The People's Dominion of North Kadana is an arctic isolationist dictatorship, with lots of territory but it is all barren frozen tundra. Their plan: heat up the world by a few degrees, making their permafrost melt and turn into arable land, so that their nation becomes more productive whilst their southerly neighbours are hit with flooding, desertification and tornadoes (don't tell the Supreme Leader that molten permafrost will not be fertile for generations due to the lack of topsoil, he is wiser than all of us and surely knows better).
The Supreme Leader has faith that his line will stay in charge for at least three generations, so we have a hundred years to play with. To make it simple, assume constant 2020's tech throughout that period. Can a single, highly motivated nation warm up the Earth by three degrees Celsius (a conservative estimate for the required temperature increase to melt Greenland) in that time period?
Assume a generally climate-apathetic global community, that is already warming up the planet a bit by themselves (they would heat it up by one degree Celsius, Kadana wants three more). It shouldn't be too hard to imagine. However, if Kadana is highly visibly wrecking the planet, the other countries may very well seize the opportunity to make it a scapegoat, and possibly even go to war.
So there must be an element of subterfuge to the operation, with reasonable excuses for everything they do that draws the attention of foreign nations. That means, building some polluting factories is okay (economic development), exploding stuff on their own territory is okay (military tests), but releasing vast quantities of artificial greenhouse gases is less feasible. Such a gas can be detected, and traced back to its point of origin, ratting them out. It's fine if many people suspect Kadana has a hand in the global warming, but there should be reasonable alternative explanations.
- Kadana has about fifty million people, most of whom have poor living circumstances, but the military is well-funded and warming up the planet is the primary military goal. Assume an annual budget of around 5 billion USD for this operation, plus a virtually unlimited domestic supply of unskilled labour.
- There are many foreign military bases around Kadana, and even trade with its closest ally is kept in check. So another factor is minimising the amount physical material that needs to leave the country. That also applies to sending stuff into space.
- Kadana has some allies on the world stage, who may be amenable to hosting mysterious factories, but none of them wish to heat up the planet. They too must be kept in the dark. However, don't worry about Kadanan defectors; few would believe this ridiculous plan without hard evidence.
What is the best way Kadana could heat up the planet?