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Many climate changes are ‘irreversible’

Words: Laura Edgar
Heatwaves / iStock-922720650

Scientists say many changes in the climate are ‘unprecedented’ and some, such as the continued rise in sea level, ‘are irreversible over hundreds to thousands of years’.

They warn that the goal of limiting global warming to 1.5°C compared with pre-industrial levels, as enshrined in the Paris agreement, will be beyond reach unless there are “rapid, sustained and large-scale reductions” of greenhouse gas emissions.

The latest Intergovernmental Panel on Climate Change (IPCC) report, Climate Change 2021: the Physical Science Basis, finds that it is “unequivocal” that human influence has warmed the atmosphere, ocean and land. The warning and the report come ahead of the UK hosting COP26 in Glasgow in November. 

Human-induced climate change is “affecting many weather and climate extremes in every region across the globe”, evidenced in extremes such as heatwaves, heavy rainfall, droughts and tropical cyclones.

The report‘s authors warn that global surface temperatures will continue to increase until at least the middle of the century under all the emissions scenarios they considered. Global warming above 1.5°C and 2°C will be exceeded during the 21st century “unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades”. 

Benefits for the quality of the air would come “quickly”; it could take 20-30 years for global temperatures to stabilise. 

Compiled by Working Group I, the report is the first instalment of the IPCC's Sixth Assessment Report, due for completion in 2022.

Hoesung Lee, chair of the IPCC, said: “The innovations in this report, and advances in climate science that it reflects, provide an invaluable input into climate negotiations and decision-making.”

IPCC Working Group I co-chair Valérie Masson-Delmotte states that the report is a “reality check”. 

“We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare.”

Across regions of the world, the report states that climate changes will increase. For 1.5°C of warming, there will be an increased number of heatwaves, longer warm seasons and shorter cold seasons. For 2°C of warming, heat extremes would “more often reach critical tolerance thresholds for agriculture and health”.

Should global warming continue, scientists say the global water cycle, such as the severity of wet and dry events, will further intensify, while increasing CO2 emissions will mean ocean and land carbon sinks could be less effective at slowing the accumulation of CO2 in the atmosphere. Also, further warming will amplify permafrost thawing, as well as the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice. 

In the world’s cities, the report warns that some aspects of climate change may be amplified, including heat, flooding from heavy rainfall and sea level rise in coastal cities.

Responding to the report, Connor Schwartz, climate lead at Friends of the Earth, said: “Every fraction of a degree now matters more than ever. Loud wake-up calls have been sounding for years but world leaders have chronically overslept, and people are paying the price with their lives. 

“If we want a habitable planet, the window is just about still open, that’s today’s report in a nutshell. 

“If the government wants to show they respect the world’s leading scientists on climate chaos, they can start by cancelling the Cambo oil field, scrapping the coal mine in Cumbria, and ending UK funding for the mega-gas project in Mozambique: they can do that today.”

Kathryn Brown, interim director of climate action at The Wildlife Trusts, sets out a "stark" warning. 

“Climate change is already affecting people, places and nature in every region of the world, and is having profound effects on wildlife in the UK – yet nature, when it’s restored, will contribute to reducing greenhouse gas emissions and improving resilience to inevitable change.

“This is hugely urgent – we need to act right now to stop burning fossil fuels, and restore nature at scale as fast as possible. The Wildlife Trusts are repairing habitats and creating new ones across the UK – nature-based solutions can help tackle the climate crisis and increase our ability to adapt to it. But nature needs time to store carbon on the vast scale that’s needed which is why we need to restore 30 per cent of our land for nature by 2030.

“Organisations that are putting nature into recovery need support to do this work – and a new designation known as wild belt is vital to protect land where nature is being repaired. All government departments must agree that we are fighting both a climate and nature crisis.  Currently we risk being undermined by destructive infrastructure projects such as HS2 and the £27 billion being spent on road building – as well as plans for new coal mines and further oil and gas in the North Sea. The government cuts to foreign aid have had a negative impact too, by undermining our diplomatic negotiating power ahead of COP26.

“We can all do something to help tackle the crisis – but the Government must change its ways, show stronger leadership, and enable everyone to play their part.”

Climate Change 2021: the Physical Science Basis can be found on the IPCC website. 

Image credit | iStock