Note that warmer air holds more moisture. When it comes into contact with cooler air, the result will be heavier precipitation - rain, snow, or sleet.http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2534
Dr. Jeff Masters, 11:31 AM GMT on September 26, 2013
Comprehensive. Authoritative. Conservative.
Those words summarize the world's most rigorous and important scientific report in history: the 2013 Intergovernmental Panel on Climate Change (IPCC) climate assessment, due to be released at 4am EDT Friday in Stockholm, Sweden. The Nobel Prize-winning IPCC has put together an amazingly authoritative and comprehensive report on a subject crucial to the future of civilization, a report that will guide policymakers worldwide as they struggle to cope with the growing chaos generated by the Great Climate Disruption that is already upon us. The first 31 pages of the report, called the "Summary For Policymakers", is what will be released Friday, and this summary will lay out a powerful scientific case that significant climate change with severe impacts is already occurring, humans are mostly responsible, the pace of climate change is expected to accelerate, and we can make choices to cut emissions of carbon dioxide and other heat-trapping gases to limit the damage.
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Q: What are some of the weaknesses of the IPCC report?
1) The report is already out-of-date, since papers had to be submitted for publication by July 2012 and published by March 2013 in order to be cited.
2) The report is tedious, complex, and difficult to read, making this vital science difficult to access. Little regard was given by the IPCC to communicating the results of the report. Science has little value if it is not understandably communicated to those who need the information. Where are the accompanying explanatory videos? Why was the report issued on a Friday, the worst day of the work week to get attention? The IPCC has devoted a very small portion of its budget to communication and outreach, leaving the interpretation of the report to others. I can understand the reluctance of the IPCC to provide a more slick and showy interpretation of the report, since they might be accused of "spinning" the science, and one of the great strengths of the IPCC report is its great science and the impartiality of the content. But the assumption that the science will speak for itself is wrong. The most powerful and richest corporations in world history--the oil companies--are waging very well-funded PR campaigns to deny the science, play up the uncertainties, and question the character of the scientists who write the report. The world's most rigorous and important scientific report in history is being kicked apart by powerful special interests whose profits are threatened by the findings.
3) Since the "Summary for Policymakers" is subject to unanimous approval by politicians, the science is potentially compromised, and the conclusions will tend to be conservative.
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4) The lower-end emissions scenario, called RCP2.6, which assumes that CO2 concentrations will reach 421 ppm by the year 2100, is highly unlikely. Earth reached 400 ppm of CO2 earlier this year, and CO2 has increased by over 2 ppm per year during the past decade. CO2 emissions are accelerating, and CO2 levels will surpass 421 ppm by the year 2023 at the current rate of acceleration. RCP2.6 requires that we slash emissions of CO2 by 50%, relative to 1990 levels, by 2050. We are currently on a pace to match or exceed the worst-case scenario considered by the IPCC (RCP8.5), where CO2 levels reach 936 ppm by the year 2100.
Commentary
The two higher-end emission scenarios of the four considered by the IPCC will very likely warm the planet more than 2°C (3.6°F) over pre-industrial levels. Two degrees Centigrade represents a "dangerous" level of warming for civilization that we must avoid, according to the 2009 Copenhagen Accord, signed by world leaders including President Obama. We will have to work very hard, and very soon, to keep warming below this 2°C "danger" level. As climate writer Elizabeth Kolbert says, holding the global temperature increase to “only” two degrees Celsius, though, is like limiting yourself to “only” a few rounds of Russian roulette: unless you’re uncommonly lucky, the result is not likely be happy. The 0.9°C warming we've experienced since 1900 has already caused a destabilization of global weather patterns, resulting in unprecedented extreme weather events and accelerating melting of polar ice caps. As a group of climate scientists wrote in 2009 at RealClimate.org,
"Even a “moderate” warming of 2°C stands a strong chance of provoking drought and storm responses that could challenge civilized society, leading potentially to the conflict and suffering that go with failed states and mass migrations. Global warming of 2°C would leave the Earth warmer than it has been in millions of years, a disruption of climate conditions that have been stable for longer than the history of human agriculture."
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