Overshooting 1.5°C doesn't have to be permanent, says Met Office

Study shows there is a greater likelihood world will surpass target and then come back down to it by 2100

'If the world doesn’t pledge larger 2030 emission reductions, then exceeding 1.5°C becomes more likely," the Met Office warned. AP

Pledges to cut greenhouse gas emissions agreed to at last year’s Cop26 are not likely to be sufficient to keep the global temperature rise to 1.5°C compared with pre-industrial levels, an analysis by the UK Met Office has shown.

The Cop26 pledges, known as Nationally Determined Contributions (NDCs), indicate further action is required at Cop27 in Sharm El Sheikh, Egypt, to keep the hope of limiting the temperature rise to 1.5°C alive.

The Met Office study, published in the journal Weather, showed there was greater likelihood the world would overshoot the 1.5°C target and then come back down to it by 2100.

“Current NDC updates still don’t take us on to pathways to limit global temperature rise to 1.5°C,” said Jason Lowe, head of climate services at the Met Office.

“If the world doesn’t pledge larger 2030 emission reductions, then exceeding 1.5°C becomes more likely.”

The Met Office study found that enacting all the pledges from Glasgow would bring annual global emissions of carbon dioxide or their equivalents down to between 45 and 49 gigatonnes by 2030.

But at that level, there are no pathways to avoid going above 1.5°C.

To give the 1.5°C threshold at least a 50 per cent chance of being met, annual emissions would need to be at about 30 gigatonnes by 2030.

Camilla Mathison, mitigations science manager at the Met Office and author on the paper, said: “If we overshoot 1.5°C, it doesn’t have to be permanent.

“With deep and rapid reductions post-2030, and development of diverse technologies for the removal of atmospheric carbon dioxide, it remains feasible to meet 1.5°C by the end of the century.”

A temporary overshoot now would mean future generations having to make bigger cuts, the Met Office study showed.

“If 1.5°C is exceeded over a sustained period of, say, several decades, then this is known as overshoot,” said lead author Andy Wiltshire, the Met Office head of earth system and mitigation science.

“The downside of not staying below 1.5°C altogether is a greater risk this century of more severe climate impacts, such as those triggered by increased melting of ice caps or collapse of an ecosystem like the Amazon rainforest.”

The NDC pledges from Cop26 cited in the Met Office study are based on an original analysis by Climate Action Tracker