What's the Difference Between 1.5°C and 2°C of Global Warming?

Flames rise as a wildfire burns in the village of Galatsona, on the island of Evia, Greece, August 9, 2021. (Reuters)
Flames rise as a wildfire burns in the village of Galatsona, on the island of Evia, Greece, August 9, 2021. (Reuters)
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What's the Difference Between 1.5°C and 2°C of Global Warming?

Flames rise as a wildfire burns in the village of Galatsona, on the island of Evia, Greece, August 9, 2021. (Reuters)
Flames rise as a wildfire burns in the village of Galatsona, on the island of Evia, Greece, August 9, 2021. (Reuters)

Over and over at the UN climate summit in Glasgow, world leaders have stressed the need to limit global warming to 1.5 degrees Celsius.

The 2015 Paris Agreement commits countries to limit the global average temperature rise to well below 2°C above pre-industrial levels, and to aim for 1.5°C.

Scientists have said crossing the 1.5°C threshold risks unleashing far more severe climate change effects on people, wildlife and ecosystems.

Preventing it requires almost halving global CO2 emissions by 2030 from 2010 levels and cutting them to net-zero by 2050 -- an ambitious task that scientists, financiers, negotiators and activists at COP26 are debating how to achieve and pay for. But what is the difference between 1.5°C and 2°C of warming?

Reuters asked several scientists to explain:

Where are we now?
Already, the world has heated to around 1.1°C above pre-industrial levels. Each of the last four decades was hotter than any decade since 1850.

"We never had such a global warming in only a few decades", said climate scientist Daniela Jacob at the Climate Service Center Germany. "Half a degree means much more extreme weather, and it can be more often, more intense, or extended in duration."

Just this year, torrential rains flooded China and Western Europe, killing hundreds of people. Hundreds more died when temperatures in the Pacific Northwest hit record highs.

Greenland saw massive melting events, wildfires ravaged the Mediterranean and Siberia, and record drought hit parts of Brazil.

"Climate change is already affecting every inhabited region across the globe," said climate scientist Rachel Warren at the University of East Anglia.

Heat, rain, drought
More warming to 1.5°C and beyond will worsen such impacts.

"For every increment of global warming, changes in extremes become larger," said climate scientist Sonia Seneviratne at ETH Zurich.

For example, heatwaves would become both more frequent and more severe.

An extreme heat event that occurred once per decade in a climate without human influence, would happen 4.1 times a decade at 1.5°C of warming, and 5.6 times at 2°C, according to the UN climate science panel (IPCC).

Let warming spiral to 4°C, and such an event could occur 9.4 times per decade.

A warmer atmosphere can also hold more moisture, resulting in more extreme rainfall that raises flood risks. It also increases evaporation, leading to more intense droughts.

Ice, seas, coral reefs
The difference between 1.5°C and 2°C is critical for Earth's oceans and frozen regions.

"At 1.5°C, there’s a good chance we can prevent most of the Greenland and west Antarctic ice sheet from collapsing," said climate scientist Michael Mann at Pennsylvania State University.

That would help limit sea level rise to a few feet by the end of the century - still a big change that would erode coastlines and inundate some small island states and coastal cities.

But blow past 2°C and the ice sheets could collapse, Mann said, with sea levels rising up to 10 meters (30 feet) - though how quickly that could happen is uncertain.

Warming of 1.5°C would destroy at least 70% of coral reefs, but at 2°C more than 99% would be lost. That would destroy fish habitats and communities that rely on reefs for their food and livelihoods.

Food, forests, disease
Warming of 2°C, versus 1.5°C, would also increase the impact on food production.

"If you have crop failures in a couple of the breadbaskets of the world at the same time, then you could see extreme food price spikes and hunger and famine across wide swathes of the world," said climate scientist Simon Lewis at University College London.

A warmer world could see the mosquitoes that carry diseases such as malaria and dengue fever expand across a wider range.

But 2°C would also see a bigger share of insects and animals lose most of their habitat range, compared with 1.5°C, and increase the risk of forest fires - another risk to wildlife.

'Tipping points'
As the world heats up, the risk increases that the planet will reach "tipping points", where Earth’s systems cross a threshold that triggers irreversible or cascading impacts.

Exactly when those points would be reached is uncertain.

Droughts, reduced rainfall, and continued destruction of the Amazon through deforestation, for example, could see the rainforest system collapse, releasing CO2 into the atmosphere rather than storing it. Or warming Arctic permafrost could cause long-frozen biomass to decompose, releasing vast amount of carbon emissions.

"That's why it's so risky to keep emitting from fossil fuels ... because we're increasing the likelihood that we go over one of those tipping points," Lewis said.

Beyond 2°C
So far, the climate pledges that countries have submitted to the United Nations' registry of pledges put the world on track for 2.7°C of warming.

The International Energy Agency said Thursday that new promises announced at the COP26 summit – if implemented - could hold warming to below 1.8°C, although some experts challenged that calculation. It remains to be seen whether those promises will translate into real-world action.

Warming of 2.7°C would deliver "unlivable heat" for parts of the year across areas of the tropics and subtropics.

Biodiversity would be enormously depleted, food security would drop, and extreme weather would exceed most urban infrastructure's capacity to cope, scientists said.

