Climate change is a) happening and b) anthropogenic (there are plenty of natural forces involved but we're the ones with our thumb on the scales). Yes, it's an existential threat to any complex, keystone species that depends on a complex web of life for survival (ie us). The various talking points of those who have reasons not to accept this, are mostly strawmen, calculated to miss the point or argue against claims nobody is making. The rest are just contradicted by the evidence. All of the talking points are summed up here (https://skepticalscience.com/argument.php) and rigorously debunked, with links to the relevant scientific papers. If anyone can come up with an argument not dealt with there, or solid evidence for why one of them is wrong, I'd be very interested to see it.
Carbon is an unpriced negative externality, and most of its forms cause more problems than just contributing to climate change (eg look at the stats for people dying of respiratory conditions in cities with bad fossil fuel pollution). Unfortunately, trying to fix that means taking money away from corporations who will fight tooth and nail, like the artificial psychopaths they are, to avoid paying to clean up their own mess (see: the story of Bhopal in the documentary The Corporation: https://archive.org/details/The_Corporation_). So while I support a revenue-neutral carbon tax, paid out equally to everyone as a citizen's dividend, I'm not holding my breath.
I tend to agree with George Monbiot that the most effective things individuals can do are stop eating animal products and stop flying in jet planes. Between them, aviation and animal farming produce the vast majority of greenhouse gas emissions. So growing salad in greenhouses (or just eating produce in season) instead of flying it around the world is sensible. Massively reducing (or ideally abolishing) animal farming, and the massive grain monocrops most of it relies on for feed, and putting most of that land back into market gardens, food forests, and wild reserves, would help a lot too.
if you wanted to reduce the risks of climate change, the right place to put resources is biotechnology. Bioengineered green plants seems like the most promising way to get CO2 out of the atmosphere (or equivalently, to produce carbon-neutral chemical fuels).
Bioengineering is just as likely to produce plants that soak up less carbon, breed uncontrollably, and spread their transgenic properties to other species of plant. I agree that green plants are definitely the most promising way to sink C02, since the C02 we're releasing back into the atmosphere was soaked up by them in the first place. But why not just use natural ones? If for no other reason than we don't have time to wait for novel ones to be developed.
If you massively increase the amount of land reserved for wild nature, the plants that grow there will soak up heaps of carbon, and the forest floor that builds up under them will soak up anywhere from twice to ten times that amount as it gets denser and more bio-diverse. As well as becoming increasingly better habitat for non-humans and providing more nature immersion opportunities for humans, which have been shown in multiple studies to have both psychological and physical benefits. It's win-win-win.
nuclear isn't bad.
The problem is that nuclear (fission) is bad. The waste problem is totally unsolved. The decommissioning problem is totally unsolved, meaning that the retired reactors we already have need to be kept contained for thousands of years, potentially longer than our civilization will last. Another problem there is that containment is also a problem that remains totally unsolved, as we saw with Fukushima. Any time we build a new nuclear fission plant anywhere near the coast or geologically active area, we're basically creating a giant time bomb that can kill and poison people for thousands of generations to come. They will not thank us for this.
Thorium reactors are an improvement, in that they can't produce another 3 Mile Island or Chernobyl. But they still produce life-destroying waste and a decommissioned reactor, both with a half-life in the thousands of years. They are, at best, a stop-gap solution for countries that have already made the mistake of building nuclear fission plants and need something to feed the waste into, to make it marginally less dangerous.
Then there is the carbon emissions involved in construction and operation of each plant (thousands of litres of concrete, extraction and transportation of the feedstocks etc). There is no reason for countries that don't already have a nuclear problem to start making one for themselves now. Especially when there are a multitude of barely explored possibilities in:
None of this is to say that there isn't snake oil being pushed out there as "climate change solutions". Of course there's greenwashing going on, and people trying to cash in on the grants and investments that are increasingly being directed into this area. The bioengineering pitch is a good example, as is the nuclear zombie's attempt to become become Great Again.
A few heuristics for assessing whether something is really about fixing climate change:
If the answer to all of these questions is "no", it might actually be about trying to address climate change. I'm sure folks here could add to this list and it may be the most useful thing a group of critical thinkers can contribute to the debate right now.