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Marty Offline OP
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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.

Q: What is the IPCC?
A: In 1988, 300 scientists and high-ranking government officials at an international conference convened by the United Nations Environmental Programme (UNEP) and the World Meteorological Organization (WMO) concluded that changes in the atmosphere due to human pollution "represent a major threat to international security and are already having harmful consequences over many parts of the globe." Immediate action was needed, they said, to negotiate a set of strict, specific targets for reducing greenhouse gas emissions. But who should coordinate such an effort? The conservative Reagan Administration and some other governments were wary of control by any group that was part of the United Nations structure. These governments proposed formation of a new, fully independent group under the direct control of representatives appointed by each government-that is, an intergovernmental panel. Responding to this pressure, the WMO and UNEP collaborated in creating the Intergovernmental Panel on Climate Change (IPCC) in 1988. The IPCC was neither a strictly scientific nor a strictly political body, but a unique hybrid. It could issue reports only with the firm agreement of a great majority of the world's leading climate scientists, plus the unanimous consensus of all participating governments. Importantly, it would put policy options on the table, but would not make explicit policy recommendations. Given these requirements, the IPCC reports tend to be quite conservative, but have unimpeachable authority.

Q: What is an IPCC report?
A: Every 5 - 6 years, the IPCC issues a massive 3,000+ page report summarizing the current state of knowledge on climate change. These "assessment reports" have been issued in 1990, 1995, 2001, 2007, and now, 2013. The latest assessment will be released in four parts:

"The Physical Science Basis" (September 2013) will describe the observed and predicted changes to Earth's climate.

"Impacts, Adaptation and Vulnerability" (March 2014) will document the dire consequences associated with the path that we're on.

"Mitigation of Climate Change" (April 2014) will outline what it will take to get us back on track to avoid the worst impacts of climate change.

The "Synthesis Report" (October 2014) will summarize all of the other reports.

The scientists who prepare the 3,000+ page report cite over 9,200 peer-reviewed scientific articles, but present no original research of their own. At least 259 authors from 39 countries drafted the part of the report being released this week, and the report was subjected to two rounds of review by 1089 experts in 55 countries beginning in December 2011. None of the scientists were paid for their work. The report was also reviewed by government representatives from 38 nations, and the final report that is being debated in Stockholm this week was revised based on the over 54,000 review comments
received. The most important part of the report is the "Summary for Policy Makers", a 31-page document that summarizes the key scientific findings, used by governments to make policy decisions on how to respond to climate change. The "Summary for Policy Makers" for "The Physical Science Basis" portion of the 2013 IPCC report is being released on September 27. The actual 1,000+ page scientific report that the "Summary for Policy Makers" summarizes is being released the following Monday (September 30.) While the "Summary for Policy Makers" is drafted by the scientists who serve as the lead authors for the IPCC report, the summary is subject to approval by the governments of the 195 member nations of the IPCC. During the final week of the approval process, politicians can weigh in and demand changes to the summary drafted by the scientists, since the final "Summary for Policy Makers" requires unanimous approval by all of the IPCC nations. The IPCC reports have the most elaborate review and approval process for any scientific report in the world. In 2007, the IPCC won the Nobel Peace Prize. In short, three words summarize the IPCC reports:

Comprehensive.
Authoritative.
Conservative.


FIgure 1. IPCC lead authors gather for a group photo at the four most recent meetings for drafting of the 2013 IPCC assessment report. Image credit: IPCC.

Q: Do errors in the IPCC reports undermine confidence in the science?
A: No. Two small errors have been found in the 3000+ pages of the 2007 IPCC report. Neither has anything to do with the basic conclusions that the globe is unequivocally warming and that human activity is the primary cause (one error was simply a typo.) The mistakes have been acknowledged and corrected and review procedures are being strengthened to avoid future errors. In a report of over 3,000 pages by hundreds of authors, it is not unusual that there would be a few minor errors. Contrarians seeking to discredit climate science, and some in the media, have blown these errors out of proportion, claiming the errors invalidate the entire IPCC report. It's like saying we need to throw out an entire phone book because two misspellings were found in it.

