I went to Cancun, Durban, Doha.
I watched the hours of negotiations, the tears, the sleeping delegates, the frustration turn to desperation as hours became days and days became weeks. Weeks became years.
This year's UNFCCC talks in Paris are COP21: the twenty-first time the world has tried to reach agreement on our future. It is no longer about simply safeguarding a planet, but preventing uncontrollable, unpredictable catastrophe on a massive scale.
In 2009, leaders met in Copenhagen carrying enormous burdens of expectation. There, they ultimately failed to achieve what they'd hoped for.
In the lead up to this year's climate negotiations in Paris, I went to Denmark with State of Green to look at Scandinavia's solutions for a carbon-free future: 40 percent of a power grid from wind energy, waste water treatment plants that turn methane into electricity, solar-powered district heating for homes in winter. The country plans to be carbon neutral by 2025.
The way we live will undoubtedly have to change. In Paris, 195 countries will be trying to work out what that looks like. I'll be there, reporting on how - and if - that happens.