In the heart of Poland’s coal country, the planet’s future lies in the balance over the next two weeks as leaders gather for the biggest climate change event in years.

Scientists, politicians, diplomats, activists and journalists will all converge in the Polish city of Katowice as leaders establish a climate change “rulebook” for countries to follow, and set the stage for more ambitious emissions cuts.

This is a crucial time for climate politics. In recent months scientists have outlined the existential threat posed by global warming, even as unashamed climate sceptics are voted into office and activists take to the streets to force action from non-committal leaders.

The summit has been described by the UN climate change executive secretary Patricia Espinosa as “Paris 2.0”, a reference to the momentous conference that saw the birth of an international climate agreement three years ago

Understanding that agreement is key to understanding the UN’s 24th “conference of the parties”, or COP24, and what it means for climate change.

What is the Paris climate agreement?

Adopted at a previous COP in 2015, the Paris climate agreement set out plans for nations to keep global warming below a target threshold.

Governments agreed to keep the increase in global average temperature to “well below” 2C above pre-industrial levels, with a stretch target to limit the increase to 1.5C. The document has been ratified by 184 parties, and it entered into force in November 2016.

Since then scientists have been investigating what these different temperature outcomes would mean for the planet. These efforts were summarised in the Intergovernmental Panel on Climate Change’s (IPCC) recent report, which painted a picture of coral reefs dying, vanishing Arctic sea ice and climate refugees forced from their homes by rising tides.

While the two temperatures included in the Paris agreement leave it open to interpretation, many took the stark results of the IPCC report as a clear sign that 1.5C is the only meaningful target.

Also contained within the Paris agreement were goals to develop national climate plans by 2020, and finalise a “work programme”, or rulebook, for implementing the agreement by 2018.

So why is COP24 so important?

Essentially, Paris set out a plan, and this event should be the start of all countries actually doing something about it.

With the 2018 deadline nearly past, this is the moment for countries to set guidelines that will govern their efforts to cut greenhouse gas emissions and transition to a green future.

Ahead of the national climate plans deadline in 2020, the summit is also an opportunity for countries to set stronger climate action into motion – action that stops the planet warming beyond 1.5C.

Richer nations also need to make it clear at COP24 that they intend to support developing nations financially in their green transition.

The new evidence that has emerged, including the UN’s own “emissions gap” report, the IPCC’s “wake-up call” and the World Meteorological Organisation’s bulletin on greenhouse gas concentrations will all feed into this process.

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Extinction Rebellion demands that the UK government reduces to net zero greenhouse gas emissions by 2025 and creates a citizens assembly to oversee changes in environmental policies. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Organised by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change PA Extinction rebellion: Climate change protesters block London bridges Demonstrators on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, calling on the British government to take action on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to call for action on what they describe as a climate and ecological emergency. Extinction Rebellion demands that the UK government reduces to net zero greenhouse gas emissions by 2025 and creates a citizens assembly to oversee changes in environmental policies. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges epa07172610 Pro environment protesters block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges A demonstrator is led away by police on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge, near the Houses of Parliament in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organised by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges epa07173093 A pro environment protester infornt of police on Lambeth bridge in London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges epa07172601 Pro environment protesters block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges epa07172698 Pro environment protesters hold a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges epa07172703 Pro environment protesters hold a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges epa07172629 Pro environment protester holds a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters

What will the “rulebook” consist of?

The Paris rulebook will spell out how countries track and report on their efforts to tackle climate change, how they communicate their plans, how progress is assessed and how they will strengthen their efforts over time. It should serve to galvanise action and make sure countries are not slacking.

Though it will apply to all countries, the rulebook will also need to allow some flexibility so that developing countries can keep up.

How do Donald Trump and the US fit into all this?

The US under president Donald Trump announced its intention in July 2017 to withdraw from the Paris agreement. However, the nation remains a party until at least November 2020, which is the earliest it is allowed to legally request to withdraw from it.

While the US is still a member, there are some tricky political dynamics that must be addressed. China is currently considered a developing country in UN climate talks, and that means it does not have to follow the same rules as developed countries. The US is unhappy about this, and wants to see China bound by the same rulebook.

What other problems are likely to come out of COP24?

Nations such as Saudi Arabia and Australia could prove problematic in the discussions, as could the host nation Poland, which is so reliant on coal that it is unlikely to be too vocal in calling for tougher climate targets.

Experts are clear that with current commitments, the world is on track for more like 3C of warming – so massive changes are needed to hit 1.5C. To get there, countries represented at the summit need to work together and trust each other.