When a devastating heat wave hit India this year, it killed more than 2,500 people and melted the pavement of New Delhi's streets. In California, where an ordinary year sees mountain snow pile six-feet-deep or more — supplying much drinking water — surveyors had nothing to measure in some spots but bare grass.

By the time 2015 is over, it is certain to go down as the warmest year on record. But if the heat was unsettling, it also set the tone for many of the headlines that defined the year, even when they ranged far beyond matters of extreme weather or changing climate.

From searing tragedies to blistering campaign rhetoric to boiling crises, the top news of 2015 made for one of the hottest years in recent memory, literally and figuratively.

In a year that visited carnage upon worshippers who opened their church to a stranger in Charleston, South Carolina, and fans who gathered on a Friday night for a rock concert in the center of Paris, the news left the public with little refuge. Headlines spotlighting bloody clashes for control of Syria and the angry debate over whether to take in those fleeing the violence, radiated heat, but often not much light.

Instead, many of the year's biggest news stories fueled a narrative of intensifying conflict.

It began just days into the new year, when two brothers who called themselves members of al-Qaida forced their way in to the offices of Paris humor magazine Charlie Hebdo and a nearby Jewish market, gunning down 17.

"Our great and beautiful France will never break, will never yield, will never bend," President Francois Hollande told those gathered days later to honor two police officers killed in the assault. But by year's end, France was hardly alone in its vulnerability.

In the U.S., the tensions of the old year bled into the new one. In Baltimore, the April death of Freddie Gray, a black man tossed in the back of a van by police officers, set off rioting whose destruction echoed that in Ferguson, Missouri, the previous year. In North Charleston, South Carolina, Tulsa and Chicago, police shootings of black men prompted resignations and indictments. A protest at the University of Missouri over racial discrimination forced the departure of the school's president.

In June, a young man invited into a Bible study at the Emanuel African Methodist Episcopal Church in Charleston, opened fire, killing nine. The shooter was white. All the victims, including the congregation's pastor, were black, killed in an attack police said was motivated by racial hatred.

But, along with the grief, the alleged killer's veneration of the Confederate flag ignited pained debate over the Civil War banner's place in modern Southern life.

"I cannot believe that we do not have the heart in this body to do something meaningful such as take a symbol of hate off these grounds," Jenny Anderson Horne, a Republican state representative, said in an emotional speech delivered on the chamber's floor. "I have heard enough about heritage."

The flag came down, at least in South Carolina. But the heat did not let up.

In July, a Kuwait-born engineer shot and killed four Marines and a sailor at a military recruiting center and a U.S. Navy Reserve center in Chattanooga, Tennessee.

In August, a live morning news broadcast erupted in gunfire when a man fired from the Roanoke, Virginia, station more than two years earlier killed a cameraman and a reporter — and filmed himself committing the crime.

In October, a 26-year-old student at a community college outside Roseburg, Oregon, shot and killed a professor and eight fellow students during their writing and English classes.

In November, three people were gunned down at a Planned Parenthood clinic in Colorado Springs. The alleged gunman, apprehended after a five-hour standoff, told authorities: "No more baby parts."

But as politicians and advocates clashed over abortion, guns, race and religious extremism, there was little, if any, movement toward resolution.

Instead, with 17 Republicans initiating bids for the presidency, campaign rhetoric often verged on explosive.

Billionaire developer Donald Trump was almost always the loudest, starting when he launched his campaign in June at the gleaming Manhattan office tower he named for himself, by assailing Mexican immigrants.

"They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people," he said.

The remark provoked anger among Latino voters. But Trump did not let up, attacking rivals, particularly Jeb Bush, whose status as an early favorite faded amid the criticism.

Others candidates, too, embraced tough talk.

After the Supreme Court legalized same-sex marriage in June, former Arkansas Gov. Mike Huckabee said the jailing of a Kentucky county clerk for refusing to issue marriage licenses to gay couples amounted to "the criminalization of her faith and the exaltation of the faith of everyone else who might be a Fort Hood shooter or a detainee at GITMO."

And with anxieties rising about how to confront Islamic State militants in Syria, Texas Sen. Ted Cruz was all-in.

"We will carpet bomb them into oblivion," he told Iowa voters in December. "I don't know if sand can glow in the dark, but we're going to find out."

The race for the Democratic nomination, meanwhile, sharpened attention on front runner Hillary Clinton. Revelations that she used a private email server for her communications as secretary of state, most notably during the 2012 terrorist attack on a U.S. diplomatic compound in Libya, dogged her campaign.

But after testifying for more than eight hours before a Republican-led investigatory committee in October, Clinton gained in polls and a potential rival, Vice President Joe Biden, stepped aside.

The heat of the campaign season was paralleled by the weather, itself. Global temperatures hit records in eight of the year's first 10 months, with scientists pointing to a potent El Nino pattern combined with accelerating human-caused climate change.

"This is all bad news for the planet," said Michel Jarraud, secretary-general of the United Nations' weather agency, in announcing that 2015 would almost certainly break the annual record for warmth set just last year.

But the most closely read statement on climate change came not from a scientist but Pope Francis — who, in fact, is trained as a chemist.

"Doomsday predictions can no longer be met with irony or disdain," he said in a June encyclical, pleading for action. "The pace of consumption, waste and environmental change has so stretched the planet's capacity that our contemporary lifestyle, unsustainable as it is, can only precipitate catastrophes..."

Francis sounded that message again when he visited the U.S. in September, taking the floor of the House of Representatives. Officials from nearly 200 countries followed through in a December conference outside Paris, culminating years of negotiation with a first-of-its-kind pact to fight climate change by reducing greenhouse gas pollution.

That step toward resolution, though, was an anomaly in a climate of rising tension.

Month after month, migrants surged into Europe from the roiling Middle East, with scores drowning in the Mediterranean, packing refugee camps as countries struggled to respond.

In Tunisia, terrorists killed 22, mostly European tourists, at a museum in March and another 39 tourists at a beach resort in June.

In October, a Russian airliner crashed in the Egyptian desert, killing 224, and a bomb was blamed. A pair of suicide bombers killed more than 40 people in Beirut in November. The Islamic State group claimed responsibility for that attack and for downing the jet, contradicting Egyptian investigators' assertion that there was no indication of any "illegal or terrorist act."

The threat, though, would not stay contained to the Middle East. On a Friday night six weeks before Christmas, eight Islamic State terrorists, wielding rifles and suicide belts, killed 130 people in closely coordinated assaults around Paris.

"This attack is the first of the storm and a warning to those who wish to learn," the group said in a communique distributed via social media.

The attack spurred a cross-border manhunt. But it simultaneously refocused attention on the civil war that has enveloped Syria since 2011, killing more than 250,000 and uprooting millions, creating a vacuum filled by Islamic extremists and, increasingly, drawing governments from far beyond the region into a vortex of conflicting agendas.

Just three weeks after Paris, Syed Farook, and his wife, Tashfeen Malik, masked and clad in tactical vests, opened fire on his co-workers in San Bernardino, California as they gathered for a holiday meeting, killing 14 and wounding 21. The couple, radicalized Muslims, were inspired by ISIS, investigators said.

The attack inflamed already intense debate over whether to allow the entry of Syrian refugees and how to confront Islamic extremism. President Obama sought to quell public distress with an Oval Office address calling for resolve and deliberate action.

"Let's not forget that freedom is more powerful than fear," he said.

But as the threat of terrorism, the complexities of war and misgivings about Islam continued to stoke the headlines, the notion that cooler heads might prevail was running up hard against anxiety.