The number of extreme rainstorms - deluges that dump 3 inches or more in a day - doubled in the U.S. Midwest over the last half-century, causing billions of dollars in flood damage in a trend climate advocates link to a rise in greenhouse gas emissions.

Across the Midwest the biggest storms increased by 103 percent from 1961 through 2011, a study released by the Rocky Mountain Climate Organization and the Natural Resources Defense Council reported on Wednesday.

Three out of four U.S. voters favor regulating carbon dioxide as a greenhouse-gas pollutant, and a majority think global warming should be a priority for the president and Congress, a survey of American attitudes on climate and energy reported on Thursday.

The survey was released one day after Rolling Stone magazine published an interview with President Barack Obama in which he suggested that climate change would become a campaign issue this year.

Planet-warming carbon dioxide emissions - similar to those caused by burning fossil fuels and other human activities now - helped heat the planet and end the last ice age some 11,700 years ago, scientists reported on Wednesday.

In a finding that offers a response to those skeptical about human-caused global warming, researchers from Harvard University, Oregon State University and other institutions reported in the journal Nature that rising temperatures followed increases in carbon dioxide.

The world's oceans are turning acidic at what could be the fastest pace of any time in the past 300 million years, even more rapidly than during a monster emission of planet-warming carbon 56 million years ago, scientists said on Thursday.

Looking back at this bygone warm period in Earth's history could offer help in forecasting the impact of human-spurred climate change, researchers said.

Environmental opponents of the Keystone XL tar sands pipeline aimed to deluge the White House and Congress with phone calls on Friday, slamming a Republican plan to speed approval of the project in exchange for extending a payroll tax cut.

"Red alert - call the White House and tell them not to back down to big oil on Keystone," environmental activist Bill McKibben said in a tweet. McKibben mobilized some 10,000 demonstrators outside the White House earlier this year to protest the pipeline.

Deaths and health problems from floods, drought and other U.S. disasters related to climate change cost an estimated $14 billion over the last decade, researchers said on Monday.

"When extreme weather hits, we hear about the property damage and insurance costs," said Kim Knowlton, a senior scientist at Natural Resources Defense Council and a co-author of the study. "The healthcare costs never end up on the tab."

The study in the journal Health Affairs looked at the cost of human suffering and loss of life due to six disasters from 2000-2009.

The world's governments and relief agencies need to plan now to resettle millions of people expected to be displaced by climate change, an international panel of experts said on Thursday.

Resettlement is already occurring at the rate of some 10 million people a year, said the report's lead author, Alex de Sherbinin. Climate-related resettlement projects are under way in Vietnam, Mozambique, on the Alaskan coast, the Chinese territory of Inner Mongolia and in the South Pacific.

To measure a country's greenhouse emissions from fossil fuels, it makes sense to consider the whole carbon supply chain, from oil well or coal mine to a consumer's shelf, scientists reported on Monday.

Currently, putting a price on climate-warming carbon dioxide generated by oil, coal, natural gas and other fossil fuels typically takes place where the fuel is burned.

However, this may not be the most effective way to calculate carbon emissions' cost, the researchers wrote in the journal Proceedings of the National Academy of Sciences.

Clean cookstoves that burn more efficiently and channel smoke outside could save millions of lives around the world, but only if the cooks themselves are part of the solution, scientists reported on Thursday.

The Global Alliance for Clean Cookstoves (cleancookstoves.org), headed by the United Nations Foundation and championed by U.S. Secretary of State Hillary Clinton, seeks to cut down on indoor air pollution in some of the globe's poorest countries, where the most common way to cook is on an open fire inside the home.

Summer monsoons that provide up to 80 percent of the water South Asia needs have gotten drier in the past half century, possibly due to aerosol particles spewed by burning fossil fuels, climate scientists said on Thursday.

Monsoon rains are driven by looping air circulation patterns over India, and the aerosols appear to have interfered with these patterns, researchers reported in the journal Science.