How Plants May Help Offset Global Warming

Could plants help to slow the march of global warming?

It's possible, suggests a new study, which finds that as climates warm around the world, plants may respond by releasing more aerosol particles into the atmosphere.

The research, published online April 28 in the journal Nature Geoscience, finds that these natural aerosols can fuel cloud formation, which may help cool a warming climate. [The Reality of Climate Change: 10 Myths Busted]

Aerosols are fine particles of solid or liquid matter, suspended in air. Most of the aerosol particles in Earth's atmosphere come from human activities such as vehicle exhaust, according to the environmental blog The Carbon Brief. Volcanic eruptions also contribute some aerosols to the atmosphere.

But a small percentage of atmospheric aerosols come from living plants, according to a news release from the International Institute for Applied Systems Analysis (IIASA), which co-sponsored the study.

Plants release gases such as water vapor and oxygen; these combine with the aerosols released from plants to form larger airborne particles that reflect sunlight and form cloud droplets.

"Everyone knows the scent of the forest," Ari Asmi, University of Helsinki researcher and co-author of the study, said in a statement. "That scent is made up of these gases."

To measure the cooling effect, researchers collected data from 11 sites around the world, measuring aerosol particle concentrations, plant gases and temperatures.

In warmer temperatures, it was revealed, plants emit more of the gases that stick to aerosol particles. These can lead to cloud formation and, as a result of cloud cover, cooler temperatures.

Other natural phenomenon may help to cool the planet: Some researchers believe that phytoplankton — microscopic plants that drift on ocean currents — may reduce carbon dioxide levels in the atmosphere and lower the atmosphere's temperature.

Other research finds that tropical rainforests, which also absorb massive amounts of carbon dioxide and release water vapor that forms clouds, are critical to stabilizing atmospheric temperatures.

It's unclear how much cooling might actually occur as a result of so-called "biogenic" aerosols.

"This does not save us from climate warming," Pauli Paasonen, lead author of the study, said in the release.

Though in some areas, such as the forests of Finland and Canada, the cooling effect can be as large as 30 percent, the overall global effect is very small, offsetting only about 1 percent of global warming, according to the study.

Nonetheless, the impact of plant-based aerosol formation is an important element in fine-tuning climate forecast models, the researchers believe.

"Aerosol effects on climate are one of the main uncertainties in climate models," Paasonen said in the release. "Understanding this mechanism could help us reduce those uncertainties and make the models better."

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Most Americans Blame Global Warming for Extreme Weather

More than half of Americans think global warming is affecting weather in the United States, according to a new nationally representative survey that measures the pulse of American sentiment on climate change.

The newly released study shows that about two out of three Americans say weather in the country has worsened over the past several years, with only one in 10 saying the weather has been improving.

Americans also have strong views about the link between global warming and extreme weather.

Nearly 50 percent of the population believes global warming made the droughts that plagued the Midwestand the Great Plains last year more severe. Similarly, 46 percent of Americans believe climate change exacerbated the effects of Superstorm Sandy, which battered the Northeast in October 2012. [Dry & Dying: Stark Images of Drought]

"Americans are continuing to connect the dots between climate change and extreme weather in the United States," said Anthony Leiserowitz, director of the Yale Project on Climate Change Communication. "They're associating climate change with some of the major events that we experienced last year, like the ongoing drought."

Half of Americans also believe global warming was to blame for last year's record-breaking temperatures. The National Oceanic and Atmospheric Administration named 2012 the warmest year on record, with every contiguous U.S. state registering above-average annual temperatures for the year.

Furthermore, 85 percent of Americans said they personally experienced one or more types of extreme weather in the past year, ranging from extreme heat (51 percent) to extreme high winds (60 percent).  

The number of Americans who were significantly harmed by extreme weather events in the past year increased to about 37 percent — up 4 to 5 percentage points since 2012, Leiserowitz told LiveScience.

"That's quite a significant number," he said. "It shows just how dramatic these extreme weather events have been."

And concern about the potential impacts of extreme weather does not appear to be dissipating. More than half of Americans (54 percent) believe extreme weather is "very" or "somewhat likely" to cause a natural disaster in their local area in the coming year.

The new report, titled "Extreme Weather and Climate Change in the American Mind," is based on a nationally representative survey jointly conducted by the Yale Project on Climate Change Communication in New Haven, Conn., and the George Mason University Center for Climate Change Communication in Fairfax, Va.

For the study, 1,045 participants over age 18 were interviewed between April 8 and April 15. The researchers report a 95 percent confidence level, with a total average margin of error of plus or minus 3 percentage points. This means that if the survey were conducted 100 times, the results would fall within 3 percentage points above or below the data collected in 95 of the 100 surveys.

The study was funded by the Surdna Foundation, the 11th Hour Project, the Grantham Foundation and the V.K. Rasmussen Foundation.

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Global warming may have fueled Somali drought

NAIROBI, Kenya (AP) — Global warming may have contributed to low rain levels in Somalia in 2011 where tens of thousands died in a famine, research by British climate scientists suggests.

Scientists with Britain's weather service studied weather patterns in East Africa in 2010 and 2011 and found that yearly precipitation known as the short rains failed in late 2010 because of the natural effects of the weather pattern La Nina.

But the lack of the long rains in early 2011 was an effect of "the systematic warming due to influence on greenhouse gas concentrations," said Peter Stott of Britain's Met Office, speaking to The Associated Press in a phone interview.

