A 2°C, 3°C, 4°C or 5°C RISE?
The rise that has already unfolded may have already crossed 2°C above pre-industrial, according to this analysis that shows that the temperature may have risen as much as 2.3°C from pre-industrial to 2020. Furthermore, the temperature rise is accelerating. In other words, the world is already in the danger zone and the question remains what the implications will be of a 3°C, 4°C and 5°C rise.
[ from an earlier post ] |
What would be the impact of a 3°C, a 4°C, or a 5°C rise?
At a 3°C rise, humans will likely go extinct, as habitat for humans (and many other species) will disappear. Such a rise will cause a rapid decline of the snow and ice cover around the globe, in turn making that less sunlight gets reflected back into space. Associated changes are discussed in more detail at this page and this page, and include that the jet stream will further get out of shape, resulting in more extreme weather events such as droughts, heatwaves and firestorms. Changes to the jet stream will also contribute to a further strengthening of storms, which threatens to at times push large amounts of hot, salty water into the Arctic Ocean, triggering eruptions of more and more seafloor methane, as discussed in an earlier post.
[ from an earlier post ] |
At 5°C rise, most life on Earth will have gone extinct. A 2018 study by Strona & Bradshaw indicates that most life on Earth will disappear with a 5°C rise (see box on the right). As the temperature keeps rising, chances are that all life on Earth will go extinct, as Earth would be left with no ozone layer to protect life from deadly UV-radiation. Furthermore, Earth would no longer have water, an essential building block of life. Soil moisture, groundwater and water in oceans would evaporate and eventually disappear into space, as discussed in an earlier post.
Much of the above was discussed in 2019 posts such as When will we die? and Most Important Message Ever.
Beyond a 5°C rise
The image below, from Song et al. (2021), shows how major mass extinctions over the past 541 million years (the Phanerozoic) are linked to temperature rises higher than 5.2°C and rates of change higher than 10°C/Myr.
The image below, from an earlier post, sums up our predicament, highlighting the rapidity of the current temperature rise and its potential magnitude.
As illustrated by the image below, the temperature has been rising for a long time and, as said, the temperature rise is accelerating, as discussed in posts such as this one and this one.
[ from earlier post ] |
Could Earth go the same way as Venus?
[ Earlier version posted at Most Important Message Ever and discussed at facebook ] |
Earth did experience high temperatures before, but it cooled down and some species did survive the mass extinctions in the past. This time, however, temperatures could keep rising, due to:
- Brighter Sun - The sun is now much brighter than it was in the past;
- No sequestration - The rapidity of the rise in greenhouse gases and of the associated temperature rise leaves species little or no time to adapt or move, and leaving no time for sequestration of carbon dioxide by plants and by deposits from other species, nor for formation of methane hydrates at the seafloor of oceans;
- No weathering - The rapidity of the rise also means that weathering doesn't have a chance to make a difference. Rapid heating is also dwarfing what weathering (and vegetation) can do to reduce carbon dioxide levels; and
- Methane, water vapor, loss of sea ice & heat sinks and further feedbacks - As the temperature rises, feedbacks increasingly kick in, such as emissions from decomposing vegetation and fires, while methane erupts from hydrates with little or no time for it to get decomposed.
A very small increase in solar irradiation – leading to an increase of the global Earth temperature, of only a few tens of degrees – would be enough to trigger an irreversible runaway process on Earth and make our planet as inhospitable as Venus, as a recent study concludes.
In conclusion, Earth could go the same way as Venus soon, considering that there could be a rise from pre-industrial of more than 18°C as early as 2026, as discussed in an earlier post and at the extinction page. Also consider the following, from a 2013 post,
Long-term scenarios foresee Earth eventually becoming uninhabitable for mammals, even if mammals would survive the current temperature rise. The image below, from Farnsworth et al. (2023), depicts Solar System bodies in accordance with their Earth Similarity Index (ESI), which is based on data such as mass, radius, and temperature, versus the Planetary Habitability Index (PHI), which is based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent.
Earth is on the edge of runaway warming
The old picture, with Earth well within
our solar system's habitable zone |
What is the habitable zone? To be habitable, a planet the size of Earth should be within certain distances from its Sun, in order for liquid water to exist on its surface, for which temperatures must be between freezing point (0° C) and boiling point (100° C) of water.
In the Wikipedia image, the dark green zone indicates that a planet the size of Earth could possess liquid water, which is essential since carbon compounds dissolved in water form the basis of all earthly life, so watery planets are good candidates to support similar carbon-based biochemistries.
If a planet is too far away from the star that heats it, water will freeze. The habitable zone can be extended (light green color) for larger terrestrial planets that could hold on to thicker atmospheres which could theoretically provide sufficient warming and pressure to maintain water at a greater distance from the parent star.
A planet closer to its star than the inner edge of the habitable zone will be too hot. Any water present will boil away or be lost into space entirely. Rising temperatures caused by greenhouse gases could lead to a moist greenhouse with similar results.
The distance between Earth and the Sun is one astronomical unit (1 AU). Mars is often said to have an average distance from the Sun of 1.52 AU. A recent study led by Ravi Kopparapu at Penn State mentions that early Mars was warm enough for liquid water to flow on its surface. However, the present-day solar flux at Mars distance is 0.43 times that of Earth. Therefore, the solar flux received by Mars at 3.8 Gyr was 0.75 × 0.43 = 0.32 times that of Earth. The corresponding outer habitable zone limit today, then, would be about 1.77 AU, i.e. just a bit too far away from the Sun to sustain water in liquid form. Venus, on the other hand, is too close to the Sun (see box below).
