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New UN review of climate science says evidence is clear and unambiguous that humans are the main cause of rapid climate change and that many damaging changes to Earth are in store without steep greenhouse gas reductions in the coming decades.
World climate scientists have outlined unprecedented changes to the Earth's physical systems caused by a warming climate and said it's "extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century." Ninety percent of the excess heat built up due to greenhouse gases over the past 40 years has gone to warm the oceans, the report said, a finding that puts into perspective the apparent slight moderation of surface air temperatures recently by persistent cool La Nina cycles and other factors. The scientists see no end to higher temperatures and increasing effects on oceans, polar regions, glaciers, coastlines and major Earth systems -- and say serious damage continuing for centuries will be inevitable unless there are "substantial and sustained reductions of greenhouse gas emissions."
In scientifically-based and painstakingly calibrated language reflecting the results of thousands of research studies in the past 7 years, the first part of the UN's Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment report was published on September 27. This part focuses on earth system and atmospheric science; parts documenting changes to living things and people, and methods of adaptation and mitigation, will follow in 2014. The IPCC consists of hundreds of working scientists serving without pay who reviewed more than 9,200 scientific publications for the first of three reports alone. The IPCC was established by the United Nations and the World Meteorological Organization in 1988 -- the same year NASA climate scientist James Hansen gave dramatic testimony to a U. S. Senate committee that global warming had been detected.
The report said that the world is likely to reach and exceed the temperature accepted by most nations as a serious danger point -- 2 degrees C [3.8 degrees F] above the pre-industrial earth temperature. The warming up to now is .85 C [1.5 F]. The IPCC calculated that less than 500 more gigatonnes of Carbon put into the atmosphere, mainly as CO2, will create the atmospheric concentration to reach the 2 degree C. point. At the current rate of human greenhouse emissions, 9.5 gigatonnes/year, we will reach that point in less than 50 years.
There will be large amounts of analysis and probably argument about this newest IPCC report. Those who for various reasons wish to stop political and social responses to the findings of science will draw attention to what they claim are crippling inconsistencies and gaps in scientific knowledge and description (as they did about the 2007 IPCC reports). The IPCC, being a survey of ongoing peer-reviewed research by scientists who tend to be skeptical and careful, attempts to be transparent about the state of knowledge of a very complex planetary system under stress. It uses a heirarchicy of terms to indicate the assessment of the validity of data and trends, ranging from "low confidence" and "extremely unlikely" (0-5% sure) to "very high confidence" and "extremely likely" (95-100 % sure).
Here are key sentences from the report:
• "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia."
• "Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
• "Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010."
• The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901–2010, global mean sea level rose by 0.19 m [7.5 inches]
• "The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification."
• "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system."
• "Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2."
For more information, please see the IPCC report, and these additional resources:
More information is also in the preliminary report from this website, in News and Views
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