According to the UN, the world is on course for a catastrophic temperature rise of 2.7°C (4.9°F) if we don't change our habits fast. Despite targets to reduce our collective carbon footprint by 2030, many countries are still polluting the planet through fossil fuels and deforestation. But which are the worst offenders? As the COP26 climate conference begins, read on to discover the 20 most polluting countries, using 1850-2021 data from climate science website Carbon Brief.