The British government estimates that between 50,000 and 100,000 people died from the famine. But the new research doesn't mean global warming directly caused those deaths.

Ethiopia and Kenya were also affected by the lack of rains in 2011, but aid agencies were able to work more easily in those countries than in war-ravaged Somalia, where the al-Qaida-linked Islamic extremist group al-Shabab refused to allow food aid into the wide areas under its control.

The peer reviewed study will appear in Geophysical Research Letters, a journal of the American Geophysical Union.

Senait Gebregziabher, the Somalia country director for the aid group Oxfam, said climate change is increasing humanitarian needs.

"In the coming decades, unless urgent action is taken to slash greenhouse gas emissions, temperatures in East Africa will continue to rise and rainfall patterns will change. This will create major problems for food production and availability," Gebregziabher said.

Stott said that the evidence is "very strong" that the planet is warming due to an increase in greenhouse gases. He noted that the study indicates that both natural causes — La Nina and the short rains — and man-made causes contributed to Somalia's drought.

The Met Office's computer modeling study found that between 24 percent and 99 percent of the cause of the failure of the 2011 rains can be attributed to the presence of man-made greenhouse gases, Stott said.

Global warming is caused by the burning of fossil fuels — coal, oil and natural gas — which sends heat-trapping gases, such as carbon dioxide, into the air, changing the climate, scientists say.

Ahmed Awale works for the non-profit group Candlelight, which is dedicated to improving conservation and the environment. He believes Somalia's climate has been changing for many decades, with rainfall patterns becoming more erratic.

"If you miss one of the two rainy seasons we have a very severe drought. The other indicator is that there is a rise in temperature," he said, adding later: "This all negatively impacts the livelihood of the people. Most of Somalis depend mostly on pastoral production."

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Even Modest Volcanic Eruptions May Mask Global Warming Effects

Volcanic eruptions, even small and moderate ones, might counter some of the effects of global warming, new research suggests.

The planet didn't heat up as much as scientists expected it to from 2000 to 2010 (though it was still the warmest decade on record), and a new study finds that chemical compounds spewed during modest eruptions around the globe could be behind the trend.

When sulfur dioxide emitted by a volcano rises up to the stratospheric aerosol layer of the atmosphere, it undergoes chemical reactions, forming particles that reflect sunlight back into space instead of letting it get to the surface of the planet. This has a cooling effect on Earth that can help mitigate the impacts of heat-trapping greenhouse gasses.

Scientists observed an increase in these sun-scattering aerosols in the atmosphere from 2000 to 2010. Some studies suggested that emissions from rapidly developing countries in Asia could be largely to blame — India and China, for example, are thought to have ramped up their sulfur dioxide output by about 60 percent over the decade through coal burning. But other studies pointed to volcanoes, which are also an important source of sulfur dioxide.

The authors of the new study used computer simulations to see which changes in the stratospheric aerosol layer could be attributed to coal burning in Asia and worldwide volcanic emissions from 2000 to 2010. The results suggested that moderate volcanic eruptions were behind the increases of aerosols in the atmosphere.

"This new study indicates it is emissions from small to moderate volcanoes that have been slowing the warming of the planet," Ryan Neely, who led the research as part of his doctoral thesis at the University of Colorado, Boulder, said in a statement.

The findings imply scientists should pay more attention to these types of eruptions when studying changes in Earth's climate, said study researcher Brian Toon, a professor at CU-Boulder, though he cautioned that in the long run, volcanoes won't be able to counterbalance global warming.

"Overall these eruptions are not going to counter the greenhouse effect," Toon said in a statement. "Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up."

Toon added that larger volcanoes can have a much bigger effect. For example, Mount Pinatubo, a volcano in the Philippines that erupted in 1991, ejected so much sulfur dioxide into the stratosphere that the planet cooled by 1 degree Fahrenheit (0.55 degrees Celsius) and stayed slightly cooler for more than two years.

The new research was detailed online in the journal Geophysical Research Letters.

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Could global warming change tornado season, too?

OKLAHOMA CITY (AP) — With the planet heating up, many scientists seem fairly certain some weather elements like hurricanes and droughts will worsen. But tornadoes have them stumped.

These unpredictable, sometimes deadly storms plague the United States more than any other country. Here in tornado alley, Oklahoma City has been hit with at least 147 tornadoes since 1890.

But as the traditional tornado season nears, scientists have been pondering a simple question: Will there be more or fewer twisters as global warming increases?

There is no easy answer. Lately, tornado activity in America has been Jekyll-and-Hyde weird, and scientists are unsure if climate change has played a role in recent erratic patterns.

In 2011, the United States saw its second-deadliest tornado season in history: Nearly 1,700 tornadoes killed 553 people. The Joplin, Mo., twister was the single deadliest in American history, killing 158 people and causing $2.8 billion in damage.

The following year, 2012, started even earlier and even busier. Through April there were twice as many tornadoes as normal. Then the twisters suddenly disappeared. Tornado activity from May to August of that year was the lowest in 60 years of record-keeping, said Harold Brooks, a top researcher at the National Weather Center in Norman, Okla.

Meanwhile, Canada saw an unusual number of tornadoes in 2012; Saskatchewan had three times the normal number.

That year, the jet stream moved north and "essentially shut down" tornadoes in the American Midwest said Greg Carbin, warning meteorologist at the federal storm center. A tremendous drought meant far fewer storms, which not only shut off the spigot on rain but on storm cells that spawned tornadoes.

