PeLeve
Well-known member
O que parece é que mesmo no meio científico não há unanimidade sobre esta questão, quanto mais nós aqui: http://www.helsinki.fi/hum/ibero/xaman/articulos/2004_01/mudancas_climaticas_globais.pdf
FILME: Uma Verdade Inconveniente
- Thread starter Mendes77
- Start date
Zell
New member
citação:Originalmente colocada por J.R.
Mendes77
O ambiente MUDA.
As alterações climáticas são NATURAIS.
Sempre aconteceram.
E agora vimos de uma Idade do Gelo (20.000 anos ou coisa que o valha)e vamos para uma quente.
É natural.
E é de uma ARROGÂNCIA presumir que o Homem pode controlar: tempestades solares, vulcões terrestres ou a variação do eixo de rotação da dita cuja.
E já agora... poluir menos não se consegue assinando acordos ridículos.
Consegue-se...... poluindo menos.
E aí os números têm sido tão "interessantes".....estes ultimos anos.
Até amanhã.
É verdade que o clima muda naturalmente mas não a esta velocidade. O problema maior pelo que tenho lido e visto nos últimos anos nem é o aumento do nível do mar.
De qualquer forma, este assunto já foi debatido umas quantas vezes noutros tópicos do género. Acho que devíamos comentar o filme depois de o vermos.
Ant?nio Alexandre Santos
Banido
Os sistema eleitoral americano é um pouco diferente. O presidente é eleito quando ganha os "grandes eleitores", isto é, em cada estado há um número determinado de grandes eleitores, tipo nº de deputados cá em Portugal.
Mas se um dos candidatos ganha, nem que seja por um voto, leva todos os grandes eleitores.
É por isso que um candidato pode ter o maior número de votos e mesmo assim não ter o maior nº de grandes eleitores. Há estados com mais nº de grandes eleitores.
Cá é diferente. É empregue o método de Hunt (acho que é assim que se escreve). Os deputados são eleitos conforme uma proporção de votos.
A questão da velocidade tb não se tem bem a certeza.
As mudanças climatéricas tb podem ser bruscas.
O problema é que não se sabe o que é causa e o que é efeito.
De qq forma a minha posição é EXACTAMENTE a do Finlândes que oPéLeve colocou.
Esta posição é a mesma de muitos "cientistas" de outras áreas que estudam os glaciares, a atmosfera, etc.....
Ler este artigo "finlandes" juntamente com o ultimo link do Excalibur
ajuda a prespectivar
.O filme é uma apresentação para o grande público da ideia: "efeito estufa é, sem dúvida, causado pela atividade industrial, fornecendo a estes uma ferramenta no combate ao capitalismo e globalização. Baseado nisto, estes exigem restrições às emissões de gases de efeito estufa (dióxido de carbono, metano, CFC, etc.) e, conseqüentemente, restrições às atividades industriais. Porém, este ponto de vista é também defendido pelos ONGs, Painel Inter-Governamental de Mudança Climática (IPCC) e a maioria dos governos".citaçãoe qualquer forma, este assunto já foi debatido umas quantas vezes noutros tópicos do género. Acho que devíamos comentar o filme depois de o vermos.
Serve para doutrinar. Não esclarecer. Infelizmente.
Nthor
Banido
Claro que não há unanimidade, a investigação cientifica precisa de fundos e quem paga obtém resultados diferentes dos das investigações independentes.
No entanto o registo fóssil não pode ser manipulado e ele diz-nos que actualmente devíamos estar no principio de mais uma época glacial (as épocas glaciais são ciclicas), com verões mais curtos e temperaturas mais baixas, mas o que estamos a ver é exactamente o contrario, verões mais longos e temperaturas mais altas, este tipo de alterações tem influenciado as correntes marítimas que são o motor do clima na terra, alterações essas que podem ser irreversíveis por muitos milhares de anos.
Situação comparavel a quando só existia uma enorme massa de terra (o pangea) que albergava no seu centro enormes desertos e que condicionavam as temperaturas em terra.
V7
Não tenhas a menor dúvida.
