When Rachel Cleetus opened her inbox last Monday to find an email from the Trump administration her first reaction was "just deep disappointment."

She was one of nearly 400 scientists and experts dismissed from working on the sixth National Climate Assessment (NCA6), a leading report of climate change's impact on the United States published every four years. 

The email stated that while the scope of NCA6 was "reevaluated", all contributors were released from their roles. 

Cleetus, a senior policy director for the climate and energy program at the US based non-profit Union of Concerned Scientists, described the dismissal of its authors as senselessly taking a "hatchet to a crucial and comprehensive US climate science report."

She says the NCA reports, which were first published in 2000 and draw on the latest scientific research, are vital to understanding how climate change is already impacting the economy, infrastructure and people's lives across the country. 

Mounting pressure on US climate science 

The email, however, was not a complete surprise, says Cleetus. "We had, of course, been dreading this," she told DW. 

Earlier last month, the White House ended funding and fired staff at the US Global Change Research Program (USGCPR), the federal program coordinating the NCA6. 

Cleetus said disbanding the authors puts the NCA6 report — which was due to be published by early 2028 and is congressionally mandated — in jeopardy and that the administration's further plans were unclear. "There's a risk that they just try to inject some junk science and create their own version."

The NCA6 news is the latest in a series of administration decisions over recent months impacting climate science bodies in the US. 

In March hundreds of employees were fired from the National Oceanic and Atmospheric Administration (NOAA), one of the world's most important sites of climate and weather research. 

In response, thousands of scientists signed an open letterto Congress arguing the dismantling of NOAA and other leading scientific institutions would amount to an "abdication of US leadership in climate science" in which it plays an outsized role.  

Employees have also been fired en masse from the Environmental Protection Agency and the Department of Energy, federal grants have been withheld, and references to climate change have been scrubbed from several federal agency websites.  

The administration also stopped NASA's chief scientist at the time from attending a meeting of the Intergovernmental Panel on Climate Change (IPCC) in China. The UN body is responsible for producing the world's leading assessments of climate change and its consequences for humanity, which is used by governments around the world to guide policy. 

Some experts say recent decisions in the US are already impacting climate science. 

"We have now observed a 10% reduction in data coming from radiosondes (weather balloons) over the USA," said Florence Rabier, director general at the European Centre for Medium-Range Weather Forecasts, emphasizing that as weather knows no borders successful prediction requires data from all over the world.  

Ripple impact beyond US 

Cleetus states that although the NCA reports are nationally focused, many of its insights are useful beyond the United States. 

"The fact that it's being generated in the US context still gives people the same underlying modeling and data methods that can be used in other places," said Cleetus, highlighting how insights on sea level rise along the US East and Gulf coasts were applicable to other sea-rise hotspots such as small island nations and coastal Bangladesh. 

The US not only has a large and well-established climate research community, it also has incredible geographical and climatological diversity, said Walter Robinson, professor of atmospheric sciences at NC State University in the US. "Therefore, results from NCA6 would be applicable all over the world."

In response to the dismissal of the NCA6 authors, the American Geophysical Union and the American Meteorological Society announced they will join forces to produce more than 29 peer reviewed journals covering all aspects of climate. 

The dismissal of NCA authors will not only negatively impact national policies which the report's scientific insights help to guide, but also international collaborations between the US and other regions such as Latin America, Africa, Asia and Europe, said Paolo Artaxo, professor of environmental physics at the University of Sao Paulo. 

"Brazil has important partnerships with the US science in terms, for instance, of developing of global climate models."

Will US scientists move overseas? 

Chennupati Jagadish, president of the Australian Academy of Science says the "decision to dismiss authors from the US National Climate Assessment is a concerning signal that undermines global climate science cooperation."

He added that there has been strong interest among US-based researchers wanting to relocate to Australia, adding that the academy had a program designed to attract scientists and innovators leaving the United States. 

In addition to the measures he has already taken against climate science, Trump last week proposed significant cuts to the 2026 federal budgets for US scientific agencies and research. 

If such budget cuts are sustained then the inevitable results will be "that the ‘center of mass' of climate research will move away from the US, to the EU, to China and other OECD nations (UK, Australia, Japan and Korea)," said Robinson. 

In Europe, there are also active efforts to attract scientists from across the pond. 

On Monday, French president Emmanuel Macron and EU Commission president Ursula von der Leyen hosted a conference exploring — among other topics — financial incentives for researchers in specific sectors, including climate and biodiversity.  

While European countries have the scientific capacity and political will to fill some of the gaps left by the NCA6 author dismissal, they are not able to plug them all, explained Sissi Knispel de Acosta, general secretary of the European Climate Research Alliance, a network supporting EU research capabilities. 

The US is a leader in climate science and financial support remains the main barrier in expanding research elsewhere, she said. "Not only institutions from the global south (like expanding scientific regions as Brazil, South Africa or India) but also in Europe, the climate science budgets are often fragmented and short-term projects."

While Cleetus feels optimistic that climate scientists in the US and elsewhere will continue to find ways to produce work, she warns "there's no way to replicate this incredible innovative scientific enterprise that we had in the United States overnight anywhere else."

Edited by: Tamsin Walker