The (ExxonMobil spill in Mayflower, Arkansas) appears to be the largest accident involving heavy crude since an Enbridge Energy pipeline spill in 2010 that dumped more than 840,000 gallons near Marshall, Mich., soiling a 39-mile stretch of the Kalamazoo River.

Late Tuesday, the federal Pipeline and Hazardous Materials Safety Administration ordered Exxon not to restart the pipeline without getting approval, because of its proximity to populated areas and waterways, and because the initial investigation had not yet uncovered the cause of the spill.

The Arkansas spill followed an accident in Utah on March 18 in which a Chevron pipeline leaked more than 25,000 gallons of diesel fuel in a wetlands area about 50 miles from Salt Lake City.

“Chevron Pipe Line Company regrets this incident, and we are committed to remediating the affected area and mitigating all impacts on the environment,” Gareth Johnstone, a Chevron spokesman, said in a statement.

The Chevron spill was the third in three years in Utah, prompting Gov. Gary R. Herbert to sharply criticize the pipeline agency at a recent news conference. “Obviously, they have not done a very good job of overseeing the pipes that travel between our states,” he said.

The safety records of both the Exxon and Chevron pipelines have been under scrutiny in recent years. Last week, the pipeline agency proposed imposing a $1.7 million fine on Exxon Mobil over a 2011 spill that dumped an estimated 63,000 gallons of oil in the Yellowstone River in Montana.

Records show that the pipeline agency has proposed a fine of about $150,000 in the same year over the company’s failure to properly test several pipelines.

In June 2010, a Chevron pipeline spilled more than 33,000 gallons of crude into Red Butte Creek near Salt Lake City. The company took more than 10 hours to respond to the spill, and it was fined $423,600, according to pipeline agency records. Seven months later, a second Chevron spill sent an additional 21,000 gallons of oil into the same area.

But a Times insider tells Grist that the decision probably means an end to the significant amount of freelance reporting that appeared in the Green blog. The insider, who’s not authorized to speak on the record about the blog’s closure, says, “I’m not 100 percent sure that we’re going to spend as much time on the environment as in the past. To a large extent that depends on the news. The paper is plastic — it reorganizes itself to meet the requirements of the world around us.” With that world getting warmer and weirder by the day, there shouldn’t be any shortage of climate and environmental news to report. If the Gray Lady is serious about keeping her green tint, that is.

The fact is the 12 hottest years on record have all come in the last 15. Heat waves, droughts, wildfires, floods — all are now more frequent and more intense. We can choose to believe that Superstorm Sandy and the most severe drought in decades and the worst wildfires some states have ever seen were all just a freak coincidence.

Or we can choose to believe in the overwhelming judgment of science — and act before it’s too late. …I urge this Congress to get together, (and) pursue a bipartisan, market-based solution to climate change, like the one John McCain and Joe Lieberman worked on a few years ago. But, if Congress won’t act soon to protect future generations, I will. I will direct my Cabinet to come up with executive actions we can take now and in the future to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy.

Heat generated by the Earth’s major cities has influenced global weather patterns and is probably responsible for winter warming in parts of North America and northern Asia, according to scientists.

So-called waste heat produced by human activities in major urban centers has altered aspects of the jet stream and other atmospheric systems, causing significant warming in some regions and cooling in others, according to a study published recently in Nature Climate Change.

“What we found is that energy use from multiple urban areas collectively can warm the atmosphere remotely, thousands of miles away from the energy consumption regions,” said lead author Guang Zhang, a research meteorologist at Scripps Institution of Oceanography in La Jolla. “This is accomplished through atmospheric circulation change.”

This heating, according to study authors, is separate from the planetary warming caused by greenhouse gases, as well as the so-called urban heat island effect. The heat island phenomenon occurs when heat is stored and re-radiated by expanses of asphalt, concrete and other building materials, making urban areas warmer than rural areas.

Overall, the waste heat produced by the globe’s cities is small. However, the heat is highly concentrated, and in many cases, positioned directly beneath major atmospheric troughs and ridges, according to study authors.

In Russia and northern Asia, the effect can increase temperatures by almost 2 degrees Fahrenheit during the winter. In the northeastern U.S. and southern Canada, the effect has raised winter temperatures by more than a degree, authors say.