Breakout climate change or runaway global warming is hypothesized to follow a tipping point in the climate system, after climate change accumulation initiates positive reinforcing feedback. This is thought to cause the climate to change rapidly until it reaches a new stable condition. This phrase can be used with reference to concerns about rapid global warming. Some astronomers use the expression of a greenhouse effect to describe a situation in which the climate deviates catastrophically and permanently from its original state - just as it did on Venus.
Although these terms are rarely used in peer-reviewed climatological literature, the literature uses phrases similar to "runaway greenhouse effect", which specifically refers to climate change that causes planetary water to boil.
Video Runaway climate change
Related terms
- At the climate tipping level reaches such a point that no additional coercion is required for major climate change changes and impacts.
- At no return point , climate impacts can not be changed on a practical time scale. An example of such an impact is the disintegration of a large ice sheet.
Maps Runaway climate change
Runaway greenhouse effect
The runaway greenhouse effect has several meanings. At least extreme, this implies enough global warming to induce feedback gain beyond control, such as the disintegration of ice sheets and the melting of methane hydrates. Most extreme, Venus-like planets with carbon-crust are baked into the atmosphere and a surface temperature of several hundred degrees, an irreversible climatic state.
Among them are wet greenhouse , which occurs when climate coercion is large enough to make water vapor (H 2 O) the main atmospheric constituent. In principle, extreme moist greenhouses may cause instability with moisture that prevents radiation into the space all of the absorbed solar energy, resulting in very high surface temperatures and ocean evaporation. However, simulations show that there are no man-made greenhouse gas (GHG) triggers that can cause instability and greenhouse effects triggered by the earth's crust.
The level of man-made climate coercion can produce runaway low-end greenhouses. Coercion 12-16 W m -2 will require carbon dioxide (CO 2 ) level to increase 8-16 times. If coercion is only caused by changes in CO 2 , it will raise the global average temperature by 16-24 Â ° C with much larger polar heating. Heating 16-24 Â ° C results in a damp greenhouse, with moisture rising to about 1% of the atmospheric mass, thus increasing the rate of hydrogen release into space. If such coercion is entirely due to CO 2 , the weathering process will remove excessive CO in the atmosphere 2 on a time scale of 10 4 - 10 5 year, long before the ocean decreased significantly. Conditions like Venus on Earth require enormous long-term coercion that is impossible until the sun shines by a few tens of percent, which will take several billion years.
Global eligibility
Burning all fossil fuels will affect the human ability to live on this planet. If the greenhouse gases of non-CO 2 O and methane (CH 4 ) increase with global warming at the same rate as in palaeoclimate records and their atmospheric chemical simulations will give about 25 % of greenhouse strength. The remaining coercion requires about 4.8 times the current CO 2 level, corresponding to the fossil fuel emissions of approximately 10,000 Gt C for the conservative assumption of an 2 Average air fraction - returns for 1000 years after peak emissions.
Calculated global warming in this case is 16 Â ° C, with polar heating around 30 Â ° C. Calculates the above-average warming of the land by about 20 Â ° C. Such a temperature would eliminate grain production in almost all agricultural areas in this world. Increased stratospheric vapor will reduce the stratospheric ozone layer.
That kind of global warming will keep most of the planet uninhabited by humans. The human body produces about 100 W of metabolic heat that must be carried away to maintain the body core temperature approaching 37 ° C, meaning that a continuous wet ball temperature above 35 ° C may lead to lethal hyperthermia. Currently, summer temperatures vary greatly on the Earth's surface, but wet bulb temperatures are more narrowly limited by the effects of moisture, with the most common values ​​of about 26-27 ° C and the highest at 31 ° C. Heating 10-12 ° C will place most of the world's current population in areas with wetbulb temperatures above 35 ° C. Given the warming of 20 ° C occurring with CO 2 4.8 times, such climate coercion will result climatic conditions that can not be tolerated even if the actual climatic sensitivity is significantly lower than Russell's sensitivity, or, if Russell Sensitivity is accurate, coercion CO 2 is required to produce an unbearable condition for humans less than the sum this.
Feedback effect
The essence of the concept of escape climate change is the idea of ​​great positive feedback in the climate system. When global temperature changes cause an event to occur that changes global temperatures, this is referred to as a feedback effect. If this effect acts in the same direction as the original temperature change, it is a destabilizing positive feedback (eg heating that causes more heating); and if in the opposite direction, it is a stabilizing negative feedback (eg heating that causes a cooling effect). If a strong positive net feedback occurs, it is said that the tipping point of the climate has been bypassed and the temperature will continue to change until the changing conditions produce negative feedback that re-climates the climate.
An example of negative feedback is that radiation leaving the Earth increases in proportion to the strength of the fourth temperature, in accordance with the law of Stefan-Boltzmann. This feedback is always operational; Therefore, while it may be overwritten by positive feedback for relatively small temperature changes it will dominate for larger temperature changes. An example of positive feedback is the ice-albedo feedback, in which the increase in temperature causes the ice to melt, which increases the amount of heat absorbed by the Earth. This feedback only operates within a limited temperature range (the ice exists, and does not cover the entire surface; after all the ice melts, the feedback stops operating).
The effects of climate feedback may involve positive feedback in the type of coercion, such as methane release due to increased methane levels; other greenhouse gases, such as when CO 2 causes methane release; or other variables, such as ice-albedo feedback.
Without climate feedback, doubling the concentration of carbon dioxide in the atmosphere will result in a global average temperature rise of about 1.2 ° C. The amount of water vapor and cloud may be the most important global climate feedback. Historical information and global climate models show a climate sensitivity of 1.5-4.5 Â ° C, with the best estimate of 3 Â ° C. This is the amplification of carbon dioxide imposed by a factor of 2.5. Some studies show lower climate sensitivity, but other studies show sensitivity above this range. Partly because of the difficulty in modeling cloud feedback, the actual climate sensitivity remains uncertain.
