This year will be the 30th UN climate summit – known as the conference of the parties (Cop) – and it is being held in Brazil. Every climate summit is crucial but Cop30 is taking place during extremely challenging times.

The US has pulled out of the Paris agreement, under which the world’s countries agreed to hold global temperature rises to “well below” 2C above preindustrial levels while “pursuing efforts” to limit heating to 1.5C.

Israel has bombed Iran, one of the global oil superpowers, while the EU, one of the champions of climate action, has been beset on multiple fronts by member states and parties that want the bloc to row back on emissions rules and environmental regulations.

So we thought it was a good time to take a look at the world’s biggest emitting countries, and their plans – constructive or otherwise – for addressing their carbon emissions. Some are autocracies, some democracies tumbling towards rightwing populism, some are straining to hold together a consensus on climate action. We will be profiling each of the top 10 emitters – according to Global Carbon Budget – over the coming months, in the run-up to Cop30.

To kick off the series, the Guardian’s environment editor, Fiona Harvey, has interviewed some of the world’s leading thinkers about how to negotiate with autocracies. We have also done a deep dive on Russia, “the canary in the coalmine”, according to one source.

In future weeks, we will cover South Korea, India, the United States, Germany, Iran, Saudi Arabia, China, Japan, and Indonesia – seeking a deeper understanding of how the pieces are going to fall in this crucial year for climate action.