Continuando
Clima: Pesquisa científica revela mistérios sobre grandes glaciações
Antártica
Foto: Júlio Fiadi
ECOLOGIA : 6/4/2004 Mais um debate científico no campo das mudanças climáticas está aberto. Uma pesquisa que acaba de ser divulgada mostra que pelo menos as duas últimas grandes glaciações ocorreram praticamente de forma simultânea nos hemisférios Sul e Norte. O estudo, liderado pelo norte-americano Michael Kaplan, da Universidade de Edinburgh, no Reino Unido, foi publicado na edição de março do boletim da Sociedade de Geologia dos Estados Unidos.
O estudo causa um ponto de viragem. A tese mais aceita até agora pelos estudiosos de paleoclimas é que a ampla distribuição do calor proveniente do Sol pelos oceanos era um mecanismo primário de alterações climáticas no passado. Com os novos resultados, surge um ponto de interrogação diferente.
“É surpreendente perceber que o clima no hemisfério Sul sofreu um rápido resfriamento durante um período em que a região recebia uma alta dose de radiação solar”, disse o também norte-americano Brad Singer, da Universidade de Wisconsin-Madison, co-autor do trabalho. “Entretanto, essa rápida sincronia da temperatura atmosférica entre os hemisférios polares realmente ocorreu durante as duas maiores fases de glaciações registradas na Terra.”
Para chegar aos resultados analisados, os cientistas utilizaram uma técnica inédita. A partir de amostras coletadas num deserto nos Andes, eles identificaram quais as alterações físico-químicas que aquelas rochas haviam sofrido em relação à exposição aos raios cósmicos.
A última grande fase de glaciação sobre os Andes – e também sobre o planeta – começou há 22 mil anos, de acordo com as análises. O clima deixou de ficar gelado há aproximadamente 16 mil anos. Os cientistas acreditam que a distribuição de calor pelos oceanos ocorreu de forma mais lenta do que se imaginava. Isso permitiu que as temperaturas fossem reduzidas com muito mais velocidade, ao menos nas épocas de glaciação.
Redação 360
Agência Fapesp
http://360graus.terra.com.br/ecologia/default.asp?did=10158&action=news
Não tenhas a menor dúvida
.Continuando
Clima: Pesquisa científica revela mistérios sobre grandes glaciações
Antártica
Foto: Júlio Fiadi
ECOLOGIA : 6/4/2004 Mais um debate científico no campo das mudanças climáticas está aberto. Uma pesquisa que acaba de ser divulgada mostra que pelo menos as duas últimas grandes glaciações ocorreram praticamente de forma simultânea nos hemisférios Sul e Norte. O estudo, liderado pelo norte-americano Michael Kaplan, da Universidade de Edinburgh, no Reino Unido, foi publicado na edição de março do boletim da Sociedade de Geologia dos Estados Unidos.
O estudo causa um ponto de viragem. A tese mais aceita até agora pelos estudiosos de paleoclimas é que a ampla distribuição do calor proveniente do Sol pelos oceanos era um mecanismo primário de alterações climáticas no passado. Com os novos resultados, surge um ponto de interrogação diferente.
“É surpreendente perceber que o clima no hemisfério Sul sofreu um rápido resfriamento durante um período em que a região recebia uma alta dose de radiação solar”, disse o também norte-americano Brad Singer, da Universidade de Wisconsin-Madison, co-autor do trabalho. “Entretanto, essa rápida sincronia da temperatura atmosférica entre os hemisférios polares realmente ocorreu durante as duas maiores fases de glaciações registradas na Terra.”
Para chegar aos resultados analisados, os cientistas utilizaram uma técnica inédita. A partir de amostras coletadas num deserto nos Andes, eles identificaram quais as alterações físico-químicas que aquelas rochas haviam sofrido em relação à exposição aos raios cósmicos.
A última grande fase de glaciação sobre os Andes – e também sobre o planeta – começou há 22 mil anos, de acordo com as análises. O clima deixou de ficar gelado há aproximadamente 16 mil anos. Os cientistas acreditam que a distribuição de calor pelos oceanos ocorreu de forma mais lenta do que se imaginava. Isso permitiu que as temperaturas fossem reduzidas com muito mais velocidade, ao menos nas épocas de glaciação.
