Relatório Charney - texto

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O Relatório Charney é um documento científico publicado em 1979 que estudou o efeito sobre a temperatura e o clima global do aumento da concentração de gás carbónico na atmosfera. Seu título original é Carbon Dioxide and Climate: A Scientific Assessment (Dióxido de Carbono e Clima: Uma Avaliação Científica), mas tornou-se mais conhecido como Relatório Charney em função do principal pesquisador envolvido, Jule Gregory Charney.

Quando Jimmy Carter assumiu o governo dos Estados Unidos em 1977, o Conselho Presidencial para a Qualidade do Ambiente encomendou um grande estudo sobre as possíveis mudanças na população e no ambiente até o fim do século XX. Durante a pesquisa foram analisados trabalhos indicando que um aumento na concentração atmosférica de gás carbônico, emitido pelas atividades humanas, provavelmente causaria um significativo aumento da temperatura global. Quando os resultados foram levados ao conhecimento do presidente em 1979, a Academia Nacional de Ciências foi chamada para avaliar essa perspectiva, porque Carter tencionava usar o carvão mineral como uma saída para a crise do petróleo, e quando ocorre a queima do carvão é libertada grande quantidade de gás carbônico.[1]

Um grupo de pesquisadores, liderados por Charney, foi incumbido da tarefa. Suas conclusões principais:[2][3]

• Se as emissões de gás carbónico continuassem nos níveis da época, a concentração na atmosfera duplicaria em algum momento da primeira metade do século XXI;
• Isso levaria a um aumento de 1,5 a 4,5 ºC na temperatura média do globo, com um equilíbrio em torno de 3 ºC;
• Todos os modelos climáticos utilizados previram um aumento significativo na temperatura;
• Latitudes mais altas (mais perto dos polos) teriam aumentos maiores na temperatura;
• Mudanças regionais no clima acompanhariam o aquecimento;
• Não há nenhum mecanismo natural conhecido que possa minimizar ou reverter esse processo, mas provavelmente a captura de calor pelo oceano retardaria o efeito final por algumas décadas.

Embora os autores tenham reconhecido que ainda havia muitas incertezas devido aos poucos dados observacionais, ao entendimento fragmentário da ciência do clima e aos primitivos modelos climáticos usados, as previsões do relatório ficaram dentro das estimativas e observações mais atuais.[3]

O relatório fez parte de um grupo de estudos empreendidos na mesma época por diferentes equipes científicas, que trouxeram pela primeira vez a questão do gás carbônico e suas implicações para o aquecimento global para dentro da arena política.[2] Desses estudos, o Relatório Charney tornou-se provavelmente o mais famoso e influente, e é considerado um trabalho notável pela precisão das suas principais previsões, tendo surgido num período em que os recursos de pesquisa e os dados disponíveis eram ainda muito limitados.[2][4][3]

Saber mais:

Alterações Climáticas - Delgado Domingos

Relatório Charney- 40 anos depois

Referências

1↑ Schoolman, Ethan. "Carter Administration". In: Philander, S. George (ed.). Encyclopedia of Global Warming and Climate Change, vol. 1. SAGE, 2012, 2ª ed., pp. 210-211

2.↑ a b c Nierenberg, Nicolas; Tschinkel, Walter R. & Tschinkel, Victoria J. "Early Climate Change Consensus at the National Academy: The Origins and Making of Changing Climate" . In: Historical Studies in the Natural Sciences, 2010; 40 (3):318–349

3.↑ a b c Bony, Sandrine et al. "Carbon Dioxide and Climate: Perspective on a Cientific Assessment". In: Asrar, Ghassem R. & Hurrell, James W. (eds.). Climate Science for Serving Society: Research, Modeling and Prediction Priorities. Springer, 2013, pp. 391-413

4↑ Perry, J. S. "The Charney Report — Creation and Consequences". In: American Geophysical Union Fall Meeting Abstracts, 2009

Charney Report- 40 years ago, scientists predicted climate change. And hey, they were right

Fonte: aqui

This month the world has been celebrating the 50th anniversary of Neil Armstrong setting foot on the Moon. But this week sees another scientific anniversary, perhaps just as important for the future of civilisation.

Forty years ago, a group of climate scientists sat down at Woods Hole Oceanographic Institution in Massachusetts for the first meeting of the “Ad Hoc Group on Carbon Dioxide and Climate”. It led to the preparation of what became known as the Charney Report – the first comprehensive assessment of global climate change due to carbon dioxide.

It doesn’t sound as impressive as landing on the Moon, and there certainly weren’t millions waiting with bated breath for the deliberations of the meeting.

