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Público, 27.01.2011
Ricardo Garcia

Quando pensa no debate sobre as alterações climáticas, o que é que mais o irrita? Por mais estranho que pareça, esta foi uma das perguntas destinadas a aproximar, numa reunião hoje em Lisboa, quem acredita e não acredita na tese de que o aquecimento global existe e é culpa do ser humano.

À volta da mesa, estavam climatologistas de renome, jornalistas internacionais, “cépticos” das alterações climáticas, outros especialistas. “Reconciliação” é a palavra-chave do encontro – iniciativa do Centro de Investigação Comum da Comissão Europeia e da Fundação Calouste Gulbenkian, e que termina amanhã com uma conferência pública.

Em causa não está discutir se a teoria climática está certa ou errada. Mas sim tentar encontrar um caminho para lidar com uma realidade complexa, onde se cruzam ciência, valores e expectativas. O objectivo é saber “como é que nós podemos iniciar um novo tipo de conversa”, afirma Ângela Pereira, especialista do Centro de Investigação Comum e uma das organizadoras do encontro. Hoje, diz Ângela Pereira, “há vozes que são ouvidas e vozes que não são ouvidas”.

O canadiano Steve McIntyre, notabilizado pelas suas críticas à forma como os cientistas construíram um gráfico que permite concluir que o aquecimento actual não tem precedentes nos últimos mil anos, não se queixa propriamente de não ser ouvido. O seu blog Climate Audit teve, no ano passado, seis milhões de visitas.

McIntyre, um matemático que esteve ligado a empresas de mineração e um dos participantes da reunião em Lisboa, é uma das personagens centrais do caso conhecido como climategate, envolvendo a divulgação de emails pirateados da universidade britânica de East Anglia. Vários desses emails sugerem que alguns cientistas evitaram franquear a McIntyre os dados de base dos seus estudos. “Se os cientistas climáticos estão preocupados com o futuro, deviam remover as desculpas para evitar que os seus opositores se lhe oponham”, disse McIntyre ao PÚBLICO.

Alguns dos cientistas envolvidos no caso climategate foram convidados para o encontro de Lisboa, mas não quiseram vir, deixando McIntyre pouco confiante no sucesso da reunião. “Sem ‘o outro lado’, vai ser difícil. Talvez apareçam da próxima vez”, disse.

Ângela Pereira afirma que não foi fácil trazer a Lisboa representantes das posições que qualifica como “alarmistas”. “Tivemos imensa dificuldade”, reitera. Do lado dos “cépticos”, alguns dos mais activos também não quiseram participar ou cancelaram a vinda à última hora. “Há pessoas que não estão interessadas em dialogar”, conclui Ângela Pereira.

Presente em Lisboa, o cientista Hans von Storch, do Centro de Investigação GKSS, na Alemanha, representa uma visão moderada. Crítico de algum alarmismo entre os cientistas climáticos, von Storch afirma que nem tudo o que os cépticos dizem é desprovido de sentido. “Os cépticos podem não conhecer todos os factos e argumentos científicos. Mas certamente não são estúpidos”, disse ao PÚBLICO.

“O primeiro ponto é saber quem são ‘os outros’. É isto o que estamos a tentar fazer aqui”, completa. “Se soubermos o que os preocupa, já será útil”.

É para aí que aponta uma das preguntas lançadas no encontro: o que é que mais o irrita? Algumas respostas: o facto de as alterações climáticas ocuparem um lugar tão central na actualidade; a ausência de auto-crítica na ciência; a ideologia entre os “negacionistas”. Outra questão procurou identificar o que é mais crítico na discussão sobre alterações climáticas. Um dos aspectos citados: o estudo da variabilidade natural do clima.

O encontro de Lisboa – do qual sairá um documento a enviar à Comissão Europeia – difere de outros mais usuais. Reuniões científicas sobre alterações climáticas são abundantes. Os cépticos, a maior parte sem ligação ao mundo formal da ciência, também reúnem-se, uma vez por ano, numa grande conferência internacional. Uma tentativa de “reconciliação”, como a que agora se realiza, é, entretanto, um evento raro.

