“We are simply talking about the very life support system of this planet.”
Hans Joachim Schellnhuber, Germany’s former chief climate scientist (2009)
“Burning all fossil fuels would create a very different planet than the one that humanity knows. The palaeoclimate record and ongoing climate change make it clear that the climate system would be pushed beyond tipping points, setting in motion irreversible changes, including ice sheet disintegration with a continually adjusting shoreline, extermination of a substantial fraction of species on the planet, and increasingly devastating regional climate extremes” and “this equates 400,000 Hiroshima atomic bombs per day 365 days per year” . James Hansen et al. 2012 and James Hansen 2012.
|Figure 1. The change in state of the planetary climate since the onset of the industrial age in the 18ᵗʰ century.|
During its last 600 million years-long history planet Earth suffered at least five major mass extinctions, defining the ends of several eras of the Ordovician, Devonian, Permian, Jurassic and Cretaceous, triggered by extra-terrestrial impacts, massive volcanic eruptions, methane release or ocean anoxia. Each of these events included the release of greenhouse gases, inducing changes in atmospheric composition and temperature (Figures 1, 2 and 3). Excepting the role of methanogenic bacteria in releasing methane, the anthropogenic mass extinction constitutes an exception: For the first time in its history the atmosphere, the oceans and the biosphere are disrupted by a living organism, namely the activity of a carbon-emitting biped mammal species.
|Fig 2B. Temperature trends for the past 65 Ma and potential geo-historical analogs for future climates (Burke et al. (2018)|
In the wake of the Pliocene (2.6-5.3 Ma-ago), with temperatures in the range of (+2°C to 3°C above pre-industrial levels) and sea levels (+25 meters) higher than at present, the development of glacial-interglacial conditions saw the appearance of Homo erectus and then Homo sapiens. Between about 10,000 and 7,000 years ago, the stabilization of the climate in the Holocene saw Neolithic agricultural civilization take hold. Anthropogenic processes during this period, denoted as the Anthropocoene (Steffen et al., 2007), led to deforestation and the demise of species, ever increasing carbon pollution of the atmosphere, temperature rise (Figures 1 and 2), acidification, radioactive contamination and a growing threat to the Earth’s life support systems.
Planetwide ecocide results from anthropogenic emission of greenhouse gases into the atmosphere, raising their combined forcing (CO₂ + CH₄ + N₂O, etc.) to levels over 500 ppm CO₂-equivalent, (Figure 3), almost doubling the pre-industrial CO₂ level of ~280 ppm, and corresponding to a rise of +3°C per doubling of CO₂ levels. The consequence of extraction and combustion of the buried products of ancient biospheres, threatens to return Earth to conditions which preceded the emergence of large mammals on land.
|Figure 3. Pre-1978 changes in the CO₂-equivalent abundance and AGGI (Annual Greenhouse Gas Index). NOAA Global Monitoring Laboratory|
The sharp glacial-interglacial oscillations of the Pleistocene (2.6 million to 10,000 years ago), with rapid mean global temperature changes of up to 5°C over a few millennia and abrupt stadials cooling events over a few years (Steffensen et al., 2008), required humans to develop an extreme adaptability, in particular mastering fire, a faculty no other species, perhaps with the exception of fire birds. Proceeding to manipulate the electromagnetic spectrum, split the atom and travel to other planets, a cultural evolution overtaking biological evolution, the power of sapiens appears to have gone out of control.
Humans have developed an absurd capacity to simultaneously create and destroy, culminating with the destruction of environments that allowed them to flourish in the first place. Possessed by a conscious fear of death and a craving for god-like immortality, there is no murderous obscenity some were not willing to perform, including the transfer of every accessible carbon molecule to the atmosphere.
Based on direct observations and the basic laws of physics, the life support systems of the biosphere are threatened by the rise of greenhouse gases and temperature by an average of more than 1.14°C since 1880, currently tracking toward 2°C. These values take little account of the masking effects of the transient mitigating effects of sulphate aerosols in the range of −0.3 to −1.8 Wm⁻², pushing mean global temperature to >1.5°C. Following the current acceleration (Figure 3), mean temperature could reach 2°C by 2030, 3°C by the 2050s and 4°C by 2100, inducing heat waves and major fires.
|Figure 4. Jet Stream, summer, 1988, NASA. Increased undulation of the Arctic boundary zone, allowing penetration of cold air masses southward and warm air masses northward;|
Overall warming of large ocean regions, reaching ~700 meter deep levels, reduces the ocean’s ability to absorb CO₂ while much of the gas is trapped in the atmosphere. As ocean heat contents rise oxygen is depleted and methane and hydrogen sulphide poisonous for marine life are produced. Models projecting global warming as a linear trajectory, outlined by the IPCC, take limited account of amplifying feedbacks and transient stadial cooling effects from the flow of ice melt water into near-polar oceans. As the circum-Arctic jet stream undulates and weakens (Figure 4), polar-ward shifts of climate zones (Figure 5) allow penetration of warm air masses into the Arctic, manifested by heat waves and fires. Conversely, injection of cold air masses from the Arctic into mid-latitudes ensues in freezing fronts producing violent snow storms, the so-called “Beast from the East”.
|Figure 5. The migration of the Sahara arid climate zone northward into southern Europe. Note the drying up of Spain, Italy, Greece and Turkey and the increased in precipitation in Northern Europe.|
As stated by Baronsky et al. (2013) in the paper “Approaching a state shift in Earth’s biosphere”: “Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence’’ and “Climates found at present on 10–48 % of the planet are projected to disappear within a century, and climates that contemporary organisms have never experienced are likely to cover 12–39 % of Earth. The mean global temperature by 2070 (or possibly a few decades earlier) will be higher than it has been since the human species evolved’’. Figure 6 outlines critical habitats and species involved in the transition.
|Figure 6. Summary of major biodiversity-related environmental-change categories expressed as a percentage of human-driven change (in red) relative to baseline (blue); Corey J. A. Bradshaw; Paul R. Ehrlich; Andrew Beattie; et al. (13 January 2021). https://www.frontiersin.org/files/Articles/615419/fcosc-01-615419-HTML-r1/image_m/fcosc-01-615419-g001.jpg – “Underestimating the Challenges of Avoiding a Ghastly Future”, in Frontiers in Conservation Science, volume 1, 13 January 2021. Red indicates the percentage of the category that is damaged, lost, or otherwise affected, whereas blue indicates the percentage that is intact, remaining, or otherwise unaffected.|
Prof Andrew Glikson, Earth and paleoclimate scientist