End of human species

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Carbon Cycle Feedback and Global Warming

Carbon is the essential backbone of most life forms presently on the planet. It is in one form or another an essential element of food and waste. However, the imbalance forced by industrialization has pushed many carbon derivatives out of the natural equilibria that have been established over millions of years between earth surface and the environments. This is what we, humans, have learned to enjoy in what is called the Holocene epoch. The carbon cycle is usually thought of as four major reservoirs of carbon interconnected by pathways of exchange. These reservoirs are:

Prior to 1750, the atmospheric concentration of carbon dioxide had been relatively stable between 260 and 280 ppm for 10,000 years. Perturbations of the carbon cycle from human activities were insignificant relative to natural variability. However, since 1750, the concentration ofcarbon dioxide in the atmosphere has risen, at an increasing rate, from around 280 ppm to nearly 380 ppm in 2005. The increase in atmospheric carbon dioxide concentration results from human activities: primarily burning of fossil fuels and deforestation, but also cement production and other changes in land use and management such as biomass burning, crop production and conversion of grasslands to croplands. While human activities contribute to climate change in many direct and indirect ways, carbon dioxide emissions from human activities are considered the single largest anthropogenic factor contributing to climate change. (reference)

The expression climate-carbon cycle feedbacks refers to the interaction between temperature change, atmospheric carbon dioxide levels and the carbon cycle by which carbon is exchanged between these natural reservoirs. Research has shown, for example, that global warming could significantly reduce the uptake and storage of carbon by land and ocean sinks (Joos et al. 2001, Matthews 2005 and 2006, Jones et al. 2006, Friedlingstein et al. 2006, Denman et al. 2007 and Meehl et al. 2007).

This risk has profound implications for climate policy. If the uptake and storage of carbon by natural sinks declines, a greater proportion of each additional unit of carbon emissions will remain in the atmosphere (called the airborne fraction). As a result, meeting any desired climate targets based on the atmospheric concentration of carbon dioxide will be more difficult, requiring a greater reduction in emissions than would otherwise be necessary. The level of understanding about the likely magnitude of carbon cycle feedbacks is relatively low, although it is developing rapidly. Advanced climate models have now been created that account for the interactions between climate change and the carbon cycle (called coupled climate-carbon cycle models). The results from these models suggest that carbon cycle feedbacks are likely to play a critical role in determining the atmospheric concentration of carbon dioxide over the coming centuries. (reference)

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Biota is the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biota of the Earth lives in the biosphere.


A mass of one gigaton equals one billion metric tons

The Holocene (see also the Anthropocene)

The term Holocene means completely recent and refers to the last ~10,000 years of the Earth's history, the time since the end of the last major glacial epoch, or ice age. Apart from small-scale climate shifts such as the Little Ice Age between about 1200 and 1700 A.D., the Holocene has been a relatively warm period between otherwise very long ice ages. The boundary between the Pleistocene and the recent is set at around 12,000 years ago, which represented a marked climatic warming phase and the beginning of the present interstadial (warm period between glaciations). The change is well established in a number of sediments, especially in Scandinavia, and corresponds to the boundary between the European Pollen Zones III/IV, the Younger Dryas/Preborial, and also the Late Glacial/Postglacial.

All other ages, epochs, and eras are represented by natural evolutionary and geological phenomena. The Holocene in contrast is distinguished by being the Age in which human activities have had a marked, and for the most part extremely detrimental, effect on the rest of the biosphere. Yet at the same time this age has witnessed the rise of civilization and the exponential development of the Noosphere. The ten thousand years of its extent are too short to see much in the way of the evolution of species and ecosystems, but natural processes of erosion and sedimentation have been supplemented by human activities and geographical impacts; the rise of towns, fields, buildings, roads, and other infrastructures. And there has been an exponential growth in human population and knowledge. (reference)

The name Holocene seems to have been proposed for the first time by Sir Charles Lyell in 1833, and adopted by the International Geological Congress in Bologna in 1885. During the Holocene mankind's activities gradually grew into a significant geological, morphological force, as recognised early on by a number of scientists. Thus, G.P. Marsh already in 1864 published a book with the title 'Man and Nature'. Stoppani already spoke of the anthropozoic era in 1873. Mankind has now inhabited or visited almost all places on Earth. He has even set foot on the moon. (reference)