Scientists say they are more certain than ever that humans are responsible for the majority of climate change.
A major new report reveals it is “extremely likely”, or 95% certain, that most of the global warming since the 1950s is down to human activity.
The Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report, which has been published after line-by-line scrutiny by scientists and policymakers, found the likelihood is up from a 90% certainty in the last IPCC study in 2007.
In a message to the conference in Stockholm, Ban Ki-moon, secretary general of the United Nations, sent his “best wishes” and “gratitude” to the IPCC, and said the “world’s eyes” are on the city today.
“Since 1990 the IPCC has provided regular, unbiased assessment of the mounting impact of a warming planet.
“You are the world’s authorities on climate change, recognised with a Nobel Peace Prize,” he said.
He added that “we need to build resilience and seize the opportunities of a low-carbon future”.
Concluding, he said: “The heat is on. Now we must act.”
Energy and climate change secretary Ed Davey said that the new report confirmed action was needed to cut greenhouse gases.
“Without urgent action to cut greenhouse gas emissions this warming will continue, with potentially dangerous impacts upon our societies and economy. This strengthens the case for international leaders to work for an ambitious, legally binding global agreement in 2015 to cut carbon emissions,” he said.
“This report is the most authoritative, credible analysis of climate change science ever.
“It represents a huge amount of work by over 250 unpaid scientific experts drawn from universities and research institutes in 39 different countries around the world.
“We owe them our gratitude because this report makes clear what is at stake if we don’t act.”
The study predicts that temperatures are set to rise by more than 1.5C above pre-industrial levels by the end of the century without ambitious action to tackle emissions, and could rise by over 4C if emissions continue to increase.
Storms will become more intense and frequent, sea levels will rise by between 26cm (10in) and 82cm (32in) by the end of the century and the oceans will become more acidic, the assessment projects.
One of the scientists leading the first section of the IPCC’s fifth assessment , which looks at the science of climate change and its causes, Thomas Stocker, said: “Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.
“Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.”
The report considered a series of scenarios for greenhouse gas emissions and their impacts on the climate.
“Global surface temperature change for the end of the 21st century is projected to be likely to exceed 1.5C relative to 1850 to 1900 in all but the lowest scenario considered, and likely to exceed 2C for the two high scenarios.
“Heatwaves are very likely to occur more frequently and last longer. As the Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions,” he said.
Niall Stuart, chief executive of Scottish Renewables, said the report was a ‘timely reminder’ of the need for carbon reduction.
“The IPCC report shows that global warming is now unequivocal and is being driven mainly by rising atmospheric concentration of CO2,” he said.
“This only serves to underline to inherent logic of government pursuing policies that encourage increasing investment in renewable energy technologies.”
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