It has been more than a month now, and Amber Bartlett has had enough of hotels and apartments and trailer homes. Of crowded rooms whose thin walls amplify the bickering of her four children. Of piles of toys and clothes overflowing from drawers and suitcases. Of not knowing, day to day, where her life is headed.

She wants to be back in her five-bedroom, three-bathroom home at 16 Starlite Road North in Mayflower, Ark.

Ryan Senia, the Bartletts' next-door neighbor, is plenty ready to go home, too. For the past month the 29-year-old electrical engineer has been sleeping on a friend's couch instead of in his bed at 20 Starlite Road North. His power tools and equipment are gathering dust in his garage. His grill sits in his backyard, unused.

The Bartletts and Senia are among 21 families who were evacuated from their homes on March 29, after an ExxonMobil pipeline spilled at least 210,000 gallons of heavy Canadian crude oil into their neighborhood.  

For the first time in human history, concentrations of carbon dioxide in the atmosphere are expected to pass 400 parts per million across much of the Northern Hemisphere in May, according to scientists who study data from the Mauna Loa Observatory, the world's longest-running CO2 monitoring station.

While crossing the 400 ppm mark isn't a "tipping point" that signals climate catastrophe, scientists told InsideClimate News, it is an important symbolic milestone that underscores government inaction on global warming. 

"This is another global emissions target that we've blown past without doing anything," said Jim Butler, director of global monitoring at NOAA's Earth System Research Laboratory. "Stronger storms, droughts, rising seas. We are already seeing the impacts of increased CO2 in the atmosphere ... How much further can we really go?" The NOAA lab operates the Mauna Loa Observatory and dozens of other greenhouse gas monitoring sites across the globe

A State Department official confirmed that for the first time the department will make public all the public comments received on its draft environmental impact statement for the Keystone XL pipeline.

In an email to InsideClimate News, the official, who requested anonymity, said the comments would be posted on Regulations.gov.

"Although the volume of comments will be extraordinarily high, the posting will maximize transparency," the official said. "We are working on the technical details and exact timing of posting the comments."

WASHINGTON—The Canadian builder of the Keystone XL pipeline has lashed out at the Environmental Protection Agency for recommending that the United States and Canada work together to reduce the emissions of greenhouse gases from the tar sands crude that the pipeline would carry to refineries on the U.S. gulf coast.

The suggestion "ignores the fundamental sovereignty of the Canadian government," said Shawn Howard, a TransCanada spokesman, in a message to reporters on Tuesday.

The EPA made its recommendation on Monday in a scathing critique of the State Department's latest environmental impact study, part of the process of deciding whether to grant the pipeline a presidential permit. The study, released in March, suggested that the pipeline would have no significant environment impact. They called it "insufficient" and asked for significant changes to protect the environment.