For much of America, tornadoes are seasonal. Typically, there are more during spring, and the numbers dwindle in the worst heat of the summer. Last year "essentially was an extended period of summertime conditions over the U.S.," Carbin said. "The real question is: What is spring now? Is it February?"

"Summer may be happening earlier and may be muscling out what we consider a transition between summer and winter," he said.

The last two seasons aren't alone in illustrating extremes in tornado activity.

Tornado record-keepers tally things like the most and least tornadoes in a month. Records for that category have been set 24 times over the past 60 years. Ten of those records have been set in the past decade — six for the fewest tornadoes and four for the most, Brooks said. Also, the three earliest starts of tornado season and the four latest have all occurred since 1997, he said.

What does that mean?

"We've had a dramatic increase in the variability of tornado occurrence," Brooks said.

The jet stream, a major player in tornado formation, has been in a state of flux, varying wildly in recent years, said Pennsylvania State University climate scientist Michael Mann.

"It's hard to predict future tornado seasons when we don't understand current tornado seasons," Brooks said between sessions at the National Tornado Summit here earlier this week. "We're not sure what's going to happen with the tornado numbers."

A new study in the Bulletin of the American Meteorological Society looks at all sorts of extreme weather, how it is changing because of global warming and how things are predicted to change in the future. The study says tornadoes and the severe thunderstorms that spawn them are the hardest to predict.

Public opinion polls show Americans blame global warming for bad tornado outbreaks, but climate scientists say that's not quite right.

One reason scientists can't figure out how global warming might affect tornadoes is that twisters are usually small weather events that aren't easily simulated in large computer models. And records of tornadoes may not have been accurate over the years as twisters twirled unnoticed around unpopulated areas.

So Brooks and others are looking at the ingredients that cause tornadoes. But even that isn't simple. They look at two main factors: moist energy in the atmosphere and wind shear. Wind shear is the difference between wind at high altitudes and wind near the surface. The more moist energy and greater the wind shear, the better the chances for tornadoes.

The atmosphere can hold more moisture as it warms, and it will likely be more unstable so that means more moist energy, several experts said. But wind shear is another matter. Brooks and Stanford University scientist Noah Diffenbaugh think there will be less of that.

That would suggest fewer tornadoes. But if there's more moist energy, that could lead to more tornadoes. One ingredient has to win out, and Brooks says it's hard to tell which one will. Diffenbaugh says recent computer simulations show the moist energy may overcome the reduced shear and produce at least more severe thunderstorms, if not tornadoes.

Given what's happening lately, Brooks believes there will be fewer days of tornadoes but more twisters on the days when they occur.

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Seth Borenstein can be followed at http://twitter.com/borenbears

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Big Chill vs. Global Warming: What's Going On?

The recent, rare snow in Jerusalem and parts of Lebanon, along with freezing temperatures for Southern California have not nixed the reality of climate change. The planet is warming, and chilled weather doesn't negate that fact, say climate experts.

In fact, such "rare" storms are expected in a warming world.

"As the globe warms, regions of the Earth that have cold winters will still have cold winters, and we will still see the random rolls of the weather dice, like we are seeing this winter," climate scientist Michael Mann of Pennsylvania State University told LiveScience. "But climate change is loading the weather dice, so that 'sixes' are becoming more common, and 'ones' are becoming less common."   

No single weather event can be pegged to climate change, which is a long-term trend that over time affects weather, and it affects the weather in different regions in different ways. Rather, as the planet warms, the chances of an extreme-weather event, including very large snowfalls, increase. That is, the dice are loaded for extreme events. [The Reality of Climate Change: 10 Myths Busted]

"Climate is the statistics of weather over the long term," Ken Caldeira, a senior scientist at the Carnegie Institute for Science at Stanford University, told LiveScience last year. "No specific weather event can by itself confirm or disprove the body of scientific knowledge associated with climate change."

Global warming with a side of chill

A big chill crept over California this weekend, with temperatures in a San Diego county dipping to 23 degrees Fahrenheit (minus 5 degrees Celsius), breaking a record set in 2007. And, according to news reports and the National Weather Service, San Diego beaches may have gotten a coating of morning frost, while a freeze warning remains in effect until Tuesday morning for the San Joaquin Valley.

Meanwhile, a storm system dumped 4-6 inches (10-15 centimeters) of snow on Jerusalem last week, killing at least eight people. And sleet and freezing rain will stretch across parts of the Southeast today and Tuesday, according to weather.com. [The World's Weirdest Weather]

Amidst the chilly headlines, however, Earth continues to break heat records left and right. "It's easy to cherry pick and find places that might be unusually cold at any given time, for example Southern California right now," Mann told LiveScience in an email. "But meanwhile, daffodils are coming up in Cincinnati.

"Over the past decade, we have seen daily records for all-time warmth broken twice as often as daily records for all-time cold," Mann wrote. "The year 2012 had the highest ratio we have ever recorded, more than four to one. That's like 'sixes' coming up four times as often as 'ones.'"

Here's how cold temperatures and snowfall can abound in some regions while the Earth warms: Warm air holds more moisture than its cold counterpart. That means if the temperature is low enough, "those warmer winters will counter-intuitively favor larger snowfall events," Mann explained.

And modest cooling is expected to result from global warming in some regions. For instance, Mann explained, models forecast a slowdown of the warm, poleward-moving ocean current in the North Atlantic, a slowing that will modestly cool that part of the ocean.