Redação 360
Agência Fapesp
http://360graus.terra.com.br/ecologia/default.asp?did=10158&action=news
É naturalíssimo
.O seu tamanho e variação é que é assunto de estudo.
http://www.atm.ch.cam.ac.uk/tour/index.html
Esta questão está longe de ser consensual, mas deve ser continuar a ser estudada com a maior atenção e rigor, porque se as piores previsões forem verdadeiras (e até podem ser...), isso pode significar... uma mudança tão profunda no planeta como a que ocorreu há 60 milhões de anos atrás.
O que mais me preocupa é a taxa de subida da temperatura média, que se não me engano, é muito superior a qualquer registo do passado conhecido. Sem dúvida, uma questão a seguir com MUITA atenção...
O que mais me preocupa é a taxa de subida da temperatura média, que se não me engano, é muito superior a qualquer registo do passado conhecido. Sem dúvida, uma questão a seguir com MUITA atenção...
Nthor
Banido
Já para não falar destes dois artigos da NGS:
http://news.nationalgeographic.com/news/2006/09/060914-arctic-ice.html
http://62.97.115.102/revista/0204/feature5/default.asp
http://62.97.115.102/revista/0806/feature5/default.asp
http://news.nationalgeographic.com/news/2006/09/060914-arctic-ice.html
http://62.97.115.102/revista/0204/feature5/default.asp
http://62.97.115.102/revista/0806/feature5/default.asp
Glaciers on the Move: Ice Ages in History
Twenty thousand years ago, a sheet of ice covered what is now the northern United States. Nowadays, you won't find glaciers in Massachusetts or Michigan, though the evidence of their passing is carved into the landscape. What brought about this dramatic change in climate? Why aren't these areas still covered in ice?
We're accustomed to thinking of our planet as stable, steady, and solid. In reality, Earth is dynamic. Our climate is changeable. The history of Earth's climate has been marked by many ice ages and warm spells, some measured in millenia and others in centuries. You may be surprised to find that there are some patterns in this changeability, though. Climate change seems to be cyclical.
A "wobbling top": The Milankovitch theory
A Serbian mathematician named Milutin Milankovitch was intrigued by this puzzle of climate change, and in the 1930s he presented a theory that might explain it. Milankovitch studied climate records, noting differences over time. He theorized that global climate change was brought about by regular changes in Earth's axis, tilt, and orbit that altered the planet's relationship to the Sun, triggering ice ages.
Earth doesn't rotate perfectly like a wheel about an axis; it spins like a wobbling top. Every 22,000 years, Milankovitch calculated, there is a slight change in its wobble. Every 100,000 years, there is a change in Earth's orbit about the Sun. Its almost circular orbit becomes more elliptical, taking Earth farther from the Sun. And finally, Milankovitch discovered, every 41,000 years there is a change in the tilt of the planet's axis, moving either the Northern or Southern Hemisphere farther from the Sun.
These cycles mean that at certain times there is less sunshine hitting Earth, so there is less melting of snow and ice. Instead of melting, these cold expanses of frozen water grow. The snow and ice last longer and, over many seasons, begin to accumulate. Snow reflects some sunlight back into space, which also contributes to cooling. Temperatures drop, and glaciers begin to advance.
The Little Ice Age
Not all ice ages occur on a large, 100,000-year scale. Some, such as the "Little Ice Age" that occurred in medieval times, are relatively brief. The Little Ice Age lasted only a few hundred years (from about 1400 to 1800), and its effects were fairly mild. Still, for the people who watched glaciers advance year to year, it was certainly dramatic. In England, the Thames froze and heavy snow fell. In France, bishops were ushered to the edge of glaciers to halt their advance with prayer.
During the last 10 million years, Earth has had 10 major ice ages and numerous smaller glaciations such as the recent Little Ice Age. Each major ice age has been followed by a warm period of about 10,000 years. We're in a warm period now—more specifically, we're at the end of one. Should we expect another major ice age soon? There's no way of knowing. Climate change may be cyclical, but it's not easy to forecast. Both day-to-day weather and long-term climate change remain difficult to predict.
http://www.learner.org/exhibits/weather/iceandsnow2.html
Hoje em dia o ciclo da variação do eixo da terra é estimado em 26000 anos.
