The slow-motion physics of Earth's heat budget (how much sunlight hits the planet, minus how much heat escapes) is cause enough for despair: the climate today was locked in a couple of decades ago, while the carbon dumped into the air today foreshadows unimaginable misery 20 years hence. We can't grasp the enormity of the damage our carbon emissions are causing because the full extent is so very delayed.
But in addition to that difficulty, we are faced with the death of truth, of a culture impervious to objectively verifiable facts in all domains. Not all the willful ignorance presents as right-wing corporate nihilism, either. Exponents of climate ignorance from the (relative) left range from green-growth fantasists to chemtrails and HAARP lunatics.
The combination of these two factors - an unprecedented global ecocide, together with a flat refusal to even attempt understanding - almost certainly dooms complex (multicellular) Life on Earth.