Most of Earth getting hotter

"But these are highly seasonal and regional effects," Mann said. "The vast majority of the globe will warm substantially over the next century, likely with profound negative consequences, if we continue to heat the planet by increasing greenhouse gas concentrations through fossil-fuel burning."

In fact, at least in the United States, 2012 was the hottest year on record, smashing the previous warmest year, 1998. And the past decade set itself apart in terms of extreme weather, from heat waves and drought to flooding, something scientists say can be, in part, attributed to climate change.

"It is very likely that several of the unprecedented extremes of the past decade would not have occurred without anthropocentric global warming," study researchers wrote in the March 25, 2012, issue of the journal Nature Climate Change. In that study, two scientists reviewed extreme weather events going back to 2000 as well as research into possible connections with global warming.

Since 1950, human-caused climate change seems to have brought on more extreme weather, with even more such extremes expected this century, reported the Intergovernmental Panel on Climate Change, the international body charged with assessing climate change, in 2011.

So far this year, the United States has set 630 records for highest maximum temperature versus 114 records for lowest minimum temperature, according to the National Climatic Data Center.

"When you step back and look at what is happening overall, it is very clear that we are seeing overall warming, and a dramatic increase in record-breaking heat around the world," said Mann, pointing out the record heat and wildfires happening in Australia right now and the record heat experienced in the United States this past summer.

"They are both symptomatic of the perceptible and profound impact that climate change is already having on our weather," Mann added.

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Global Warming Brings Earlier Spring Flowers

The warmest springs on record caused flowers to bloom at their earliest dates in decades at two historic sites, according to new research.

The findings, published online today (Jan. 16) in the journal PLoS ONE, show just how much climate change has altered ecosystems throughout the temperate areas of the United States. The study used 161-year-old data on flowering times from Henry David Thoreau's notebooks, as well as nearly 80-year-old data from the famous naturalist Aldo Leopold.

Scientists had previously described the Thoreau records but they hadn't combined the two naturalists' findings until now.

"Record warm temperatures (in 2010 and 2012) have resulted in record early flowering times," said study researcher Elizabeth Ellwood of Boston University. [8 Ways Global Warming Is Already Changing the World]

Famous naturalists

Henry David Thoreau was one of the most iconic figures of the 19th century. The famous naturalist and poet wrote the book "Walden" about his years living at idyllic Walden Pond in Concord, Mass. Starting in 1852 and at different points throughout his life, he also created the first "spreadsheets of flowering dates" for many well-known flowers, including the wild columbine, the pink-lady slipper orchid and the marsh marigold, Ellwood said.

Similarly, the naturalist Leopold took detailed records of first flowering times at a site called "The Shack" in wilderness near the Wisconsin River, starting in 1935.

"It's the iconic equivalent to Walden Pond for Wisconsinites," Ellwood told LiveScience.

While scholars knew of these flowering observations, many were scattered in different libraries and archives, and no one had systematically analyzed their patterns, she said.

Hotter springs, earlier blooms

To do so, Ellwood and her colleagues gathered all of Thoreau's flowering records from several archives. They then compared flowering dates with spring temperatures for 32 different flowering plants.

They found that as temperatures warmed over the last 161 years, the date of first blooms of the season crept forward, too — about 10 days earlier than when Thoreau first visited the site. During the record-breaking years of 2010 and 2012, flowering happened a full 20 to 21 days earlier. The average spring temperature at Walden Pond has increased about 6 degrees Fahrenheit (3.4 degrees Celsius) since Thoreau's time.

Similarly, at The Shack, as average spring temperatures rose about 3 degrees Fahrenheit (1.7 degrees Celsius) over the last eight decades, first flowering came a week early for the 23 species they studied. During the hottest years in the United States (2010 and 2012), flowering came 24 days earlier than in Leopold's time.

Still adapting

The research may have tracked just two sites, but has broad implications, said Elizabeth Wolkovich, a climate change ecologist at the University of British Columbia who was not involved in the study.

"One is deep within the country and one is on the coast," Wolkovich said.

That means the findings probably apply to temperate climates throughout a large swath of the United States, she told LiveScience.

Though Thoreau and Leopold's works have highlighted how much climate change alters ecosystems, in some ways, the findings are good news.

At some point, the climate will get too hot for plants to survive without evolving, but the fact that the plant flowering time is still changing in step with the temperature means they haven't hit that point yet, said David Inouye, a University of Maryland biologist who was not involved in the study.

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AP-GfK Poll: Science doubters say world is warming

WASHINGTON (AP) — A growing majority of Americans think global warming is occurring, that it will become a serious problem and that the U.S. government should do something about it, a new Associated Press-GfK poll finds.

Even most people who say they don't trust scientists on the environment say temperatures are rising.

The poll found 4 out of every 5 Americans said climate change will be a serious problem for the United States if nothing is done about it. That's up from 73 percent when the same question was asked in 2009.

And 57 percent of Americans say the U.S. government should do a great deal or quite a bit about the problem. That's up from 52 percent in 2009. Only 22 percent of those surveyed think little or nothing should be done, a figure that dropped from 25 percent.

Overall, 78 percent of those surveyed said they believe temperatures are rising, up from 75 percent three years earlier. In general, U.S. belief in global warming, according to AP-GfK and other polls, has fluctuated over the years but has stayed between about 70 and 85 percent.

The biggest change in the polling is among people who trust scientists only a little or not at all. About 1 in 3 of the people surveyed fell into that category.

