近日，美國總統特朗普宣布退出聯合國應對氣候變化的《巴黎協定》。消息傳來，輿論嘩然。儘管特朗普在競選時就曾這樣說過，並表示美國不會為綠色氣候基金出資，但人們以為那主要是為了爭取選票，何況特朗普團隊在這一問題上意見不一，國務卿蒂勒森、國防部長馬蒂斯都是明確主張繼續留在協定里的。特朗普前些時候訪問歐洲，歐洲國家領導人也一致表示維護《巴黎協定》。但任性的特朗普一意孤行，仍然作了這個錯誤決定。

《巴黎協定》來之不易。從上世紀90年代以來，在聯合國主導下，國際社會在共同應對氣候變化問題上艱難地逐漸凝聚起共識，在1997年底達成了《京都議定書》，1999年底又舉行了哥本哈根氣候峰會。峰會表明，在應對氣候變化問題上，國際社會既有共識，又有分歧，分歧還不小，而情況也很複雜。為了克服分歧，尋求最大公約數，國際社會又經過數年艱難磋商和談判，終於在2015年12月的巴黎氣候峰會上達成協定，確保到本世紀末把全球溫度控制在比工業化前水平高2攝氏度之內，力爭控制在1.5攝氏度以內；根據“共同但有區別的責任”各國自主決定減少溫室氣體排放目標；發達國家向發展中國家提供資金、技術援助。這些共識是經過千辛萬苦的談判才得來的，是各國都作出了犧牲並經過種種妥協才達成的，是人類應對氣候變化漫長道路上的偉大里程碑。不到一年，協定就已正式生效，成為歷史上生效最快的國際條約之一，反映了人心所向。

但在美國國內，關於氣候變化的共識還並不牢固，許多人尤其是共和黨人對氣候變化還有懷疑。有的主張應當應對氣候變化，但“一切都要由市場來主導”。如果真是一切都由市場來決定，新能源就發展不起來，因為傳統能源比新能源便宜得多，天然氣和煤是最便宜的。而新能源惟其新，需要研發、適應，自然成本較高，但它代表能源發展的方向，是有前途的。

特朗普退出《巴黎協定》，也是與奧巴馬對着乾的一個舉措。競選中，特朗普就發誓要把奧巴馬的政治遺產一項一項地顛覆掉。果真，他一上任就把矛頭對準了奧巴馬的醫保改革，同時也對準了奧巴馬政府所採取的應對氣候變化的一系列措施，把白宮網站上關於應對氣候變化的網頁都刪除了。他結束了“針對煤炭的戰爭”，允許被奧巴馬政府關閉的煤礦重新開工。他要增加化石能源的產量，以此來創造就業崗位。他廢除了奧巴馬頒佈的“清潔電力計劃”，認為這給美國經濟帶來太大負擔。他選用了一貫反對環保的人做環保署長，大幅度削減了美國環保部門的經費，認為那是浪費納稅人的錢。最後，他終於退出了《巴黎協定》。

特朗普所採取的措施確實能創造一些就業崗位，但同時也扼殺了另外一些就業崗位。據美國能源部統計，2016年美國煤炭業就業人數超過8.6萬人，但在太陽能產業創造的就業崗位遠多於此數，達到37.4萬。特朗普可能以此創造了部分就業機會，但他卻錯失了全球低碳經濟所代表的有着廣闊發展前景的商業機會。特朗普討好了一部分人（他說他代表匹茲堡人，意思是代表美國老工業區），同時也得罪了更多的人。就在他宣布之後，美國各地持續舉行遊行表示反對。一些美國州長、市長紛紛表示在他們的州、他們的城市將繼續實行節能減排，加州、紐約州、華盛頓州結成了“氣候聯盟”，名為“市長全國氣候行動日程”的組織表示要採取和遵守符合《巴黎協定》目標的行動。美國很多跨國公司都反對特朗普的決定，有的業界領袖甚至退出特朗普的商業顧問委員會以示抗議。

美國“退約”會給國際社會攜手應對氣候變化的努力帶來消極影響，但不會逆轉這個大勢。特朗普宣布之後，國際社會譴責之聲四起，歐洲國家紛紛表示堅守《巴黎協定》。法國總統馬克龍甚至向美國科學家發出邀請，歡迎他們到法國從事與應對氣候變化有關的研究。特朗普此舉確實進一步損傷了美國的信譽，損害了美國的軟實力。特朗普如此實行其“美國優先”原則，把他認定的美國利益置於國際社會共識之上，一個國家，大如美國，怎麼可以在嚴肅的國際條約問題上這樣出爾反爾，不負責任，以後國際社會還怎麼跟它打交道呢？

