The world's getting hotter, the sea's rising and there's increasing evidence neither are naturally occurring phenomena.
So saysÂ a report from the U.N. International Panel on Climate Change,Â a document released every six years that is considered the benchmark on the topic. More than 800 authors and 50 editors from dozens of countries took part in its creation.
The summary for policymakers was released early Friday, while the full report, which bills itself as "a comprehensive assessment of the physical science basis of climate change," will be distributed Monday. Other reports, including those dealing with vulnerability and mitigation, will be released next year.
The politics of oil and ecology have put President Obama between a rock and hard place, as he faces a decision on whether or not to permit construction of a new pipeline. The squeeze just got tighter with a new, negative environmental assessment.
The Keystone XL pipeline will give America energy independence, thousands of jobs, important industrial infrastructure and won't cost taxpayers a dime, say proponents. Many of them are Republican lawmakers.
It is dangerous, inherently filthy and must be stopped, say opponents, some of whom are Democrats who helped get the president elected.FULL STORY
Global warming has propelled Earth's climate from one of its coldest decades since the last ice age to one of its hottest - in just one century.
A heat spike like this has never happened before, at least not in the last 11,300 years, said climatologist Shaun Marcott, who worked on a new study on global temperatures going back that far.
Things are set to get much worse in the future.FULL STORY
Until recently, the main threat to the lives of sea butterflies, tiny snails with winglike lobes that float in ocean currents, had been the fish and birds that rely on them as an important source of food.
But a new, less visible menace is emerging, scientists say, as the parts of the ocean that the snails inhabit become more acidic as a result of the burning of fossil fuels by humans.
In a study published this month, a group of international scientists say they have discovered that the snails' shells are being severely eaten away by the rising acidity in an area of the Southern Ocean near Antarctica.
This is the first evidence of the changing chemistry of the oceans affecting living organisms in their natural environment, according to the scientists, whose paper was published Sunday in the journal Nature Geoscience.FULL STORY
When Siku the polar bear cub was introduced to the public late last year, he quickly became an Internet sensation, with his own Web and Facebook pages. But with fame often comes responsibility, and officials at Denmark's Scandinavian Wildlife Park said Siku would have an important burden to shoulder.
"Siku is going to be an ambassador for polar bears, for global warming," park director Frank Vigh-Larsen said in December.
Siku's official first day on the job was Monday, International Polar Bear Day.
Beginning Monday, the wildlife park, in cooperation with Polar Bears International and explore.org, a philanthropic media organization, will showÂ a daily live look-in at Siku from 9 a.m. to 11 a.m. ET at explore.org/siku and polarbearcam.com. You can also follow along again on Tuesday at CNN.com/live.
â€śWeâ€™re launching the Siku Cam on International Polar Bear Day, which is a day of action on climate change,â€ť Robert Buchanan, president and CEO of Polar Bears International, said in a press release. â€śOur goal with the Siku Cam is for people to fall in love with this little cub and become inspired to reduce their carbon footprint to help save arctic sea ice.â€ť
Siku is named after the environment of the polar bear, with siku being the most commonÂ word for sea ice in the Inuit language across the Arctic. The bears hunt on the sea ice,Â and as it disappears, so do opportunities for the bears to eat, the polar bear conservationists say.
The National Snow and Ice Data Center reports that the Arctic ice cover is near record lows, with the January 2012 Arctic ice cover the fourth lowest ever recorded.
"Based on the satellite record, before 2005 average January ice extent had never been lower than 14 million square kilometers (5.41 million square miles). January ice extent has now fallen below that mark six out of the last seven years," the NSIDC website says.
Many scientists blame global warming, fueled by carbon dioxide emissions, for the decline in sea ice. Polar Bears International says two-thirds of the estimated 20,000 to 25,000 polar bears in the wild could disappear by the middle of this century if carbon dioxide emissions are not cut.
