Representatives of 40 nations will convene at the White House on Thursday for the start of a two-day climate summit the Biden administration organized to seek pledges to cut greenhouse gas emissions.

Those promises are critical to lowering heat-trapping gases that have plunged the planet into a precarious state, and the details of how nations aim to achieve those cuts are critical too.

The talks, to be held virtually, will focus first on high-emitting countries before turning to remarks from Cabinet, business, state and local officials, White House representatives said. They said the summit will not include bilateral meetings or side “Zoom rooms.”

Climate pledges are known for being vague. But the details on financing, adaptation, industries, youth and economic inequality that emerge during the talks will highlight hurdles to cutting global emissions. They’ll also flag points of tension in the run-up to international talks scheduled for November in Glasgow, Scotland, where delegates for nearly every country are expected to appear.

Digging past the headline numbers and comments, here are 10 themes to follow in the talks:

America’s target

On Thursday, President Joe Biden will announce a target to cut emissions across the economy by 50 to 52 percent from 2005 levels by 2030, roughly doubling the target the Obama administration set in its commitment under the Paris climate agreement of 2015. At that time, the administration said it would cut domestic emissions 25 percent from 2005 levels by 2025, and the U.S. is not on track to meet that deadline.

Environmental groups and experts had mixed reactions to the goal, which had previously been reported as 50 percent. Many called for a more robust target and a focus on curbing emissions of methane, a highly potent greenhouse gas.

The big dogs

Six years after the Paris climate agreement, the first time major emitters China and India made concrete climate commitments with deadlines, a cluster of nations is to blame for the bulk of emissions.

Now the No. 2 emitter behind China, the U.S. is the largest historical emitter of greenhouse gas, responsible for about one-quarter of all emissions since the Industrial Revolution.

Counted together, the 27-country European Union is the No. 3 source globally, followed by India, Russia, Japan, Brazil, Indonesia, Iran and Canada. Together, those 10 countries are responsible for two-thirds of global emissions, according to the World Resources Institute.

What commitments will those countries make? How do they plan to hit those targets? Those questions will be on the lips of diplomats, journalists and scientists worldwide.

U.S. credibility

The summit is intended to show the U.S. reclaiming a global leadership role on climate, but some international skepticism is expected. President Barack Obama made ample commitments to fighting climate change only to see President Donald Trump reverse his climate legacy, including a withdrawal from the Paris deal.

While Biden moved swiftly to rejoin Paris, other countries may wonder what will happen if a different American president switches course again in four years. National Climate Adviser Gina McCarthy told NPR this week that the administration wants to focus on the future.

“This is not a time when I think we have to apologize for the past. Clearly, I wish we didn’t lose the four years of the prior administration, and I wish we could take that time back because the time is now to really make big moves forward,” McCarthy said. “But we are ready and poised to not just make a strong commitment, but the world leaders are saying ‘yes’ to this invitation.”

Rich and poor nations

The Paris agreement called for the world’s wealthier countries to contribute a total of $100 billion annually by 2020 to address the climate mitigation needs of poorer countries. Experts say rich nations missed that mark. Under Obama, America pledged to contribute $3 billion directly to the Green Climate Fund to help poorer countries move to cleaner energy and mitigate climate impacts. 

Just one-third of that money was delivered before Trump canceled the remaining payments. The Biden administration included $1.2 billion in its fiscal 2022 budget request and said it will allocate more money.

Private financing

In a report for the United Nations, independent experts said the contributions from industrialized nations provide the foundation for global climate financing, but it will take private sector money to produce the trillions needed to properly arrest global emissions and tackle the crisis. 

“Without a fundamental and vast shift in private finance and in the financial system as a whole, the climate goals of net-zero carbon by 2050 and those of the Paris Agreement cannot be met,” the report says.

Cities and states

As the Trump administration was reversing or diluting more than 100 Obama-era climate policies, states, towns and counties pursued separate efforts to meet America’s Paris-related pledges. 

The Center for American Progress last year highlighted how many states had taken action toward “a 100 percent clean energy future” by promoting renewable energy sources, implementing tailpipe emission standards and creating other programs to reduce greenhouse gas emissions. That kind of movement could help bolster U.S. credibility on its long-term commitment to addressing the crisis.

Twelve governors urged Biden this week to “create a clear regulatory path to ensuring that all vehicles sold in the United States are zero-emission,” arguing they have already accelerated the transition to zero-emission vehicles. Leading the pack is California, which is requiring that by 2035 all new cars sold in the state be zero-emission vehicles.

Who’s there?

Most of the world’s countries will not appear at the talks, limited to the nations behind the bulk of the world’s emissions.

The 100 countries that emit the least make up only 3.6 percent of global greenhouse gases and are among the most exposed to climate perils.

Pacific island nations, like Tuvalu, Fiji, Vanuatu, Nauru and Kiribati, typically band together at international climate talks and demand cuts from the industrialized world.

Those low-lying countries were not invited to the talks, though Radio New Zealand reported Wednesday that heads of state for the Marshall Islands and New Zealand were invited.

Boats and planes

Maritime shipping and aviation together account for about 5 percent of global emissions.

But they are notoriously difficult to attribute to a particular country, and the Paris agreement did not address either industry directly.

Presidential climate envoy John Kerry said Tuesday that zeroing out all emissions from shipping by 2050 is critical to tackling climate change.

“We have to decarbonize the international shipping sector, which currently produces as much greenhouse gas pollution as a G-7 country,” Kerry said.

Standout voices

Democrats in Washington have signaled a whole-of-government campaign to fight rising emissions, and those comments have come often from unusual figures in the administration, including national security chiefs.

White House officials said Defense Secretary Lloyd Austin and Director of National Intelligence Avril Haines will speak, along with a series of Cabinet officials.

Younger generations will bear a disproportionate brunt of climate impacts, as Swedish climate activist Greta Thunberg, who is expected to make an appearance, often notes.

Congressional response

After the Clinton administration whipped support for the Kyoto climate agreement in 1998, which the U.S. signed, the White House never submitted the deal to the Senate for ratification.

Likewise, the Obama administration did not send its agreement to the Paris deal to the Senate for approval, arguing it was not technically a treaty, while Republicans disagreed.

Congress, and the House in particular, has a limited role in foreign affairs. But members of both parties may push for the Biden administration to submit any climate treaties it reaches to the Senate, with Republicans angling to vote them down and Democrats maneuvering to assert themselves in global environmental politics.