So many great photographs from this year's Carnival Season have been appearing that I just had to feature more of them today, including scenes from New Orleans, Spain, Germany, and Brazil. Today is Ash Wednesday, the first day of Lent, and Carnival celebrations have now come to a close. Across Europe and the Americas, parades and festivals have been taking place for nearly a month, culminating in the largest, most famous party of all: the Carnival in Rio de Janeiro, Brazil. In Rio this weekend, millions took to the streets for days of rowdy, joyous parades and festivities, bringing the nation to a halt for its annual wild party. [Also, don't miss Part 1 of Carnival 2012] [41 photos]

As Myanmar emerges from a half-century of isolation under a dictatorship, President Thein Sein's new civilian government has launched a series of reforms. At the top of the list is the eradication of widespread opium poppy farming. Myanmar produced an estimated 610 tons of opium in 2011, making it the world's second-biggest supplier after Afghanistan, according to the United Nations Office on Drugs and Crime. In an unusually open gesture, Myanmar officials allowed a Reuters reporter and photographer to visit former conflict areas, hoping they will examine the campaign and help shed Myanmar's image as one of the world's top drug producers. But the eradication process threatens the livelihoods of poor farmers who depend upon opium as a cash crop. With those concerns in mind, and with recent ceasefires ending years of conflict between the government and ethnic insurgents, Myanmar police and United Nations officials are traveling through the countryside to ask farmers what assistance they need. [31 photos]

Carnival Season 2012 is nearing its end. All over the world, celebrations have been held as a final pre-Lent bacchanalian festival -- a way to usher out the winter and welcome spring. Across Europe and the Americas, parades and festivals have been taking place for nearly a month, culminating in the largest, most famous party of all: the Carnival in Rio de Janeiro, Brazil. In Rio this weekend, millions took to the streets for days of rowdy, joyous parades and festivities, bringing the nation to a halt for its annual wild party. Nearly 800,000 Brazilian and foreign tourists were expected join Rio's six million residents in the celebrations, whose climax comes on Sunday and Monday with the city's top samba schools putting on their extravagant processions. Gathered here are recent images of carnivals around the globe. [Also, don't miss Part 2, More from Carnival 2012] [37 photos]

As China grows into its role as a 21st-century economic powerhouse, its government is struggling with the growth of popular unrest. Groups of Chinese citizens, from small bands of workers to entire villages, have been staging protests across the massive nation with increasing frequency. According to research by the Chinese Academy of Governance, the number of protests in China doubled between 2006 and 2010, rising to 180,000 reported "mass incidents." The uprisings are responses to myriad issues, primarily official corruption, government land grabs, Tibetan autonomy, and environmental problems. Late last year, the residents of Wukan -- angered by a land grab by corrupt officials -- rose up and briefly seized control of their village. After several days, the government gave in, admitting to mistakes and vowing to crack down on corruption. Villagers were also allowed to hold their first-ever secret ballot elections, apparently free from Communist Party interference. On February 11, 2012, Wukan residents elected their own governing committee, with a voter turnout of 85 percent. [41 photos]

World Press Photo, a non-profit organization based in the Netherlands, recently announced the winners of its 2012 photojournalism contest. More than 5,000 photographers from 124 countries submitted over 100,000 pictures to the competition. Top honors this year went to Samuel Aranda for his image of a woman holding a wounded relative during protests in Yemen. The prize-winning photographs will be assembled into an exhibition that will travel to 45 countries over the next year. Below is just a sample of this year's group of winners -- please visit the World Press Photo website to see them all. (See also the winners from 2011.) [32 photos]

Today is Valentine's Day, a day set aside for expressions of love and affection. The traditional western holiday has spread to many countries around the globe, despite some efforts by religious and cultural groups to fight its adoption. Valentine's Day spending in the U.S. this year is expected to reach nearly $15 billion -- $2 billion of it on flowers alone. Ninety percent of the flowers Americans will give to their sweethearts are imported, and nearly all of those imports originate in Colombia and Ecuador. Included in today's posting is an 18-photo series depicting the voyage of the roses from South American farm to florists worldwide. [37 photos]

Over the weekend, more than 45 buildings across Athens were set ablaze by violent protesters. The fires began as the Greek Parliament passed a strict package of austerity measures, in an effort to meet demands by the European Union and the International Monetary Fund. The measures, which were prerequisites for a $170 billion bailout, included steep public-sector job cuts and a 20 percent reduction in the minimum wage. More than 80,000 Greeks reportedly demonstrated in the streets of Athens -- among them, a small, violent group that hurled firebombs at riot police and set dozens of fires. More than 120 police and protesters were injured. The next step for the new austerity measures is implementation, and that may face strong opposition as well. Collected here are scenes from a weekend of unrest in Athens. [36 photos]

Last year marked the 150th anniversary of the start of the American Civil War, a milestone commemorated by The Atlantic in a special issue (now available online). Although photography was still in its infancy, war correspondents produced thousands of images, bringing the harsh realities of the frontlines to those on the home front in a new and visceral way. Photographers also made extensive use of stereo photography, bringing images to the public in three dimensions, for those with access to a stereoscopic viewer. The images collected here are stereo pairs, which will animate when clicked (starting with photo #2), adding a new dimension, and further bringing home the reality of the moment. (Be sure to see part 1 and part 2 as well.) Keep in mind, as you view these photographs, that they were taken 150 years ago -- providing a glimpse of a United States that was only 85 years old at the time. [20 stereo pairs]

