It is barely detectable by the naked eye, but it is here - you just have to look hard enough: Climate change.
Emissions from factories, cars and other sources are causing the global average temperature to rise according to the majority of scientists.
But for years, claims have been met by counter-claims, meetings, conventions, industry lobbying and now voices from scientists and politicians who disagree with efforts to reduce emissions.
Many people are left wondering: What is really happening, what can I believe and is anyone making a difference?
Christiana Figueres heads the UN's attempts to tackle climate change.
She explains: "I don’t look at the waves as much as I look at the current. We have waves and we have spikes up and down. But the important thing is: Are we moving in the right direction? Yes. Are we moving in the right direction at the right pace? No."
On this episode of Talk to Al Jazeera, the UN's climate chief discusses the state of the climate change debate.