Other climate scientists are more optimistic: they argue that if we allow atmospheric CO2 to rise to 450 ppm, a level associated with a two-degree Celsius temperature rise, we have a 66.6% chance of avoiding catastrophe. That still leaves a one-in-three chance of catastrophe – worse odds than playing Russian roulette.
其他气候学家则更加乐观：他们指出，如果我们让大气二氧化碳上升至450 ppm，并由此带来2摄氏度的气温升高，我们仍有66.6%的机会避免灾难。这意味着仍有三分之一的可能爆发灾难——比俄罗斯轮盘赌的风险还高。据预计，我们将在2038年超过450 ppm。