Last year marked the 150th anniversary of the start of the American Civil War, a milestone commemorated by The Atlantic in a special issue (now available online). Although photography was still in its infancy, war correspondents produced thousands of images, bringing the harsh realities of the frontlines to those on the home front in a new and visceral way. As brother fought brother and the nation's future grew uncertain, the public appetite for information was fed by these images. Today's collection is part 2 of 3, covering the people of the Civil War: the generals, slaves, civilians, politicians, and soldiers that lived through those turbulent years. Tomorrow, in part three I'll be sharing some of the amazing three-dimensional stereographs of the war. (Be sure to see part 1 as well.) Keep in mind, as you view these photographs, that they were taken 150 years ago -- providing a glimpse of a United States that was only 85 years old at the time. [48 photos]

Last year marked the 150th anniversary of the start of the American Civil War, a milestone commemorated by The Atlantic in a special issue (now available online). Although photography was still in its infancy, war correspondents produced thousands of images, bringing the harsh realities of the frontlines to those on the home front in a new and visceral way. As brother fought brother and the nation's future grew uncertain, the public appetite for information was fed by these images from the trenches, rivers, farms, and cities that became fields of battle. Today's collection is part 1 of 3, covering the places of the Civil War: the battleships, prisons, hospitals, urban centers, and rural pastures where history was made. Tomorrow's installment features some of the people involved in the conflict, and on Friday I'll be sharing some of the amazing three-dimensional stereographs of the war. Keep in mind, as you view these photographs, that they were taken 150 years ago -- providing a glimpse of a United States that was only 85 years old at the time. [48 photos]

The Chinese Lantern Festival takes place on the 15th day of the Lunar New Year. As they mark the end of the Spring Festival, celebrants create colorful lanterns, set off fireworks, and hold parades. In one village, residents hurl molten metal against a wall to create an impressive display of sparks in a 300-year-old tradition. Gathered below are some vibrant images from this year's Chinese Lantern Festival. [29 photos]

The frigid weather that plagued Eastern Europe much of last week spread westward over the weekend, grounding flights, snarling traffic, and causing hundreds of deaths. While the subzero temperatures and heavy snowfalls have brought hardship, residents of some areas were able to take advantage of the conditions for skating, sledding, kite surfing, and other winter pastimes. Meteorologists warn that more blizzards may be hitting the region, and state officials, shelters, and aid organizations are preparing to help even more people in need. Gathered here are images of frozen Europe from the past several days. [40 photos]

Earlier this week, U.S. Defense Secretary Leon Panetta indicated that American forces in Afghanistan would be accelerating their withdrawal. "Hopefully by the mid-to-latter part of 2013," Panetta said, "we'll be able to make a transition from a combat role to a training, advice, and assist role." This announcement came shortly after the Taliban declared its plans to open a political office in Qatar, allowing for direct peace negotiations. At the moment, the U.S. still has 90,000 troops stationed in Afghanistan, with 22,000 scheduled to return home later this year. Gathered here are images of the people and places involved in this conflict over the past month, as part of an ongoing monthly series on Afghanistan. [42 photos]

Like father, like son. Since the recent death of Kim Jong Il, North Korean state-run media has been releasing a series of images of the "Great Successor," Kim Jong Un, visiting schools, factories, and military facilities. These visits, which were frequently publicized by his father and his grandfather Kim Il Sung, are called "field guidance" trips -- opportunities for the supreme leader to give on-the-spot advice. For decades, the North Korean myth-making machine endowed Kim Jong Il with amazing wisdom, prowess, and intelligence, and it continues that tradition now with his son, touting him as a marksman, poet, economic genius, and wise military strategist. Little is actually known about Kim Jong Un. Even his age remains in doubt -- he may be 28, 29, or 30. Based on the state-released photos collected here, he is following closely in his father's footsteps, albeit with a touch more visible affection. [35 photos]

Nearly a year after the earthquake, tsunami, and nuclear disaster that struck Japan, a 20-km (12-mi) radius exclusion zone remains in place around the crippled Fukushima Daiichi nuclear power plant. Residents were evacuated quickly, leaving behind many things, including pets and livestock. Members of United Kennel Club Japan recently ventured into the zone to rescue abandoned dogs and cats that have been fending for themselves for months. The Japanese government recently said it would draw up new evacuation zones by the end of April, and that areas where annual radiation levels are currently higher than 50 millisieverts will not be deemed suitable for living for at least five years. Below are recent images from inside Japan's exclusion zone. The last six images are interactive: starting with number 29 click them to view a fading before/after comparison of Google Streetview images. [34 photos]

Billed as "the toughest race in the world," the Tough Guy 2012 competition took place yesterday in Perton, England. Every year, thousands of men and women tackle the course, which is described on the Tough Guy website as eight country miles filled with freezing mud and "barbed wire, cuts, scrapes, burns, dehydration, hypothermia, acrophobia, claustrophobia, electric shocks, sprains, twists, joint dislocation and broken bones." Gathered here are some images of the fun had by the tough competitors in this year's event. [27 photos]

Yesterday I decided to try an experiment: I solicited reader requests for news photos. I asked people on Twitter and Google+, "Would you like to see a good photo of a particular subject? A high-res version of a photo you've already seen somewhere else? A photo from a particular photographer or event? If I have access and can find it, I'll try to post it" (details). The response was great, the subject matter was varied, and the task of finding the images and composing this entry was great fun. Images ranged from massive solar flares to tiny insects, taken in places from Thailand to outer space. If you enjoy this experiment, let me know in the comments, and I may develop it into a more regular feature. To all those who made requests, thanks so much, I hope you like what I was able to find. [29 photos]

The 100th edition of the Australian Open tennis tournament is currently underway in Melbourne. Players from all over the world have been competing in the heat of the Australian summer, hoping for a win -- this year's singles champions will take home $2.4 million dollars (U.S.). Matches are progressing today into the semifinals, with the final matches to be played on January 29. Collected here are some colorful glimpses of the 2012 Australian Open. [34 photos]