IPCC report: global warming is 'unequivocal'
Man's influence on climate change is "clear", according to the latest IPCC report which states that global warming is "unequivocal".
9:22AM BST 27 Sep 2013
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The new assessment by the Intergovernmental Panel on Climate Change states that it is "extremely likely" humans have been the principal cause of warming since the 1950s.
Without making "substantial and sustained reductions" of greenhouse gas emissions, the world can expect an increase of extreme weather including heatwaves and heavy rainfall.
Three out of four future climate change scenarios, based on projected levels of gas and aerosol emissions, suggest that by the end of this century global temperatures are likely to reach 1.5C higher than pre-industrial levels.
In the two highest of the four scenarios, warming by 2100 is expected to exceed 2C, the benchmark after which there are likely to be dangerous effects on the planet.
The effects of climate change will continue for several hundred years even if emissions of carbon dioxide stop, the report states.
Scientists and politicians from 195 countries have been working late into the night all week to finalise details of the document.
In an official statement issued to press on Friday morning, the panel said: "Human influence on the climate system is clear. This is evident in most regions of the globe.
"It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. The evidence for this has grown."
Warming in the climate system is "unequivocal" and changes seen since the mid 20th century have been "unprecdented over decades to millenia", they added.
The discussions, which took place at a brewery-turned-conference facility in central Stockholm were frustratingly slow but there is understood to have been little of the infighting between nations that has characterised past meetings.
One delegate told the Telegraph on Thursday night: "The good news is that the Saudis are not objecting to every word like used to happen [at previous meetings].
"It is pretty tame compared to the early years of the IPCC when you used to have a real scrum between people like the Chinese, who could be quite difficult. There is no-one in there saying climate change isn't real."
The summary for policymakers is a condensed version of a much larger report running to thousands of pages, which will be released on Monday.
It states that the atmosphere and oceans have become warmer, with the oceans absorbing more than 90 per cent of the extra heat energy accumulated between 1971 and 2010.
In fact, many scientists believe that warming of the deep oceans, on which data is still uncertain, has been masking climate change at the surface. This could explain why atmospheric temperatures have barely changed in the past 15 years during the so-called "pause", they say.
Political delegates from the UK and other leading countries such as the US and Brazil are understood to have pushed hard for the report to make explicitly clear that the comparative lack of warming during the past decade and a half does not mean climate change has stopped.
Sir Mark Walport, the Government chief scientific adviser, said the challenge for scientists in overcoming scepticism about man-made climate change was one of "communication."
He told BBC's Radio 4 Today programme: "Scientists have got to communicate this. There are some people that don't want to confront the policy decisions and they say 'the easiest way we can do this is rubbish the science.' They can't do this, it's absolutely robust."
The summary states: "Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years, which begins with a strong El Nino, is smaller than the rate calculated since 1951."
The report makes clear that each of the past three decades has been successively warmer at the Earth's surface than any preceding decade since 1850, and that 1983-2012 was likely the warmest 30-year period of the past 1,400 years.
Concentrations of carbon dioxide, methane and nitrous oxide in the atmosphere have reached levels unprecedented in the past 800,000 years, including a 40 per cent increase since pre-industrial times.
The report also states that sea levels have risen by 19cm since 1901, and that they will continue to rise during this century as surface temperature rises and the Arctic sea ice continues to shrink and thin and glaciers around the world recede.
The oceans are also set to become more acidic as they absorb more carbon.
Qin Dahe, co-chair of the working group, said: "Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased.
"As the ocean warms, and glaciers and ice sheets reduce, global mean sea level will continue to rise, but at a faster rate than we have experienced over the past 40 years."
Thomas Stocker, the other co-chair of the group, added: "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 gases.
"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.
"As a result of our past, present and expected future emissions of CO2, we are committed to climate change, and effects will persist for many centuries even if emissions stop."
Ed Davey, the Energy and Climate Change Secretary, said solutions to the problem of man-made greenhouse gases accumulating in the atmosphere “must be set in motion today.”
He said: “The risks and costs of doing nothing today are so great, only a deeply irresponsible government would be so negligent.
“Without urgent action to cut greenhouse gas emissions this warming will continue, with potentially dangerous impacts upon our societies and economy.”
The report strengthened the case for international leaders to work for an “ambitious, legally binding global agreement” in 2015 to cut carbon emissions, he added, thanking the scientists behind it for making clear “what is at stake if we don’t act.”