Within that highly skeptical group, 61 percent now say temperatures have been rising over the past 100 years. That's a substantial increase from 2009, when the AP-GfK poll found that only 47 percent of those with little or no trust in scientists believed the world was getting warmer.

This is an important development because, often in the past, opinion about climate change doesn't move much in core groups — like those who deny it exists and those who firmly believe it's an alarming problem, said Jon Krosnick, a Stanford University social psychologist and pollster. Krosnick, who consulted with The Associated Press on the poll questions, said the changes the poll shows aren't in the hard-core "anti-warming" deniers, but in the next group, who had serious doubts.

"They don't believe what the scientists say, they believe what the thermometers say," Krosnick said. "Events are helping these people see what scientists thought they had been seeing all along."

Phil Adams, a retired freelance photographer from Washington, N.C., said he was "fairly cynical" about scientists and their theories. But he believes very much in climate change because of what he's seen with his own eyes.

"Having lived for 67 years, we consistently see more and more changes based upon the fact that the weather is warmer," he said. "The seasons are more severe. The climate is definitely getting warmer."

"Storms seem to be more severe," he added. Nearly half, 49 percent, of those surveyed called global warming not just serious but "very serious," up from 42 percent in 2009. More than half, 57 percent, of those surveyed thought the U.S. government should do a great deal or quite a bit about global warming, up from 52 percent three years earlier.

But only 45 percent of those surveyed think President Barack Obama will take major action to fight climate change in his second term, slightly more than the 41 percent who don't think he will act.

Overall, the 78 percent who think temperatures are rising is not the highest percentage of Americans who have believed in climate change, according to AP polling. In 2006, less than a year after Hurricane Katrina devastated New Orleans, 85 percent thought temperatures were rising. The lowest point in the past 15 years for belief in warming was in December 2009, after some snowy winters and in the middle of an uproar about climate scientists' emails that later independent investigations found showed no manipulation of data.

Broken down by political party, 83 percent of Democrats and 70 percent of Republicans say the world is getting warmer. And 77 percent of independents say temperatures are rising. Among scientists who write about the issue in peer-reviewed literature, the belief in global warming is about 97 percent, according to a 2010 scientific study.

About 1 in 4 people surveyed think that efforts to curb global warming would hurt the American economy, a figure down slightly from 27 percent in 2009 when the economy was in worse shape. Just under half, 46 percent, think such action would help the U.S. economy, about the same as said so three years ago.

The AP-GfK poll was conducted Nov. 29-Dec. 3 by GfK Roper Public Affairs and Corporate Communications. It involved landline and cellphone interviews with 1,002 adults nationwide. Results for the full sample have a margin of error of plus or minus 3.9 percentage points; the margin of error is larger for subgroups.

The latest AP-GfK poll jibes with other surveys and more in-depth research on global warming, said Anthony Leiserowitz, director of Yale University's Project on Climate Change Communication. He took no part in the poll.

When climate change belief was at its lowest, concerns about the economy were heightened and the country had gone through some incredible snowstorms and that may have chipped away at some belief in global warming, Leiserowitz said. Now the economy is better and the weather is warmer and worse in ways that seem easier to connect to climate change, he said.

"One extreme event after another after another," Leiserowitz said. "People have noticed. ... They're connecting the dots between climate change and this long bout of extreme weather themselves."

Thomas Coffey, 77, of Houston, said you can't help but notice it.

"We use to have mild temperatures in the fall going into winter months. Now, we have summer temperatures going into winter," Coffey said. "The whole Earth is getting warmer and when it gets warmer, the ice cap is going to melt and the ocean is going to rise."

He also said that's what he thinks is causing recent extreme weather.

"That's why you see New York and New Jersey," he said, referring to Superstorm Sandy and its devastation in late October. "When you have a flood like that, flooding tunnels like that. And look at how long the tunnel has been there."

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Associated Press Director of Polling Jennifer Agiesta, News Survey Specialist Dennis Junius and writer Stacy A. Anderson contributed to this report.

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Online:

The poll: http://www.ap-gfkpoll.com

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Seth Borenstein can be followed at http://twitter.com/borenbears

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WHY IT MATTERS: Global warming

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

EDITOR'S NOTE _ One in a series examining issues at stake in the election and their impact on people

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Record-High Antarctic Sea Ice Levels Don't Disprove Global Warming

Distracting from the news that Arctic sea-ice extent reached a record low on Sept.16 is a widely circulating blog article claiming that at the opposite end of the Earth, Antarctic sea ice is more than making up for the losses.

In the post, climate change skeptic and blogger Steven Goddard states that Antarctic sea ice reached its highest level ever recorded for the 256th day of the calendar year on Sept. 12. He reasons that the Southern Hemisphere must be balancing the warming of the Northern Hemisphere by becoming colder (and thus, net global warming is zero).

The National Snow & Ice Data Center (NSIDC), which tracks sea ice using satellite data, explains on its website why Antarctic ice has weathered global warming more robustly than Arctic ice. Goddard dismisses the explanation, concluding instead, "Antarctic and Arctic ice move opposite each other. NSIDC's dissonance about this is astonishing."

Despite its lack of scientific support, Goddard's post has garnered attention around the Web. In a Forbes.com column about the record high Antarctic sea ice, skeptic James Taylor writes, "Please, nobody tell the mainstream media or they might have to retract some stories and admit they are misrepresenting scientific data."

But if anyone had asked an actual scientist, they would have learned that a good year for sea ice in the Antarctic in no way nullifies the precipitous drop in Arctic sea-ice levels year after year — or the mounds of other evidence indicating global warming is really happening.

