The most formal manifestation of the scientific consensus on climate change is an organization called the Intergovernmental Panel on Climate Change. Headquartered in Geneva, under the aegis of the United Nations, it coordinates the volunteer efforts of several thousand scientists, industry experts, nonprofit researchers, and government representatives into reports issued every five to seven years. These reports underpin virtually every climate-based decision on Earth, from the US military’s threat assessments to the Paris climate agreement itself.

So it’s maybe surprising that the IPCC is a shoestring operation, running on just over $4.3 million a year. It gets that money from about 25 different countries, plus a few UN groups. Historically, the biggest chunk of that money comes from the US. Or rather, it used to.

Congress and the Trump administration effectively zeroed out America’s nearly $2 million contribution for 2017, and the 2018 budget explicitly bars the State Department from giving the IPCC money. Congress, remember, has the power of the purse. But the budget starts and ends with Trump: first as a proposal, and finally as a bill he signs into law. Removing the IPCC from the budget doesn’t necessarily put the organization in an immediate bind; it has savings. But it could leave US scientists out of many important scientific discussions—and leave the US underprepared as climate change progresses.

The UN established the IPCC as an independent research organization in 1988, because member nations were worried about the rising chorus of alarming climate science. They wanted a group to review the research and deliver actionable recommendations to the UN. The IPCC’s fifth assessment came out in 2014, and the sixth is due in 2022.

Every country that wants to participate can do so, and the IPCC’s executive committee selects delegates based on the needs of the working groups—not just scientists, but industry representatives, nonprofit experts, and other climate-interested professions. “The US people that work in these groups are generally selected by the DOE or by the EPA," says Daniel Kammen, a UC Berkeley energy physicist who has been working with the IPCC since 1999. "They get a letter saying you are requested, and the US will cover your travel with the understanding that all the work you do is volunteer.”

Those volunteers don’t conduct any new research. Rather, they review the existing literature in order to present a consensus on climate change, its impacts, and how the world can prepare for the worst of them. Numerous subgroups investigate the nuances in renewable energy, agriculture, sea level rise, and so on. Most of that work happens remotely. The only thing the IPCC pays for is flying the delegates to working group meetings once or twice a year—flights that eat up the bulk of the organization’s budget.

The working group meetups are the meat and potatoes of the IPCC. They decide the focus of the big reports. Which is why the US pulling out its funds could bite back. “The topics we are mostly concerned about, like climate change and drying soils, and the impacts of that on US farmers, will get less attention,” says Kammen. The US only accounts for 2 percent of the Earth’s surface, so it makes a big difference when US scientists are present to stand up for domestic interests.

Despite the IPCC’s relative low cost and undeniably outsized scientific importance, Republican lawmakers have been trying to zero out the US’s contribution for years. It's a familiar dance: Early every year, the State Department sends a budget request to the appropriations committees in both the Senate and House of Representatives. And every year, the respective committees write back, detailing their thoughts on which programs do and don't deserve money. For most of Barack Obama’s presidency, the notes from the House of Representatives have trashed environmental programs, including the payouts to the IPCC. But then the bill would make its way to the Senate, and some politician or aide would work these programs back into the budget. And because the amount was so small ($2 million is less than a percent of a percent of the total US budget), the quibble apparently wasn't worth expending political capital over.

Until 2017. Last December, right before leaving office, Obama did in fact sign a funding resolution into law that included an IPCC payout. However, it wasn’t an actual budget, and only funded the government for a few months. In May of 2017, a new appropriations bill made it through both halves of Congress, and Trump signed it into law. The $2 million IPCC funding—along with nearly $12 million for the UN Framework Convention on Climate Change, which oversees the Paris agreement—was gone.