But the Charney Report is an exemplar of good science, and the success of its predictions over the past 40 years has firmly established the science of global warming.

What is this ‘greenhouse gas’ you speak of?

Other scientists, starting in the 19th century, had already demonstrated that carbon dioxide was what we now call a “greenhouse gas”. By the 1950s, scientists were predicting warming of several degrees from the burning of fossil fuels. In 1972 John Sawyer, the head of research at the UK Meteorological Office, wrote a four-page paper published in Nature summarising what was known at the time, and predicting warming of about 0.6℃ by the end of the 20th century.

But these predictions were still controversial in the 1970s. The world had, if anything, cooled since the middle of the 20th century, and there was even some speculation in the media that perhaps we were headed for an ice age.

The meeting at Woods Hole gathered together about 10 distinguished climate scientists, who also sought advice from other scientists from across the world. The group was led by Jule Charney from the Massachusetts Institute of Technology, one of the most respected atmospheric scientists of the 20th century.

The Report lays out clearly what was known about the likely effects of increasing carbon dioxide on the climate, as well as the uncertainties. The main conclusion of the Report was direct:

We estimate the most probable warming for a doubling of CO₂ to be near 3℃ with a probable error of 1.5℃.

In the 40 years since their meeting, the annual average CO₂ concentration in the atmosphere, as measured at Mauna Loa in Hawaii, has increased by about 21%. Over the same period, global average surface temperature has increased by about 0.66℃, almost exactly what could have been expected if a doubling of CO₂ produces about 2.5℃ warming – just a bit below their best estimate. A remarkably prescient prediction.

Reception of the article

Despite the high regard in which the authors of the Charney Report were held by their scientific peers at the time, the report certainly didn’t lead to immediate changes in behaviour, by the public or politicians.

But over time, as the world has continued to warm as they predicted, the report has become accepted as a major milestone in our understanding of the consequences our actions have for the climate. The current crop of climate scientists revere Charney and his co-authors for their insight and clarity.

Strong science

The report exemplifies how good science works: establish an hypothesis after examining the physics and chemistry, then based on your assessment of the science make strong predictions. Here, “strong predictions” means something that would be unlikely to come true if your hypothesis and science were incorrect.

In this case, their very specific prediction was that warming of between 1.5℃ and 4.5℃ would accompany a doubling of atmospheric CO₂. At the time, global temperatures, in the absence of their hypothesis and science, might have been expected to stay pretty much the same over the ensuing 40 years, cooled a bit, possibly even cooled a lot, or warmed a lot (or a little).

In the absence of global warming science any of these outcomes could have been feasible, so their very specific prediction made for a very stringent test of their science.

The Charney Report’s authors didn’t just uncritically summarise the science. They also acted sceptically, trying to find factors that might invalidate their conclusions. They concluded:

We have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO₂ to negligible proportions or to reverse them altogether.

The report, and the successful verification of its prediction, provides a firm scientific basis for the discussion of what we should do about global warming.

Over the ensuing 40 years, as the world warmed pretty much as Charney and his colleagues expected, climate change science improved, with better models that included some of the factors missing from their 1979 deliberations.

This subsequent science has, however, only confirmed the conclusions of the Charney Report, although much more detailed predictions of climate change are now possible.

Read more: Climate change or climate crisis? To really engage people, the media should talk about solutions

The Charney Report: 40 years ago, scientists accurately predicted climate change

This month the world has been celebrating the 50th anniversary of Neil Armstrong setting foot on the Moon. But this week sees another scientific anniversary, perhaps just as important for the future of civilisation.

Forty years ago, a group of climate scientists sat down at Woods Hole Oceanographic Institution in Massachusetts for the first meeting of the "Ad Hoc Group on Carbon Dioxide and Climate". It led to the preparation of what became known as the Charney Report—the first comprehensive assessment of global climate change due to carbon dioxide.

It doesn't sound as impressive as landing on the Moon, and there certainly weren't millions waiting with bated breath for the deliberations of the meeting.

But the Charney Report is an exemplar of good science, and the success of its predictions over the past 40 years has firmly established the science of global warming.

What is this 'greenhouse gas' you speak of?

Other scientists, starting in the 19th century, had already demonstrated that carbon dioxide was what we now call a "greenhouse gas". By the 1950s, scientists were predicting warming of several degrees from the burning of fossil fuels. In 1972 John Sawyer, the head of research at the UK Meteorological Office, wrote a four-page paper published in Nature summarizing what was known at the time, and predicting warming of about 0.6℃ by the end of the 20th century.