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. Naomi Oreskes, in Chapter Six of her book, "Merchants of Doubt", recounts the haggling that led up to the approval of the 1995 Summary for Policy Makers. Government delegates for Saudi Arabia, Kuwait, and other major oil exporting nations demanded a change to the statement the scientists had drafted, "The balance of evidence suggests an appreciable human influence on climate." For two whole days, the scientists haggled with the Saudi delegate over the single word "appreciable". Nearly 30 different alternatives were discussed before IPCC chair Bert Bolin finally found a word that both sides could accept: "The balance of evidence suggests a discernible human influence on climate." The term "discernible" established a middle ground by suggesting that human-caused climate change was detectable, but the level of that influence was subject to debate. This sentence would go on to become one the most famous scientific statements ever made about climate change, but it was more conservative than what the scientists wanted.

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."

I'll have a full analysis of the new IPCC report Friday morning. I will also be offering expert commentary live on http://www.democracynow.org Thursday morning during their 8am - 9am EDT news hour, and on The Weather Channel beginning at 7 am EDT on Friday. The 2013 Summary For Policymakers will be available on the IPCC website beginning at 4 am EDT Friday.

Jeff Masters


Joined: Oct 1999
Posts: 84,397
Marty Offline OP
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Landmark 2013 IPCC Report: 95% Chance Most of Global Warming is Human-Caused

"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes 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." Thus opens the landmark 2013 Intergovernmental Panel on Climate Change (IPCC) report issued today. Working without pay, hundreds of our most dedicated and talented climate experts have collaborated over a six-year period to create the most comprehensive and authoritative scientific document on climate change ever crafted. The first 31 pages of what will be a 4,000-page tome was released this morning after an all-night approval session that stretched until 6:30 this morning in Stockholm, Sweden. This "Summary For Policymakers" lays 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 emission of carbon dioxide and other heat-trapping gases that will limit the damage.

Q: How much has the planet warmed, and what has caused the warming?
The report documents that Earth's surface temperature warmed by 0.85°C (1.5°F) between 1880 - 2012. Two-thirds of this warming (0.6°C, 1.1°F) came after 1950. Human-emitted heat-trapping gases likely were responsible for 0.5 - 1.3°C of this post-1950 warming, while human-emitted aerosol particles reflected away sunlight and likely caused cooling (-0.6° - 0.1°C change in temperature.) Climate change due to variations in solar energy, volcanic dust, and natural sources of heat-trapping greenhouse gases were likely responsible for a small -0.1° - 0.1°C change in temperature since 1950. The sun was in a cool phase between 1978 - 2011, and the report estimates that lower solar output cooled Earth's climate slightly during this period. The influence of cosmic rays on climate over the past century was to weak to be detected, they said. In short, the report shows little support for a significant natural component to global warming since 1950. In fact, natural effects may well have made Earth cooler than it otherwise would have been. The report says that "The best estimate of the human-induced contribution to warming is similar to the observed warming over this period." In other words, close to 100% of the observed warming is due to humans.


Figure 1. The changing view of the IPCC's assessment reports on the human contribution to climate change.

Q: How have the IPCC reports changed through time?
1990: The report did not quantify the human contribution to global warming.

1995: "The balance of evidence suggests a discernible human influence on climate."

2001: Human-emitted greenhouse gases are likely (67-90% chance) responsible for more than half of Earth's temperature increase since 1951.

2007: Human-emitted greenhouse gases are very likely (at least 90% chance) responsible for more than half of Earth's temperature increase since 1951.

2013: Human-emitted greenhouse gases are extremely likely (at least 95% chance) responsible for more than half of Earth's temperature increase since 1951. This is the same confidence that scientists have in the age of the universe, or that cigarettes are deadly, according to an excellent AP article published this week by Seth Borenstein.