Vários dos maiores cientistas climáticos, incluindo alguns envolvidos no climategate, estiveram recentemente noutro encontro em Lisboa, para debater o estado da arte dos estudos sobre o clima no passado. Agora foi a vez de alguns líderes do movimento que contesta estes cientistas. Mesmo que por acaso, Portugal parece estar-se a transformar num ponto focal do debate climático.

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http://www.sciencedaily.com/releases/2010/06/100614160209.htm

 


Increased yields of crops -- such as this maize in Kenya -- have not only helped feed the world, but have reduced greenhouse gas emissions. (Credit: Marshall Burke)

ScienceDaily (June 14, 2010) — Advances in high-yield agriculture over the latter part of the 20th century have prevented massive amounts of greenhouse gases from entering the atmosphere -- the equivalent of 590 billion metric tons of carbon dioxide -- according to a new study led by two Stanford Earth scientists.

The yield improvements reduced the need to convert forests to farmland, a process that typically involves burning of trees and other plants, which generates carbon dioxide and other greenhouse gases.

The researchers estimate that if not for increased yields, additional greenhouse gas emissions from clearing land for farming would have been equal to as much as a third of the world's total output of greenhouse gases since the dawn of the Industrial Revolution in 1850.

The researchers also calculated that for every dollar spent on agricultural research and development since 1961, emissions of the three principal greenhouse gases -- methane, nitrous oxide and carbon dioxide -- were reduced by the equivalent of about a quarter of a ton of carbon dioxide -- a high rate of financial return compared to other approaches to reducing the gases.

"Our results dispel the notion that modern intensive agriculture is inherently worse for the environment than a more 'old-fashioned' way of doing things," said Jennifer Burney, lead author of a paper describing the study that will be published online by the Proceedings of the National Academy of Sciences.

Adding up the impact

The researchers calculated emissions of carbon dioxide, methane and nitrous oxide, converting the amounts of the latter two gases into the quantities of carbon dioxide that would have an equivalent impact on the atmosphere, to facilitate comparison of total greenhouse gas outputs.

Burney, a postdoctoral researcher with the Program on Food Security and the Environment at Stanford, said agriculture currently accounts for about 12 percent of human-caused greenhouse gas emissions. Although greenhouse gas emissions from the production and use of fertilizer have increased with agricultural intensification, those emissions are far outstripped by the emissions that would have been generated in converting additional forest and grassland to farmland.

"Every time forest or shrub land is cleared for farming, the carbon that was tied up in the biomass is released and rapidly makes its way into the atmosphere -- usually by being burned," she said. "Yield intensification has lessened the pressure to clear land and reduced emissions by up to 13 billion tons of carbon dioxide a year."

"When we look at the costs of the research and development that went into these improvements, we find that funding agricultural research ranks among the cheapest ways to prevent greenhouse gas emissions," said Steven Davis, a co-author of the paper and a postdoctoral researcher at the Carnegie Institution at Stanford.

To evaluate the impact of yield intensification on climate change, the researchers compared actual agricultural production between 1961 and 2005 with hypothetical scenarios in which the world's increasing food needs were met by expanding the amount of farmland rather than by the boost in yields produced by the Green Revolution.

"Even without higher yields, population and food demand would likely have climbed to levels close to what they are today," said David Lobell, also a coauthor and assistant professor of environmental Earth system science at Stanford.

"Lower yields per acre would likely have meant more starvation and death, but the population would still have increased because of much higher birth rates," he said. "People tend to have more children when survival of those children is less certain."

Avoiding the need for more farmland

The researchers found that without the advances in high-yield agriculture, several billion additional acres of cropland would have been needed.

Comparing emissions in the theoretical scenarios with real-world emissions from 1961 to 2005, the researchers estimated that the actual improvements in crop yields probably kept greenhouse gas emissions equivalent to at least 317 billion tons of carbon dioxide out of the atmosphere, and perhaps as much as 590 billion tons.

