Abrupt climate change is defined as a large-scale change in the global climate system, and occurring over a short period of geologically and climate time (a few decades or less). This change causes significant disruption in natural systems and cause significant social and economic disruption, which could possibly put humanity at risk.
Issues and state of knowledge at the beginning of the XXI century
A brutal and catastrophic warming could put humanity in short-term risk, a climate hypothesis that was first presented as highly speculative and subject to more science fiction than a serious prospective, before taking consistency scientist from the Rio Summit (June 1992) and the difficulties of implementing the Kyoto Protocol. This possibility is beginning to be considered by the futurists, including the Intergovernmental Panel on Climate Change (IPCC) under the aegis of the UN, then a university report synthesis and evaluation that a large and abrupt changes may jeopardize all or part of humanity, biodiversity or societies and ecosystems to adapt capacities. The large press is gradually echoed, referring to the international climate negotiations “more difficult than on nuclear disarmament” and risking “the future of humanity“.
The new projections of sea level rise for the end of this century exceed the projections in the IPCC AR4 report (0.28 ± 0.10 to 0.42 ± 0.16 m ascent), but there is no certainty.
There is no evidence yet of strong anthropogenic changes in precipitation in North America, but with the progress of the models and the lack of sufficient improvement in GHG emissions, the forecasts are more pessimistic than at first IPCC intercourse, particularly regarding the risk of heat waves and severe summer droughts and persistent phenomenon may have already begun, but it still could not be distinguished from the natural variability of hydroclimats in the southwest of North America .
The problems posed by an abrupt climate change
They would be particularly related to the following phenomena:
- the rapid melting of glaciers and ice caps, leading to a rise in sea level and water issues;
- general and radical change of hydrological cycles and local climates;
- a sudden change in the flow of water bodies and hot and cold air, with disruption of saltwater layers;
- exacerbation of global warming (if the climate shock is not going in the direction of cooling) by wildfires and especially via the rapid release of the atmosphere of methane hydrates from permafrost and coastal fund;
- eco-epidemiological risk; climatic zones of the changes allow microbes to colonize areas where their hosts have not acquired natural immunity;
- increased risk of natural disasters (floods, droughts, fires, diseases and even earthquakes or tsunami following a rebalancing eustatic (sum of rebalancing of tectonic stress induced by changes in weight distribution [and sea ice] weighing over crust land.
… and consequently
- increased health, technological and industrial risks
- increased risk of social crisis (sudden influx of refugees, displacement of crop areas and urbanization, etc.)
- fishery resources issues including changes related to salinity, temperature and the thermohaline circulation, etc.
Possible causes of abrupt climate change
In the past
The majority of past extinctions appears due to sudden climatic changes.
Paleoecological and paleoclimatic data available suggest that the causal element of the very sharp fluctuations in climate in the past seems to have been a natural hazard. We know two types:
- Extra-planetary hazard: For example, the fall of the Chicxulub meteorite is often cited as the underlying cause of the collapse of biodiversity in the late Jurassic, but it seems (Courtillot 2004) as volcanic eruptions (induced or independent of meteoritic impact) that have left gigantic traps (in the Deccan, Ethiopia) have most drastically disrupted the climate for hundreds of years at a rate exceeding the rate of possible evolutionary adaptations of species. In particular, the crisis of the Siberian traps is associated with the slaughter of the Permian.
- Volcanism: Significant and measurable disruptions following the eruption of Pinatubo (1991) and in 1783 -1784, that of Laki (Icelandic eruption cloud which left a mark in European mortality records (Courtillot, 2005). In 1815 the eruption of Tambora also had consequences of global climate, with strong disturbances in 1816. A volcanic widespread phenomenon could have much more important and lasting consequences. Earthquakes and Tsunami could perhaps become more frequent and significant in the case of sudden cooling or warming, following the rebalancing eustatic changes induced by masses of polar glaciers and water bodies (lakes, seas ..).
Translated from Wikipedia