"If we can keep warming below 3°C we likely remain within our adaptive capacity as a civilization, but at 2.7°C warming we would experience great hardship," said Mann.



Border Town’s Residents Rebuild in South Lebanon as Hezbollah Leader Calls for Israeli Withdrawal 

A bulldozer equipped with a drill works on the rubble of destroyed houses, caused by the Israeli air and ground offensive, in the town of Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)
A bulldozer equipped with a drill works on the rubble of destroyed houses, caused by the Israeli air and ground offensive, in the town of Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)
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Border Town’s Residents Rebuild in South Lebanon as Hezbollah Leader Calls for Israeli Withdrawal 

A bulldozer equipped with a drill works on the rubble of destroyed houses, caused by the Israeli air and ground offensive, in the town of Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)
A bulldozer equipped with a drill works on the rubble of destroyed houses, caused by the Israeli air and ground offensive, in the town of Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)

Sabah Abdullah comes to her hometown in Lebanon every morning and sits next to her destroyed home. She is waiting for experts from Hezbollah's construction arm to compensate her for the damage caused by the Israel-Hezbollah war that has left her homeless.

The 66-year-old woman from Khiam now rents a home in the nearby village of Kawkaba and is repairing her small grocery store, which was badly damaged by the 13-month war that ended in late November as a result of a US-brokered ceasefire. The war has left more than 4,000 people dead and over 16,000 wounded in Lebanon and caused damage worth billions of dollars.

“Damage can be compensated but the loss of souls cannot be replaced,” said Abdullah as she sat on a plastic chair in the sun outside her shop.

Israeli forces will remain in parts of southern Lebanon

The 60-day ceasefire that was supposed to end on Jan. 27 with an Israeli withdrawal from Lebanon and Hezbollah ending its armed presence along the border area was extended until Tuesday. But an Israeli official said Monday that Israeli forces will remain in five strategic locations in southern Lebanon after the deadline.

One of these locations is the Hamamis hill on the southern outskirts of Khiam. On Monday, bulldozers could be seen from a distance at work building what appeared to be fortifications in an apparent sign that Israel’s military is planning to stay long beyond Tuesday’s deadline.

Israeli bulldozers work on the Hamamis hill near the town of Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)

Hezbollah leader Sheikh Naim Qassem said in a speech Sunday that Israel has to fully withdraw from Lebanon on Tuesday, saying “there is no pretext for five points nor other details.” He added that the Lebanese state should prevent Israel from staying in the country after Tuesday as stated in the ceasefire deal.

The Israel-Hezbollah war began a day after Hamas carried out its deadly attack in southern Israel on Oct. 7, 2023 killing 1,200 people and taking about 250 people hostage triggering the Israel-Hamas war. The Israel-Hezbollah war intensified as of Sept. 23, when Israel expanded its attacks and killed Hezbollah’s longtime top leader and one of its founders, Hassan Nasrallah.

Widespread damage in Khiam

Khiam, one of the largest towns close to the Israeli border, suffered widespread damage, including entire blocks that were turned to piles of debris, while graffiti left behind by Israeli troops could be seen on the walls as well as inside homes. The town's cemetery suffered severe damage, with many graves blown out.

On Monday, workers were removing debris in different locations in Khiam as many residents come during the day to spend a few hours at their homes and leave before sunset since the town still has no electricity or running water. New poles were being put in place by the country’s state-run electricity company as the infrastructure suffered severe damage.

“In Khiam everyone was martyred,” read a graffiti on a wall in Arabic. “Khiam is Golani’s graveyard,” another one read referring to Israel’s Golani Brigade.

In a building on the eastern edge of Khiam, a woman showed a journalist a Star of David sprayed in red at the entrance of her apartment. The woman, who asked not to be named for safety reasons, then walked through her apartment showing a reporter the damage in the sitting room and kitchen.

Lebanese citizens check the destruction on their house caused by the Israeli war, in their hometown Khiam, southern Lebanon, Monday, Feb. 17, 2025. (AP)

Abdallah said when she first came to Khiam days after the ceasefire went into effect in late November, she found that hungry cats and dogs inside her badly damaged shop had eaten cakes, croissants and chocolates. The metal door of her shop was blown wide open, she said.

Seeing her home, which was built by her late father, destroyed saddened her but Abdallah said she is happy that none of her siblings or relatives were hurt during the war.

‘The future is obscure’

Abdallah said that soon after the war ended, Hezbollah’s construction arm Jihad al-Binaa paid her $12,000, of which $8,000 were to compensate her for lost furniture and $4,000 for a year's rent.

Abdallah said that since the Israel-Hezbollah war began she rented a house in Marakaba and had spent most of her savings and was selling some of her jewelry. She said she is now waiting for government experts to visit her and estimate the losses to pay her for rebuilding her two-story house that she shared with her brother.

“I will rebuild my house but the future is obscure. We live close to the border,” Abdallah said, referring to repeated wars with Israel over the past decades.

Another Khiam resident, Dalal Abdallah, said if Israel decides to stay in Lebanon, Israel will be eventually forced to leave again.

“Valuable blood and souls were paid for this land,” she said. She added that “no one should think that we will leave our land.”