La terra, geografia | El clima | Identificació del problema | Conseqüències i previsions | Accions | Debat ( El problema del Canvi climàtic )
IDENTIFICACIÓ DEL PROBLEMA, L’EFECTE HIVERNACLE.
L’energia del sol és absorbida per l’atmosfera i pel terra, que escalfa uns 14º. Una part és fixada per les plantes en la fotosíntesi. Retorna fora per reflexió dels núvols i aerorols i radiació del terra. Part d’aquesta radiació és aturada per gasos com el diòxid de carboni que fan un efecte d’hivernacle. L’augment d’aquests gasos, per combustió de combustibles fòssils, i per disminució dels boscos que capturen CO2 i retornen oxígen, augmenta l’efecte hivernacle i la temperatura del planeta.
https://www.lenntech.com/greenhouse-effect/global-warming-history.htm
The greenhouse effect was proposed by Joseph Fourier in 1824, discovered in 1856 by Eunice Newton Foote,[281] expanded upon by John Tyndall,[282] and investigated quantitatively by Svante Arrhenius in 1896.[283]The hypothesis was reported in the popular press as early as 1912.[284] The scientific description of global warming was further developed in the 1930s through the 1960s by Guy Stewart Callendar.
1896 S’identifica el CO2 com responsable de l’absorció de radiació infraroja amb un efecte hivernacle.
Svante Arrhenius (1859-1927) was a Swedish scientist that was the first to claim in 1896 that fossil fuel combustion may eventually result in enhanced global warming. He proposed a relation between atmospheric carbon dioxide concentrations and temperature. He found that the average surface temperature of the earth is about 15oC because of the infrared absorption capacity of water vapor and carbon dioxide. This is called the natural greenhouse effect. Arrhenius suggested a doubling of the CO2 concentration would lead to a 5oC temperature rise. He and Thomas Chamberlin calculated that human activities could warm the earth by adding carbon dioxide to the atmosphere. This research was a by-product of research of whether carbon dioxide would explain the causes of the great Ice Ages. This was not actually verified until 1987.
1950 Mesures més precises determinen que l’excés de CO2 no és absorbit del tot pels oceans. It is thought that only nearly a third of anthropogenicCO2 is absorbed by oceans. Les dades de temperatura mitjana semblen indicar que anem cap a una nova edat glacial.
1976 Stephen Schneider had first predicted global warming in 1976. This made him one of the world’s leading global warming experts.
1980 Es confirma l’augment de temperatura, l’efecte hivernacle causat per les emissions de CO2 i la modificació del territori disminuint la superfície de boscos que l’absorbeixen (Però un bosc fosc absorbeix més llum que un camp agrícola).
1988 Les naciones unides funden el IPCC, el Grup Intergovernamental sobre el Canvi Climàtic.
Als ’90 algunes de les dades són qüestionades.
Global anthropogenic greenhouse gas emissions in 2010 were equivalent to 49 billion tonnes of carbon dioxide (using the most recent global warming potentials over 100 years from the AR5 report). Of these emissions, 65% was carbon dioxide from fossil fuel burning and industry, 11% was carbon dioxide from land use change, which is primarily due to deforestation, 16% was from methane, 6.2% was from nitrous oxide, and 2.0% was from fluorinated gases.[70] Using life-cycle assessment to estimate emissions relating to final consumption, the dominant sources of 2010 emissions were: food (26–30% of emissions);[71] washing, heating, and lighting (26%); personal transport and freight (20%); and building construction (15%).
https://en.wikipedia.org/wiki/Global_warming
CONSEQÜÈNCIES i PREVISIONS
Els principals efectes són l’augment del nivell del mar, sequera, fenòmens meteorològics extrems com onades de calor, huracans i pluges torrencials.
Això afectarà sobretot les zones de latituds properes a l’equador.
A concern is that positive feedbacks will lead to a tipping point, where global temperatures transition to a hothouse climate state even if greenhouse gas emissions are reduced or eliminated. A 2018 study tried to identify such a planetary threshold for self-reinforcing feedbacks and found that even a 2 °C (3.6 °F) increase in temperature over pre-industrial levels may be enough to trigger such a hothouse Earth scenario
MITIGACIÓ i ACCIONS
Climate change can be mitigated through the reduction of greenhouse gas emissions or the enhancement of the capacity of carbon sinks to absorb greenhouse gases from the atmosphere.[192] There is a large potential for future reductions in emissions by a combination of activities, including energy conservation and increased energy efficiency; the use of low-carbon energy technologies, such as renewable energy, nuclear energy, and carbon capture and storage; decarbonizing buildings and transport; and enhancing carbon sinks through, for example, reforestation and preventing deforestation.
There are diverse opinions on how people could mitigate their carbon footprint. One suggestion is that the best approach is having fewer children, and to a lesser extent living car-free, forgoing air travel, and adopting a plant-based diet.[215] Some disagree with encouraging people to stop having children, saying that children “embody a profound hope for the future”, and that more emphasis should be placed on overconsumption, lifestyle choices of the world’s wealthy, fossil fuel companies, and government inaction.
1998 the Kyoto Protocol was negotiated in Kyoto, Japan. It requires participating countries to reduce their anthropogenic greenhouse gas emissions (CO2, CH4, N2O, HFCs, PFCs, and SF6) by at least 5% below 1990 levels in the commitment period 2008 to 2012. The Kyoto Protocol was eventually signed in Bonn in 2001 by 186 countries. Several countries such as the United States and Australia have retreated.
2016 Acord de Paris amb l’objectiu de limitar l’escalfament global per sota dels 2ºC, que compromet cada país a establir objectius per mitigar el canvi climàtic i informar-ne regularment.
https://ec.europa.eu/clima/policies/international/negotiations/paris_en
DEBAT
The global warming problem came to international public attention in the late 1980s.[258] Significant regional differences exist in how concerned people are about climate change and how much they understand the issue.[21] In 2010, just a little over half the US population viewed it as a serious concern for either themselves or their families, while 73% of people in Latin America and 74% in developed Asia felt this way.[259] Similarly, in 2015 a median of 54% of respondents considered it “a very serious problem”, but Americans and Chinese (whose economies are responsible for the greatest annual CO2 emissions) were among the least concerned.
From about 1990 onward, American conservative think tanks had begun challenging the legitimacy of global warming as a social problem. They challenged the scientific evidence, argued that global warming would have benefits, feared that concern for global warming was some kind of socialist plot to undermine American capitalism,[264] and asserted that proposed solutions would do more harm than good.
In the 20th century and early 2000s some companies, such as ExxonMobil, challenged IPCC climate change scenarios, funded scientists who disagreed with the scientific consensus, and provided their own projections of the economic cost of stricter controls.[269] In general, since the 2010s, global oil companies do not dispute that climate change exists and is caused by the burning of fossil fuels.[270] As of 2019, however, some are lobbying against a carbon tax and plan to increase production of oil and gas,[271] but others are in favour of a carbon tax in exchange for immunity from lawsuits which seek climate change compensation.
Infografia BBC, a nivell individual el que té més impacte és deixar de menjar carn vermella.