Human role in warming 'more certain' - UN climate chief
By Roger Harrabin
Scientists are more certain than ever that greenhouse gases from human activities are heating the planet, the head of the UN's climate panel says.
Rajendra Pachauri made the comments in an interview with BBC News.
The panel is due to deliver its latest report on the state of the climate later this week in Stockholm, Sweden.
Its last report was criticised after an error on glaciers unveiled other flaws, but Prof Pachauri said procedures had been reformed and strengthened.
He also dismissed suggestions of a slowdown in global warming.
"There’s definitely an increase in our belief that climate change is taking place and that human beings are responsible,” he told me.
"I don't think there is a slowdown (in the rate of temperature increase). I would like to draw your attention to the World Meteorological Organization which clearly stated on the basis of observations that the first decade of this century has been the warmest in recorded history.
"And I think the rest will be brought out by the report itself when it’s released."
Prof Pachauri’s insistence that warming has not slowed hints at a focus of debate this week in Stockholm: Global temperatures have not been increasing as fast as scientists predicted, and several governmentsinsist that this puzzle is properly addressed in the final summary.
Have computer climate models overestimated the sensitivity of the planet to increasing CO2? Or has excess heat been stored up in oceans whence it will emerge to super-heat the planet in decades to come? Or both?
Or just perhaps it could be something else.
Unprecedented change
The draft says a doubling of CO2 concentrations in the atmosphere above pre-industrial levels (expected by mid-century) is likely to result in a temperature rise globally of between 1.5 and 4.5C.
Any rise above 2C could risk major changes on Earth, according to projections, but the results of recent modelling involves a downward tweak at the bottom of the range, offering the tantalising prospect to politicians that if humans are very lucky, they could get away with rising CO2 emissions for a bit longer than previously expected.
The panel is struggling to offer a definitive answer as to why warming is not happening at the rate previously projected. But it will be anxious to ensure that the likelihood of a fortunate escape for humanity should not be overplayed.
It is expected to say that greenhouse gas emissions from human activities have already warmed the ocean, melted snow and ice, raised sea levels and increased climatic extremes.
It will also warn that unless emissions are cut soon, we are likely to suffer severe changes in the climate unprecedented for hundreds of thousands of years.
Prof Pachauri’s leadership of the panel has been strongly supported by developing countries, although he has faced criticism in the West. He told me he had no plans to retire after the forthcoming report.
He said the panel enjoyed massive support, with 3,000 people volunteering to act as authors, 831 of whom were selected.
Tightening procedures
In the detailed text of its last report, the UN panel made a controversial mistake on glaciers.
Prof Pachauri said: "We made one mistake about the glaciers melting by 2035 - for which we have apologised. That was totally out of character because we always give a range for these things and it somehow slipped through.
"But it wasn’t included in the technical summary or the summary for policymakers, it just somehow escaped attention.
“What we did say about the glaciers was in substance not all that wrong – the glaciers are melting across the globe so that is something we stand by.
“This time we have been doubly careful... [that] we don’t have any mistake of that type. And I hope that [the report] will reassure everyone that human influence is having a major impact on the Earth's climate.”
Prof Pachauri said he anticipated attempts to discredit the panel. But he claimed evidence of extreme events was persuading more and more people, especially in the US, that humans were taking a risk with the climate.
Indeed, the report is expected to say it is very likely that manmade climate change has produced higher precipitation in America.
"Hopefully,” he said, “there are enough sane and sensible people in the public who will ultimately prevail."
The broader question is whether science itself will prevail over politics. Whatever the pronouncements of the UN panel, emissions are expected to continue to increase into the foreseeable future as politicians weigh risks to energy bills and competitiveness against risks to the planet.
The UN Secretary-General Ban Ki-moon has re-confirmed that he will invite world leaders to a climate summit next year in an attempt to galvanise action.
Climate: Growing certainties on warming and human role
Over the past 23 years, UN scientists have issued progressively stronger assertions about climate change.
They have moved from a sketchy warning that heat-trapping carbon gases emitted by fossil fuels will cause a "greenhouse" effect to the conviction that this effect is now having an impact on Earth's climate.
Following are extracts from the Intergovernment Panel on Climate Change's assessment reports, the latest of which will be published from Friday.
First Assessment Report (1990)
"... emissions resulting from human activities are substantially increasing atmospheric concentrations of greenhouse gases...
"These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface."
Second Assessment Report (1995)
"Most of these studies have detected a significant change and show that the observed warming trend is unlikely to be entirely natural in origin...
"... the balance of evidence suggests that there is a discernible human influence on global climate.
"... the average rate of warming [in projections for the 21st century] would probably be greater than any seen in the last 10,000 years, but the actual annual to decadal changes would include considerable natural variability."
Third Assessment Report (2001)
"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.
"... the projected rate of warming is much larger than the observed changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years, based on paleoclimate data."