Twenty thousand years ago, a sheet of ice covered what is now the northern United States. Nowadays, you won't find glaciers in Massachusetts or Michigan, though the evidence of their passing is carved into the landscape. What brought about this dramatic change in climate? Why aren't these areas still covered in ice?
We're accustomed to thinking of our planet as stable, steady, and solid. In reality, Earth is dynamic. Our climate is changeable. The history of Earth's climate has been marked by many ice ages and warm spells, some measured in millenia and others in centuries. You may be surprised to find that there are some patterns in this changeability, though. Climate change seems to be cyclical.
A "wobbling top": The Milankovitch theory
A Serbian mathematician named Milutin Milankovitch was intrigued by this puzzle of climate change, and in the 1930s he presented a theory that might explain it. Milankovitch studied climate records, noting differences over time. He theorized that global climate change was brought about by regular changes in Earth's axis, tilt, and orbit that altered the planet's relationship to the Sun, triggering ice ages.
Earth doesn't rotate perfectly like a wheel about an axis; it spins like a wobbling top. Every 22,000 years, Milankovitch calculated, there is a slight change in its wobble. Every 100,000 years, there is a change in Earth's orbit about the Sun. Its almost circular orbit becomes more elliptical, taking Earth farther from the Sun. And finally, Milankovitch discovered, every 41,000 years there is a change in the tilt of the planet's axis, moving either the Northern or Southern Hemisphere farther from the Sun.
These cycles mean that at certain times there is less sunshine hitting Earth, so there is less melting of snow and ice. Instead of melting, these cold expanses of frozen water grow. The snow and ice last longer and, over many seasons, begin to accumulate. Snow reflects some sunlight back into space, which also contributes to cooling. Temperatures drop, and glaciers begin to advance.
The Little Ice Age
Not all ice ages occur on a large, 100,000-year scale. Some, such as the "Little Ice Age" that occurred in medieval times, are relatively brief. The Little Ice Age lasted only a few hundred years (from about 1400 to 1800), and its effects were fairly mild. Still, for the people who watched glaciers advance year to year, it was certainly dramatic. In England, the Thames froze and heavy snow fell. In France, bishops were ushered to the edge of glaciers to halt their advance with prayer.
During the last 10 million years, Earth has had 10 major ice ages and numerous smaller glaciations such as the recent Little Ice Age. Each major ice age has been followed by a warm period of about 10,000 years. We're in a warm period now—more specifically, we're at the end of one. Should we expect another major ice age soon? There's no way of knowing. Climate change may be cyclical, but it's not easy to forecast. Both day-to-day weather and long-term climate change remain difficult to predict.
http://www.learner.org/exhibits/weather/iceandsnow2.html
Hoje em dia o ciclo da variação do eixo da terra é estimado em 26000 anos.
"Ancient Observations Link Changes in Sun's Brightness and Earth's Climate" by Kevin D. Pang and Kevin K. Yao; EOS, Transactions of the American Geophysical Union, Volume 83, number 43, 22 October 2002, pages 481+.
This is an article written for scientists. The authors track 9 cycles of changes in solar brightness over the last 1800 years, and then correlate these with various changes in the Earth's climate. As you undoubtedly know, an especially suspicious correlation is that of a period of no sunspots (and hence low solar activity) corresponding with the Maunder Minimum of ~1645 to 1715 A.D, a period of extreme cold in Europe. Because of the complexity of effects on the Earth's climate, the jury is still out on whether this period of a Little Ice Age was indeed caused by the lack of solar activity. However, the correlations are intriguing and continue to be discussed at scientific meetings such as the AGU. You can find lots more about the Maunder Minimum and its relationship to sunspots on the web.
http://solar-center.stanford.edu/sun-on-earth/glob-warm.html
This is an article written for scientists. The authors track 9 cycles of changes in solar brightness over the last 1800 years, and then correlate these with various changes in the Earth's climate. As you undoubtedly know, an especially suspicious correlation is that of a period of no sunspots (and hence low solar activity) corresponding with the Maunder Minimum of ~1645 to 1715 A.D, a period of extreme cold in Europe. Because of the complexity of effects on the Earth's climate, the jury is still out on whether this period of a Little Ice Age was indeed caused by the lack of solar activity. However, the correlations are intriguing and continue to be discussed at scientific meetings such as the AGU. You can find lots more about the Maunder Minimum and its relationship to sunspots on the web.
http://solar-center.stanford.edu/sun-on-earth/glob-warm.html
Viewpoint: The Sun and climate change
Satellites now monitor solar activity constantly
By Dr Paal Brekke from the European Space Agency
Natural processes involving changes in the Sun could have at least as powerful an effect on global temperature as increased emissions of carbon dioxide (CO2).