Kopparapu calculates that the Solar System’s habitable zone lies between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. In other words, Earth is on the edge of runaway warming.
Kopparapu says that if current IPCC temperature projections of a 4 degrees K (or Celsius) increase by the end of this century are correct, our descendants could start seeing the signatures of a moist greenhouse by 2100.
Kopparapu argues that once the atmosphere makes the transition to a moist greenhouse, the only option would be global geoengineering to reverse the process. In such a moist-greenhouse scenario, not only are the ozone layer and ice caps destroyed, but the oceans would begin evaporating into the atmosphere's upper stratosphere.
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The video below, Science Snippets: Loss of All Life on Earth Explained ... Again - by Guy McPherson, describes our precarious situation.
Links
• What the IPCC impacts report is hiding
https://arctic-news.blogspot.com/2022/02/what-the-ipcc-impacts-report-is-hiding.html
• Most Important Message Ever
• Most Important Message Ever
• When Will We Die?
https://arctic-news.blogspot.com/2019/06/when-will-we-die.html
• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html
• Human Extinction by 2022?
• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html
• Human Extinction by 2022?
https://arctic-news.blogspot.com/2021/11/human-extinction-by-2022.html
• Warning of mass extinction of species, including humans, within one decade
• Warning of mass extinction of species, including humans, within one decade
https://arctic-news.blogspot.com/2017/02/warning-of-mass-extinction-of-species-including-humans-within-one-decade.html
• When will humans go extinct?
• When will humans go extinct?
https://arctic-news.blogspot.com/2022/02/when-will-humans-go-extinct.html
• Accelerating Methane Rise
https://arctic-news.blogspot.com/2022/02/accelerating-methane-rise.html
• Earth is on the edge of runaway warming
https://arctic-news.blogspot.com/2013/04/earth-is-on-the-edge-of-runaway-warming.html
• Habitable zones around main-sequence stars: new estimates - by Ravi Kumar Kopparapu et al. (2013)
http://iopscience.iop.org/0004-637X/765/2/131
• Habitable Zone - Wikipedia
http://en.wikipedia.org/wiki/Habitable_zone
• Earth is closer to the edge of Sun's habitable zone (2013)
http://physicsworld.com/cws/article/news/2013/mar/25/earth-is-closer-to-the-edge-of-suns-habitable-zone
• Updated model for identifying habitable zones around stars puts Earth on the edge
http://www.gizmag.com/habitable-zone/26051/
• Accelerating Methane Rise
https://arctic-news.blogspot.com/2022/02/accelerating-methane-rise.html
• Earth is on the edge of runaway warming
https://arctic-news.blogspot.com/2013/04/earth-is-on-the-edge-of-runaway-warming.html
• Habitable zones around main-sequence stars: new estimates - by Ravi Kumar Kopparapu et al. (2013)
http://iopscience.iop.org/0004-637X/765/2/131
• Habitable Zone - Wikipedia
http://en.wikipedia.org/wiki/Habitable_zone
• Earth is closer to the edge of Sun's habitable zone (2013)
http://physicsworld.com/cws/article/news/2013/mar/25/earth-is-closer-to-the-edge-of-suns-habitable-zone
• Updated model for identifying habitable zones around stars puts Earth on the edge
http://www.gizmag.com/habitable-zone/26051/
• 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
• Tardigrades have a fatal weakness after all (2020)
https://bigthink.com/hard-science/tardigrades-extremophiles
• Thermotolerance experiments
on active and desiccated states
of Ramazzottius varieornatus
emphasize that tardigrades are
sensitive to high temperatures - by Ricardo Neves et al. (2020)
https://www.nature.com/articles/s41598-019-56965-z
• The projected timing of abrupt ecological disruption from climate change - by Christopher Trisos et al. (2020)
https://pubmed.ncbi.nlm.nih.gov/32322063
• Extreme Space-Weather Events and the Solar Cycle - by Mathew Owens et al. (2021)
• The projected timing of abrupt ecological disruption from climate change - by Christopher Trisos et al. (2020)
https://pubmed.ncbi.nlm.nih.gov/32322063
• Extreme Space-Weather Events and the Solar Cycle - by Mathew Owens et al. (2021)
https://link.springer.com/article/10.1007/s11207-021-01831-3
• Ancient volcanic eruption destroyed the ozone layer
https://phys.org/news/2021-06-ancient-volcanic-eruption-ozone-layer.html
• The Toba supervolcano eruption caused severe tropical stratospheric ozone depletion - by Sergey Osipov et al. (2021)
https://www.nature.com/articles/s43247-021-00141-7
• Ancient volcanic eruption destroyed the ozone layer
https://phys.org/news/2021-06-ancient-volcanic-eruption-ozone-layer.html
• The Toba supervolcano eruption caused severe tropical stratospheric ozone depletion - by Sergey Osipov et al. (2021)
https://www.nature.com/articles/s43247-021-00141-7
https://www.presidentti.fi/en/news/president-niinisto-in-arkhangelsk-if-we-lose-the-arctic-we-lose-the-whole-world
• Thresholds of temperature change for mass extinctions - by Haijun Song et al. (2021).
discussed on facebook at https://www.facebook.com/groups/arcticnews/posts/10161394256549679
• Climate extremes likely to drive land mammal extinction during next supercontinent assembly - by Alexander Farnsworth et al. (2023)
https://www.nature.com/articles/s41561-023-01259-3
discussed on facebook at https://www.facebook.com/groups/arcticnews/posts/10161398911689679
discussed on facebook at https://www.facebook.com/groups/arcticnews/posts/10161398911689679