This week, the U.N.'s International Panel for Climate Change gathered to finalize its fifth assessment report regarding the state of the environment, stating that global warming is "extremely likely" to have been human caused.
These are the strongest words yet on the issue -- and it was something those gathered outside in Stockholm felt the need to scream about as they took it as confirmation that governments should take action. But as some screamed, others who are skeptical questioned.
People scream outside the United Nations Intergovernmental Panel on Climate Change (IPCC) to demand immediate political action on Climate debate on September 27, 2013 in Stockholm.
The panel said it was more certain than ever that humans were the cause of global warming and predicted temperatures would rise another 0.3 to 4.8 degrees Celsius this century. (Photo: JONATHAN NACKSTRAND/AFP/Getty Images)
The IPCC completed its fifth assessment report, which is important as it drive's some governments to take action against climate change. There has long been a debate over whether action should be taken to mitigate climate change and, if so, what. (Photo: JONATHAN NACKSTRAND/AFP/Getty Images)
It took 259 authors from 39 countries and more than 54,000 comments to draft the report, which for weeks has been leaked through the media ahead of its final release.
But now a summary of the report for policymakers is out with the full 2,000-page document expected to be released Monday. It contained few surprises as many of the findings had been leaked in advance.
(From L to R) Moderator Jonathan Lynn, Secretary-General of the WMO Michel Jarraud, Chairman of the Intergovernmental Panel on Climate Change (IPCC) Rajendra K Pacahauri, Co-Chair working group 1 Thomas Stocker and Co-Chair working group 1 Dahe Qin present the first volume of its Fifth Assessment Report, first overview since 2007 of scientific evidence for climate change on September 27, 2013 in Stockholm. The report, based on a huge number of measurements globally, has been discussed this week at the IPCC's meeting in Stockholm, bringing together hundreds of leading scientists. (Photo: JONATHAN NACKSTRAND/AFP/Getty Images)
Here are some of its key findings from the report summary:
- Global warming is "unequivocal," and since the 1950's it's "extremely likely" that human activities have been the dominant cause of the temperature rise.
- Concentrations of CO2 and other greenhouse gases in the atmosphere have increased to levels that are unprecedented in at least 800,000 years. The burning of fossil fuels is the main reason behind a 40 percent increase in C02 concentrations since the industrial revolution.
- Global temperatures are likely to rise by 0.3 to 4.8 degrees C, or 0.5-8.6 F, by the end of the century depending on how much governments control carbon emissions.
- Most aspects of climate change will continue for many centuries even if CO2 emissions are stopped.
- Sea levels are expected to rise a further 10-32 inches (26-82 centimeters) by the end of the century.
- The Greenland and Antarctic ice sheets have been losing mass over the past two decades. Glaciers have continued to melt almost all over the world. Arctic sea ice has shrunk and spring snow cover has continued to decrease, and it is "very likely" that this will continue.
- It's "virtually certain" that the upper ocean has warmed from 1971 to 2010. The ocean will continue to warm this century, with heat penetrating from the surface to the deep ocean.
One of the most controversial subjects in the report was how to deal with a purported slowdown in warming in the past 15 years. Climate skeptics say this "hiatus" casts doubt on the scientific consensus on climate change.
Many governments had objections over how the issue was treated in earlier drafts and some had called for it to be deleted altogether.
In the end, the IPCC made only a brief mention of the issue in the summary for policymakers, stressing that short-term records are sensitive to natural variability and don't in general reflect long-term trends.
Here are a few reactions to the summary from so-called climate skeptics compiled by blog "Watts Up With That":
- Andrew Monford, a British global warming critic with the blog Bishop Hill: The general theme of obscurantism runs across the document. Whereas in previous years the temperature records have been shown unadulterated, now we have presentation of a single figure for each decade; surely an attempt to mislead rather than inform. And the pause is only addressed with handwaving arguments and vague allusions to ocean heat.
- Bob Tisdale, Watts Up With That: They’re still misleading the public. Everyone knows (well, many of us know) their models can’t simulate the natural processes that cause surface temperatures to warm over multidecadal timeframes, yet they insist on continuing this myth.
- Dr. Judith Curry, Georgia Tech: Well, IPCC has thrown down the gauntlet – if the pause continues beyond 15 years (well it already has), they are toast. Even though they still use the word ‘most’ in the attribution statement, they go all out and pretty much say it is all AGW: ”The best estimate of the human induced contribution to warming is similar to the observed warming over this period.” In case you haven’t been paying attention, ‘extremely likely‘ in the attribution statement implies 95% confidence. Exactly what does 95% confidence mean in this context?
- Anthony Watts, Watts Up With That?: When you still push increasing confidence in predictions while the IPCC referenced models fail to model reality, and this has been pointed out worldwide in media, it becomes a “jump the shark” moment where the advocacy speaks far louder than the science.
The importance of the report is that policymakers often use it to spur governments to action. Even if action is taken to curb greenhouse gas emissions at this point, working group co-chair Thomas Stocker said in a statement, "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.”
The Associated Press contributed to this report.