Climate scientists have already looked at changes related to Sun spot activity - a cycle of approximately 11 years - and long-term changes in the Sun's brightness, which has a cycle that lasts for centuries.
They have discounted the effect of both on the temperature increase over the last century because they either happen over too short a timescale, or they are too weak.
But so far they have omitted to take two other factors into account:
Changes in the amount of ultraviolet radiation from the Sun affect the ozone layer. This is a very important part of the atmosphere where lots of chemical reactions take place that govern the way the rest of the atmosphere works;
The Sun's magnetic field and solar wind - mainly in the form of electrons and protons coming out of the Sun - protects the entire Solar System by acting as a sort of shield from cosmic rays (very energetic particles and radiation from outer space).
This shield does not stop all the cosmic rays from getting though, and its effectiveness varies with the long-term changes in the activity of the Sun, which can rise and fall on a timescale of centuries.
Cloud cover
One of the effects that cosmic rays have is to influence how cloudy the Earth is.
So if the Sun undergoes long-term changes in activity - which it does - the amount of cosmic rays reaching the Earth will also vary over the same timescale, and so will the planet's overall cloudiness.
The amount of cloud affects the amount of radiation from the Sun reaching the planet surface, which in turn affects the global temperature.
Data collected from satellites show that the amount of low clouds over the Earth closely follows the amount of cosmic rays reaching the Earth. </u>
The resulting warming due to this effect over the last century could be comparable to the amount of warming people think has been due to the greenhouse effect.
Add to that the other effects due to the Sun, and greenhouse gases become less than 50% responsible for rising global temperatures.
Little effect
The other side of this coin is that reducing greenhouse emissions will have much less effect in halting rising temperatures than some people think, and it might have hardly any effect at all.
Our continued use of fossil fuels could make little difference to the climate
The energy emitted from the Sun drives the climate system, and natural changes in its behaviour can have a far greater effect than human behaviour.
Thus, some people may ask: "So why bother worrying about greenhouse gases, and adding billions to the costs of industry to force them to cut emissions, when it could well be a pointless exercise?"
If the Sun is indeed the main contributor to the recent climate change, the money may be better spent providing clean air in big cities and clean drinking water to the Third World.
The author is a solar physicist serving as the European Space Agency's deputy project scientist for the Esa-Nasa Solar and Heliospheric Observatory (Soho)
http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/climate_change/1026375.stm
Satellites now monitor solar activity constantly
By Dr Paal Brekke from the European Space Agency
Natural processes involving changes in the Sun could have at least as powerful an effect on global temperature as increased emissions of carbon dioxide (CO2).
Climate scientists have already looked at changes related to Sun spot activity - a cycle of approximately 11 years - and long-term changes in the Sun's brightness, which has a cycle that lasts for centuries.
They have discounted the effect of both on the temperature increase over the last century because they either happen over too short a timescale, or they are too weak.
But so far they have omitted to take two other factors into account:
Changes in the amount of ultraviolet radiation from the Sun affect the ozone layer. This is a very important part of the atmosphere where lots of chemical reactions take place that govern the way the rest of the atmosphere works;
The Sun's magnetic field and solar wind - mainly in the form of electrons and protons coming out of the Sun - protects the entire Solar System by acting as a sort of shield from cosmic rays (very energetic particles and radiation from outer space).
This shield does not stop all the cosmic rays from getting though, and its effectiveness varies with the long-term changes in the activity of the Sun, which can rise and fall on a timescale of centuries.
Cloud cover
One of the effects that cosmic rays have is to influence how cloudy the Earth is.
So if the Sun undergoes long-term changes in activity - which it does - the amount of cosmic rays reaching the Earth will also vary over the same timescale, and so will the planet's overall cloudiness.
The amount of cloud affects the amount of radiation from the Sun reaching the planet surface, which in turn affects the global temperature.