Q: Did the new report change the plausible range of global warming?
A. Yes. The "climate sensitivity" is defined as how much the planet would warm if the amount of atmospheric CO2 doubled. A variety of studies have arrived at very different estimates of the exact CO2 sensitivity of the climate, and the 2007 IPCC report gave a range of the most plausible values: 2 to 4.5�C, with 3�C deemed the most likely value. Recent research indicates that a sensitivity as low as 1.5�C may be possible, so the IPCC widened the range of the most plausible values: 1.5 to 4.5�C. The new lower limit of 1.5�C is a best-case scenario that appears no more likely than the high end of 4.5�C. Furthermore, even the lowest sensitivity scenario would not negate the need for emissions reductions. Current trends show that emissions are on track to increase far beyond doubling, which would create dangerous temperature rise even in a low-sensitivity climate. (Note that they give a small but worrisome possibility--0 to 10% chance--that the climate could warm by more than 6�C for a doubling of CO2.)


Figure 2. Average of NASA's GISS, NOAA"s NCDC, and the UK Met Office's HadCRUT4 monthly global surface temperature departures from average, from January 1970 through November 2012 (blue), with linear trends applied to the time frames Jan '70 - Oct '77, Apr '77 - Dec '86, Sep '87 - Nov '96, Jun '97 - Dec '02, Nov '02 - Nov '12. Climate change skeptics like to emphasize the shorter term fluctuations in global temperatures (blue lines) and ignore the long-term climate trend (red line.) The global surface temperature trend from January 1970 through November 2012 (red line) is +0.16°C (+0.29°F) per decade. Image credit: skepticalscience.com.

Q: What does the IPCC say about the "speed bump" in surface global warming over the past 10 - 15 years?
Much attention has been given in the press to the fact that the rate of surface warming over the past fifteen years has been slower than during previous decades. The report notes that due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years (1998-2012) of 0.05 °C per decade, which begins with a strong El Ni�o, is smaller than the rate calculated since 1951 of 0.12 °C per decade. However, the recent slow-down in surface warming is likely to be a mere "speed bump" on the highway of global warming, caused by natural variability. We have seen such "speed bumps" before, as well as short, sharp downhill stretches where surface warming speeds up. For example, climate scientist Stefan Rahmstorf writes at realclimate.org that "the warming trend of the 15-year period up to 2006 was almost twice as fast as expected (0.3°C per decade), and (rightly) nobody cared. We published a paper in Science in 2007 where we noted this large trend, and as the first explanation for it we named "intrinsic variability within the climate system". Which it turned out to be." Physics demands that the massive amounts of heat-trapping carbon dioxide humans have dumped into the atmosphere must cause significant warming, but the chaotic complexity of the system is expected to obscure the magnitude of the long-term trend on time scales of a few years to a decade. The attention being to this latest "speed bump" on the highway of global warming is a direct result of a well-funded PR effort by the fossil fuel industry. One has to look at the total warming of the atmosphere, oceans, land, and ice to judge the true progress of global warming, not just the surface temperature. There has been no slowdown in total global warming when we regard this entire system, as I argued in a post earlier this year. More than 90% of the energy of global warming goes into the oceans, and the reason for the relative lack of surface warming this decade is that more heat than usual is being stored in the oceans. That heat will be released to the atmosphere at some point, removing the "speed bump".

The new IPCC report says that there is medium confidence that the "speed bump" in surface warming is due in roughly equal measure to natural multi-year unpredictable variability in the weather, and to changes in the amount of sunlight reaching the surface due to volcanic eruptions and the downward phase of the current solar cycle. Most of the climate models do not reproduce this lower surface warming rate during the past 10 - 15 years. There is medium confidence that this difference between models and observations is due to natural climate variability that is impossible to predict (for example, the El Ni�o/La Ni�a cycle), with possible contributions from the models' inadequate handling of volcanic eruptions, changes in solar output, and changes in light-reflecting aerosol particles, and, in some models, a too-strong response to heat-trapping gases. For an explanation of why arguments about the global warming "slowdown" are misleading and should not offer any consolation, see this explainer from Skeptical Science and this one from the Union for Concerned Scientists.

