The issue:
People love to talk about the weather, especially when it's strange like the mercifully ended summer of 2012. This year the nation's weather has been hotter and more extreme than ever, federal records show. Yet there are two people who aren't talking about it, and they both happen to be running for president.
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Where they stand:
In 2009, President Barack Obama proposed a bill that would have capped power plant carbon dioxide emissions and allowed trading of credits for the right to emit greenhouse gases, but the measure died in Congress. An international treaty effort failed. Obama since has taken a different approach, treating carbon dioxide as a pollutant under the law. He doubled auto fuel economy standards, which will increase the cost of cars but save drivers money at the pump. He's put billions of stimulus dollars into cleaner energy.
Mitt Romney's view of climate change has varied. In his book "No Apology," he wrote, "I believe that climate change is occurring" and "human activity is a contributing factor." But on the campaign trail last year he said, "We don't know what's causing climate change on this planet." He has criticized Obama's treatment of coal power plants and opposes treating carbon dioxide as a pollutant and the capping of carbon dioxide emissions, but favors spending money on clean technology. Romney says some actions to curb emissions could hurt an already struggling economy.
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Why it matters:
It's worsening. In the U.S., July was the hottest month ever recorded and this year is on track to be the nation's warmest. Climate scientists say it's a combination of natural drought and man-made global warming. Each decade since the 1970s has been nearly one-third of a degree warmer than the previous one.
Sea levels are rising while Arctic sea ice was at a record low in September. U.S. public health officials are partially blaming unusually hot and dry weather for an outbreak of the deadly West Nile virus that is on pace to be the worst ever. Scientists blame global warming for more frequent weather disasters, with the World Health Organization saying: "Climatic changes already are estimated to cause over 150,000 deaths annually." Others put the toll lower.
Emissions of carbon dioxide and other greenhouse gases from the burning of fossil fuels are trapping more of the sun's heat on Earth. One study showed that 97 percent of the scientists who publish about climate in peer-reviewed journals say global warming is man-made. So do just about every major science society and institution that has weighed in.
But limiting carbon dioxide emissions from coal and oil would be costly, with billions of dollars in changes to the U.S. economy only a starting point. Similarly the price of not doing anything is extraordinarily high because of costly and deadly extreme weather. People will pay either way in taxes, energy prices, insurance premiums, disaster relief, food prices, water bills and changes to our environment that are hard to put a price tag on, says MIT economist Henry Jacoby.
A NASA study this year found the most extreme type of weather, which statistically should happen on less than 0.3 percent of the Earth at any given time, is now more common. Until recently, the most extreme year was in 1941 when extremes covered 2.7 percent of the globe. From 2006 to 2011 about 10 percent of the globe had that extreme weather, with a peak of 20 percent, the study said. That was before this year's record extremes started.
The issue of man-made global warming is "totally missing" from the campaign between Obama and Romney, says Jacoby. It should be talked about, he says, because "we're running a serious risk of passing a much-damaged planet to our descendants."
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Seth Borenstein can be followed at http://twitter.com/borenbears
