppm CO2e. So, 23,3 divided by 3,7 is 6,2.
So we have 6,2 years before we reach 550 ppm CO2e in the atmosphere, which will get us to 3 degrees Celsius of warming above preindustrial. This takes us to the summer of 2029.
And what is this 3 degrees Celsius above preindustrial? It is something very decisive.
It is, according to climate scientist Sam Carana, the point when the extinction of the human race takes place. He often touts this fact. That our sensitivity to warming is that big. You can read an example of his warnings in
this blogpost. I quote from it:
"The earlier analysis concludes that the rise from pre-industrial to 2020 could be as much as 2.29°C, which would mean that the thresholds set at the Paris Agreement have already been crossed and the rise from pre-industrial may well exceed 3°C soon, in turn effectively making 3°C the (new) threshold that should not be crossed, the more so since humans will likely go extinct with a 3°C rise..."
So ecologist professor
Guy McPherson's warning that the human race might face extinction around 2030, might very well be on spot. Guy came to this conclusion already 2002, according to the Wikipedia-article above about him. See the following youtubeinterview about it with Guy:
"Dr. Guy Mcpherson Predicts Human Extinction by 2030", posted September 3, 2022.
2030 is maybe the earliest date for the beginning of the extinction of the human race, and I would put perhaps 2045 as the latest possible date. It takes time for the climate to warm up, to realise the potential of the high levels of greenhouse gases. And there is also a time lag between emissions and the climate warming potential of the emissions. Maybe "
climate sensitivity", which is a very important notion in this context, is smaller than official data allows. Or maybe it's bigger, so that we will go extinct even before 2030, maybe already 2026, as Sam Carana believes. Just see the variability of the estimates in the Wikipedia-article above about climate sensitivity (the numbers are all about how much temperature will rise after a doubling of the amount of carbon dioxide halt in the atmosphere, above the preindustrial benchmark):
The first calculation of climate sensitivity that used detailed measurements of absorption spectra, as well as the first calculation to use a computer for numerical integration of the radiative transfer through the atmosphere, was performed by Syukuro Manabe and Richard Wetherald in 1967. Assuming constant humidity, they computed an equilibrium climate sensitivity of 2.3 °C per doubling of CO2, which they rounded to 2 °C, the value most often quoted from their work, in the abstract of the paper. The work has been called "arguably the greatest climate-science paper of all time" and "the most influential study of climate of all time."
A committee on anthropogenic global warming, convened in 1979 by the United States National Academy of Sciences and chaired by Jule Charney,estimated equilibrium climate sensitivity to be 3 °C (5.4 °F), plus or minus 1.5 °C (2.7 °F). The Manabe and Wetherald estimate (2 °C (3.6 °F)), James E. Hansen's estimate of 4 °C (7.2 °F), and Charney's model were the only models available in 1979. According to Manabe, speaking in 2004, "Charney chose 0.5 °C as a reasonable margin of error, subtracted it from Manabe's number, and added it to Hansen's, giving rise to the 1.5 to 4.5 °C (2.7 to 8.1 °F) range of likely climate sensitivity that has appeared in every greenhouse assessment since..." In 2008, climatologist Stefan Rahmstorf said: "At that time [it was published], the [Charney report estimate's] range [of uncertainty] was on very shaky ground. Since then, many vastly improved models have been developed by a number of climate research centers around the world." "
My comment: The last time earth had 400 ppm of carbon dioxide in the atmosphere, 3 million years ago, seas were at least 9,1 meters higher, and temperatures were 2-3 degrees Celsius warmer than today, in the Pliocene era (for those who believe in evolution, I don't). It gives some perspective. See for example this article in "National Geographic" about it. See also this article: "Crossing 400ppm: Welcome to the Pliocene", for more information. Remember, we are already at around 424 ppm of carbon dioxide (only carbon dioxide), this year.
(1) Scientists does not agree about these things. According to this blogpost on May 7, 2023, by Sam Carana on the Arctic News blog, the levels of methane alone in the atmosphere in May 2023 translates to 398 ppm CO2e. The levels of nitrous oxide (N2O) translates to 91.85 ppm CO₂e. And then he says: "Further drivers of climate change are CFCs, HCFCs and HFCs, which NOAA gives about twice as much radiative forcing as N₂O."
398 + 91.85 + 2 X 91.85 = 673.55
673.55 + 424 = 1097.55 ppm CO2e, almost double the amount that NOAA gave as CO2e.
