In his article, Christopher Swope explains what a Green Bond is, the global interest that cities and investment are getting on this tool, as well some general questions, doubts and possible outcomes arising from its implementation.  He assets saying that Green Bonds are becoming important on these days because of many environmental agreements are heading around the globe, especially the Paris Climate Agreement. The cost of its implementation goes more than "US$ 12 trillion over 25 years". In consequence, climate finance is an important topic for development seeing Green Bonds as an important financial tool in combating the effects of global warming.  Mr. Swope explains Green Bonds as debts instruments or marketing tool which will help in the financial implementation of environmental initiatives. The emission of Green Bonds has been increasing since the present decade passing from "US 3 billion in 2012 to 42 billion in 2015". The market of Green Bonds is growing quickly. Cities are loaning money to green urban initiatives related to renewable energy, sustainable transportation, water infrastructure and others. World cities such as Gothenburg in Sweeden, Johannesburg in South Africa and some other towns in the state of Massachusetts have used Green Bonds to the injection of capital to green initiatives. Mr. Swope considers that the emission of such instrument is worthy especially in advance or first world economies. He also declares that third world cities should be more careful in Green Bond emission focusing on building financial worthiness to attract investors.  Green Bonds are getting a lot of interest for cities and investors. Cities gain in the development of a strong market of investors willing to place their capital in environmental projects. On the other hand, investors are seeing the promotion of environmental initiatives as something safe with low-risk investment. Also, Mr. Swope is seeing a positive change of social conscience identifying more investors willing to place their money in positive actions like it is environmental protection.  Although the Green Bond's Market is growing every day, there are some inquiries and doubts about the Green Bonds implementation. The first doubt that comes to mind it is if really Green Bonds are promoting green actions. Willing to stop corruption and fraud, many cities have developed a framework which certifies and validates the investment. Mr. Swope also suggests the implementation of a third party to the evaluation of the green proposal. Another doubt is related to the extra cost for the cities' staff when a Green Bond is issued. Reporting informs to investors, tracking the proper use of money, validation of activities and plans take time, however, Mr. Swope concludes that it all depends on the effectiveness of the city's staff and its procedures.