The 25th Conference of the Parties, or COP 25, run by the United Nations (UN), has started.
It's where representatives from more than 200 countries meet to talk about how the world's governments should tackle climate change.
The climate conference is happening in Madrid, Spain and will go on for two weeks.
Ahead of the conference the UN Secretary General António Guterres warned that "the point of no return was no longer over the horizon".
Why is the conference important?
The conference is important because it's where countries will discuss how they can deal with climate change and get their country to net zero emissions.
That means emissions from homes, transport, farming and industry will have to be avoided completely or - in the most difficult examples - offset by planting trees or sucking CO2 out of the atmosphere.
In order to do this nearly 200 countries signed the Paris agreement in 2015 - this agreement meant that the countries pledged to try and keep the warming of the planet below 2 degrees Celsius, 1.5 is the number that scientists say that we should hit by 2050.
So what's the deal with the temperature?
The UN Environment Programme showed that there's a climate change gap between the plans that governments have to cut emissions and what's needed to keep the planet under 1.5C.
Basically governments need to work harder at cutting greenhouse gases in order to meet their targets.
The hope is that governments around the world commit to new terms to make sure the target is met.
Along with lots of government representatives, climate activist Greta Thunberg will be there.
Greta is making the journey to Madrid by boat as it's one of the most eco-friendly ways to travel.
She is due to arrive a few days after the start of the conference and is expected to make a speech.