Climate change

(Image composite ilustrating main factors affecting climatic change, https://commons.wikimedia.org/wiki/File:Climate_change-en.svg)

A climate change represents a lasting change (from decades to millions of years) of statistical parameters (mean parameters, variability) of the overall climate of the Earth or its various regional climates. These changes may be due to intrinsic process of the Earth, to outside influences or, more recently, to human activities.

Anthropogenic climate change is the result of greenhouse gas emissions generated by human activities altering the atmospheric composition of the planet. To this are added the evolution of natural variations in climate.

In the work of the Intergovernmental Panel on Climate Change, the term “climate change” refers to any change in time, whether due to natural variability or human activity.

In contrast, in the United Nations Framework Convention on Climate Change, the term refers only to changes due to human activities. The Framework Convention uses the term “climate variability” to describe natural climate change.

The Greek philosopher Theophrastus, in his book Winds, writes that on the Cretan mountains we could already see the ruins of ancient cities, abandoned sites, formerly inhabited or cultivated land, depopulated long time ago for climatic reasons.

Old variations

(Evolution of average global temperatures of 500 million years, https://fr.wikipedia.org/wiki/Fichier:All_palaeotemps.png)

(Graph of temperatures of 2 past millennia highlighting the medieval climate optimum, the Little Ice Age, which follows the breakdown of global warming, https://fr.wikipedia.org/wiki/Fichier:2000_Year_Temperature_Comparison.png)

The earlier phases of human history show the paleoclimatology. It can track, over continental drift and periods of successive glaciations, changes related to climate change that affected the soil and species.

…
+ Upto 450 000 years ago: Waalian Interglacial
– Until 400,000 years ago: Günz or Nébraskien
+ Upto 350 000 years ago: Cromer or Aftonien Interglacial
– Until 320,000 years ago: Mindel , Elster or KansienGlaciation + until 270,000 years ago: Holstein or Yamouthien Interglacial
– Until 200,000 years ago: Riss, Saal, or Illinoien Glaciation
+ Upto 125 000 years ago: Eem, Eemian or Sangamonian Interglacial
– Until 70 000 years ago: Würm, Wisconsin or Weichselian Glaciation
+ Upto 11,625 years ago: the Holocene Interglacial (Holocene climatic optimum) sometimes referred to as the Holocene “new warming”

… Beginning of written human history and observation of climate changes by chroniclers.

– Climate Change between 535-536 observed by the Byzantine Procopius.
+ From the tenth century to the fourteenth century, the Medieval Warm Period is a localized heating to Europe and North America.
– The 1550s to the 1850s remains the Little Ice Age.
+ The last phase is contemporary and attempts to describe the multiple effects of global warming. It is separate from the rest because of the constant anthropogenic interference with the climate balance since the advent of the industrial revolution and control of polluting energy sources by mankind.

Recent global warming

Global warming was first mentioned by several authors, and modeled by Svante Arrhenius in 1896. The English-language original term global warming was coined by the climatologist Wallace Broecker in the journal Science on August 8 1975. Since, the Intergovernmental Panel on Climate Change says that global warming tends to increase and the classic cycles and climate regulation processes are outdated since 1950, including thawing of permafrost containing methane (CH4), whose action on the greenhouse effect is 25 times greater than carbon dioxide (CO2) and the melting of polar ice and glaciers increases the uptake by soils and oceans solar radiation. During the more frequent heat waves, vegetation slows its growth and thus its ability to remove carbon from the atmosphere. It would be a shift towards a strong global imbalance magnitude, without already know if a point of no return is reached.

The Intergovernmental Panel on Climate Change does not conduct research in its own name but has the task of evaluating the information scientific, technical and socio-economic information relevant to understanding the scientific basis of the risks linked to climate change of human origin, identify the possible consequences of this change and consider possible adaptation and mitigation strategies. The ten warmest years since 1850 are all subsequent to 1998.

Drought and desertification

(Areas vulnerable to desertification)

Drought phenomena, salinisation and desertification may be aggravated by climate change, particularly in the Sahel and the Gobi desert that stretch. Desertification can itself contribute to local and global changes in climate, such as through the burning of savannahs or steppes, being a major source of dust (aerosols that can affect rainfall) and albedo (more important that a vegetated areas).

Translated from Wikipedia