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Kelly sees the issue of climate change as "the most horrific weapon of mass destruction in the world," and called for cooperation in tackling climate change.

[Wilmington, Delaware, XNUMXrd Reuters] – Democratic Byde who secured victory in the US presidential election ... → Continue reading


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Climate change

Climate change(Kikouhendo,British: climatic variation) Is the word地球 OfclimateIt is a word used for the change of.In the most common sense,temperatureIn addition to thePrecipitation amount,(I.e.Used for climate change on all time scales, including all factors.There are natural and anthropogenic causes of climate change.However, recent usage, especiallyEnvironment issuesIn the context of, the current average temperature rise of the Earth's surfaceGlobal warmingSpecified in the study of.

International efforts for research and recommendations on climate changeUnited NationsUNFCCC (Framework Convention on Climate Change) Is adjusted. At UNFCCCclimate changeThe term artificial change, non-artificial changeclimate variabilityI use it properly.Anthropogenic climate changeIs used as a word to indicate the possibility of human influence.

IPCCSame inclimate changeThe term is used to collectively describe both artificial and non-artificial changes, and in the Japanese translation (as a term that includes "climate change").Climate changeMay be written as.

Causes of climate change

Causes of climate changeInternal factorsとExternal factorThere is.Internal factors are interactions that occur within the Earth's climate system, and external factors are also called climate drivers, solar activity,volcanic eruption, Sea salt particles, soilaerosolNatural origins such as (dust) and artificial origins brought about by human activity (Greenhouse gasand so on.

Specific examples of "climate change consequences and factors" that are generally agreed among scientists are as follows.

  • 10 yearsGlacial / interglacialThe cycle is the earthOrbital elementIt is dominated by (seasonal and geographical changes in solar radiation) and overall changes in solar radiation (mainly changes in external factors).
  • Ice sheet coreThe sudden temperature change () that occurred during the Last Glacial Period discovered inLaurentide Ice SheetAnd it is thought to be related to the change in internal factors caused by this (change in internal factors).
  • Little Ice Age TheSolar radiationIt may have been caused by changes in volcanic activity, or a combination of both (mainly changes in external factors).

Internal factors

weather Theカ オ スでMechanicsTypicallynon-linearIt is known that.Climate (average weather) is such a system that it is difficult to clarify.For the past 40 years, in response to changes in various elements of the Earth's orbitIce sheet coreIt shows a non-chaotic phenomenon, as seen in the record of a large swinging cycle.However, a phenomenon that changes significantly in the short term should be expressed as chaos.Such changes do not appear to occur in the current climatic conditions.

Thus, the climate system will change between chaotic and non-chaotic depending on the state of external factors.

Feedback mechanism

If some factor (eg, a change in solar radiation) changes the climate, there is a mechanism that amplifies or diminishes its effect.thesePositivefeedback,Negative feedbackCalled.As far as it is known, the climate system is said to be stable due to these feedbacks, and no positive feedback has so far been found to lead to runaway.[1]..One of the reasons is the presence of strong negative feedback between the temperature and the radiant energy emitted.IPCCChapter 3 of the Third Report (Section 1) discusses the feedback mechanism in more detail.[2]..However, it is said that the possibility that runaway will not occur is not zero because there are factors such as the following methane emission phenomenon from permafrost that are insufficiently analyzed.[1].

The following are examples of positive feedback effects.

Ice-Albedo Feedback
The snow-covered areaAlbedo(Reflectance of sunlight) is high, but the ground surface below it has a low albedo and easily absorbs the radiant energy of the sun.When the ground surface warms up slightly, the snow and ice surface melts and the ground increases, causing the repeated phenomenon of melting more snow.[3].. As a typical oneArctic OceanMelting of sea ice[4]By seawaterSun lightIncreased absorption has been widely reported in recent years.[5][6].
permafrostMethane release from
The permafrost melts as the temperature rises, and the decomposition of the trapped organic mattermethaneIt has been pointed out that the release (which has a greenhouse effect 20 times that of carbon dioxide) will contribute to positive feedback.At present, it is suspected that these polar lands may be a slight sink of carbon as a whole, but the process of carbon release is complicated and the uncertainty of this conclusion is great.[7][1].
Role of carbon dioxide in the 10-year glacial/interglacial cycle
This cycle isOrbital elementHowever, the effect is too small, and it is generally believed that changes in carbon dioxide enhance the signal.Carbon dioxide increases with a slight rise in temperature, the temperature rises further due to the greenhouse effect, and carbon dioxide increases repeatedly.[Source required].

One of the negative feedback effects is the existence of natural reservoirs () such as the surface of the earth and the ocean and biosphere that absorb carbon dioxide from the atmosphere.From the existence of this level of feedback effect, it is easy to simply predict that the carbon dioxide emitted into the atmosphere is only of human origin, but the relationship between temperature changes and atmospheric carbon dioxide levels is explained. Is difficult.For example, rising temperatures can reduce soil carbon and climate changes can reduce rainforests, so it cannot be determined to be negative and may work positively.About the negative feedback effect of living thingsBiological pumpThe hypothesis is known.

External factor

Factors of natural origin

Obviously, external factors of natural origin are as important as internal factors have played an important role in past climate change.