"Antarctic sea ice hasn't seen these big reductions we've seen in the Arctic. This is not a surprise to us," said climate scientist Mark Serreze, director of the NSIDC. "Some of the skeptics say 'Well, everything is OK because the big changes in the Arctic are essentially balanced by what's happening in the Antarctic.' This is simply not true." [Former Global Warming Skeptic Makes a 'Total Turnaround']

Projections made from climate models all predict that global warming should impact Arctic sea ice first and most intensely, Serreze said. "We have known for many years that as the Earth started to warm up, the effects would be seen first in the Arctic and not the Antarctic. The physical geography of the two hemispheres is very different. Largely as a result of that, they behave very differently."

The Arctic, an ocean surrounded by land, responds much more directly to changes in air and sea-surface temperatures than Antarctica, Serreze explained. The climate of Antarctica, land surrounded by ocean, is governed much more by wind and ocean currents. Some studies indicate climate change has strengthened westerly winds in the Southern Hemisphere, and because wind has a cooling effect, scientists say this partly accounts for the marginal increase in sea ice levels that have been observed in the Antarctic in recent decades.

"Another reason why the sea-ice extent in the Antarctic is remaining fairly high is, interestingly, the ozone hole," Serreze told Life's Little Mysteries. This hole was carved out over time by chlorofluorocarbons, toxic chemicals formerly that were used in air conditioners and solvents before being banned. "The ozone hole affects the circulation of the atmosphere down there. Because of the ozone hole, the stratosphere above Antarctica is quite cold. Ozone in the stratosphere absorbs UV light, and less absorption [by] ozone makes the stratosphere really cold. This cold air propagates down to the surface by influencing the atmospheric circulation in the Antarctic, and that keeps the sea ice extensive."

But these effects are very small, and Antarctic sea-ice levels have increased only marginally. In the coming decades, climate models suggest rising global temperatures will overwhelm the other influences and cause Antarctic sea ice to scale back, too.

The extent of Arctic sea ice at its summertime low point has dropped 40 percent in the past three decades. The idea that a tiny Antarctic ice expansion makes up for this — that heat is merely shifting from the the Southern Hemisphere to the Northern and therefore global warming must not be happening — is "just nonsense," Serreze said.

Follow Natalie Wolchover on Twitter @nattyover or Life's Little Mysteries @llmysteries. We're also on Facebook & Google+.

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Is Global Warming Fueling Colorado Wildfires?

DENVER — Devastating wildfires scorching the state of Colorado are linked to a nasty streak of hot weather across the central part of the country, but it's tougher to link them definitively to global warming, climatologists say.

Earlier research has found broad trends linking earlier spring weather, rising temperatures and increased forest fires, suggesting that climate change may play a role in fires like the Waldo Canyon blaze outside of Colorado Springs, which has burned more than 18,000 acres and consumed about 300 homes here. But linking a specific fire to the long-term trend of global warming isn't possible.

"You can't say it's climate change just because it's an extreme condition," said Colorado state climatologist Nolan Doesken. So far, Doesken told LiveScience, the spring of 2012 looks much like the spring of 1910, when warm temperatures hit early. That year, he said, was a bad one for fires. [Images: Devastating Colorado Fires]

Fire weather

The Waldo Canyon fire began on June 23 and has ripped through neighborhoods west of Colorado Springs, destroying a yet-unreleased number of homes. Just 130 miles (209 kilometers) to the north, the High Park wildfire outside of Fort Collins is well into its second week and has burned more than 87,000 acres. That fire killed one 62-year-old woman who was caught in her home.

Other significant fires in the state include a 300-acre blaze 1.5 miles (2.4 km) outside of Boulder, a 9,168-acre blaze near Mancos in the southwestern part of the state and a 23,400-acre wildfire in rugged terrain in the San Juan National Forest, also in the southwestern part of the state.

The immediate driver of these fires is a lack of moisture and a ridge of heat that has settled over the central United States, said New Jersey state climatologist Dave Robinson, who also directs the Global Snow Lab at Rutgers University. After record snowpack last year, the Rocky Mountains did a 180 this year, Robinson said, seeing little moisture and early snowmelt.

"March and April are supposed to be your snowy months [in Colorado], and they weren't," Robinson told LiveScience. "Thus, the fire danger."

Meanwhile, a high-pressure system in the central part of the country is preventing cloud formation and allowing the sun to bake the ground, heating things up. On Tuesday (June 26) alone, 251 daily heat records were broken across the nation, according to the National Climatic Data Center. In the past week, more than 1,000 new daily heat records were put on the books. [The World's Weirdest Weather]

Climate change connection

Climate models predict that in a warming world, the West and Southwest will become drier and hotter — conditions ripe for wildfires. Whether recent hot summers and active fires are a sign of the change already happening is still under debate, though.

"Some would say there is a pattern, because we have had several years with exceptionally large fires over western states, particularly the Southwestern states, Arizona, New Mexico, Texas and Colorado in particular," Doesken said. "Others would say, no, not enough data points yet to show that."

This year has been extreme in terms of heat and dryness, he said, as was 2002 (a record-breaking year for fires in Colorado). So far, 2012's weather looks very similar to the weather of 1910. That year, spring was warm and dry, which fed into a hellish fire season. Among the blazes was the Great Fire of 1910, also known as "the Big Burn," which destroyed 3 million acres of forest in Washington, Idaho and Montana.

