With the stroke of a pen at a signing ceremony inside EPA headquarters on Tuesday, President Trump issued an executive order that rolls back his predecessor’s efforts to protect the environment and combat climate change.

The main target of this sweeping directive is the Clean Power Plan (CPP). Developed under the umbrella of the Clean Air Act by an executive order from President Obama, this set of EPA regulations aimed to reduce greenhouse gas emissions from coal-fired power plants. More specifically, its goal was to cut emissions 32% below 2005 levels by 2030.  It also sought to replace the coal-fired plants with a mix of natural gas, solar, wind, and hydroelectric power. Now, with this new Trump order in place, the EPA will have to begin the process of re-writing and withdrawing these policies.

Other key points of this omnibus executive order include: nullifying rules on methane emissions from oil and gas operations, lifting the moratorium on coal leases on federal lands, and scrapping the requirement for government agencies to consider the climate impact of policy decisions – the so-called “social cost of carbon”.

Just before signing the document, President Trump, who has called climate change a hoax, said, “My administration is putting an end to the war on coal.” According to Federal Reserve Economic Data, however, coal mining jobs have been declining for decades largely because of automation and the availability of cheap natural gas.  Moreover, the US Department of Energy reports that the number of coal jobs in the US is less than 75,000 while there are nearly 650,000 people employed in renewable energy.

Given the variety of items included in this presidential order, its full implementation is expected to play out over two very different time scales. Policies about coal leases and the social cost of carbon, for example, are expected to go into effect straight away. However, it will likely take years for the EPA to fully revise or withdraw all the Obama-era climate regulations. There will also certainly be a plethora of legal challenges from environmental groups and states, which will slow the process. New York and California have already declared their intentions to fight any effort to lift greenhouse gas regulations.

On the international front, the order did not say whether the US will remain a formal party to the Paris Agreement – the global pact signed in 2015 to combat climate change.  But in gutting the CPP, the Trump Administration has sent a clear message that it has no intention of following through on the greenhouse gas reduction pledges made by the US as part of the non-binding accord.

Executive orders give presidents the opportunity to promote their policy priorities in lieu of Congressional action. However, as seen on Tuesday, they are fragile things that can be easily undone by the next occupant of the Oval Office. In the end, this type of waffling back and forth on environmental policy generates a number of problems, both domestically and internationally. It creates an atmosphere of uncertainty that makes planning for long-term projects, like energy infrastructure and global agreements, extremely difficult.

Smoke billows from a coal-fired power plant near Farmington, NM. Credit: DOE/Los Alamos National Laboratory