â€śOur goal with the Siku Cam is to create awareness and inspire change,â€ťÂ Vigh-Larsen said in a press release. â€śAnd we are resolute that his image may only be used to advance those ends.â€ť
Siku's secret to saving ice may be melting hearts. Check out these pictures and try not to smile.
U.S. carbon emissions plunged during the 2007-2009 recession, and conservation efforts, a weak recovery and more use of natural gas will help keep those levels down for another 15 years, the Energy Department reported Monday.
Coal-fired power plants will remain the largest source of U.S. electricity throughout that period at nearly 40% of total output, the department projects in its annual report on the future of energy. But the Energy Information Administration's 2012 report finds that emissions of the greenhouse gases blamed for a warming climate are likely to remain below their 2005 levels until 2027.
"These projections reflect increased energy efficiency throughout the economy, updated assessments of energy technologies and domestic energy resources, the influence of evolving consumer preferences and projected slow economic growth," the agency's acting administrator, Howard Gruenspecht, said in a statement accompanying the report.
Overall, the share of fossil fuels as an energy source is expected to drop from 83% to 77% in 2035, the report states.FULL STORY
Editor's note: This post is part of theÂ Overheard on CNN.comÂ series, a regular featureÂ that examines interesting comments and thought-provoking conversations posted by the community.
"Oh great, next thing you know sharks will be walking on land and snapping peoples heads off."
Researchers say they've found 57 animals that are a cross between two genetically different but closely related species of shark off the coast of Australia. Scientists say it may be an indication the creatures are adapting to climate change.
Climate change is a bit controversial, and it always gets people talking. Many readers said they didn't believe that climate is the reason why hybrid sharks are being found, and some found the research flawed. There were also some who defended the study. FULL POST
Earth's Arctic ice is disappearing. In fact, the director of the National Snow and Ice Data Center told CNN last week that, within three decades, the top of the world would be practically ice free during the summer.
This week scientists are saying, not so fast. You might want to plan for that ice-free Arctic Ocean summer sail about 50 or 60 years from now.
That's because new computer models run by researchers at the National Center for Atmospheric Research in Boulder, Colorado, show the ice cap could just as easily expand as contract in periods of up to 10 years at a time.
â€śOne of the results that surprised us all was the number of computer simulations that indicated a temporary halt to the loss of the ice,â€ť NCAR scientist Jennifer Kay, the lead author of a new study on the Arctic ice, said in a news release.
The Arctic will be practically ice-free during the summer within three decades, the top U.S. ice observer says. But climate change could bring some good with the bad, he adds.
"I'm a climate scientist, but I'm also a realist on this," said Mark Serreze, director of the National Snow and Ice Data Center.
Pirates in the Indian Ocean are hijacking scientists' ability to collect data on climate change, researchers say.
Ann Thresher of the Commonwealth Scientific and Industrial Research Organization, in an e-mail interview Friday with CNN, said the threat of piracy has effectively shut off a critical portion of the Indian Ocean to research.
" This is affecting weather observations," Thresher said. "All data that feeds into measurements of climate change, ocean heat content, weather prediction and the prediction of ocean currents.â€ť
Former vice president and environmental advocate Al Gore sharply criticized President Obama's "failed" approach to global warming Wednesday.
"President Obama has thus far failed to use the bully pulpit to make the case for bold action on climate change," Gore wrote in a "Rolling Stone" article published online.
Although he acknowledged the political difficulty in taking a stand on the issue, Gore said the president has facts to back up his opinions.FULL STORY
OK, so apparently Australia's interior desert is overrun with more than a million camels that nobody owns.
Furthermore, Australia is looking for ways to reduce its agricultural greenhouse gas emissions under something known as the Carbon Farming Initiative.
How are these facts related, you say? We're glad you asked.
It seems these feral camels are known to, well, emit a lot of greenhouse gases, if you get our meaning.
In response, an Australian entrepreneur has submitted a proposal to the initiative to improve the air down under by shooting the dromedaries where they stand.
Or, as a headline on the Australian blog The Register concisely put it: FARTING DEATH CAMELS MUST DIE.