The report said the global average temperature had risen by 0.6 degrees Celsius (1.08 degrees Fahrenheit) between 1901 and 2000.
Human activity was "likely" to be the cause of warming, a term meaning a probability of more than 66 percent.
Fourth Assessment Report (2007)
"Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.
"Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic [man-made] greenhouse gas concentrations."
The report said that warming over the previous 100 years was 0.74 C (1.33 F), and 11 of the previous 12 years had been the warmest on record.
Human activity was "very likely" the cause of warming, meaning a probability of more than 90 percent.
Fifth Assessment Report (draft version seen by AFP)
"In the northern hemisphere, the period 1983-2012 was very likely the warmest 30-year period of the last 800 years and likely the warmest period of the last 1,400 years.
"....Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5-1.3 C [0.9-2.3 F] over the period 1951-2010."
"...There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level and changed some climate extremes in the second half of the 20th century."
Human activity was "extremely likely" to be the cause of this warming, meaning between 95 and 100 percent probability.
The draft attributes an observed slowing in warming from 1998 to 2012—a phenomenon cited by skeptics as evidence that warming is not man-made—to a temporary cooling cycle in the weather system and lower-than-expected solar activity.
Temperatures since 1901 have risen by 0.89 C (1.6 F), it says.
Additional warming this century is estimated to range from 1.0 to 3.7 C (1.8-6.6 F), and sea level rise from 40 to 62 centimetres (16-24.8 inches), according to four projections based on how much carbon is emitted.
As in past reports, these estimates are an average. Each projection gives a wide margin of variation either side of the figure.
Evidence mounts for human role in climate change
by Ben Deighton
Complex computer models have helped the IPCC make climate forecasts. © UPSCALE | Credits: Natural Energy Research Council (NERC) and UK Met Office Joint Weather and Climate Research Programme (JWCRP).
Scientists are more certain than ever that humans are the cause of global warming, the Intergovernmental Panel on Climate Change (IPCC) said in its most authoritative report to date, drawing on millions of scientific observations - many of which were gathered by scientists in Europe.
The data used to compile the report includes that gathered by the EU-funded airship PEGASOS, which has been measuring the air quality over Europe to link air pollution to climate change, and RECONCILE, which helped find the first ever observed hole in the ozone layer in the Arctic region.
In its fifth assessment report, released on 27 September, the IPCC concluded that there is an at least 95 % likelihood that humans are the dominant cause of global warming. That makes them the surest they have ever been that humans are causing climate change.
Scientists are able to be so categorical because of the number of research papers that have been taken into account in producing the report. It cites over 9 200 scientific publications, more than three quarters of which have been published since the previous assessment in 2007, and bases its conclusions on millions of observations.
‘Up to now it is the only endeavour of this kind of science in the world,’ said Dr Anastasios Kentarchos, the deputy head of the Climate Change and Natural Hazards Unit at the European Commission’s Directorate-General for Research and Innovation, who was present during the discussions in Stockholm running up to the publication of the report. ‘This is a huge pool of scientists that on a voluntary basis are giving their brains and their minds for five years to do this work,’ he added referring to the IPCC report.
Unprecedented in 800 000 years
Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800 000 years, the report said.
The EU’s in-house science service, the Joint Research Centre, has provided critical data on worldwide emissions through its EDGAR database, which models emissions of greenhouse gases and air pollutants.
The rise in greenhouse gases is likely to mean that global temperatures will increase by over 1.5 degrees Celsius by the end of this century, when compared to the 1850 to 1900 period, according to all but the lowest scenario considered by the report.
‘Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system,’ said Thomas Stocker, the co-chairman of the IPCC group that assesses the physical science basis for climate change.
Climate models
Complex computer models, such as those developed by the EU-funded ENSEMBLES project, are required to allow the panel to make such forecasts. The project has modelled the simultaneous activity of the oceans, land and the atmosphere to show that the world will experience further measurable climate change.
The European airship PEGASOS. © PEGASOS
Other research groups concentrated on specific aspects, like Ice2Sea, which forecasts that by 2100 storm surges along Europe’s coastline could be up to 1 metre higher than they are today, presenting challenges to flood defences and natural habitats.
However, more data is needed to improve the accuracy of the models, for example by understanding the role of the permafrost, the permanently frozen layer of soil, in the Arctic regions on greenhouse gas levels. That's now being done by the EU-funded PAGE21 project, which brings together permafrost researchers from Europe, Canada, Russia, the US, and Japan.
‘The more observations you build, the better you understand the drivers of climate change and you can validate more accurately the next generation of climate models,’ said Dr Kentarchos.
Future research should concentrate on improving the capacity of climate models to make forecasts on a regional scale, providing data that is useful for farmers as they plan how best to use their land, or governments as they decide where to invest money to protect their citizens from climate change.
‘The models are useful to stakeholders when they give you trustworthy information at the right regional or sub-regional scale,’ said Dr Kentarchos.
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