中國諺語中有許多信守承諾的說法，如“一諾千金”，“言必信，行必果”。中國在作出承諾時是十分慎重的，在履行承諾時是十分認真的。《巴黎協定》描繪的綠色低碳發展道路與中國生態文明建設戰略高度契合，中國政府宣布，中國的自主節能減排不與別國家掛鉤，將堅持不懈地繼續下去。

Recently President Donald Trump announced the US withdrawal from the Paris Climate Agreement of the United Nations. There has been a public outcry in response. Trump had already in his campaign vowed to do so and to stop paying into the Green Climate Fund. That was mostly regarded as rhetoric to win over voters, and Trump's team apparently had different opinions on the question. Both Secretary of State Rex Tillerson and Defense Secretary Jim Mattis expressly argued for staying in. When Trump visited Europe not long ago, all of his hosts expressed support for the Paris Agreement. However, Trump decided to go ahead with this wrong decision.

The Paris Agreement had not come easily. Since the 1990s, the international community had struggled mightily to build consensus to jointly deal with climate change. The Kyoto Protocol was adopted at the end of 1997 and the Copenhagen Summit was held in late 1999. It was apparent from the summit that the international community had both agreement and major differences. The situation was a complex one. In order to overcome those differences and find the greatest common denominator, the world community had years of tough consultation and negotiation and finally reached agreement at the Paris Climate Summit in December 2015. In the agreement, countries vow to hold the global average temperature increase to within 2 degrees Celsius (or better, 1.5 degrees); they would decide on their own the specific targets of emission reduction according to the 'common but differentiated responsibilities'; developed countries would provide financial and technological assistance to developing counties. The common understanding had been obtained through tough negotiations and with all countries making sacrifices and compromises. It was a great milestone, marking mankind's long journey to deal with climate change. The agreement had come into force within just one year, reflecting the will of nations.

However, inside the US, there is not yet a solid consensus on climate change. Many people, Republicans in particular, still have doubts. Some other people support coping with climate change by 'relying on the market'. Should everything be determined by the market, it would not be possible for new energies to develop since using traditional energies is far cheaper than developing new ones, natural gas and coal being the cheapest. But renewable new energies offer more promise for the future.

The withdrawal by Trump is also a move against Obama administration. During his campaign, Trump vowed to overthrow Obama's political legacies one after another. So immediately after taking office he targeted both Obamacare and the series of measures taken by the previous administration to deal with climate change. Even the relevant pages on White House website were deleted. He put an end to what he called the 'war on coal' and allowed the reopening of mines closed by the Obama administration. He wanted to increase production of fossil fuels to create jobs. He killed Obama's Clean Power Plan, accusing it of burdening the US economy. He chose an environment skeptic to head the Environmental Protection Agency and reduced substantially the agency's budget (saying it's a waste of taxpayers' money). Now finally he announced withdrawal from the Paris Agreement.

Indeed measures taken by Trump will create some jobs, but they will at the same time kill other jobs. According to statistics of the Department of Energy, the coal industry employed about 86,000 workers in 2016, but the solar power industry created374,000 jobs that year. With this move, the US may lose very promising business opportunities of the global low-carbon economy. He may have fawned on some people, maybe those in old industrial zones, but he has also displeased many with such a move. Demonstrations have been held across the US. Some governors and mayors have vowed to continue energy-saving and emission reduction in their states and cities. California, New York and Washington have formed a 'climate alliance' and the Mayors' National Climate Action Agenda promised to act in observance of the Paris Agreement objectives. Many American multinational corporations opposed Trump's decision and some industrial leaders even left Trump's business advisory council in protest.

The US withdrawal will have a negative impact on the global effort to cope with climate change but will not reverse the overall trend. The international community has condemned the Trump announcement. European countries expressed their determination in observing the Paris Agreement. French President Emmanuel Macron even invited American scientists to continue their climate-change research in France. Trump's move has indeed further hurt American reputation and soft power. Trump is actually exercising his 'American first' principle by placing assumed American interests above international agreements. How can a big country like the US go back on its own words and act so irresponsibly on a serious question of an international treaty? How should the international community engage the US in the future?

There are many Chinese sayings about the importance of honoring one's commitment, as there are many in English. China is cautious when making a commitment and serious when translating it into action. The path of green and low-carbon development outlined in the Paris Agreement fits beautifully with China's strategy to develop an ecological civilization. As such, the Chinese government has announced that it will not link energy saving or emission reduction to any other country's action and will pursue the objectives unswervingly.