The environment beat was a busy one in 2015. The year started with US Senator James Inhofe tossing a snowball onto the Senate floor in a bizarre attempt to demonstrate that human-caused climate change is a hoax, and ended with 195 countries signing a landmark deal on reducing heat-trapping carbon emissions, just before a Christmas marked by springlike weather across eastern North America.

Between all that the world kept heating up. The past year is expected to top 2014 as the hottest on record. The Middle East, India, Europe, and southeast Asia sweltered under a summer heat wave that left thousands dead, while late fall brought flooding to southern India, killing hundreds more. Wildfires wracked Indonesia and the parched American West.

Meanwhile, coal and oil slumped worldwide as solar and wind power started cutting into electricity markets. The International Energy Agency says non-hydroelectric renewable energy will make up almost half of all new electric capacity built between now and 2020, and total renewables—including hydroelectric and biofuels—are expected to be about a quarter of global electric production by then. Environmentalists scored a victory when Obama rejected the Keystone XL pipeline that would have linked Canada's tar sands to the refineries of the US Gulf Coast, while oil companies got a win when the United States lifted a ban on exporting its own crude that dated back to the embargoes of the 1970s.

All that is to say that 2016 has some pretty big shoes to fill if it wants to be more environmentally eventful than last year. Is it up to the task? We asked some experts to fill us in on what we'll be talking about in our year-end pieces this December.

The same conditions that made 2015 all but certain to be the hottest year on record are expected to continue into 2016, raising the odds that global average temperatures could hit a third straight annual high.

"If that were to happen, it would be remarkable," Pennsylvania State University climatologist Michael Mann told VICE. "That suggests that we have entered a new realm where the climate change signal is so profound that we're literally breaking records each year." And while the Pacific warming trend known as El Nino is drawing a lot of the blame, Mann said, "The more important story is how climate change is exacerbating this El Nino to give us unprecedented weather impacts around the world."

Aside from the record-breaking temperatures, heat-trapping greenhouse gases keep building up in the atmosphere. Monthly carbon dioxide concentrations ran over 400 parts per million for most of 2015—the first time that's happened since regular records started being kept in the late 1950s, when the figure was around 315 ppm. Last year's extremes played out as a taste of what the world can expect if those levels continue to rise.

But Mann said what keeps him up at night is the possibility that scientists have underestimated the speed and extent that the climate is changing. For instance, he and others will be watching an unusual cold patch in the north Atlantic Ocean that's likely the result of fresh water running off melting Greenland glaciers. Mann said that's a possible indication that the ocean currents that bring warm water northward—and heat to western Europe—may be stalling.

"It bears a striking resemblance to the fingerprint that we predict for this slowdown," Mann said. If that continues, "We may be witnessing that particular climate phenomenon playing out in real time, way ahead of schedule. Models predict we shouldn't see this until later this century."

But 2015 wasn't all doom and gloom, and a number of events last year gave us reason for hope in 2016 and beyond. Pope Francis putthe weight of the billion-member Roman Catholic Church behind efforts to rein in carbon emissions, and Obama used a trip to an Arctic conference in Alaska to highlight the problems of a warming world.

Perhaps the most significant climate change action happened in Paris, when the world's top emitters put up plans to reduce their carbon output in hopes of keeping global warming down to 2 degrees Celsius (3.6 Fahrenheit) over pre-industrial times. Unfortunately, analyses by several groups say the carbon cuts promised in Paris only get us to 3 degrees C (5.4 F) at best.

"Right now, there is a disconnect between the goal of the agreement—to keep warming below 2 degrees and possibly try for 1.5 degrees—and the climate change commitments countries have put forward," Kelly Levin, senior associate for the climate program at the World Resources Institute, told VICE. "What we don't know is whether that will be aligned in the future. What we hope is the cooperation that we saw in Paris will only get stronger and stronger over time."

It's now up to the governments who signed the Paris pact to live up to their promises. The agreement calls for countries to review their progress every five years and beef up their efforts as needed.

And the changes can't come soon enough, said Rob Bailey, research director for the British think-tank Chatham House. Bailey told VICE that the gap between the Paris agreement and the emissions cuts needed to hit 2 Celsius amounts to about 16 billion metric tons of carbon dioxide emissions a year by 2030.

