Mount Everest is visible from Kathmandu for first time in living memory

1) Strong effects are obvious in the data; conversely, if you have to dig deep and play with statistical significance to prove there's a connection, the effect is very weak - it's a scientific curiosity, sure, but "to zeroth order of approximation" you may as well say it doesn't exit.

2) When ascertaining the possible impact of something in the future, your estimate will be more accurate if you have a clue about mechanisms of action involved.

Microplastics seem to fail both heuristics at the moment - there isn't any obvious impact that we've measured, and there isn't any obvious mechanism of action that could imply serious danger. There most likely are issues caused by them - however, we've been living with them for decades now, so if this was an emergency-level threat, we'd probably see something by now.

Compare that with worrying whether coffee/red meat/artificial sweetener/vaccine/5G will give you cancer - maybe it will, maybe it won't, but if the chance of it was remotely worth worrying about, it would be blindingly obvious in the data by now. Contrast that with "no evidence of human transmission" - not enough data to check heuristic 1, fails heuristic 2 due to similarity to other coronaviruses with known mechanisms of human-to-human transmission.

Climate change passes both #1 and #2. There is known, first-principles mechanism of action that you can dig into like into a fractal, if you want to explore consequences for various aspects of the ecology and society. There is a known mechanism of action that makes it into an actual threat - food shortages, mass migrations, political unrest, leading to wars, starvation, suffering and death. We know how fragile our civilization is (present COVID-19 situation makes a lot of weak points clearly visible). There's lot of historical data supporting the above and the threat evaluation - for instance, we're seeing how increasing average temperatures are impacting agriculture and habitability of some regions on Earth.

One more clarification: the reason climate change is dangerous is not because it threatens plants and animals. It's because it threatens human civilization. We care about nature not because it is, but primarily because we need it to live. Moreover, since almost no one would enjoy suddenly being thrown back to preindustrial age on a thoroughly broken planet, we can safely say that the concern is about survival of existing civilization, not survival of human species (not to mention, you can't fix the damage without technology, and you won't have technology when civilization collapses). Human civilization is very fragile.

Also: just saying "tail risks" isn't meaningful. You have to actually estimate the sum of the tail to determine whether it's even worth paying attention to. Which circles us back to heuristics #1 and #2, which - in my opinion - say that microplastics are a secondary issue to climate change.

I've lived here since the earthquake, have only seen Everest from my rooftop in the capital one single time.

There are about 99% fewer vehicles on the road as we are in complete lockdown however the brick kilns that are located in the valley are probably the bigger polluters. Local neighbourhood garbage pickup guys regularly burn plastic.

Btw, burning biomass would not change the problem. Wood and charcoal is biomass too.