Developed countries only
It will be easier to come to an agreement with developed countries only, but the developing world will massively contribute to climate change in the long run, if left unaccounted for.
As the president of the United States crafting national and international strategies for dealing with climate change, you have made a series of decisions. Let's analyze the implications of each of your choices.
First, you decided to subsidize renewable energy. This was a great decision as you have made the transition to low-cost renewable energy alternatives easier. Over time, the wind and nuclear energy industries will use your subsidies to innovate and drive down their costs. As renewable energy costs decrease, more and more businesses will spurn fossil fuels for renewables to fuel their industrial efforts. This will help the US meet its future emission reduction goals.
Second, you chose to engage with developed countries around the world in order to craft a comprehensive agreement on climate change. As a coalition, the countries involved agreed to share technology and set binding emissions standards. Collectively, the developed world will do its part to ensure the world does not reach the two degree Celsius tipping point that climate change scientists warn about. However, you must keep in mind that developing countries will control the future of climate change.
Overall, you have done a good job. You made solid progress with regards to domestic energy policy. Furthermore, you crafted a solid agreement with the developed world to ramp up its climate change response. Hopefully, your efforts will result in cooperation with developing countries later on.