The Kingdom of Denmark is preparing to claim ownership of the North Pole, according to a Danish media report.
In a document leaked to the Danish newspaper Information, Denmark will ask the United Nations to recognize the North Pole as a geologic extension of Greenland, the vast Arctic island that is a Danish territory. Danish Foreign MinisterÂ Lene Espersen confirmed the annexation attempt, Information reported.
At its peak this winter, Arctic Ocean ice covered the smallest area since satellites started measuring it in 1979, researchers report.
Arctic sea ice probably reached its maximum extent for the year on March 7, at 5.65 million square miles, according to the University of Colorado-Boulderâ€™s National Snow and Ice Data Center.
That figure was 463,000 square miles (about the size of South Africa) less than the 1979-2000 average of 6.12 million square miles, and was about the same as in the winter of 2006, the center reported.
At its end-of-summer minimum in September, Arctic sea ice extent was the third-lowest since 1979.
Sea ice extent is the primary measure for assessing the condition of the ice cover, according to the National Oceanic and Atmospheric Administration.
The NOAA website has a time-lapse video showing how sea ice fluctuates and moves during winter.
â€śIâ€™m not surprised by the new data because weâ€™ve seen a downward trend in winter sea ice extent for some time now,â€ť National Snow and Ice Data Center scientist Walt Meier told Science Daily.
The seven lowest measurements of end-of-winter sea ice have been recorded in the last seven years, he told Science Daily.
CNN is going to the Arctic Circle â€“ and we want you to be part of the journey.
Our special correspondent, environmental activist Philippe Cousteau, grandson of acclaimed explorer Jacques Cousteau, will be accompanied by CNN producer Matt Vigil and cameraman Darren Bull. Theyâ€™ll battle the sub-zero elements and the threat of polar bears on a two-week mission to report on the work of the Catlin Arctic Survey.
The Arctic Circle that rings the North Pole is known as ground zero for climate change.
Weâ€™ll explore the work done by scientists who are collecting data and samples to find out how melting ice is impacting ocean currents, marine life and the climate and weather conditions around the world.
We want your questions for the CNN team and the scientists. You might want to know what itâ€™s like working in such extreme conditions, what challenges the CNN team faces, or more about the science theyâ€™re carrying out.
Comment here and weâ€™ll pass on your questions. They might become part of our coverage!
A mummified ancient forest unearthed north of the Arctic Circle may give researchers clues about what to expect as climate change again affects the polar region.
Joel Barker, a researcher at The Ohio State University, stumbled on the forest's remnants while camping last year on Canada's Ellesmere Island, just 500 miles from the North Pole.
The forest stood more than 1,000 miles north of the northernmost trees of today.
The trees and their branches, leaves, needles and roots were perfectly preserved from when they were buried in an avalanche 2 million to 8 million years ago, when the Arctic climate was getting colder, according to Canada's CBC News.
"Mummified forests aren't so uncommon, but what makes this one unique is that it's so far north. When the climate began to cool 11 million years ago, these plants would have been the first to feel the effects," Barker said in an OSU news release.
"And because the trees' organic material is preserved, we can get a high-resolution view of how quickly the climate changed and how the plants responded to that change."
He presented his findings Friday at the American Geophysical Union conference in San Francisco.
Barker next plans to study tree rings to learn how past climate conditions stressed plant life and predict how the Arctic ecosystem will respond to global warming.
Global warming isn't such a bad thing, a leading Russian climatologist told a conference last week.
The effects of rising temperatures will save on heating, increase farm production and open northern sea channels, said Vladimir Klimenko of the Moscow Power Engineering Institute, according to a Moscow Times article.
On the downside, several Siberian and Far Eastern Russian cities will have to be rebuilt, Klimenko conceded in his report to Russian and German scholars at a conference sponsored by the Alexander von Humboldt Foundation, a German organization that supports scientific study.
Regardless, "the reduction of heating alone outweighs all the negative results [of global warming] by many times," Klimenko said, according to Moscow Times. If the savings are used wisely, "then something can be achieved," he said.