Change in solar radiation

The most important external factors of nature are(I.e.Although it is a change in the amount of radiation due to activity, the amount of solar radiation that reaches the earth is not uniformly distributed geographically and temporally.The amount of solar radiation changes on a short time scale (1 to 100 years) depending on the solar cycle, and changes on a scale of 100 to 1000 years due to periodic changes in the earth's orbit.Considering a longer time (1 million years), the phenomenon that the sun itself becomes hot is added.

Several other mechanisms have been proposed as factors that influence celestial activity on global climate change. For example,Equatorial quasi-biennial oscillation(QBO;quasi-biennial oscillation) And solar activity[8][9][10],Arctic oscillationRelationship between (AO; arctic oscillation) and solar activity[11][12][13]And so on. Of the moonTidal forceChange ofエ ル ニ ー ニ ョ,La NiñaIt has been pointed out that the relationship with[14].. This is the tidal force of the moonHot salt circulationIt is also said to affect[15][16][17].

carbon dioxide

The Earth's current atmosphere has a carbon dioxide concentration of 370 ppm (0.037%), but during most of the last 6 million years, the carbon dioxide concentration in the atmosphere has varied between 6000 and 400 ppm. It was lower than 40ppm in the last year (before the Industrial Revolution)[13](Graphic of carbon dioxide in the Phanerozoic atmosphere and average temperature[14]See also).Compared to past geological times, there is very little carbon dioxide in the atmosphere today ([15]). In the history of the earth from 6 million years ago to the present, the carbon dioxide concentration is 400ppm or less.CarboniferousAnd the currentQuaternaryOnly.

Examples of changes due to natural origin

Glacial / interglacialThe 10-year cycle is an example of changes due to natural external factors. Two relatively widespread events over the last 1000 years, with relatively warm temperaturesMedieval warm seasonWas coldLittle Ice AgeThese changes were caused by natural causes, since the human factors are considered to be small in that era. The Little Ice Age is thought to be due to a decline in solar activity or an increase in volcanic activity, but it is not yet clear about the Middle Ages warm period. A few researchers argue that the warming that has been occurring since 1860 may be due to a natural cause of the recovery process from the Little Ice Age.[16].

Factors resulting from human activities

Anthropogenic factors are humankind (Homo sapiens) Refers to activities.The largest is carbon dioxide released in large quantities in the process of burning fossil fuels since the Industrial Revolution in Europe, most of which has been released since 1945.Other factors include deforestation, surfaceAlbedoChanges in agriculture and other land uses, effects on carbon cycle and methane production, and emission of man-made aerosols.

Anthropogenic greenhouse gas

One of the major human factors isGreenhouse gasAnd the increase in emissions isGreenhouse effectBringIndustrial revolutionSince its inception, large amounts of anthropogenic greenhouse gases have been released into the atmosphere. IPCCSince 1750, carbon dioxide concentration has increased by 31%, methane by 151%, nitrogen oxides by 17%, tropospheric ozone by 36%, and "most of the artificial carbon dioxideFossil fuelIt is produced by burning. Methane gas is also increased in livestock, fuel, and rice production, and is about 66% of the amount released from wetlands due to natural factors.[17]Was announced.

Evaluation of the relative importance of various factors

The relative importance of each of the proposed options depends on the time of interest, for example, anthropogenic factors are expected to be insignificant for pre-1750 climate change. However, this is recently reported by Ruddiman et al.[18][19] [20] Arguing that the deforestation and rice cultivation from 8000 years ago have increased carbon dioxide and methane levels. Schmidt et al. refute this, saying that the methane record is unlikely to have artificial significance.

Anyway, its importance can be evaluated through the quantification of the factors involved.The response of internal factors to external factors is betterClimate modelIt can be estimated by climate simulation using. 

Radiative forcing

The influence of external factorsRadiative forcingIt is compared with the idea. If the radiative forcing works positively on the planet, it causes warming, and if it works negatively, it causes cooling. The unit is the work amount per area W/m2.IPCC'S third report summarizes the impact of radiative forcing on the current climate.[21].


[How to use footnotes]
  1. ^ a b c Commentary on feedback on global warming (National Institute for Environmental Studies) that Coco wants to know
  2. ^ 7. Physical Climate Processes and Feedbacks[1]
  3. ^ 7.5.1 Snow Cover and Permafrost[2]
  4. ^ The thinner and thinner Arctic sea ice, JAXA Earth Observation Research Center (EORC), April 2008, 4
  5. ^ NHK Special Arctic cataclysm
  6. ^ Nikkei Economy, 2008 May 05 Articles
  7. ^ AR4 WG2 Chapter15, P.662
  8. ^ [3]
  10. ^ Astronomy Reports, Vol.45, No.12, 2001, 1012.[5]
  11. ^ GEOPHYSICAL RESEARCH LETTERS, VOL.32, L22703, 2005[6]
  12. ^ K. LABITZKE, Meteor. Z., 2005[7]
  13. ^ GEOPHYSICAL RESEARCH LETTERS, VOL.32, L23817, 2005[8]
  14. ^ GEOPHYSICAL RESEARCH LETTERS, VOL.28, NO.1, 25, 2001[9]
  15. ^ Nature, 2000, 405 (6788) 775[10]
  16. ^ Science, 2002, 298, no.5596, 1179[11]
  17. ^ Journal of Marine Research, 64, 797, 2006[12]


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