I think, very broadly, climate change can be tackled by collective action or/and technologies which make climate-friendly action economically favorable. There was a lot of progress recently on the second part, including sizable contribution of Germany: rapidly growing contribution of renewables, electric transport, better heating and insulation, etc?
I think good people putting themself to work on an important goal can achieve a lot for common good, I see this a lot in my area of research and technology.
I realize there is a danger of thinking "technology will solve all" and relaxing, but what I am saying that it's part of the solution, and at least a cause for some optimism fueling further action.
Furthermore, I see that as Europe gained a privileged position due to historical circumstances, it is its moral duty to leverage this position for helping to advance the necessary technologies.
For the first part it's harder since there is no consensus but I suspect this will be facilitated by progress in technology (yet, it's important to work on consensus).
Also I see that some understanding of the need to act is increasing in the Western Europe population, is it not?
Maybe part of the challenge with US, Arab spring, and far right, is that after the fall of Soviet Union there was too much confidence in neoliberal system automatically bringing democracy, prosperity, and fairness everywhere. While delivering democracy as a gift of historic process is somehow antithetic to the idea of democracy, which implies active agency, individual and collective action. People grew complacent assuming that all gets solved for them by the market, and politics became sometimes a dirty word. Instead, it'd be better if people continued to practice political discourse about tough questions in respectable but honest way. But now it is becoming next to impossible to avoid engagement, which makes some people loose any hope, some turn to fascism, and some searching for a better solution. I think the last, better, way is not yet lost.
Technology development itself raises further difficult political questions, about ownership of new tools deriving from commons (like LLM AI), viability of common space in privately managed companies (social networks), and so on. People need to be engaged in this else the decisions will be made for them and not in their interest (even if their consent may be sometimes formally acquired following some misleading campaign).
This potential for action, and recent history of progress, in two related directions, technology and political agency, seems to be the cause for optimism.
Even raise of fascism, as worrying as it is, indicates that people are striving for change, they just do not see a better option since it is not sufficiently developed and communicated to them yet.