A 2018 study by Strona & Bradshaw indicates that most life on Earth will disappear with a 5°C rise. The first question therefore is whether and how fast such a rise could eventuate.

Furthermore, global heating projections for the year 2100 may seem rather irrelevant to many people, as they do not expect to be alive by the year 2100. A second question therefore is what makes most sense, focusing on the year 2100, or on how much temperatures could rise over the next decade.

A recent study points at a tipping point of 1,200 ppm CO₂e when marine stratus clouds start to disappear, resulting in an additional global heating of eight degrees Celsius (8°C or 14.4°F). In other words, such a rise from clouds feedback would clearly suffice to cause extinction of most life on Earth.

On May 15, 2019, scripps.ucsd.edu recorded a carbon dioxide level of 415.7 ppm at Mauna Loa, Hawaii. NOAA recorded a methane level of 1.867 ppm for December 2018. As shown at the FAQ page, methane is 150 times as potent as a greenhouse gas over the next ten years compared to carbon dioxide. Accordingly, this 1.867 ppm of methane causes global heating of 280.05 ppm CO₂e.

Imagine a burst of methane erupting from the seafloor of the Arctic Ocean that would add an amount of methane to the atmosphere equal to twice the methane that is already there. Twice the 1.867 ppm of methane is 3.734 ppm, which at 150 times the potency of carbon dioxide translates into a CO₂e of 560.1 ppm.

Adding this to the current levels of carbon dioxide and methane results in a level of 1255.85 ppm CO₂e, well exceeding the 1,200 ppm CO₂e tipping point and thus triggering the extra 8°C rise.

A recent paper by Natalia Shakhova et al. shows that the outlook is much more grim than many people realize. From the paper: "Releases could potentially increase by 3–5 orders of magnitude, considering the sheer amount of CH4 preserved within the shallow ESAS seabed deposits and the documented thawing rates of subsea permafrost."

Methane levels as high as 2.975 ppm were recorded on June 11, 2019, at 469 mb. A peak this high is likely to have originated from the seafloor. Another MetOp image shows a solid-colored magenta area over the ESAS that afternoon, further indicating that large amounts of methane did erupt earlier that day from destabilizing sediments in the ESAS.

As said, a rapid temperature rise could make virtually all species on Earth go extinct. As the above-mentioned study points out, even the most robust lifeforms on Earth will likely disappear with a 5°C rise, as species on which they depend will die.

For mammals, which depend on a lot of other species, extinction is likely to come earlier. When looking at near-term human extinction, a 3°C rise from preindustrial will likely suffice to cause extinction.

In 2019, the global temperature could already be 1.85°C above preindustrial and a rapid temperature rise could take place over the next few years.

A lot of good action is possible, as described in the Climate Plan, which offers the greatest amount of flexibility in local implementation, within the constraints of the need to act on climate change as acknowledged, e.g. at the Paris Agreement.

Nonetheless, humans likely are already functionally extinct, as is most life on Earth. This may come as a surprise to many people, but that shouldn't stop people from doing the right thing.

The image reflects the joint CO₂e impact of carbon dioxide and methane. In addition, there is the impact of further greenhouse gases, such as nitrous oxide and CFCs, as described in a recent post. There are more warming elements, such as albedo loss associated with the decline of the snow and ice cover. These warming elements could jointly push up the temperature rise to some 10°C above preindustrial, while the clouds feedback could add a further 8°C on top of that.

Sulfates do have a cooling effect, but this effect may fall away as society grinds to a halt and stops co-emitting sulfates alongside other emissions in the process of burning fuel, as Guy McPherson has pointed out repeatedly, e.g. in a recent post and in videos, added to the post.

From the post 'When Will We Die?', at:
https://arctic-news.blogspot.com/20…/…/when-will-we-die.html