This response is focused on the US since that’s the place I already have a very good idea of the current laws and challenges affecting climate action. I’d start by passing the following legislation immediately:

• Mandate remote work options for all positions that can be performed remotely. We saw during the pandemic how much commuting to the office negatively impacts the environment as well as people’s lives.
• Carbon tax with a gradual but short (say 4 year) implementation period where it rachets up to the full tax value for carbon emissions directly created by the industry. The carbon tax is intended to make polluting and wasteful choices far more expensive than cleaner alternatives as well as raise tax dollars for significant infrastructure redevelopment
• Create new taxes and tax breaks plus subsidies for rental properties with poor insulation to encourage updating all rental properties to have modern insulation (and similar tax breaks and subsidies for homeowners to upgrade their insulation)
• Federally allow the construction of ADUs in all residential zone types (likely also creating a more relaxed permitting process and building code for ADUs to reduce cost and encourage their construction)
• Federally allow 2 family housing in all single family zoning (meaning a single family zoned lot can now have the main dwelling converted into a duplex plus an ADU constructed, tripling the permitted density)
• Federal tax break and subsidy for the purchase, maintenance and use of bicycles including ebikes and bike trailers (many places are bikable but people just don’t choose to bike. For example, every small town is mostly bikable within town save for any highways that cut through them, and residential streets are very safe places to bike even if they don’t contain dedicated bike infrastructure)
• Gradually but significantly increase annual vehicle registration fees, racheting them from the current ~$120 per year to ultimately cost several thousand dollars per year, with some discounts available to those who do not live in an incorporated community, NEVs and classic cars, thereby greatly discouraging vehicle ownership and car commuting. Also instituting significantly higher registration fees for heavier vehicles

In the longer term I’d also take the following steps:

• Use carbon taxes to fund a massive transit shift away from private cars to build more railroads and better bike infrastructure
• Nationalize the north American freight rail network and turn all railroads into rail operators, and either an existing federal agency or a new agency takes over maintainance, dispatching and expansion of the rail network, significantly lowering the bar for new railroad services and companies to be created
• Massively expand Amtrak services with many new routes and expanded service on existing routes

And for an even longer term cultural shift to encourage slower growth I’d pass the following legislation:

• Impliment UBI as an eventual replacement for all social safetynet programs. Probably a value of around $1k/month per adult and $3k/month per retiree/disabled adult would make it enough that creative individuals could live entirely off of the UBI but low enough to still encourage working. Most importantly this UBI would be decoupled from the stock market so stock market crashes would not affect people’s ability to retire. This fits into climate legislation as it removes one of the primary incentives for infinite economic growth (saving for retirement)
• Strong right to repair legislation combined with minimum warranty terms of 5-10 years (plus minimum expectations for warranties such as limiting how long a repair/replacement may take to receive) for products to ensure higher quality construction
• Greatly expand the EPA’s powers so that a nimble agency can forcibly stop companies from finding new ways to legally pollute our world, as well as providing a second mandate to the EPA to help consumers live more sustainably (this could come in the form of EPA-funded repair workshops and tool libraries for example, probably also EPA-funded vehicle rentals including ebike and ebike trailer rentals so that people can more easily go car-free)

And that’s what I have off the top of my head. Start with the changes that will make a big impact without requiring individual lifestyle change, and in the longer term financially encourage a more sustainable lifestyle. Removing the financial forces that encourage wasteful resource consumption can be all of the incentive needed for people to live much more sustainably and can be enough to put the world’s climate goals within reach