人类活动造成了气候变化，这点"勿庸置疑"，而且迫切需要采取行动。政府间气候变化问题小组(Intergovernmental Panel on Climate Change)上周五发布的报告突显了前者，而此前在达沃斯世界经济论坛(World Economic Forum¹)上的讨论表明，与会各方正就后者日渐达成共识。目前的挑战是采取行动。

Man-made climate change is "unequivocal" and demands urgent action. Yesterday's report from the Intergovernmental Panel on Climate Change underlined the former point, while discussions at the World Economic Forum in Davos last week demonstrated the growing consensus² on the latter. The challenge now is action.

政府间气候变化问题小组的警告是严厉的：到2100年，全球气温可能会升高约3摄氏度，升温幅度在2摄氏度至4.5摄氏度之间，而4.5摄氏度将接近上个冰川期与目前的温差。

The IPCC's warning is stark³: temperatures are likely to rise by about 3°C by 2100, with a range of 2°C to 4.5°C. The latter would be close to the difference between the last ice age and today


适应气候变化将成为人类反应的一部分，原因之一是气温已在显著上升：大气层中温室气体含量已较工业革命前的水平高出50%。但减缓温室气体总量的增长也颇为关键，理想状态是将其控制在550 ppm（1ppm为百万分之一）以下--这仍是工业革命前水平的两倍。

Adaptation is going to be part of the response, not least because a substantial rise in temperatures is already on the way: the stock of greenhouse gases in the atmosphere is already 50 per cent above pre-industrial levels. But it is also essential to mitigate⁴ growth in the stock, ideally to keep it below 550 parts per million, which would still be double the pre-industrial levels.

按照目前的趋势，大气中温室气体的浓度只需要30年就可能达到这一水平。要阻止温室气体浓度进一步上升，届时温室气体排放量必须减至比尼古拉斯o斯特恩爵士(Sir Nicholas Stern)所谓的"一切照常"（即历史趋势继续延伸下去）至少低50%的水平。

On present trends, the atmosphere is likely to reach such a concentration in just three decades. To prevent levels rising further, emissions⁵ will need to be reduced to at least 50 per cent below what Sir Nicholas Stern called "business as usual" - that is, the continuation of historic trends - by then.

斯特恩有关气候变化的报告显示，好消息是，实现这些目标的经济成本可能只需全球生产总值的1%。坏消息则是，需要马上对长期投资决策进行重大改革，特别是在电力领域。

The good news, suggests the Stern review of climate change, is that the economic costs of achieving these objectives might be as little as 1 per cent of global gross product. The bad news is that big changes to long-lived investment decisions will be required soon, particularly in the power sector⁶.

出于这一原因，全球（特别是商界）需要提出一个可预测且有效的方案，取代将于2012年到期的《京都议定书》(Kyoto protocol⁷)。要实现这一点，有关各方必须在2010年完成相关谈判，因此在今年取得进展，特别是主要高收入国家与五大发展中国家（巴西、中国、印度、墨西哥和南非）之间的谈判取得进展，将至关重要。

For this reason, the world - and business, above all - needs a predictable and effective replacement⁸ for the Kyoto protocol, which expires in 2012. If this is to happen, negotiations⁹ will need to be completed by 2010, so progress this year, particularly in discussions between the leading high-income countries and five significant developing countries (Brazil, China, India, Mexico and South Africa) is essential

不过，这在很大程度上取决于美国。美国的温室气体排放量占全球总量的四分之一。没有美国的主动参与，达成一项有效国际协议的几率将微乎其微。美国并非一定要签署协议，但它确实需要提出一项控制排放的有效方案，能与全球减排方案有所关联。

Much depends, however, on the US, which is responsible for a quarter of all emissions. Without willing American engagement, the chances of an effective international agreement are minimal¹⁰. The US does not have to sign a treaty. But it does need to put in place an effective scheme for emissions control that can be linked to a global one.

那时，只有到那时，重要的发展中国家才可能被纳入一个有效的框架中。但它们将不会同意接受与高收入国家同样的限制--这种立场没错，不仅因为问题不是它们造成的，而且它们还有压倒性的发展目标。

Then, and only then, are the important developing countries likely to be drawn¹¹ into an effective framework. But they will not agree to the same limits as the high-income countries - and rightly so. Not only have they not caused the problem, but they have overriding¹² development objectives.

下一步是达成一个框架，不仅要对发展中国家承担的成本进行补偿，还要鼓励尽可能高效率地利用能源资源。高收入国家从发展中国购买排放权，是实现这一目标的一种方式。实行共同税体制，伴之以跨境转移制度，则是另一种方式。

The way forward is a framework that compensates¹³ developing countries for the costs they bear, but also encourages the most efficient possible use of energy resources. The buying of rights to emit by high-income countries from developing countries is one way to achieve this result. A common tax regime, with accompanying cross-border transfers, would be another.

不过，需要采取的关键措施有三点：对全球范围内的碳排放制定一个明确且可预测的价格；大举增加可再生能源、核能以及碳捕捉和封存技术领域的研发投资；在全球范围安排最佳技术的转移。

The crucial requirements, however, are three: a clear and predictable price for carbon emissions across the world; much increased investment in research and development in renewables, nuclear power and carbon capture and storage; and arrangements for transfer of best technology across the globe.

这是全球面临的一个巨大的长期挑战，这个挑战对当代乃至未来数代人都将带来种种涉及公正的难题。人类能否解决这一问题，是对其处理自身行为后果能力的一次考验。迄今为止，人类并未取得成功，但我们再也失败不起了。

This is a huge, long-term and global challenge that involves difficult questions of justice both within and across generations. Humanity's ability to address it is a test of its capacity to manage the consequences of its own actions. So far it has failed. It can afford to do so no longer