Global warming

From Wikipedia, the free encyclopedia

Global warming is the increase in the average measured temperature of the Earth's near-surface air and oceans since the mid-20th century, and its projected continuation.

Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.^[1][2] The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the increase since the mid-twentieth century is "very likely" due to the increase in anthropogenic greenhouse gas concentrations.^[3][2] Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.^[4][5] These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,^[6] including all of the national academies of science of the major industrialized countries.^[7][8][9] While individual scientists have voiced disagreement with these findings,^[10] the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.^[11][12]

Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.^[3] This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.^[3]

Increasing global temperature is expected to cause sea levels to rise, an increase in the intensity of extreme weather events, and significant changes to the amount and pattern of precipitation, likely including an expanse of the subtropical desert regions.^[13]. Other expected effects of global warming include changes in agricultural yields, modifications of trade routes, glacier retreat, mass species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.

Solar variation

Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity.^[29][30][31]

A paper by Peter Stott and other researchers suggests that climate models overestimate the relative effect of greenhouse gases compared to solar forcing; they also suggest that the cooling effects of volcanic dust and sulfate aerosols have been underestimated.^[32] They nevertheless conclude that even with an enhanced climate sensitivity to solar forcing, most of the warming since the mid-20th century is likely attributable to the increases in greenhouse gases.

Two researchers at Duke University, Bruce West and Nicola Scafetta, have estimated that the Sun may have contributed about 45–50 percent of the increase in the average global surface temperature over the period 1900–2000, and about 25–35 percent between 1980 and 2000.^[33]

A different hypothesis is that variations in solar output, possibly amplified by cloud seeding via galactic cosmic rays, may have contributed to recent warming.^[34] It suggests magnetic activity of the sun is a crucial factor which deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate.^[35]

One predicted effect of an increase in solar activity would be a warming of most of the stratosphere, whereas an increase in greenhouse gases should produce cooling there.^[36] The observed trend since at least 1960 has been a cooling of the lower stratosphere.^[37] Reduction of stratospheric ozone also has a cooling influence, but substantial ozone depletion did not occur until the late 1970s.^[38] Solar variation combined with changes in volcanic activity probably did have a warming effect from pre-industrial times to 1950, but a cooling effect since.^[3] In 2006, Peter Foukal and colleagues found no net increase of solar brightness over the last 1,000 years. Solar cycles led to a small increase of 0.07 percent in brightness over the last 30 years. This effect is too small to contribute significantly to global warming.^[39][40] One paper by Mike Lockwood and Claus Fröhlich found no relation between global warming and solar radiation since 1985, whether through variations in solar output or variations in cosmic rays.^[41] Henrik Svensmark and Eigil Friis-Christensen, the main proponents of cloud seeding by galactic cosmic rays, disputed this criticism of their hypothesis.^[42] A 2007 paper found that in the last 20 years there has been no significant link between changes in cosmic rays coming to Earth and cloudiness and temperature.

Cara Mudah Cegah Global Warming

Greenhouse effect

From Wikipedia, the free encyclopedia

The greenhouse effect refers to the change in the thermal equilibrium temperature of a planet or moon by the presence of an atmosphere containing gas that absorbs and emits infrared radiation.^[1] Greenhouse gases, which include water vapor, carbon dioxide and methane, warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. As a result of its warmth, the atmosphere also radiates thermal infrared in all directions, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system.^[2][3][4][5] This mechanism is fundamentally different from the mechanism of an actual greenhouse, which instead isolates air inside the structure so that heat is not lost by convection and conduction, as discussed below. The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on by John Tyndall in the year 1858 and first reported quantitatively by Svante Arrhenius in his 1896 paper.^[6]

In the absence of the greenhouse effect and an atmosphere, the Earth's average surface temperature^[7] of 14 °C (57 °F) could be as low as −18 °C (−0.4 °F), the black body temperature of the Earth.^[8][9][10]

Anthropogenic global warming (AGW), a recent warming of the Earth's lower atmosphere as evidenced by the global mean temperature anomaly trend ^[11], is believed to be the result of an "enhanced greenhouse effect" mainly due to human-produced increased concentrations of greenhouse gases in the atmosphere^[12] and changes in the use of land^[13].

The greenhouse effect is one of several factors which affect the temperature of the Earth. Other positive and negative feedbacks dampen or amplify the greenhouse effect.

In our solar system, Mars, Venus, and the moon Titan also exhibit greenhouse effects according to their respective environments. In addition, Titan has an anti-greenhouse effect and Pluto exhibits behavior similar to the anti-greenhouse effect

Cara Mudah Cegah Global Warming

Menggagas Kesadaran Diri
(Salah Satu Proses Menanggulangi Global Warming)
Oleh; W. Choerul CaAhyadi feat Angga Prasetya Ramadhan*

