Carbon dioxide (CO₂) reached an average daily concentration of 422.06 ppm on April 26, 2022, at Mauna Loa, Hawaii.
Furthermore, very high methane (CH₄) concentrations were recorded recently at Mauna Loa, Hawaii, with surface flask readings appearing to be as high as 1955 ppb.
Such a 387 ppm CO₂e could be added almost immediately by a burst of seafloor methane less than the size of the methane that is currently in the atmosphere (about 5 Gt). There is plenty of potential for such an abrupt release, given the rising ocean heat and the vast amounts of methane present in vulnerable sediments at the seafloor of the Arctic Ocean, as discussed in posts such as this one.
The 1200 ppm CO₂e clouds tipping point could also be crossed even without such an abrupt seafloor methane release. Carbon dioxide and methane levels are rising rapidly. The above image shows carbon dioxide concentration with a trend added, based on NOAA 1980-2021 mean global annual carbon dioxide data, illustrating how carbon dioxide concentration could cross 750 ppm by the end of the year 2029.
|[ see also the importance of methane ]|
High carbon dioxide scenarios typically stop at the year 2100 and rarely do concentrations reach higher than 1200 ppm.
2020 analysis by Malte Meinshausen et al., the SSP5-8.5 scenario is extended to the year 2300 and a carbon dioxide concentration of well over 2100 ppm is reached around 2240.
In conclusion, there is plenty of scientific consideration of the potential for high concentrations of carbon dioxide and methane to eventuate, but it is typically ignored or waved away as too distant in the future to worry about.
In other words, what's lacking is analysis of abrupt catastrophic climate change.
Climate change danger assessment
The image below expands risk assessment beyond its typical definition as the product of the severity of impact and probability, by adding a third dimension: timescale.
|[ click on images to enlarge ]|
The image on the right, adapted from ESA, shows land surface temperatures as high as 65°C (149°F) in India on April 26, 2022. Note that land surface temperatures can be substantially higher than air temperatures.
Another issue is humidity. The more water vapor there is in the air, the harder temperature peaks are to bear.
Meanwhile, recent research found that in practice the limit will typically be lower and depending on circumstances could be as low as a wet-bulb temperature of 25°C.
In the video below, Guy McPherson also discusses the danger of combined high heat and humidity.
A 2018 study (by Strona & Bradshaw) indicates that most life on Earth will disappear with a 5°C rise. Humans, who depend for their survival on many other species, will likely go extinct with a 3°C rise, as illustrated by the image below, from an earlier post.
• NOAA - Global Monitoring Laboratory, Recent Daily Average CO₂ at Mauna Loa, Hawaii, U.S.
• NOAA - Global Monitoring Laboratory, Methane (surface flasks) at Mauna Loa, Hawaii, U.S.
• The Importance of Methane
• Clouds feedback and tipping point
• NOAA - Globally averaged marine surface annual mean carbon dioxide data
• NOAA - Globally averaged marine surface annual mean methane data
• NOAA - Mauna Loa CO2 weekly mean and historical comparisons
• Methane rise is accelerating
• NOAA Mauna Loa CO₂ annual mean data
• NOAA globaly averaged marine surface annual mean methane data
• Is the IPCC creating false perceptions, again?
• The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500 - by Malte Meinshausen et al.
• Clausius–Clapeyron relation
• Urban heat island
• Heat dome
• ESA - Heatwave across India
• Evaporative Demand Increase Across Lower 48 Means Less Water Supplies, Drier Vegetation, and Higher Fire Risk
• It could be unbearably hot in many places within a few years time
• The emergence of heat and humidity too severe for human tolerance - by Colin Raymond et al.
• Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects (PSU HEAT Project) - by Daniel Vecellio et al.
• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
• Jet Stream
• When Will We Die?
• Climate Plan