The 2015 Parisian Climate Change Agreement, signed by over 190 countries, is the first ever legally binding global climate deal. While it was signed in December 2015, the document will not be in full effect until 2020. It was signed during the United Nations Climate Change Conference, in Paris (thus the name). For the agreement to fully become legally binding, 55 signing countries that produce over 55% of the gas emissions of the world need to adapt the rules set in the agreement into their own legislations.
The conference’s high cost was widely criticised, having taken 170 million USD or 180 million €. In response to the concerns raised about the high costs, France stepped up and, as the host country, offered to cover 20% of the cost themselves. They ended up paying for slightly more than those 20%, and the gesture was widely praised as a step in the right direction-the willingness to commit to it all was internationally appreciated. Within the country itself, many felt that the money could have been better spent-as is often the case with large financial spending of any nation.
At the time of the initial conference, there were demonstrations, worldwide, in favour of a strong and binding agreement, uniting the attending states in their desire to do good for the environment. At the time of the conference Paris had banned public gatherings due to the recent terrorist attacks, however law enforcement made an exception, allowing thousands to gather in order to express their favour for this agreement. In addition to this demonstration, there was another at the time, and that illegal gathering involved several violent clashes and injured policemen as well as over 300 arrests. The two demonstrations were held separately however.
There have been some concerns about some countries not being entirely happy with that, especially the US being rather hesitant. Without big players like the US and Russia the agreement was doomed to fail. That being said, there are meetings set for 2016 and 2017, during which certain aspects are set to be renegotiated-treating those big players more kindly and making it easier for them to implement it into their own legal bodies.
The general idea is that global warming should be limited to no more than 2°C. The short-term goal is no more of an increase than 1.5°C, with the secondary goal of stopping global emissions from rising any higher than they currently are, the long-term goal here being the overall reduction of them, which will not happen for a good while.
In addition to the overall reduction of emissions and global warming, the signing governments also agreed on other things-to periodic meetings and milestones. This means that they will meet every 5 years, continually supply information to other members as well as their public about their progress on the goals. In addition to those meetings, smaller regional meetings have also been spoken about-however those are voluntary and not required.
At every future meeting, they agreed to set new short- and midterm goals for themselves. The constant progress reports have been implemented in different ways in different countries, however they generally equate to a yearly report published and made accessible as well as half-yearly updates on it. These reports are made available by the government, but they are created, then fact-checked by independent scientists.
While there are a lot of other countries that signed this agreement, the EU took on a rather central role in the whole affair, especially supporting climate-positive actions and also financially supporting companies and individuals that are doing extraordinary work towards that, and even going so far as helping other countries (mostly developing countries) out in their own efforts to meet the goals, as most of the signing countries are aware the most effort will be required from them, despite the often unfavourable political and economic situations in those countries.
References: http://ec.europa.eu/clima/policies/international/negotiations/paris/index_en.htm
https://en.wikipedia.org/wiki/2015_United_Nations_Climate_Change_Conference