Up to 25,000 people are expected in Glasgow, including world leaders, negotiators and journalists.
This will be the biggest circle jerk the world has ever seen.
Paris accord: The Paris Agreement united all the world's nations - for the first time - in a single agreement on tackling global warming and cutting greenhouse-gas emissions. and no nations have accomplished what they agreed to do at The Paris Agreement.
COP26: What is the Glasgow climate conference and why is it important?
https://www.bbc.com/news/science-environment-56901261
What will be decided at COP26?
Most countries will set out their plans to reduce emissions before the summit starts - so, we should get a sense of whether we are on track beforehand.
But during the two weeks we can expect a flurry of new announcements.
Many are expected to be very technical - including rules still needed to implement the Paris Agreement, for example.
But some other announcements could include:
Making a faster switch to electric cars
Speeding up the phasing out of coal power
Cutting down fewer trees
Protecting more people from the impacts of climate change, such as funding coastal-defence systems.
Tens of thousands of campaigners and businesses will also be there to hold events, network - and hold protests. Extinction Rebellion, for example, are calling for an immediate end to the use of fossil fuels.
At the end of the conference, some form of declaration is expected.
Every country will be required to sign up and it could include specific commitments.
As host nation, the UK will likely want all countries to back a strong statement that recommits to net zero emissions by 2050 - as well as big reductions by 2030.
It will also want specific pledges on ending coal, petrol cars and protecting nature.
Developing countries will want a significant financial package over the next five years, to help them adapt to rising temperatures.
Anything short of this is likely to be judged inadequate because there simply isn't more time to keep the 1.5C goal alive.
However, some scientists believe world leaders have left it too late and no matter what is agreed at COP26, 1.5C will not be achieved.