STOCKHOLM, Sweden, September 27, 2013 (ENS) – “Human influence on the climate system is clear. This is evident in most regions of the globe,” finds a new assessment by the Intergovernmental Panel on Climate Change, IPCC, released today.
“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,” states the report, the latest in a series issued once every seven years.
“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. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased,” reports the Summary for Policymakers of the IPCC Working Group I assessment report, “Climate Change 2013: the Physical Science Basis,” approved on Friday by the 195 member governments of the IPCC in Stockholm.
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850, the report finds.
A total of 209 lead authors and 50 review editors from 39 countries, and more than 600 contributing authors from 32 countries, contributed to the preparation of this Working Group I report. More than 1,000 expert reviewers worldwide contributed their expertise in preparation of this assessment.
“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 of the China Meteorological Administration, Beijing, co-chair of IPCC Working Group I.
Thomas Stocker of the University of Bern, Switzerland, 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.”
At a news conference today Stocker called climate change “the greatest challenge of our time … It threatens our planet, our only home.”
“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 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,” Stocker said.
The report finds with high confidence that 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.
Stocker concluded, “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 of CO2 stop.”
Projections of climate change are based on a new set of four scenarios of future greenhouse gas concentrations and aerosols, spanning a wide range of possible futures.
The Working Group I report assessed global and regional-scale climate change for the early, mid-, and later 21st century.
“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,” said Qin.
Rajendra Pachauri, chair of the IPCC, said, “This Working Group I Summary for Policymakers provides important insights into the scientific basis of climate change. It provides a firm foundation for considerations of the impacts of climate change on human and natural systems and ways to meet the challenge of climate change.”
These are among the aspects assessed in the contributions of Working Group II and Working Group III to be released in March and April 2014. The IPCC Fifth Assessment Report cycle concludes with the publication of its Synthesis Report in October 2014.
In his reaction to the report’s findings, U.S. Secretary of State John Kerry took aim at climate deniers. “This is yet another wakeup call,” said Kerry. “Those who deny the science or choose excuses over action are playing with fire.”
“Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or common sense should be willing to even contemplate,” he said.
“Boil down the IPCC report and here’s what you find: Climate change is real, it’s happening now, human beings are the cause of this transformation, and only action by human beings can save the world from its worst impacts,” said Kerry.
“This isn’t a run of the mill report to be dumped in a filing cabinet. This isn’t a political document produced by politicians. It’s science. It builds on the most authoritative assessments of knowledge on climate change produced by scientists, who by profession are conservative because they must deal in what is observable, provable and reviewable by their peers,” Kerry said.
“If this isn’t an alarm bell, then I don’t know what one is,” he said. “If ever there were an issue that demanded greater cooperation, partnership, and committed diplomacy, this is it. What one country does impacts the livelihoods of people elsewhere – and what we all do to address climate change now will largely determine the kind of planet we leave for our children and grandchildren.”
The United States is the world’ second largest greenhouse gas emitter, recently surpassed by China. But now, Kerry says the United States is “deeply committed to leading on climate change.”
“We will work with our partners around the world through ambitious actions to reduce emissions, transform our energy economy, and help the most vulnerable cope with the effects of climate change,” said Kerry. “We do so because this is science, these are facts, and action is our only option.”
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