COP stands for the conference of parties. It’s an international summit, or meeting, that takes place every year to discuss climate change. It is held by the UN and it’s used to address issues about climate change on an international level. Basically it’s a huge discussion where the countries that are members of the UN review how well they’ve all done in trying to limit the rising temperature on earth that year. The first COP meeting was held in Berlin, in March 1995. Personally I only know the COP conference that took place in Paris a few years ago. COP21, or the Paris Agreement, refers to the binding international treaty that the UN countries made in Paris to keep the temperature rise to no more than 2 extra degrees. Though, they wanted to try to keep it within 1.5 degrees. I cannot find anywhere if there was a meeting that was more successful than the other, but since the Paris Agreement is the most famous one, I’m guessing it’s the one that made the greatest impact. This year they met in Egypt for COP22 to discuss their actions.