But these predictions were still controversial in the 1970s. The world had, if anything, cooled since the middle of the 20th century, and there was even some speculation in the media that perhaps we were headed for an ice age.

The meeting at Woods Hole gathered together about 10 distinguished climate scientists, who also sought advice from other scientists from across the world. The group was led by Jule Charney from the Massachusetts Institute of Technology, one of the most respected atmospheric scientists of the 20th century.

The Report lays out clearly what was known about the likely effects of increasing carbon dioxide on the climate, as well as the uncertainties. The main conclusion of the Report was direct: "We estimate the most probable warming for a doubling of CO₂ to be near 3℃ with a probable error of 1.5℃."

In the 40 years since their meeting, the annual average CO₂ concentration in the atmosphere, as measured at Mauna Loa in Hawaii, has increased by about 21%. Over the same period, global average surface temperature has increased by about 0.66℃, almost exactly what could have been expected if a doubling of CO₂ produces about 2.5℃ warming—just a bit below their best estimate. A remarkably prescient prediction.

Reception of the article

Despite the high regard in which the authors of the Charney Report were held by their scientific peers at the time, the report certainly didn't lead to immediate changes in behavior, by the public or politicians.

But over time, as the world has continued to warm as they predicted, the report has become accepted as a major milestone in our understanding of the consequences our actions have for the climate. The current crop of climate scientists revere Charney and his co-authors for their insight and clarity.

Strong science

The report exemplifies how good science works: establish an hypothesis after examining the physics and chemistry, then based on your assessment of the science make strong predictions. Here, "strong predictions" means something that would be unlikely to come true if your hypothesis and science were incorrect.

In this case, their very specific prediction was that warming of between 1.5℃ and 4.5℃ would accompany a doubling of atmospheric CO₂. At the time, global temperatures, in the absence of their hypothesis and science, might have been expected to stay pretty much the same over the ensuing 40 years, cooled a bit, possibly even cooled a lot, or warmed a lot (or a little).

In the absence of global warming science any of these outcomes could have been feasible, so their very specific prediction made for a very stringent test of their science.

The Charney Report's authors didn't just uncritically summarize the science. They also acted sceptically, trying to find factors that might invalidate their conclusions. They concluded: "We have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO₂ to negligible proportions or to reverse them altogether."

The report, and the successful verification of its prediction, provides a firm scientific basis for the discussion of what we should do about global warming.

Over the ensuing 40 years, as the world warmed pretty much as Charney and his colleagues expected, climate change science improved, with better models that included some of the factors missing from their 1979 deliberations.

This subsequent science has, however, only confirmed the conclusions of the Charney Report, although much more detailed predictions of climate change are now possible.

Fonte: Phys.org

Aquecimento global é uma certeza estatística

Estação Rei Sejong do Centro Coreano de Investigação Antártica.

O aquecimento global e as alterações climáticas são há vários anos facto quase unânime na comunidade científica. Apesar desta unanimidade, mantém-se no debate público um panorama mais confuso, fruto da influência desproporcionada de grupos de pressão céticos e negacionistas, que por vezes encontram aliados políticos de peso, como nas presidências de George W. Bush ou Donald Trump.
Um artigo publicado na revista Nature Climate Change vem encerrar qualquer dúvida científica razoável que restasse sobre o assunto. Em três breves páginas, uma equipa de cientistas norte-americanos, canadianos e escoceses passa em revista três momentos-chave nos saberes sobre o assunto. O primeiro é o chamado relatório Charney da Academia de Ciências dos EUA, que começou a estabelecer em 1979 os primeiros modelos climáticos e como a queima de combustíveis fósseis e subsequente aquecimento da atmosfera deixariam um sinal empiricamente detetável. O segundo é um artigo científico de Klaus Hasselman, também de 1979, que estabeleceu uma abordagem sólida para detetar esse sinal. Por fim, também a partir dessa altura, ficaram disponíveis satélites capazes de detetar as emissões de micro-ondas pelas partículas de oxigénio na atmosfera, o que permitiu acumular desde então quatro décadas de dados fiáveis sobre as temperaturas no planeta.
Cruzando todos os dados de satélite sobre as temperaturas, acumulados nas últimas quatro décadas, e os modelos referidos, a equipa liderada por Benjamin Santer concluiu que a evidência de aumento de temperatura pela ação humana ultrapassou já desde 2005 o nível "de ouro" em termos de prova estatística, conhecido como sigma cinco: a probabilidade de o aumento de temperaturas registado se dever à variabilidade natural do clima, e não à ação humana, é de cerca de um num milhão.
Perante este dados, os cientistas afirmam que "a humanidade não se pode dar ao luxo de ignorar estes sinais".