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A rise of 18°C or 32.4°F by 2026?

A catastrophe of unimaginable proportions is unfolding. Life is disappearing from Earth and all life could be gone within one decade. Study after study is showing the size of the threat, yet many people seem out to hide what we’re facing.

In the Arctic alone, four tipping points look set to be crossed within a few years:

  1. Loss of the Arctic sea ice’s ability to act as a buffer to absorb incoming ocean heat
  2. Loss of Arctic sea ice’s ability to reflect sunlight back into space (albedo)
  3. Destabilization of sediments at the seafloor of the Arctic Ocean 
  4. Permafrost melt

Crossing these tipping points triggers a number of feedbacks to kick in, including even more absorption of heat by the Arctic Ocean, further changes to the Jet Stream resulting in even more extreme weather, seafloor methane release, water vapor feedback and emissions from land such as CH₄ (methane), N₂O (nitrous oxide) and NOx (nitrogen oxide), due to permafrost melt, storms and forest fires. Temperatures also threaten to rise strongly over the next few years as sulfate cooling falls away while more black carbon and brown carbon gets emitted as more wood gets burned and more forest fires occur.

A recent study points at yet another tipping point, i.e. the disappearance of marine stratus clouds, which could result in a global temperature rise of eight degrees Celsius (8°C or 14.4°F) . In the model used in the study, the tipping point starts to occur at 1,200 ppm CO₂e, i.e. a stack of greenhouse gases including CH₄, N₂O, CO₂ and H₂O.

In the simulation, cloud changes did trigger a surface warming of some 8°C globally at 1,300 ppm CO₂e as stratocumulus decks did break up into cumulus clouds and evaporation strengthened, and the average longwave cooling at the level of the cloud tops dropped to less than 10% of its value in the presence of stratocumulus decks.

This 8°C rise would come on top of the warming that would already have occurred due to other warming elements, resulting in a total rise of as 18°C or 32.4°F from preindustral, as pictured on the right.

We’re currently at ~500 ppm CO₂e, so another 700 ppm would take us up to 1200 ppm. If 1 ppm equals 7.81 Gt of CO₂, then 700 ppm equals 5467 Gt of CO₂, which at a GWP for methane of 130 (10-year horizon) could be reached instantly with a burst of methane of some 42 Gt, i.e. less than Natalia Shakhova’s warning that 50 Gt of methane is ready for release at any time. And of course, there are further warming elements, in addition to methane and CO₂.

As an earlier study points out, life on Earth will already have disappeared with a 5°C rise (see box on the right).

How precious life is

It took a long time for life to evolve on Earth. At first, hardly any species could live on land, as there was no ozone layer to protect them from UV radiation. Also, there was no oxygen in the air to breathe. Life formed some 3 billion years ago and bacteria first developed the ability to decompose carbon dioxide (and produce oxygen) some 2.3  billion years ago.

Then, worm-like creatures started to multiply strongly, using more and more oxygen and producing more and more carbon dioxide. Eventually, this resulted in a sharp fall in oxygen levels, leading to extinction of these species. This first mass extinction was followed by a spike in oxygen as both the species in the oceans and plants on land continued to produce oxygen, while these first animals went extinct.

Temperature changes dominate in subsequent mass extinctions, and each time it took life a long time to recover. We’ve now entered the Sixth Mass Extinction, as oxygen levels are falling, oceans are acidifying and species are going extinct at accelerating rates. The speed at which temperatures and greenhouse gas levels are now jointly rising is so large and so unprecedented in Earth’s history that many doubt that there will be any life left on Earth by 2026.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan.

The Climate Plan

The Climate Plan suggests that the best response to this threat is implementation of multiple lines of action (the green lines on the image below, from the Climate Plan).

The green lines of action each need to be implemented in parallel, i.e. no line of action should wait for another, nor should action on one line be used as an excuse to delay action on another line. Where lines of action are grouped together in three parts, numbers merely show relationships with the kinds of warming pictured at the top of the image.

Examples of implementation of these lines of action are depicted in the image below. For more, see the Climate Plan.

Links

• Possible climate transitions from breakup of stratocumulus decks under greenhouse warming, by Tapio Schneider et al.
https://www.nature.com/articles/s41561-019-0310-1

• High CO2 Levels Can Destabilize Marine Layer Clouds (News release associated with above study)
https://www.caltech.edu/about/news/high-cosub2sub-levels-can-destabilize-marine-layer-clouds

• Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing, by Sebastiaan van de Velde et al.
https://www.nature.com/articles/s41467-018-04973-4

• Brock University-led team discovers way of tapping into and testing Earth’s prehistoric air
https://brocku.ca/brock-news/2016/07/brock-university-led-team-discovers-way-of-tapping-into-and-testing-earths-prehistoric-air

• Extinction Alert
https://arctic-news.blogspot.com/2019/02/extinction-alert.html

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

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