While US President Donald Trump has struggled with the realities of passing legislation during his first 100 days in office, there is one realm that seems an easier target but which could have a devastating effect: climate change.

Passing a new healthcare bill was not something that Trump and Congressional Republicans could manage before the 100-day milestone but they have found that rolling back Obama-era policies aimed at tackling climate change is much simpler.

Through executive order Trump has paved the way for two new oil pipelines halted under the previous administration; he has championed the coal industry, with his administration even pausing a rule that stopped coal plants dumping toxic material into public waterways; and he nominated and saw confirmed a new head of the Environmental Protection Agency (EPA) who has hinted at doubts about the scientific consensus on man-made climate change.

On a more global scale, Trump has threatened to pull out of the Paris Agreement – the accord signed by 195 countries including Russia and China with the aim of reducing the threat of climate change.

"None of that makes America great again," Congressman Gerald Connolly, a Representative from Virginia, told IBTimes UK of the environmental rollback. "All of that's a retreat".

Connolly is co-chair of the Sustainable Energy and Environmental Caucus, also known as the 'Green Dogs', a group of representatives who advocate greener policymaking. In front of a banner emblazoned "Climate, Jobs, Justice", several members stood in front of the Capitol building on Thursday to "highlight the president's assault on the environment".

At the moment, the group seem to be in the congressional minority – but they're not shying away from the fight. The Green Dogs will be playing a more pronounced role, Connolly said, in attempting to push back on Trump propositions – not only the rollbacks but the "negative initiatives that had not previously been contemplated".

'We're just beginning to fight'

A suggested budget that would cut the EPA's budget by 31% is one such initiative, alongside scrapping coastal clean-ups that he said would "set back our clean water efforts in America by a decade".

"The more we highlight what they're doing, the more we mobilise the scientific community and we mobilise public opinion... We're just beginning to fight and this a fight we intend to win," Connolly said.

The scientific community showed that they were mobilised last weekend when thousands descended on Washington for the Science March. Today (Saturday 29 April), the 100th day of Trump's presidency, there will be another march – the People's Climate March – which organisers said could halt traffic in the capital.

It is the start of a backlash Connolly described as inevitable.

"The entire scientific community is awakening to the threat that this presidency and its supporters in Congress represent," he claimed.

Outside Congress and marches, other parts of the scientific community are organising against the threat of the Trump administration. Before Trump's inauguration one group of scientists undertook to save as much government environmental data as possible, worried that the incoming administration would censor and delete stats it did not like.

'Highly vulnerable'

Another group fighting back is Climate Advisors, a policy consultancy in Washington which produces the Trump Back Tracker – a regular analysis of the vulnerability of Obama-era climate policies to Trump and, they said, "what that means for the US climate pollution trajectory".

Their first update warned of the "Trump Effect" – a half a gigaton increase in pollutants by 2025. This came after the group's analysis found that 55% of Obama's 2015 climate goals were highly vulnerable to reversal under the new administration.

With a Congress seemingly tipped against them and a White House ready to dismantle previous legislation on the environment, it might seem surprising that campaigners are not disheartened. "We're just getting organised," Connolly said.

Congressional green dogs outside the capitol
The Sustainable Energy and Environmental Caucus hold a press conference outside the US Capitol Building James Tennent / IBT Media