Without the emission reductions from yield improvements, the total amount of greenhouse gas pumped into the atmosphere over the preceding 155 years would have been between 18 and 34 percent greater than it has been, they said.

To calculate how much money was spent on research for each ton of avoided emissions, the researchers calculated the total amount of agricultural research funding related to yield improvements since 1961 through 2005. That produced a price between approximately $4 and $7.50 for each ton of carbon dioxide that was not emitted.

"The size and cost-effectiveness of this carbon reduction is striking when compared with proposed mitigation options in other sectors," said Lobell. "For example, strategies proposed to reduce emissions related to construction would cut emissions by a little less than half the amount that we estimate has been achieved by yield improvements and would cost close to $20 per ton."

The authors also note that raising yields alone won't guarantee lower emissions from land use change.

"It has been shown in several contexts that yield gains alone do not necessarily stop expansion of cropland," Lobell said. "That suggests that intensification must be coupled with conservation and development efforts.

"In certain cases, when yields go up in an area, it increases the profitability of farming there and gives people more incentive to expand their farm. But in general, high yields keep prices low, which reduces the incentive to expand."

The researchers concluded that improvement of crop yields should be prominent among a portfolio of strategies to reduce global greenhouse gases emissions.

"The striking thing is that all of these climate benefits were not the explicit intention of historical investments in agriculture. This was simply a side benefit of efforts to feed the world," Burney noted. "If climate policy intentionally rewarded these kinds of efforts, that could make an even bigger difference. The question going forward is how climate policy might be designed to achieve that."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Stanford University. The original article was written by Louis Bergeron.

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de http://www.drroyspencer.com/2010/06/may-2010-uah-global-temperature-update/

June 4th, 2010 by Roy W. Spencer, Ph. D.


YR MON GLOBE NH SH TROPICS
2009 1 0.251 0.472 0.030 -0.068
2009 2 0.247 0.564 -0.071 -0.045
2009 3 0.191 0.324 0.058 -0.159
2009 4 0.162 0.316 0.008 0.012
2009 5 0.140 0.161 0.119 -0.059
2009 6 0.043 -0.017 0.103 0.110
2009 7 0.429 0.189 0.668 0.506
2009 8 0.242 0.235 0.248 0.406
2009 9 0.505 0.597 0.413 0.594
2009 10 0.362 0.332 0.393 0.383
2009 11 0.498 0.453 0.543 0.479
2009 12 0.284 0.358 0.211 0.506
2010 1 0.648 0.860 0.436 0.681
2010 2 0.603 0.720 0.486 0.791
2010 3 0.653 0.850 0.455 0.726
2010 4 0.501 0.799 0.203 0.633
2010 5 0.534 0.775 0.293 0.710

UAH_LT_1979_thru_May_10

The global-average lower tropospheric temperature remains warm: +0.53 deg. C for May, 2010. The linear trend since 1979 is now +0.14 deg. C per decade.Tropics picked up a bit, but SSTs indicate El Nino has ended and we may be headed to La Nina. NOAA issued a La Nina Watch yesterday.

In the race for the hottest calendar year, 1998 still leads with the daily average for 1 Jan to 31 May being +0.65 C in 1998 compared with +0.59 C for 2010. (Note that these are not considered significantly different.) As of 31 May 2010, there have been 151 days in the year. From our calibrated daily data, we find that 1998 was warmer than 2010 on 96 of them.

As a reminder, three months ago we changed to Version 5.3 of our dataset, which accounts for the mismatch between the average seasonal cycle produced by the older MSU and the newer AMSU instruments. This affects the value of the individual monthly departures, but does not affect the year to year variations, and thus the overall trend remains the same as in Version 5.2. ALSO…we have added the NOAA-18 AMSU to the data processing in v5.3, which provides data since June of 2005. The local observation time of NOAA-18 (now close to 2 p.m., ascending node) is similar to that of NASA’s Aqua satellite (about 1:30 p.m.). The temperature anomalies listed above have changed somewhat as a result of adding NOAA-18.

[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT's are individually calibrated in a laboratory before being installed in the instruments.]

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