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Climate Change 2013: the Physical Science Basis
Intergovernmental Panel on Climate Change (IPCC), IPCC.ch
From the Press Release:
Human influence on the climate system is clear. This is evident in most regions of the globe, a new assessment by the Intergovernmental Panel on Climate Change (IPCC) concludes.
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, thanks to more and better observations, an improved understanding of the climate system response and improved climate models.
Warming in the climate system is unequivocal and since 1950 many changes have been observed throughout the climate system that are unprecedented over decades to millennia. Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850, reports the Summary for Policymakers of the IPCC Working Group I assessment report, Climate Change 2013: the Physical Science Basis, approved on Friday by member governments of the IPCC in Stockholm, Sweden.
“Observations of changes in the climate system are based on multiple lines of independent evidence. 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,” said Qin Dahe, Co-Chair of IPCC Working Group I.
Thomas Stocker, the other Co-Chair of Working Group I 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." “Global surface temperature change for the end of the 21st century is projected to be likely to exceed 1.5°C relative to 1850 to 1900 in all but the lowest scenario considered, and likely to exceed 2°C for the two high scenarios,” said Co-Chair Thomas Stocker. “Heat waves 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 added…
Carbon Brief’s guide to the IPCC report
Staff, Carbon Brief
As global greenhouse gas emissions continue to rise, the earth is warming, snow and ice is melting, and sea levels are rising. These are the confident conclusions from a brand new report from the Intergovernmental Panel on Climate Change (IPCC).
The full report runs to several thousand pages, but scientists have distilled its contents into a 36-page summary – intended to capture the findings most relevant to policymakers. Here are the bits you need to know about…
(27 September 2013)
Climate Panel Says Upper Limit on Emissions Is Nearing
Justin Gills, New York Times
For the first time, the world’s top climate scientists on Friday formally embraced an upper limit on greenhouse gases while warning that it is likely to be exceeded within decades if emissions continue at a brisk pace, underscoring the profound challenge humanity faces in bringing global warming under control.
A panel of experts appointed by the United Nations, unveiling its latest assessment of climate research, reinforced its earlier conclusions that global warming is real, that it is caused primarily if not exclusively by human emissions, and that it is likely to get substantially worse unless efforts to limit those emissions are rapidly accelerated.
Going well beyond its four previous analyses of the emissions problem, the Intergovernmental Panel on Climate Change endorsed a “carbon budget” for humanity — an upper limit on the amount of the primary greenhouse gas, carbon dioxide, that can be emitted from industrial activities and forest destruction…
Climate scientists not involved in writing the new report said that, in reality, the authors had made a series of conservative choices in their assessment of the scientific evidence…
“The I.P.C.C. is far from alarmist — on the contrary, it is a highly conservative organization,” said Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany, whose papers on sea level were among those that got discarded. “That is not a problem as long as the users of the I.P.C.C. reports are well aware of this. The conservatism is built into its consensus structure, which tends to produce a lowest common denominator on which a large number of scientists can agree.”…
(27 September 2013)
Is global warming in a hiatus? Not if you measure global heat content
Prof. Andy Pitman, The Conversation
On September 27 2013 the 5th Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) will be released.
One part of this report will address the so-called “warming hiatus”. This is the argument that warming has stopped, with the further assertion in some quarters that we therefore have nothing to worry about in the future.
It is a fact, based on observations of air temperature, that the rate of global warming measured as surface air temperature has slowed over the past 15 years. The last decade is still the warmest in the past 150 years.
If you measure global heat content then global warming has not slowed. If you measure other indices including sea level rise or ocean temperatures or sea ice cover global warming has not slowed… However, the warming trend in air temperatures has slowed over the last 15 years. There is a great deal of interest in this “hiatus” in the sense of whether it points to some fundamental error in climate science. The slowing in the rate of warming over the last 15 years is not in the least surprising. We have seen a combination of the solar minimum, anthropogenic aerosol emissions and back-to-back La Niñas.
What is surprising – and what is deeply concerning to me and almost entirely missed in the media commentary – is that we have not cooled dramatically over the last 15 years…
(19 September 2013)
Global warming: why is IPCC report so certain about the influence of humans?
Dana Nuccitelli, The Guardian
100 percent of the global warming over the past 60 years is human-caused, according to the IPCC’s latest report.
The fifth Intergovernmental Panel on Climate Change (IPCC) report states with 95 percent confidence that humans are the main cause of the current global warming. Many media outlets have reported that this is an increase from the 90 percent certainty in the fourth IPCC report, but actually the change is much more significant than that. In fact, if you look closely, the IPCC says that humans have most likely caused all of the global warming over the past 60 years… The IPCC elaborates further. What’s causing global warming: human greenhouse gas emissions.
"The observed warming since 1951 can be attributed to the different natural and anthropogenic drivers and their contributions can now be quantified. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3 °C over the period 1951−2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C."
What’s not causing global warming: natural external factors like solar activity, and natural internal factors like ocean cycles.
"The contributions from natural forcings are likely to be in the range of −0.1°C to 0.1°C, and from internal variability likely to be in the range of −0.1°C to 0.1°C."…
This is why there’s a 97 percent consensus amongst climate experts and in the climate science literature that humans are causing global warming. The scientific evidence on this question is overwhelming….
(27 September 2013)
Climate Skeptic Groups Launch Global Anti-Science Campaign
Katherine Bagley, InsideClimateNews.org via Bloomberg
Conservative groups at the forefront of global warming skepticism are doubling down on trying to discredit the next big report by the Intergovernmental Panel on Climate Change (IPCC). In recent weeks, they’ve been cranking out a stream of op-eds, blogs and reports to sow doubt in the public’s mind before the report is published, with no end in sight.
"The goal is to inform the public, scientific community and media that the upcoming IPCC report doesn’t have all the science to make informed judgments," said Jim Lakely, a spokesman for the Heartland Institute, a libertarian think tank based in Chicago that has been spearheading the efforts.
To try to shape coverage of the findings, the Heartland Institute released a 1,200-page report on Wednesday by the provocatively titled Nongovernmental International Panel on Climate Change (NIPCC). The 10-year-old coalition of "nongovernment scientists and scholars" disputes the reality of man-made climate change…
(19 September 2013)
Big business funds effort to discredit climate science, warns UN official
Fiona Harvey and Graham Readfearn, The Guardian
Big companies are paying contrarians to undermine the work of climate scientists, according to a top UN official speaking before the release of a landmark review of climate science this weekby international researchers next Friday.
Halldór Thorgeirsson, a director who reports to the head of the UN body that governs the on-going high level international climate negotiations, said that scientists would need to be prepared for a counter-blast from sceptics.
"Vested interests are paying for the discrediting of scientists all the time. We need to be ready for that," he said.
His outspoken views will set the tone for a fractious meeting of the world’s leading climate scientists, kicking off on Monday in Stockholm, that will set out the evidence that the world’s governments use when formulating policies to deal with global warming for decades to come. More than 800 scientists have contributed to the report, the final details of which will be hammered out in a gruelling four-day session next week…
(20 September 2013)