Data collected from satellites show that the amount of low clouds over the Earth closely follows the amount of cosmic rays reaching the Earth. </u>
The resulting warming due to this effect over the last century could be comparable to the amount of warming people think has been due to the greenhouse effect.
Add to that the other effects due to the Sun, and greenhouse gases become less than 50% responsible for rising global temperatures.
Little effect
The other side of this coin is that reducing greenhouse emissions will have much less effect in halting rising temperatures than some people think, and it might have hardly any effect at all.
Our continued use of fossil fuels could make little difference to the climate
The energy emitted from the Sun drives the climate system, and natural changes in its behaviour can have a far greater effect than human behaviour.
Thus, some people may ask: "So why bother worrying about greenhouse gases, and adding billions to the costs of industry to force them to cut emissions, when it could well be a pointless exercise?"
If the Sun is indeed the main contributor to the recent climate change, the money may be better spent providing clean air in big cities and clean drinking water to the Third World.
The author is a solar physicist serving as the European Space Agency's deputy project scientist for the Esa-Nasa Solar and Heliospheric Observatory (Soho)
http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/climate_change/1026375.stm
Muito intressante de ler dos quais estes excertos talvez..... sejam os menos intressantes[:I].
The Discovery of Global Warming
(...)
The climate known to history seemed to be a lucky anomaly. (Paleoclimatologist William Ruddiman suggested that this was no coincidence. Perhaps the rise of agriculture, with its deforestation and rice paddies, had added enough methane and CO2 to the atmosphere to dampen the normal ice-age cycle?) The well-recorded history of the most recent century or so happened to show even more unusual stability, compared with what new evidence was revealing about severe variations in earlier millennia.
(...)
A lesson about how science proceeds can be learned from this history. Asked about the discovery of abrupt climate change, many climate experts today would put their finger on one moment: the day they read the 1993 report of the analysis of Greenland ice cores. Before that, nobody confidently believed that the climate could change massively within a decade or two; after the report, nobody felt sure that it could not. So wasn't the preceding half-century of research a waste of effort? If only scientists had enough foresight, couldn't we have waited until we were able to get good ice cores, and settle the matter once and for all with a single unimpeachable study?
(...)
http://www.aip.org/history/climate/rapid.htm
E não esquecendo o Finlândes.... me despeço deste tópico com calor
The Discovery of Global Warming
(...)
The climate known to history seemed to be a lucky anomaly. (Paleoclimatologist William Ruddiman suggested that this was no coincidence. Perhaps the rise of agriculture, with its deforestation and rice paddies, had added enough methane and CO2 to the atmosphere to dampen the normal ice-age cycle?) The well-recorded history of the most recent century or so happened to show even more unusual stability, compared with what new evidence was revealing about severe variations in earlier millennia.
(...)
A lesson about how science proceeds can be learned from this history. Asked about the discovery of abrupt climate change, many climate experts today would put their finger on one moment: the day they read the 1993 report of the analysis of Greenland ice cores. Before that, nobody confidently believed that the climate could change massively within a decade or two; after the report, nobody felt sure that it could not. So wasn't the preceding half-century of research a waste of effort? If only scientists had enough foresight, couldn't we have waited until we were able to get good ice cores, and settle the matter once and for all with a single unimpeachable study?
(...)
http://www.aip.org/history/climate/rapid.htm
E não esquecendo o Finlândes.... me despeço deste tópico com calor
Zell
New member
Ontem vi um documentário sobre o tema no Sic Noticias e foi nítido que quem trabalha para o governo, se tem opiniões contrárias, rapidamente é levado a fazer o discurso "oficial". Ex-membros das mesmas organizações, ex-colegas dessas mesmas pessoas têm uma opinião muito menos optimista quanto ao futuro e não acreditam que os seus ex-colegas digam o que mandam cá para fora de livre vontade. Ninguém nessas organizações diz o que quer que seja à comunicação social ou dá palestras, etc, sem o conteúdo ser analisado pelos seus superiores...
Acho que não é preciso dizer mais nada.
Acho que não é preciso dizer mais nada.
michaelreznor
Banido
esse 'teu' prius liberta tanto co2 como um bom diesel...
[
]ld