Climate change will increase the likelihood of "severe, pervasive and irreversible impacts" for people and ecosystems if action is not taken, the Intergovernmental Panel on Climate Change (IPCC) has warned.
The IPCC published its fifth assessment report (AR5) yesterday, which it says is the most comprehensive assessment of climate change ever taken.
AR5 was put together by more than 800 lead authors, more than 1,000 contributing authors and over 2,000 expert reviewers. More than 30,000 scientific papers were assessed.
This “synthesis report” brings together the findings of the three reports the IPCC has released since September 2013, which cover the physical science, impacts and adaptation and mitigation. As such, many of its headline messages have previously been published.
The IPCC says that AR5 is more certain than previous assessments that greenhouse-gas emissions have been the dominant cause of observed warming since the mid-20th century.
The report states that global economic growth would not be strongly affected by action to reduce climate change. If no action is taken, the IPCC calculates that consumption, which it uses as a proxy for economic growth, will grow by 1.6–3% a year over the 21st century. Ambitious mitigation would reduce this by around 0.06 percentage points, it says.
These economic estimates of mitigation costs do not account for the benefits of reduced climate change, nor do they account for the numerous co-benefits associated with human health, livelihoods and development, the IPCC points out.
“Compared to the imminent risk of irreversible climate change impacts, the risks of mitigation are manageable,” said Youba Sokona, co-chair of IPCC working group III.
To keep a good chance of staying below a 2ºC rise in global temperature, and at manageable costs, emissions should drop by 40–70% globally between 2010 and 2050, falling to zero or below by 2100, the IPCC says.
Ed Davey, secretary of state for energy and climate change, said: “The UK has been leading the world – and bringing the world with us. The historic agreement to cut carbon emissions in Europe by at least 40% by 2030 effectively means our climate change act is being replicated across Europe – just as it’s being copied in countries across the world as they seek to cap and cut their own emissions.”
However, Green MEP Molly Scott-Cato said that the report backed her party’s stance that the targets agreed in Europe were “tragically unambitious”.
Nick Molho, executive director of the Aldersgate Group said that the report provided both “a clear warning and a message of hope”.
“It has made it crystal clear that man-made climate change is a reality but has also shown that prompt, cost-effective and coordinated action by the world’s governments can help limit the detrimental impacts that unabated climate change would have on the natural environment and the world economy. It is now time for governments to deliver a deal at the pace and scale required by climate science,” he said.
Meanwhile, leaders from 18 businesses, including those from the aggregate, construction, insurance and engineering sectors, have written to the Daily Telegraph, arguing that politicians and media reports undermining the UK Climate Change Act 2008 are unhelpful and create uncertainty for business.
“Our businesses are convinced that Britain can and should be a world leader, and that far from being a burden to UK plc, clear commitment to tackling climate change will open up opportunities for businesses both at home and abroad,” the letter states.