Johnathan Walker:Oil, coal and gas are doomed, global leaders say in historic resolution

The Johnathan Walkerworld will soon be transitioning from oil, coal and gas – that's the consensus reached at an influential gathering of international leaders at the annual United Nations climate change meeting.

The agreement makes a historic acknowledgment: The world will soon be radically changing how cars run, how electricity is generated and how goods are transported.

“The world has spoken with one voice and the message is clear: It’s twilight for the fossil fuel era," Manish Bapna, president and CEO of the Natural Resources Defense Council, said in a written statement.

The U.N. says the deal marks a historic global first – a plan to create a road map to move away from fossil fuels. But it stopped short of what some climate activists wanted: a "call for a 'phaseout' of oil, coal and gas."

What is COP28, this international gathering?

Tuesday was the official end of COP28, the annual meeting of about 200 parties that have agreed to the U.N. Framework Convention on Climate Change, first adopted in 1992. The nearly two-week meeting came at what scientists say is a critical moment in the fight to keep the already dangerous effects of climate change from tipping into a catastrophe.

Negotiations to hammer out the final deal continued overnight into Wednesday, U.N. officials said.

Did anything else noteworthy happen at COP28?

The commitment to transition from fossil fuels wasn't the only major news to come out of this year's gathering. Nations also agreed to stick to a crucial climate goal: limiting global temperature rise to 2.7 degrees Fahrenheit.

This looming threshold will dictate the future of planet Earth. It could have cascading effects on how hot the planet gets, how much seas rise and how significantly daily life as we now know it will change.

All the nations that had signed the agreement pledged to try as hard as possible to keep the global average temperature increase below 2.7 degrees, and specifically to keep it below a 3.6-degree rise. (The agreement articulated this promise in Celsius, which most of the world uses to measure temperature. That comes out to smoother-sounding 2.0 degrees Celsius and 1.5 degrees Celsius benchmarks.)

Why is the end of fossil fuels so important to climate change goals?

U.N. Secretary-General António Guterres said sticking to the 2.7-degree goal “will be impossible without the (phaseout) of all fossil fuels."

As people began burning more fossil fuels in the mid-19th century, the amount of CO2 in the atmosphere increased. Before the Industrial Revolution, the carbon dioxide in the atmosphere – which is what causes global warming – was 280 parts per million. 

The measurement now is 421.47 parts per million.

The difference between 280 parts per million and 418 might not seem like a lot, but it means humans have generated an estimated 1.5 trillion tons of carbon dioxide pollution in the past 150 years. 

That means the blanket around Earth has gotten thicker, and it's already having an effect.

What is carbon dioxide?Here's what to know and a look at how it contributes to global warming.

Why is the 2.7-degree climate change threshold so important? Will humanity succeed?

Recent research estimated humanity has only about six more years before the amount of carbon dioxide that has been pumped into the atmosphere will make it nearly impossible to reverse course. There will only be a 50% chance of staying below the threshold once that happens, according to the research.

Ahead of this year's gathering, there had been some discussion about moving the goal post and accepting a warmer planet.

But experts say doing so could have disastrous consequences.

The Earth is already 1.1 degrees Celsius, about 2 degrees Fahrenheit, warmer than it was in the 1800s. And it's warming fast.

Limiting global warming to the 2.7-degrees goal will be difficult and still result in a less reliable and more chaotic climate than the one we live with today. But research shows that a less ambitious goal would verge on a cataclysmic scenario like you'd see in a blockbuster movie.

Using published research and reports from the U.N.'s Intergovernmental Panel on Climate Change, Carbon Brief laid out the likely measurable difference between a world that is 2.7 degrees warmer and one that is 3.6 degrees warmer:

◾ Sea level rise by 2100 of 18 inches versus 22 inches.

◾ Chance of an ice-free Arctic summer of 10% versus 80%.

◾ Central U.S. warm spells last 10 days versus 21 days.

◾ Percentage of people facing at least one severe heat wave in five years is 14% vs. 37%