Humans appear to be mainly concerned about any one issue at a time, and while COVID-19 is claiming the lives of millions Homo sapiens appears to be increasingly oblivious to the growing threat to billions of humans and to nature, including the inhabitability of large regions and extinguishment of habitats.
The almost universal assumption as if a reduction in greenhouse gas emissions is in itself sufficient to prevent further warming is misleading, since positive feedbacks from land and ocean would continue to raise greenhouse levels and temperatures.
Such feedback effects include:
- increased evaporation with warming, water vapor being a greenhouse gas;
- melting ice decreasing the albedo effect of Earth, exposing dark rock surfaces, reducing the albedo of the polar terrains and sea ice in surrounding oceans, enhancing infrared absorption and heating;
- burnt and desiccated vegetation decreasing the albedo;
- decreased absorption and solubility of CO₂ in warming oceans;
- release of CO₂ and methane from drying vegetation, from melting permafrost and from bogs.
With a Miocene CO₂ level in the range of ~400-500 parts per million and mean temperatures up to 18.4°C, the atmosphere is tracking toward super-tropical temperatures, which would render large regions uninhabitable.
Anthropocene temperature rise rates are at least an order of magnitude higher than the mean temperature rise since the Last Glacial Maximum:
- Given the current mean global land and ocean temperature of 14°C, i.e. 6.2°C warmer than the mean ~7.8°C temperature of the Last Glacial Maximum (LGM) (~19,000–23.000 years-ago), the mean warming of (~0.00026°C/year rate; 6°C/23.000 years) is an order of magnitude slower than during the Anthropocene.
- Late Holocene/Anthropocene: 1.04°C/250 years ~0.004°C/year). This relegates the current global warming to an unprecedented category during the last ~3 million years and longer.
But even before such high mean temperatures is reached, the weakened jet stream climate zone boundary, allowing penetration of cold and warm fronts, allowing clashes between air and water masses of contrasting temperatures, would lead to storminess, disrupting human agriculture and habitats, as is already happening in northern Europe and within the Arctic circle.
- The acceleration in rising concentration of greenhouse gases and the lag in consequent rising temperatures;
- The extent to which ice melt flow from Greenland and Antarctica may slow down further warming in certain regions, such as the north Atlantic and the Southern Ocean;
- Further anthropogenic emissions and/or draw-down of atmospheric CO₂.
The University of New South Wales,
Kensington NSW 2052 Australia
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The Event Horizon: Homo Prometheus and the Climate Catastrophe