Incerteza e política

A questão de fundo, de um ponto de vista político, é como gerir o risco associado às alterações climáticas mesmo aceitando que existem incertezas sobre as projecções oferecidas pelo IPCC. Se traduzirmos a incerteza em probabilidade e assumindo, por hipótese, que os cépticos estão correctos, estariamos perante um cenário de elevado impacte mas baixa probabilidade. Assumindo que damos igual crédito a cada um dos lados, teriamos elevado impacte e probabilidade intermedia. Na prática, a balança da evidência favorece claramente as projecções (e observações) disponíveis pelo que estamos perante um cenário de elevado impacte e alta probabilidade.

Mas deixemos as probabilidades de lado e pensemos nos custos de tomar uma decisão errada num contexto de alterações climáticas. Se os cépticos estiverem correctos e as alterações climáticas não forem mais do que variabilidade natural, em breve a tendência de aquecimento registada durante o século 20 seria revertida e entrariamos um ciclo de arrefecimento ou estabilização das temperaturas. As políticas que entretanto tivessem sido tomados, no sentido de "descarbonizar" a economia, teriam sido precipitadas mas não teriam sido erradas pois, mais tarde ou mais cedo, deveriam ter sido implementadas. Portanto, no pior dos cenários, o erro político teria consistido em gastar recursos que poderiam ter sido gastos noutras actividades mas que teriam ajudado a precipitar mudanças estruturais na economia que são praticamente inevitáveis. Em contraste, os custos sociais, económicos e políticos de nada fazer no caso das projecções disponíveis serem correctas são extremamente elevados. Por exemplo, o desaparecimento de nações insulares e o aumento de aridez em zonas que já de si são áridas provocariam migrações em massa e situações de instabilidade política sem precedentes na história recente.

Vem este razoado a propósito de um artigo da revista "The Economist" que recomendo e que pode ser lido na íntegra aqui. Em baixo segue um trecho que me parece particularmente relevante:

"Some scientists think that the planet is already on an irreversible journey to dangerous warming. A few climate-change sceptics think the problem will right itself. Either may be correct. Predictions about a mechanism as complex as the climate cannot be made with any certainty. But the broad scientific consensus is that serious climate change is a danger, and this newspaper believes that, as an insurance policy against a catastrophe that may never happen, the world needs to adjust its behaviour to try to avert that threat.

The problem is not a technological one. The human race has almost all the tools it needs to continue leading much the sort of life it has been enjoying without causing a net increase in greenhouse-gas concentrations in the atmosphere. Industrial and agricultural processes can be changed. Electricity can be produced by wind, sunlight, biomass or nuclear reactors, and cars can be powered by biofuels and electricity. Biofuel engines for aircraft still need some work before they are suitable for long-haul flights, but should be available soon.

Nor is it a question of economics. Economists argue over the sums, but broadly agree that greenhouse-gas emissions can be curbed without flattening the world economy.

A hard sell
It is all about politics. Climate change is the hardest political problem the world has ever had to deal with. It is a prisoner’s dilemma, a free-rider problem and the tragedy of the commons all rolled into one. At issue is the difficulty of allocating the cost of collective action and trusting other parties to bear their share of the burden. At a city, state and national level, institutions that can resolve such problems have been built up over the centuries. But climate change has been a worldwide worry for only a couple of decades. Mankind has no framework for it. The UN is a useful talking shop, but it does not get much done.

The closest parallel is the world trading system. This has many achievements to its name, but it is not an encouraging model. Not only is the latest round of negotiations mired in difficulty, but the World Trade Organisation’s task is child’s play compared with climate change. The benefits of concluding trade deals are certain and accrue in the short term. The benefits of mitigating climate change are uncertain, since scientists are unsure of the scale and consequences of global warming, and will mostly accrue many years hence. The need for action, by contrast, is urgent.

The problem will be solved only if the world economy moves from carbon-intensive to low-carbon—and, in the long term, to zero-carbon—products and processes. That requires businesses to change their investment patterns. And they will do so only if governments give them clear, consistent signals. This special report will argue that so far this has not happened. The policies adopted to avoid dangerous climate change have been partly misconceived and largely inadequate. They have sent too many wrong signals and not enough of the right ones.

That is partly because of the way the Kyoto protocol was designed. By trying to include all the greenhouse gases in a single agreement, it has been less successful than the less ambitious Montreal protocol, which cut ozone-depleting gases fast and cheaply. By including too many countries in detailed negotiations, it has reduced the chances of agreement. And by dividing the world into developed and developing countries, it has deepened a rift that is proving hard to close. Ultimately, though, the international agreement has fallen victim to domestic politics. Voters do not want to bear the cost of their elected leaders’ aspirations, and those leaders have not been brave enough to push them.

Copenhagen represents a second chance to make a difference. The aspirations are high, but so are the hurdles. The gap between the parties on the two crucial questions—emissions levels and money—remains large. America’s failure so far to pass climate-change legislation means that a legally binding agreement will not be reached at the conference. The talk is of one in Bonn, in six months’ time, or in Mexico City in a year.

To suggest that much has gone wrong is not to denigrate the efforts of the many people who have dedicated two decades to this problem. For mankind to get even to the threshold of a global agreement is a marvel. But any global climate deal will work only if the domestic policies through which it is implemented are both efficient and effective. If they are ineffective, nothing will change. If they are inefficient, they will waste money. And if taxpayers decide that green policies are packed with pork, they will turn against them."