Earth is running a high fever. October 2015 was not only the hottest October on record, according to NASA, NOAA and the Japan Meteorological Agency, but it was the highest monthly anomaly in 135 years of temperature data. 2015 is now widely expected to end up as the hottest year on record, a title currently held by 2014.

Luckily, Earth also has a big doctor's appointment coming up: the highly anticipated Paris climate talks, where world leaders hope to reach a new treaty for curbing global climate change. Previous efforts like this have repeatedly failed to put a dent in rising temperatures, but there are a few reasons why this time might be different.

The Paris conference, which starts Nov. 30, has been eyed for several years as our last good chance to rein in the carbon dioxide emissions that fuel climate change. It's part of a long U.N. debate over CO2 dating back to the 1992 Earth Summit in Brazil, and it's meant to accomplish what diplomats couldn't at the hyped 2009 talks in Copenhagen: replace the Kyoto Protocol with a "longer-term vision." The goal is to stop warming before it exceeds 2 degrees Celsius (3.6 Fahrenheit), a level at which scientists say we can still avoid the most severe effects of climate change.

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Getting 195 countries to agree on anything is daunting, but these talks are especially tricky due to the economics and politics of carbon emissions. Despite a shared need to reduce CO2 levels in the atmosphere — which are now at 400 parts per million, higher than ever before in human history — many countries have spent years resisting CO2 limits over economic insecurities and international rivalries.

Yet as the dangers of climate change grow clearer, and clean energy grows cheaper, some of that discord is melting away. After the failure in Copenhagen six years ago, negotiators set 2015 as the target for "a protocol, another legal instrument or an agreed outcome with legal force" that applies to all 195 countries. Pressure has been mounting ever since, and hopes are once again high as the date approaches.

Of course, it's entirely possible the talks will break down in Paris, as they have so often elsewhere. But a few key factors have changed since 2009, altering the climate of negotiations just enough to make optimism seem reasonable again.

Barack Obama and Xi JinpingObama and Xi announce their countries' new climate deal on Nov. 12, 2014. (Photo: Feng Li/Getty Images)

U.S. and China

Of all the CO2 humans release every year by burning fossil fuels, more than 40 percent comes from these two countries. They're traditionally rivals at U.N. climate talks, often citing each other in their explanations for opposing CO2 limits.

But the tone has changed lately, as highlighted by a surprise announcement from U.S. President Barack Obama and Chinese President Xi Jinping in November 2014. The U.S. pledged to cut its CO2 emissions by 26 to 28 percent from 2005 levels within a decade, doubling the previous pace of cuts. And Xi said China's still-rising CO2 output will finally peak in 2030, offering the first specific date for that goal.

"We have a special responsibility to lead the global effort against climate change," Obama said at the time. "We hope to encourage all major economies to be ambitious — all countries, developing and developed — to work across some of the old divides, so we can conclude a strong global climate agreement next year."

That time is here, and the warming of U.S-Chinese climate relations does bode well. They couldn't make it work in Copenhagen, but their recent deal has raised hopes they'll bridge the gap between other developed and developing countries in Paris.

solar panelsThe cost of solar panels, like these in southern France, has fallen 70 percent since 2009. (Photo: Boris Horvat/Getty Images)


The recent growth of natural gas is already helping reduce U.S. emissions by displacing coal, which releases more CO2 than gas when burned. The EPA's Clean Power Plan will introduce the country's first CO2 limits for power plants, part of a broader shift away from coal for electricity. This month, the U.K. announced it will close all of its coal-fired power stations by 2025, switching mainly to gas instead.

And beyond fossil fuels, renewable energy has also been booming since 2009. The International Energy Agency (IEA) predicts renewables will represent the largest single source of electricity growth until 2020, and U.S. federal analysts expect that to remain the case through 2040. Better technology and more consumers means renewable energy is getting cheaper, too, especially solar and wind power. The total module cost of solar panels declined by about 60 percent from 2011 to 2014, for example, and is projected to fall another 30 to 40 percent in coming years.

Pope FrancisPope Francis' encyclical on climate change cast the issue in new light for many. (Photo: Andreas Solaro/Getty Images)


Obama and Xi aren't the only ones who've built momentum for the Paris talks. An array of public figures have rallied support over the past year, including scientists, politicians and celebrities as well as highly influential religious leaders.

In October, the Dalai Lama called climate change a human responsibility, saying "This is not a question of one nation or two nations. This is a question of humanity." And in June, Pope Francis made history by dedicating an encyclical to climate change, in which he said the issue requires "a new and universal solidarity." Hints of that were on display at last year's People's Climate March, which drew more than 400,000 people to New York and spawned 200 similar rallies around the world.

Before Copenhagen, only 27 countries had submitted national climate pledges for CO2 cuts, but more than 150 have already done so for Paris. That isn't everyone, but given the low bar set by past U.N. climate talks, it's progress. If those pledges are fully implemented, it would set Earth on a course to keep warming within 2.7 degrees Celsius by 2100, according to Climate Action Tracker. And while that's not quite the target of 2 degrees, it beats the 3.1 degrees projected a year ago.

memorial at Eiffel TowerCrowds gather in Paris to honor the victims of this month's terrorist attacks. (Photo: Christopher Furlong/Getty Images)


Following the Nov. 13 terrorist attacks in Paris, authorities decided to cancel some large marches that were planned for the climate talks due to security concerns. But as French Foreign Minister Laurent Fabius said in a statement Nov. 14, there was no question of postponing the negotiations themselves: "This is an absolutely essential step against climate change and of course it will take place."

Many have echoed that sentiment, arguing the climate talks are not only too urgent, but that they offer a fitting rebuke to the ideology of terrorists. World leaders uniting for common good "will be an important statement by the world that no one will interrupt the business of the global community — certainly not despicable, cowardly acts of terror," U.S. Secretary of State John Kerry said in Paris this week.

Christiana Figueres, the U.N. official in charge of climate talks, agrees. Referring to the conference by its official acronym (COP21, for "21st Conference of Parties"), she recently suggested on Twitter that now is an apt time for pulling together.

The attacks have already inspired broad international solidarity, even helping ease recent tension between Russia and the West, and some observers expect that to have a "tonal" effect on climate negotiations. "The resolve of world leaders is going to be redoubled to gain an agreement and show that they can deliver for populations around the world," a former aide to President Bill Clinton tells Politico. "The likelihood for a successful agreement has only increased because of these attacks."

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.