What is the 1.5°C climate target and why does it matter? Top UK experts say world will miss limit

Earth will likely record the hottest year on record by 2027 (Owen Humphreys / PA)
Earth will likely record the hottest year on record by 2027 (Owen Humphreys / PA)

Leading British climate scientists have said they believe the target to limit global warming to 1.5°C will be missed.

Professor Sir Bob Watson, former head of the UN climate body, told the BBC that he was “pessimistic about achieving even 2°C”.

This summer, Europe, China, and the US are experiencing extreme heat. And this week, Rome hit a record temperature of 41.8°C, while China recorded a worryingly high 52°C.

Global leaders agreed they would try to limit the temperature increase due to climate change to 1.5°C, at a UN conference in Paris in 2015.

In the interview aired on Thursday, Professor Sir Bob Watson, who is currently emeritus professor of the UK’s Tyndall Centre for Climate Research, said: “I think most people fear that if we give up on the 1.5 [Celsius limit] which I do not believe we will achieve, in fact I’m very pessimistic about achieving even 2°C, that if we allow the target to become looser and looser, higher and higher, governments will do even less in the future.”

While Lord Nicholas Stern, chairman of the Grantham Research Institute on Climate Change and the Environment, also agreed later that day during an interview with BBC’s WATO programme: “I think 1.5 is probably out of reach even if we accelerate quickly now, but we could bring it back if we start to bring down the cost of negative emissions and get better at negative emissions. Negative emissions means direct air capture of carbon dioxide.”

Scientists have recently warned that Earth will likely breach the 1.5°C climate threshold in the next five years.

Research from the World Meteorological Organisation (WMO) found that there is a 66 per cent chance of Earth recording a global average temperature of more than 1.5°C above pre-industrial levels by 2027.

There is also a 98 per cent chance of the hottest year on record being broken within the same timeframe.

What is the significance of 1.5°C?

When the Paris Agreement — the global treaty on climate change — was negotiated in 2015, there was a strong and ultimately successful push by nations such as low-lying islands to include the 1.5°C target in the deal because they felt letting temperatures go any higher would threaten their survival.

As a result, countries pledged to keep global temperature rises to well below 2°C above pre-industrial levels and pursue efforts to limit warming to 1.5°C over the long-term.

Will limiting temperature rises to 1.5°C really make a difference?

Yes, according to a special report by the UN’s climate science body, the Intergovernmental Panel on Climate Change (IPCC), in 2018.

It found a 2°C rise would lead to more heatwaves, extreme rainstorms, water shortages, and drought, greater economic losses and lower crop yields, higher sea levels, and greater damage to nature.

In one of its most sobering findings, the report said coral reefs would decline by 70-90 per cent with global warming of 1.5°C, but would all but vanish in a 2°C world.

A report from the IPCC previously warned that every additional 0.5°C temperature rise leads to clear increases in the intensity of heatwaves, rainstorms, and flooding, and droughts in some regions.

With the world already experiencing more damaging climate extremes at 1.2°C of warming, 1.5°C is not seen as a safe level, but things get much worse if it goes above that.

Is it game over if the world warms by more than 1.5°C?

No. Scientists say the 1.5°C or 2°C thresholds are not cliff edges that the world will fall off, but that every bit of warming makes a difference, so it is important to curb temperature rises as much as possible.

As Professor Richard Betts, from the Met Office Hadley Centre, puts it: “Like the speed limit on a motorway, staying below it is not perfectly safe and exceeding it does not immediately lead to calamity, but the risks do increase if the limit is passed.

“Limiting warming to 1.5°C clearly needs much more urgent emissions cuts than is currently happening but, if the target is still breached, we should not assume all is lost and give up — it will still be worth continuing action on emissions reductions to avoid even more warming.”

Are we off track to meet a 1.5°C limit?

Yes, way off track. The 2018 IPCC report said to limit temperature rises to 1.5°C, the world would have to cut carbon emissions by 45 per cent on 2010 levels by 2030, and to net zero — with any remaining pollution absorbed by measures such as planting trees — by 2050.

An assessment from the UN showed the national plans for cutting emissions put forward by countries under the Paris Agreement would lead to a 16 per cent increase in emissions on 2010 levels by the end of the decade.

Other analysis suggests that, even with the latest pledges and targets, we are heading for around 2.4°C of warming.