Slow
The slow feedback effect - especially the change in ice layer size and atmospheric CO level 2 - strengthens the sensitivity of the total Earth system by the amount that depends on the time scale being considered.
There are known examples of the Earth's climate which generates a great response to small forcings. The bait effect of CO 2 is believed to be part of the transition between the glacial and interglacial periods, with the orbital imposition that provides the initial trigger.
Book chapter 2006 by Cox et al. consider the possibility of future climate change feedback in the future due to changes in soil carbon cycles:
Here we use a simple soil carbon-balance model to analyze the conditions necessary for land-to-source land transitions, and answer questions; can the soil carbon cycle lead to escaping climate feedback? [...] Simple soil carbon balance models have effective parameters that represent climate and photosynthetic susceptibility to CO 2 , and sensitivity of respiration and soil photosynthesis to temperature. This model is used to indicate that (a) the carbon sink-to-source transition is inevitable beyond some limited concentration of CO 2 provided some simple conditions are met, (b) the critical value of CO 2 is less well known because of the uncertainty parameters of the soil carbon cycle and especially in the climate sensitivity to CO 2 , and (c) that the actual carbon climate of landing (feedback or linear instability) the future is unlikely given that the land currently acts as a carbon sink.
Quick
In general, the sensitivity of feedback feedback quickly depends on the initial climatic conditions. Rapid feedback effects include changes in water vapor and aerosol levels, as well as changes in cloud cover and extent of sea ice.
Methane and klathrat deposits
Methane deposits that are potentially unstable are in the permafrost region, which is expected to retreat as a result of global warming, as well as clathrates, with the clathrate effect possibly taking millennia to act entirely. The potential role of methane from klathrat in a near-future escape scenario is uncertain, as studies show a slow methane release, which may not be considered 'escape' by all commentators. The runaway effects of klathrate gun can be used to describe faster methane release. Methane in the atmosphere has a high global warming potential, but is damaged relatively quickly to form CO 2 , which is also a greenhouse gas. Therefore, slow release of methane will have long-term effects by adding CO 2 to the atmosphere.
To model clathrates and other greenhouse gas reservoirs along with their precursors, global climate models must be 'combined' into the carbon cycle model. Most global climate models today do not include modeling of methane deposits.
Current risk
The scientific consensus in the IPCC's Fourth Assessment Report is that "anthropogenic warming can cause some sudden or irreversible effects, depending on the extent and magnitude of climate change." Note however that this statement is about the weaker situation of "runaway change". The text prepared for the IPCC Fifth Assessment Report states that "the erupting greenhouse effect" - analogous to Venus - appears to have almost no chance of being induced by anthropogenic activity. "
Estimates of the total size of carbon reservoirs in permafrost and arctic clathrates vary widely. It is recommended that at least 900 gigatons of carbon in permafrost exist throughout the world. Furthermore, it is believed there are about 400 gigatons of carbon in the methane clathrate in the permafrost region with 10,000 to 11,000 gigatons worldwide. It is quite large that if 10% of the stored methane is released, it will have an effect equivalent to a factor of increase in atmospheric CO 2 concentration. Methane is a powerful greenhouse gas with a higher global warming potential than CO 2 .
Concerns about the release of this methane and carbon dioxide are associated with arctic shrinkage. Recent years have witnessed a record low Arctic sea ice. It has been suggested that the rapid melting of sea ice can initiate rapid feedback melting the arctic permafrost. Methane clathrates on the seafloor have also been predicted to shake, but much slower.
However, the release of methane from clathrates is believed to be slower and chronic than disaster and that the effects of the 21st century of such releases are likely to be 'significant but not catastrophic'. It further notes that 'much of the methane from dissociated gas hydrates will never reach the atmosphere', as it can be dissolved into the oceans and biologically divided. Other studies have shown that atmospheric release can occur during major releases. These sources suggest that the effects of clathrate weapons alone will not be sufficient to cause 'catastrophic' climate change in a lifetime.
Hansen et al. 2013 indicates that the Earth can become a large, uninhabitable part and notes that this does not even require the burning of all fossil fuels, due to higher climate sensitivity (3-4 Ã, Â ° C or 5,4-7,2 Ã, Â ° F) based on 550 ppm scenarios. Burning all fossil fuels will warm the land an average of about 20 ° C (36 ° F) and warm the pole 30 ° C (54 ° F). The preceding estimates are based on the assumption that the use of fossil fuels will continue until the reserves run out, and predict the greenhouse effect, a climate similar to Venus. Ongoing research determines whether such climatic conditions might occur on Earth.
Paleoclimatology
Events that can be described as uncontrollable climate change may have occurred in the past.
Clathrate gun
Hypothesis gun clathrate shows abrupt climate change due to the massive release of methane gas from methane clathrates on the ocean floor. It has been speculated that the Permian-Triassic and Paleocene-Eocene Thermal Maximum extinction events are caused by the massive release of clathrates.
Snowball Earth
Geological evidence suggests that ice-albedo feedback causes sea ice to progress near the equator at some point in Earth's history. The modeling work suggests that such an event would indeed be the result of the stand-alone ice-albedo effect, and that such conditions can pass through the accumulation of CO 2 from volcanic outgassing.
See also
- Climate change suddenly
- Methane removal in the Arctic
- Avoiding dangerous climate change
- Climate change feedback
- Climate sensitivity
References
Source of the article : Wikipedia
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