Shorter heating seasons will save Russia 3 billion tons of oil by 2050 and 17 billion tons by 2150, Klimenko said.
At the same time, the growing season will lengthen and more land will be available for farming as northern climates warm up, he said.
Russia's Arctic coast will be ice-free for 105 days by 2100, and the Barents and Pechora seas will be open to navigation year-round, he predicted.
Andrei Shmakin of the Institute of Geography of the Russian Academy of Sciences told the Moscow Times that global warming will cause droughts in Russia's south, heavy snowfalls in Siberia and icebergs on the seas, negating any imagined benefits.
Polar bears are not native to Iceland. But they have been arriving on its shores as their homes melt inÂ the North Pole, a symbol of how climate change is affecting our world.
Or at least that's how Icelandic artist Bjargey Ă“lafsdĂłttir sees it, inspiring her contribution to the worldâ€™s first global climate art project.
"350 EARTH" is a series of giant public art displays around the planet to help raise awareness about the climate crisis before the UN Climate Meetings begin Monday in Cancun, Mexico, according to the event's organizers.
Each art installation is designed to be large enough to be visible from space, and the majority of the projects are being photographed by satellites operated by a Colorado-based company, Digital Globe.
The projects are intended to show the artists' perceptions of how climate change is affecting our world and offer visions of how to can solve the crisis.
In Iceland, Ă“lafsdĂłttir collaborated with a rescue team to create a polar bear out of hundreds of red tents at the base of a melting Icelandic glacier. The image is inspired by the Nazca lines of Peru and children's drawings, and it seeks to highlight diminishing glaciers and sea ice, as well as the uncertain future polar bears face.
"Art can convey in a different way than science the threat that climate change poses to our planet,â€ť 350.org founder and environmental author Bill McKibben said. â€śThe worldâ€™s best scientists have tried to wake up politicians to the climate crisis; now weâ€™re counting on artists to help."
TheÂ temperatures of Earth's largest lakes have risen in the past 25 years as a result of climate change, according to a new NASA study.
NASA used satellite data to measure the surface temperatures of 167 lakes worldwide and found an average warming rate of .81 degrees Fahrenheit per decade andÂ in some lakes, as much as 1.8 degrees Fahrenheit per decade, NASA said Tuesday.
The greatest increases were in the mid- to high- latitudes of the Northern Hemisphere, in a pattern consistent with changes associated with global warming, said Simon Hook, a scientistÂ with NASA's Jet Propulsion Laboratory in California.
"The key thing is itâ€™s an independent study that provides a new of piece evidence that warming's taking place; and it's made possible through a comprehensive view that the satellite data provides, by allowing us to look over the entire world, as opposed to a particular region," he said.
"From a scientific point of view, small differences in lake temperatures can have big change in a lake's ecosystem -Â a new fish species that people don't want, new plants; so from our point of view, what we want to do next is understand what theÂ impact of these changes is going to be on the lake's ecosystem."
Editor's Note: Learn about the top 10 CNN Heroes of 2010 and vote for the CNN Hero of the Year at CNNHeroes.com.
In a couple of weeks, mayors from cities around the world will convene at the World Mayors Summit on Climate in Mexico City to pledge their commitment to combating global warming.
Over half of the world's population now live in cities, writes CNNâ€™s Matthew Knight, and they have â€śan enormous power to demand of their local governments an improvement in their climate policy," says Anke Stoffregen, communications manager for ICLEI – Local Governments for Sustainability, a partner in the conference.
So what are mayors doing to make their cities more livable? What role are they playing in the struggle against global warming?
For the next couple of weeks, we're offering tiny things that you can do to make the world a better place.
Today's "Be A Hero" challenge: Hold cities accountable for climate change.
Record a question for the mayors on video and upload it to iReport or submit a text question in the comments here.
Then we'll get answers. The best questions will be asked at the conference, and the answers will be turned into highlights for CNN International TV and CNN.com/environment.