"That's the same as the current emissions of the US and China combined," Bailey said.

"The hope is that incrementally, in 5 year cycles, that gap will be narrowed, but we're a long way behind."

China and the United States are the top two sources of greenhouse gases, according to the IEA. Together, they made up about 14 billion of the 32-plus billion tons of carbon dioxide and other compounds released worldwide in 2013, the agency estimates. Still-developing China has pledged to peak and start reducing emissions by 2030, while the United States has promised to cut emissions by up to 28 percent below 2005 levels by 2025.

But despite its less-than-perfect ambitions, the climate pact has sent a clear signal that the world is willing to invest in a low-carbon future, Bailey said. And that's going to put added pressure on coal and oil, which hit the skids in 2015.

"I spoke to a former oil executive in December, and his words were: 'The genie is well and truly out of the bottle now,' " Bailey said. "The expectation is that even though the commitments that governments are putting forward aren't really sufficient, they actually mark the starting point of a global transition."

Saudi Arabia and the oil cartel OPEC continued their full-throttle game of chicken with their Western rivals, fueling a global glut that drove crude prices down to a fraction of their 2014 highs. After years of battling regulators and conservationists, Royal Dutch Shell returned to the seas off Alaska—only to walk away disappointed, writing off $7 billion in the process. And investors turned bearish on coal as utilities turned to cleaner-burning natural gas to run power plants and the wind and solar power started to extend into power grids.

China, which became the world's biggest coal consumer as it industrialized, is investing heavily in renewables as it tries to reduce both its carbon emissions and its horrific smog. And developing countries that are just now building an electrical grid are opting for "a more organic, decentralized model" of renewables, Bailey said.

"As other regions in the world also start to drive renewables further and further and deeper and deeper onto their grids in search of decarbonizing their power sectors and achieving their Paris commitments, this is a pattern that is going to play out globally," he said.

One of the biggest environmental disasters of 2015 had nothing to do with oil or coal, however. Over the summer, fires set to clear land for palm oil and paper plantations in the Indonesian rain forest raged out of control, wreathing much of the country and some of its neighbors in choking haze. On some days, they spewed more carbon dioxide and other heat-trapping gases into the sky than the entire US economy.

A reported crackdown by Indonesia's government on the people and companies implicated in the blaze appears to have stalled, Rolf Skar, forest campaign director for Greenpeace USA, told VICE. But a number of consumers don't want their money going to companies that burn down rainforests in countries like Indonesia or Brazil—and they're putting pressure on companies that do by boycotting their products.

"It's trending in the right direction, and we're seeing companies be surprised by it," Skar said. "It wasn't long ago that I was hearing from large companies in the US that Americans didn't care about these issues, and now they're scrambling to catch up."

They're doing that by trying to reassure consumers that they're good corporate citizens, he said—a trend he believes is likely to continue in 2016.

"You see a shift driven by some of the main players in a sector that people don't have to vote with their dollars every time they buy a burger or a bottle of shampoo," Skar said. "It just becomes standard business practices."

Speaking of voting, the world's No. 2 source of carbon emissions, the United States, has a big election coming up. Most leaders of the party that controls both houses of Congress and is seeking to regain the presidency still insist there's no such thing as man-made climate change. That's left the rest of the world wondering whether an incoming Republican administration in Washington would junk the Paris agreement, Bailey said.

"That would be a disaster for the international process," he said. A US renunciation of its Paris pledges "would make it almost completely impossible" to reach more ambitious goals in the future, he believes.

In the end, it's largely up to us. Who we vote for, what car or soap we buy, even what we choose to eat—Bailey suggests easing up on the meat, by the way—all have impacts that ripple across the globe. The sum of our decisions today will shape the world to come.

So pay attention, because right now our behavior is making the experts we talked to kind of nervous.

"We're seeing a lot of things that appear to be happening faster than the models predicted, and that raises the distinct threat that the impacts are going to be even worse than our current best estimates," Mann said. "Those are the kind of things that keep me up at night."

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