Some studies do suggest that climate change is already affecting western wildfires. In 2006, researchers at the Scripps Institute of Oceanography in California analyzed 1,166 fires between 1970 and 2003 and found a dramatic increase in fire potency in the late 1980s. Though wildfire is a natural part of the western landscape, the researchers concluded that a warming climate was ramping up warm winters and springs, exacerbating natural fire cycles.

More recently, an analysis of 1,500 years of fire and tree-ring data revealed that a combination of climate change and human forest use could explain modern "megafires," the kind that destroy large swaths of forest. Fires were associated with a dry year following several wet years, because the moist periods allow undergrowth to spring up and provide fire fuel in dry years, researchers reported in May in the journal The Holocene. The study found that human activities such as livestock grazing and suppression of small fires compounded the problem, creating denser forests ripe for large blazes.

Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+. 

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Climate scientists say warming could exceed 3.5 C

Climate researchers said Thursday the planet could warm by more than 3.5 degrees Celsius (6.3 degrees Fahrenheit), boosting the risk of drought, flood and rising seas.

The UN's target is a 2 C (3.6 degree Fahrenheit) limit on warming from pre-industrial levels for manageable climate change.

In a report issued on the penultimate day of new UN talks in Bonn, scientists said Earth's average global temperature rise could exceed the dangerous 3.5 C (6.3 F) warming they had flagged only six months ago.

Marion Vieweg, a policy researcher with German firm Climate Analytics, told AFP the 3.5 C (6.3 F) estimate had been based on the assumption that all countries will meet their pledges, in themselves inadequate, to reduce greenhouse-gas emissions.

New research has found this is not "a realistic assumption," she said, adding that right now "we can't quantify yet how much above" 3.5 C (6.3 F) Earth will warm.

The monitoring tool is called Climate Action Tracker (CAT), a joint project of Climate Analytics, Ecofys and the Potsdam Institute for Climate Impact Research in Germany.

Her colleague, Bill Hare, said the gap between countries' promised interventions and the reality was "getting bigger."

Projections are for greenhouse-gas overshoot of between nine and 11 billion tonnes per year beyond the annual 44-billion-tonne ceiling needed by 2020 to achieve the 2 C (3.6 F) target.

At the moment, the world emits about 48 billion tonnes of these gases, including CO2 and methane.

The United States accounts for six billion tonnes, China seven and the European Union (EU) five, the CAT said.

The 195 parties to the UN Framework Convention on Climate Change (UNFCCC) are meeting in the former German capital of Bonn for the first time since they agreed in Durban, South Africa, last December to forge a new global pact.

The accord would be completed by 2015 and take effect in 2020.

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Global warming winner: Once rare butterfly thrives

WASHINGTON (AP) — Global warming is rescuing the once-rare brown Argus butterfly, scientists say.

Man-made climate is threatening the existence of many species, such as the giant polar bear. But in the case of the small drab British butterfly, it took a species in trouble and made it thrive.

It's all about food. Over about 25 years, the butterfly went from in trouble to pushing north in Britain where it found a veritable banquet. Now the butterfly lives in twice as large an area as it once did and is not near threatened, according to a study in Friday's issue of the journal Science.

Decades ago, the brown Argus "was sort of a special butterfly that you would have to go to a special place to see and now it's a butterfly you can see in regular farmland or all over the place," said study co-author Richard Fox, an ecologist at Butterfly Conservation, a science and advocacy group in the United Kingdom.

Global warming helping the brown Argus is unusual compared to other species and that's why scientists are studying it more, said study co-author Jane Hill, a professor of ecology at the University of York.

Biologists expect climate change to create winners and losers in species. Stanford University biologist Terry Root, who wasn't part of this study, estimated that for every winner like the brown Argus there are three loser species, like the cuckoo bird in Europe. Hill agreed that it's probably a three-to-one ratio of climate change losers to winners.

As the world warms, the key interactions between species break down because the predator and prey may not change habitats at the same time, meaning some species will move north to cooler climes and won't find enough to eat, Root said.

"There are just so many species that are going to go extinct," Root said.

What makes the brown Argus different is that it found something new to eat, something even better than its old food, the less common rockrose plant, Hill said. The new food is a geranium and it is more widespread.

"It's almost like the whole of the buffet is now open to it," Hill said.

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Online:

Science: http://www.sciencemag.org

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Seth Borenstein can be followed at http://twitter.com/borenbears

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8 Ways Global Warming Is Already Changing the World

Over the last 100 years, global temperatures have warmed by about 1.33 degrees Fahrenheit (0.74 degrees Celsius) on average. The change may seem minor, but it's happening very quickly — more than half of it since 1979, according to the Intergovernmental Panel on Climate Change.

Though it can still be difficult to tease out how much climate change plays in any given weather event, changes are occurring.

In the spirit of Earth day, here's a look at our marvelous blue marble and the ways people and other living things are responding to global warming. [50 Amazing Facts About Earth]

1. Moving the military northward

As the Arctic ice opens up, the world turns its attention to the resources below. According to the U.S. Geological Survey, 30 percent of the world's undiscovered natural gas and 13 percent of its undiscovered oil are under this region. As a result, military action in the Arctic is heating up, with the United States, Russia, Denmark, Finland, Norway, Iceland, Sweden and Canada holding talks about regional security and border issues. Several nations, including the U.S., are also drilling troops in the far north, preparing for increased border patrol and disaster response efforts in a busier Arctic.

