Thank you for opening this topic and sharing your thinking on this. I am quite new to EA and have been working on initiatives to try and help avert the worst outcomes of climate change on-and-off for several years, so very much welcome the discussion about increasing the focus on that in EA.
I wanted to address two main points:
1. If we expand our definitions of x-risk and s-risk to include the extinction of any species of life, or suffering of any life forms, then that dramatically increases the weight you might place on addressing climate change (or more broadly, biodiversity loss).
The recent UN IPBES assessment (basically the IPCC for biodiversity loss) finds that up to 1 million species are at risk of extinction due to humanity's impact on biodiversity (including the contribution of climate change).
Once extinct, each of those species is gone, forever, along with any form of value it had been creating and could potentially create in the future, for humans, other life, or living ecosystems in general.
Together with the excellent arguments you present for increasing our focus on climate change due to x-risks and s-risks to humans, this makes climate change a compelling problem to tackle right now. Especially if you consider Urgency. We have such a short time-window of 10–30 years we have to dramatically transform how we generate and use energy globally (which basically means transforming most of the underlying infrastructure and systems for how we live, stay warm, eat, move around and make things).
2. I also wanted to address your question of whether climate change can actually be tackled meaningfully (specifically mitigation i.e. cutting emissions), as that is something I have dived into some personal research on since the latest Extinction Rebellion global actions.
A lot of good work has been done in this area, with organisations like Drawdown compiling (and quantifying) solutions for the global context.
Zooming in on the UK perspective, the Committee on Climate Change, who independently advise the Government on the topic, have done rigorous modelling to assess how fast the UK could move to a net-zero carbon emissions. They concluded that we can "feasibly" achieve this by 2050 with an annual investment of 1–2% of GBP.
The question this raises for me is: could we therefore invest at a faster rate to set a more ambitious goal e.g. 2025 (as Extinction Rebellion demands), 2030 (as Norway has set) or 2035?
UK GDP is about £2,000bn.
Naively, instead of investing 2% of GDP (£40bn/year) x 30 years = £1,200bn in total, could we instead choose to invest 6% of GDP (£120bn/year) x 10 years = £1,200bn in total?
And by doing that, could we set an example to the world that increases global ambition and causes many other countries to set more aggressive targets, dramatically increasing our chances of avoiding the most catastrophic climate change outcomes, alleviating much human and animal suffering and saving many species from extinction?
For those interested in more detail, I've written more about specifically what I believe needs to happen in the UK here: UK declared a Climate Emergency — what needs to happen now.
I believe that coming together as a global society to solve climate change (as we did in the 1980s with ozone depletion, which was significantly less complex) will give us a huge amount of confidence and experience as a species in tackling large-scale risks.
Would love everyone's thoughts on my arguments above and the viability and cost-effectiveness of a 10–15 year burst of investment in climate change mitigation now to avoid cross-species x-risk and s-risks?