Destronar o Rei Carvão

MELBOURNE – No início deste ano, a concentração de dióxido de carbono na atmosfera atingiu as 400 partes por milhão (ppm). A última vez em que houve tanto CO2 na nossa atmosfera foi há três milhões de anos, quando o nível do mar era 24 metros mais elevado do que é hoje. Agora, o nível do mar está a subir outra vez. Em Setembro passado, o gelo marinho do Árctico cobriu a mais pequena área jamais registada. Todos menos um dos dez anos mais quentes desde 1880, altura em que se iniciaram os registos globais, ocorreram no século vinte e um.

Alguns cientistas do clima acreditam que as 400 ppm de CO2 na atmosfera já são suficientes para nos empurrar para além do ponto crítico, a partir do qual arriscamos uma catástrofe climática que transformará milhares de milhões de pessoas em refugiados. Dizem que precisamos de fazer descer a quantidade de CO2 atmosférico para as 350 ppm. Esse número está por trás do nome escolhido pela 350.org, um movimento popular com voluntários em 188 países que tenta resolver o problema da mudança climática.

Outros cientistas do clima são mais optimistas: argumentam que se deixarmos o CO2 atmosférico subir até 450 ppm, um nível associado a um aumento de temperatura de 2° Celsius, teremos 66,6% de probabilidades de evitar a catástrofe. Isso ainda nos deixa uma hipótese em três de catástrofe – probabilidades piores que as da roleta Russa. E está previsto que ultrapassaremos as 450 ppm em 2038.

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