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Editor’s Note: CNN Opinion columnist John D. Sutter is reporting on a tiny number – 2 degrees – that may have a huge effect on the future. He’d like your help. Tell him how you fear climate change could affect you personally, and you could be part of CNN’s coverage.

You can also subscribe to the “2 degrees” newsletter or follow him on Facebook, Twitter and Instagram. He’s jdsutter on Snapchat. You can shape this coverage.

(CNN) —  

Four months and 1,300 miles ago, Erlend Moster Knudsen started running. Starting line: Arctic Norway. Destination: a U.N. climate change summit in Paris.

I met the aerobically inclined climate scientist on the road last week in northern France. He ran (he is on his fourth pair of shoes) while I biked behind him, struggling to keep up.

Freezing rain and snow pelted our faces as we traveled past misty fields, tile-roofed villages and Edward Scissorhands shrubbery. The whole thing was exhausting, but Knudsen, a 29-year-old with sandy hair, a scraggly beard and a Spandex-meets-DayGlo wardrobe, wasn’t fazed by any of it. He seemed to thrive on the Fargo-like conditions.

“I love the snow!” he said, darting up a hill.

These are difficult times, as I don’t need to remind you. ISIS is on everyone’s mind, especially here in France, where at least 130 people were killed in a recent terror attack. Fear cloaks this country like a persistent fog, and many observers worry that the threat of terror will infect the upcoming U.N. climate change summit, called COP21, which begins Monday in a Parisian suburb.

But spending a day with Knudsen gave me a healthy dose of optimism in addition to sore thighs. There’s ample reason to believe the U.N. talks will help shove the world off of fossil fuels and toward a cleaner future. All we have to do is what Knudsen recommends: Put one foot in front of the other, remember why we’re here, and carry with us an important collection of stories.

Another form of terror

Like Knudsen’s past several months, my year has been a prelude to the Paris summit.

But with, you know, less running.

I’ve spent most of 2015 taking your questions about climate change and turning them into stories as part of CNN’s Two° series. If you’ve been reading along, you know that 2 degrees Celsius is the number at the center of the upcoming Paris negotiations.

Pretty much every country in the world has signed a treaty saying that 2 degrees Celsius of warming, measured since the Industrial Revolution, is all we can tolerate. Cross that line, and we’re expected to supercharge droughts, make storms more intense, commit low-lying islands to a watery death as seas rise, push millions more into poverty and put many plants and animals at risk of extinction. It’s not an exact trigger point (1.9 degrees of warming is monumentally less catastrophic than 2.1 degrees, for instance), but diplomats had to draw a line in the sand.

And everyone agrees that 2 degrees of warming is too much.

Yet we don’t act like it. We’ve already warmed the climate about 1 degree Celsius. We’re essentially locked into 1.5 degrees of warming based on all of the pollution we’ve pumped into the atmosphere, primarily by burning fossil fuels for heat and electricity. And pollution-reduction pledges logged by more than 140 countries in advance of the Paris talks promise to slow warming only to an estimated 2.7 degrees by the end of the century.

Signs of warming abound: 2015 promises to be the hottest year on record; a heat wave in India killed 2,300 people this summer; air pollution is killing far more people all the time; floods in the United States likely have been made worse by higher-than-normal tides; there’s evidence that a drought in Syria helped create conditions that led to the rise of ISIS.

We humans, however, are excellent at ignoring long-term global problems – like climate change. We focus on what’s right in front of us. The recent terror attacks are tragic, and many lives will never be the same because of them. They should not be minimized.

But climate change is another form of terror – and it’s one we’re wreaking on ourselves.

Can we avoid climate apocalypse?

’Worst-case scenario’

Being pessimistic about that is understandable, especially since previous attempts to use international politics to fix the climate problem largely have failed.

Before I spent a day with the running climate scientist, I spoke with Yvo de Boer, former head of the United Nations Framework Convention on Climate Change, the group that gets diplomats together to talk about the climate crisis. De Boer famously was moved to tears when a previous round of climate negotiations started to collapse.

“There’s a certain risk that political ambition trips over bureaucratic complexities,” he told me by phone. “There is this 50-odd-page document, which still contains many areas of disagreement. That stands between the beginning of the Paris conference and a successful outcome at the end. Very often at these conferences, the devil is in the detail.

“My worst-case scenario,” he continued, “is the one that we seem to see at almost every climate conference, which is that it needs to go into significant overtime.”

With 2 degrees on the horizon, there’s no time for delay.

Recently, there was much optimism ahead of the Paris climate talks. China and the United States, the world’s two biggest polluters, have pledged significant cuts in carbon pollution. The Obama administration rejected the Keystone XL pipeline, which was a symbolic boost for efforts to get the world off of dirty fuels like oil and coal. The Pope has been helping people finally see climate change as a moral crisis, one that will hit the world’s poor the hardest. And solar power is getting much cheaper.

But along came ISIS. Now, massive public demonstrations at COP21 have been canceled, and a malaise hangs over the entire process.

COP21: Police, protestors clash in Paris as world leaders arrive

Knudsen, the running climate scientist, thought about abandoning his Pole to Paris journey because of the terror attacks on November 13. He canceled public events he’d planned in Brussels, and he knows that his arrival in Paris probably will