2. Altering breeding seasons

As temperatures shift, penguins are shifting their breeding seasons, too. A March 2012 study found that gentoo penguins are adapting more quickly to warmer weather, because they aren't as dependent on sea ice for breeding as other species.

It's not just penguins that seem to be responding to climate change. Animal shelters in the U.S. have reported increasing numbers of stray cats and kittens attributed to a longer breeding season for the felines.

3. High-country changes

Decreased winter snowfall on mountaintops is allowing elk in northern Arizona to forage at higher elevations all winter, contributing to a decline in seasonal plants. Elk have ravaged trees such as maples and aspens, which in turn has led to a decline in songbirds that rely on these trees for habitat.

4. Altered Thoreau's stomping grounds

The writer Henry David Thoreau once lovingly documented nature in and around Concord, Mass. Reading those diaries today has shown researchers just how much spring has changed in the last century or so.

Compared to the late 1800s, the first flowering dates for 43 of the most common plant species in the area have moved forward an average of 10 days. Other plants have simply disappeared, including 15 species of orchids.

5. Changed "high season" at national parks

When's the busiest time to see the Grand Canyon? The answer has changed over the decades as spring has started earlier. Peak national park attendance has shifted forward more than four days, on average, since 1979. Today, the highest number of visitors now swarm the Grand Canyon on June 24, compared with July 4 in 1979.

6. Genetic changes

Even fruit flies are feeling the heat. According to a 2006 study, fruit fly genetic patterns normally seen at hot latitudes are showing up more frequently at higher latitudes. According to the research, the gene patterns of Drosophila subobscura, a common fruit fly, are changing so that populations look about one degree closer in latitude to the equator than they actually are. In other words, genotypes are shifting so that a fly in the Northern Hemisphere has a genome that looks more like a fly 75 to 100 miles (120 to 161 kilometers) south.

7. Hurting polar bears

Polar bear cubs are struggling to swim increasingly long distances in search of stable sea ice, according to a 2011 study. The rapid loss of sea ice in the Arctic is forcing bears to sometimes swim up to more than 12 days at a time, the research found. Cubs of adult bears that had to swim more than 30 miles (48 kilometers) had a 45 percent mortality rate, compared with 18 percent for cubs that had to swim shorter distances.

8. More mobile animals

Species are straying from their native habitats at an unprecedented rate: 11 miles (17.6 km) toward the poles per decade. Areas where temperature is increasing the most show the most straying by native organisms. The Cetti's warbler, for example, has moved north over the last two decades by more than 90 miles (150 km).

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

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Study: Water vapor may help 'flatten global warming trend'

Why the Earth's surface temperature hasn't warmed as expected over the past decade continues to be a puzzle for scientists. One study out earlier this month theorized that the Earth's climate may be less sensitive to greenhouse gases than currently assumed.Another surprising factor could be the amount of water vapor way up in the stratosphere, according to a new study out Thursday in the journal Science.

Water vapor, a potent, natural greenhouse gas that absorbs sunlight and re-emits heat, is "a wild card" of global warming, says the paper's lead author, senior scientist Susan Solomon of the National Oceanic and Atmospheric Administration in Boulder, Colo. Solomon was also a co-chair of one of the groups within the Intergovernmental Panel on Climate Change that put out the definitive forecast of global warming in 2007.

In the Science paper, Solomon and her colleagues found that a drop in the concentration of water vapor in the stratosphere "very likely made substantial contributions to the flattening of the global warming trend since about 2000."

While climate warming is continuing — the decade of 2000 to 2009 was the hottest on record worldwide — the increase in temperatures was not as rapid as in the 1990s.

The stratosphere is the layer of the atmosphere just above the troposphere, which is the layer of air here at the planet's surface. (The troposphere goes from the surface up to about 8 miles, and the stratosphere is from about 8 to 30 miles above the surface.)

The decline in water vapor in the stratosphere slowed the rate of surface warming by about 25%, compared to that which would have occurred due to carbon dioxide and other greenhouse gases, notes the study. Specifically, the planet should have warmed 0.25 degree F during the 2000s, but because of the influence of the water vapor, it rose just 0.18 degree F.

"We call this the 10/10/10 paper," says Solomon. "10 miles above your head, there is 10% less water vapor than there was 10 years ago."

Why did the water vapor decrease? "We really don't know," says Solomon, "We don't have enough information yet."

The findings are "surprising," says Bill Randel, an atmospheric chemist at the National Center for Atmospheric Research, who was not part of the study. He said it was surprising how big an effect such a very little change in stratospheric water vapor has had on the surface climate.

These fluctuations in water vapor could be part of a feedback loop. Although it's known that water vapor in the troposphere increases as the climate warms — and is a major climate feedback that is well simulated in global climate models — in sharp contrast, models do a poor job of simulating water vapor in the stratosphere, according to the paper.

But Solomon points out this isn't an indication that predictions on global warming are overstated: "This doesn't mean there isn't global warming," notes Solomon. "There's no significant debate that it is warmer now than it was 100 years ago, due to anthropogenic (man-made) greenhouse gases."

And how will this water vapor affect future global warming? "We really don't know the answer to this," says Solomon. "If the water changes are due to the specific way the sea-surface temperature pattern looks right now, then it may well not be linked to the overall warming. It could just be a source of variability from one decade to another as the ocean pattern slowly changes. Or it could be linked to the overall warming of the tropics, in which case it could continue to 'put the brakes on.' Only time will tell, and more data."

Contributing: Associated Press

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