Joe Manchin, the centrist West Virginia senator and coal company owner who has repeatedly thwarted Joe Biden’s attempts to pass legislation to tackle the climate crisis, shocked Washington on Wednesday by saying he will support a bill aimed at cutting planet-heating emissions.

The $369bn package has been touted by jubilant Democrats as the largest climate bill ever in the US, and even the world. It still faces obstacles before passing but the support of Manchin, a crucial swing vote in an evenly divided US Senate, appears to augur well for its chances. So what’s in the legislation?

The basics of the bill

The climate spending is part of a broader package, known as the Inflation Reduction Act, that totals $739bn. The majority of this bill, however, is dedicated to confronting the climate crisis, with $369bn dedicated to the crisis over the next 10 years.

It’s part of a reconciliation budget that can only be passed with all 50 Democratic votes in the Senate, due to unified Republican opposition, meaning Manchin’s acquiescence was critical.

What does it include to address the climate emergency?

The bulk of the bill allows for large tax credits for clean energy, such as solar and wind power, to allow such projects to go ahead on a grand scale. States and utilities will also get $30bn to help the transition to renewable, zero carbon electricity.

A new $27bn “clean energy technology accelerator” will be created to help advance renewable technologies, $3bn will be given to the US postal service to electrify its fleet of trucks and there will be a new program to drive down leaks of methane, a potent greenhouse gas, from oil and gas drilling operations.

A further $20bn will be spent to promote climate-friendly agricultural practices and another $5bn to make American forests better prepared for the wildfires that increasingly threaten them due to global heating.

What will people be able to access directly from this bill?

The legislation includes a tax credit worth up to $7,500 for people who want to buy a new electric car, which has until now largely been the preserve of wealthier Americans.

There is also a $9bn scheme, focused on low-income households, to electrify home appliances and make dwellings more energy efficient. Further tax credits, spread out over the next decade, will make it easier to buy heat pumps, rooftop solar and water heaters.

Disadvantaged communities that suffer the brunt of fossil fuel pollution have also been recognized, with $60bn dedicated to environmental justice projects across the US.

Are there any criticisms of the bill?

The spending is a big reduction on the $550bn initially envisioned by Biden and Democratic leaders but sunk by Manchin’s opposition. The final bill amounts to far less, even over 10 years, than what the US spends annually on its military.

The bill doesn’t include any mechanism to specifically phase out fossil fuels, the primary cause of the climate crisis, and, indeed, looks to lock in their use for decades to come due to a compromise struck with Manchin. Under the deal, regulations around drilling will be loosened and new leases will be offered in places such as the Gulf of Mexico and Alaska. Environmentalists have called this arrangement a “climate suicide pact”.

How significant is this?

Despite its imperfections, the bill is expected by both its authors and independent analysts to allow the US to cut its emissions by 40% by 2030, based on 2005 levels. This brings the US close to Biden’s goal of slashing emissions in half this decade, which scientists have said is imperative if the world is to avoid catastrophic climate change.

What does it mean for the world?

The US is the world’s largest economy, the world’s second largest carbon polluter and a superpower in diplomatic and military might. Its failure, thus far, to meaningfully act on the climate crisis has constrained global efforts and so this legislation, if passed, could prove to be an “historic turning point”, as Al Gore, the former US vice-president, put it.

World governments meeting later this year at UN climate talks in Egypt could be emboldened to do more to cut their own emissions, while the direct impact of the US reductions could mean that heatwaves, floods and other disasters will be less severe than they would have been otherwise.