Environmentalists suffered a setback on Tuesday when British Columbia re-elected a premier who left the door open for approval of two oil pipelines that would carry tar sands oil across B.C. to the Pacific Coast, where it could be exported to the world market.

Despite trailing in the polls, incumbent Christy Clark, the leader of B.C.'s Liberal Party, defeated Adrian Dix and his New Democratic Party. Dix had opposed both pipelines, and environmental groups had hoped his win would signal the end of the projects.

The two Canadian pipelines—along with the proposed Keystone XL pipeline across the United States—are crucial to the expansion of Canada's oil sands industry, which is based in the province of Alberta. The industry hopes to double in size over the next decade, but because Alberta is landlocked, more pipelines are needed to get the oil to the coast.

Like the Keystone project, the Canadian pipelines face grassroots opposition from local landowners and environmental groups.

As if the public debate about global warming wasn't complex enough, a new field in climate research is coming of age, grabbing media attention and spawning seemingly contradictory headlines.

The work, called attribution research, doesn't challenge the scientific consensus that climate change is happening. Instead, it strives to understand the regional effects of global warming by determining whether increased greenhouse gas levels did—or didn't—cause a particular weather event. But the findings can be confusing. For instance, scientists say that climate change made Hurricane Sandy worse, but that it had nothing to do with historic floods in Thailand. Warming probably didn't cause this year's severe winter storm, Nemo, but it may have supercharged it. It caused some droughts, but not others.

Adding to the confusion is a trend that worries some experts: People on both sides of the climate divide tend to promote only those attribution studies that support their beliefs. Whether a conscious decision or not, this selective use of research is further polarizing the national conversation on climate change, experts told InsideClimate News.

In the latest show of force by opponents of the Keystone XL pipeline, a group of 150 major Democratic donors sent a letter Friday to President Obama, urging him to reject the controversial application from TransCanada for permission to send more than 800,000 barrels of tar sands oil a day from Alberta to the Texas Gulf Coast.

The signatories comprise business leaders, philanthropists and celebrities—including clean energy entrepreneurs Vinod Khosla, Jigar Shah and Steve Kirsch, long-time Obama bundler Wendy Abrams and actress Blythe Danner.

For more than a month, residents of Mayflower, Ark. have been told not to worry about lingering fumes from a March 29 oil spill that shut down a neighborhood and forced the evacuation of 22 homes.

"Overall, air emissions in the community continue to be below levels likely to cause health effects for the general population," Arkansas regulators wrote on a state-operated website that tracks Mayflower's air monitoring data.

Despite these reassurances, residents have suffered headaches, nausea and vomiting—classic symptoms of short-term exposure to the chemicals found in crude oil.

"Figuring out how to protect people after a disaster like this is very hard," said Aaron Bernstein, a public health expert and associate director of Harvard's Center for Health and the Global Environment. "People living near the spill early on could definitely have gotten sick" from the concentrations present in the air.