Global warming atau dalam bahasa Indonesianya adalah pemanasan global. Isu pemanasan global begitu hangat mencuat, seakan-akan menggeser isu-isu lainnya semisal HAM, teroris dan isu-isu kemanusian yang lainnya. Memang tidak dapat dipungkiri isu ini melaju pesat hingga ke desa-desa, khususnya negara Indonesia. Bahkan anak sekolah dasar juga fasih mengucapkan istilah global warming dan pertemuan-pertemuan dalam lingkup Rt/Rw jua latah dalam arus yang sama (global warming).
Apa itu global warming? Setidaknya kata itu dapat diartikan sebagai kejadian naiknya temperatur rata-rata atmosfer, laut dan daratan bumi (www.wikipedia.org). Akibat dari pemanasan global adalah berdampak pada mencairnya es yang berada di kutub, dan ketika ini terjadi maka air laut akan melimpah ruah, yang pada akhirnya mampu meneggelamkan bumi ini. Begitu dahsyatnya dampak yang akan terjadi.
Pertemuan di Bali yang membahas tentang konferensi perubahan iklim sudah rampung dilangsungkan, tapi apa yang dihasilkan (diputuskan)? Kekuatan politik dan ekonomi masih mewarnai konferensi tersebut. Negara-negara produsen rumah kaca (negara-negara maju, (G8)) bersikukuh dengan asumsi bahwa pemanasan global tidak seutuhnya dihasilkan dari efek rumah kaca. Keselamatan manusia semakin terancam. Belum selesainya isu-isu teroris yang masih membekas, kini giliran saudara muda isu (global warming) muncul menakutkan kehidupan manusia di dunia.
Gejala apa gerangan dunia ini? Benarkah global warming adalah hal yang pasti mengancam kehidupan manusia ataukah sekedar ”lipat isu” belaka. Entahlah. Akan tetapi isu ini sudah akut dibahas oleh berbagai kalangan. Tentu, dapat menjadi bahan diskusi panjang di warung kopi dan jalan-jalan.
Penulis sendiri dipaksa untuk percaya dengan adanya isu global warming ini, hegemoni isu ini memang kuat, karena dampak yang mengancam habitat manusia memang mengerikan, ini yang menjadi titik krusial, kenapa dan mengapa global warming di-isukan. Sejurus dengan itu, perlu adanya injeksi kesadaran dari semua unsur yang ada. Kesadaran menjadi kunci pokok untuk melakukan berbagai hal yang lebih baik tentunya. Dewasa ini, seakan-akan kita tidak memiliki kesadaran akan akibat dan dampak membalak hutan, membuang sampah sembarangan, eksploitasi sumber daya alam secara besar-besaran, penambangan liar, serta banyak lagi perilaku jahanam yang setiap saat dapat dilakukan oleh manusia.
Kesadaran diri akan kerugian kolektif haruslah dipahami dari pada keuntungan materi secara personal akibat hal-hal yang menyimpang. Tentunya, kembali kepada individu masing-masing, karena kesadaran memang berawal dari dalam diri setiap manusia. Isu global warming tetap berlanjut dan mencengkram degup jantung manusia, manusia tak pernah aman hidup di dunia ini. Manusia semakin dikejar-kejar oleh ancaman, hidup semakin tidak berarti walau kecanggihan terus membahana. Tentunya, kecanggihan itu sendiri yang akan mengancam kehidupan massal manusia.
Hal terpenting adalah, sadar diri dan sadar posisi! Inilah salah satu prinsip dasar yang patut ditanam bagi setiap manusia. Kesadaran akan bahaya membalak hutan, kesadaran akan membuang sampah sembarangan, kesadaran akan penambangan liar yang akan berakibat buruk. Maka satu kata yaitu hentikan dan jangan teruskan!
Apakah kita akan menikmati keindahan dunia kisaran waktu 100 tahun kedepan? atau 1000 tahun kedepan?, sadarkah kita saat ini, bahwa apa yang kita lakukan telah merugikan banyak pihak, sadarkah kita saat ini apa yang kita perbuat hanya menguntungkan untuk diri kita, sadarkah kita saat ini bahwa banyak ketimpangan yang terjadi, sadarkah kita, sadarkah kita, sadarkah kita......???
Apapun bentuk solusi yang ditawarkan untuk melakukan penanggulangan global warming jika tidak dilandasi dengan kesadaran pribadi dan kemudian menuju kesadaran kolektif, maka hanyalah isapan jempol belaka. Undang-undang HAM telah terbentuk namun masih banyak pelangggaran HAM. Pelanggaran-pelanggaran produk hukum masih sering kita temukan, ini tentu berawal dari ketidaksadaran akan produk peraturan yang dihasilkan. Menjadi mubah apa yang dirumuskan.
Sekali lagi perlu kita hembuskan isu kesadaran untuk melakukan pembenahan dalam berbagai dimensi yang ada. Geser isu global warming ini dengan isu kesadaran posisi dan kesadaran diri sambil terus berlalu melakukan pembenahan. Pembenahan infrastruktur, pembenahan sosial, pembenahan budaya, pembenahan ekonomi dan sebagainya. Salah satunya isu global warming ini, dan ketika kita sudah memiliki kesadaran yang total, setidaknya global warming akan mengucapkan salam perpisahan bagi umat manusia untuk waktu yang lama. Sadarlah wahai manusia bahwa kerusakan di bumi dan di laut adalah ulah manusia semata (terjemah bebas dari salah satu ayat Al-Quran).