Q: What does the IPCC say about drought?
A: Drought and reduction in water availability due to decreased mountain snow and ice is the greatest threat civilization faces from climate change, since it attacks the two things we need to live--water and food. Unfortunately, the report makes no mention of drought in the text, and we will have to wait for the March 2014 release of the "impacts" portion of the report to hear more about the threat drought poses to society. Today's report does mention drought in one of their two tables, giving "low confidence"--a 20% chance--that we have already observed a human-caused increase in the intensity and/or duration of drought in some parts of the world. This is a reduction in confidence from the 2007 report, which said that it was more likely than not (greater than 50% chance.) However, the forecast for the future is the same as in the 2007 report: we are likely to see dry areas get dryer due to human-caused climate change by 2100. In particular, there is high confidence (80%) in likely surface drying in the Mediterranean, Southwest U.S., and Southern Africa by 2100 in the high-end emissions scenario (RCP8.5), in association with expected increases in surface temperatures and a shift in the atmospheric circulation that will expand the region of sinking air that creates the world's greatest deserts.

Q: What does the IPCC say about sea level rise?
A: Global average sea level has risen 7.5" (19 cm) since 1901. Sea level has accelerated to 1.5" (3.2 cm) per decade over the past 20 years--nearly double the rate of rise during the 20th century. The report projects that sea level will rise by an extra 0.9 - 3.2' (26 to 98 cm) by 2100. While the maximum sea level rise expected has gone up since the 2007 report, when the IPCC did not even consider melt from Greenland and Antarctica because of the primitive state of glacier science then, the new upper bound (3.2') is still is a very conservative number. IPCC decided not to include estimates from at least five published studies that had higher numbers, including two studies with rises of 2 meters (6.6 feet.) This is in contradiction to NOAA's December 2012 U.S. National Climate Assessment Report, which has 6.6 feet (2.0 meters) as its worst-case sea level rise scenario for 2100. Even this number may be too low; at a presentation Thursday in New York City for Climate Week, glaciologist Dr. Jason Box, who knows as much about Greenland's ice sheets as any person alive, explained that Greenland's contribution to global sea level rise doubled over the past ten years. If Greenland's melt rate continues to double every ten years until 2100, Greenland alone will contribute 4.6' (1.4 meters) of global sea level rise, he said. If the doubling time becomes every nine years, then Greenland will cause 16.4' (5 meters) of sea level rise by 2100. His best-guess number for global sea level rise by 2100 is 4.7' (1.5 meters), but warns that our models used to predict melting of ice of Greenland have large unknowns.

Long-term sea level rise is expected to be much greater. The IPCC report states with "very high confidence" that 119,000 - 126,000 years ago, during the period before the most recent ice age, sea levels were 16 - 33 feet (5 - 10 meters) higher than at present. Melting of Greenland "very likely" contributed 1.4 - 4.3 meters of this rise, with additional contributions coming from Antarctica. Temperatures at that time weren't more than 2°C warmer than "pre-industrial" levels during that period. Two of the four scenarios used for the report project we will exceed 2°C of warming by 2100, with "high confidence", raising the possibility that we could see sea level rises of many meters over time scales of 1,000 years or so. The report expects sea level rise reach 3.3 - 9.8' (1 - 3 meters) by 2300, assuming CO2 levels rise above 700 ppm (close to what the higher-end RCP6.0 scenario prescribes.)

Q: What does the IPCC say about ocean acidity?
A: The world's oceans have seen a 26% increase in acidity since the Industrial Revolution, as the average pH has dropped from 8.2 to 8.1. Under all report scenarios, the acidification of the world's oceans will increase, with the pH falling by another 0.06 - 0.32 units. According to a 2012 study in Science, the current acidification rate is likely the fastest in 300 million years, and "may have severe consequences for marine ecosystems."

Q: How about hurricanes?
A: The new report gives "low confidence"--a 20% chance--that we have observed a human-caused increase in intense hurricanes in some parts of the world. This is a reduction from the 2007 report, which said that it was more likely than not (greater than 50% chance.) The IPCC likely took note of a landmark 2010 review paper, "Tropical Cyclones and Climate Change", authored by ten top hurricane scientists, which concluded that the U.S. has not seen any long-term increase in landfalling tropical storms and hurricanes, and that "it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes." The 2013 IPCC report predicts that there is a greater than 50% chance (more likely than not) that we will see a human-caused increase in intense hurricanes by 2100 in some regions; this is a reduction from the 2007 report, which said this would be likely (66% chance or higher.)

Q: How about extreme weather events?
"Changes in many extreme weather and climate events have been observed since about 1950. It is very likely that the number of cold days and nights have decreased and the number of warm days and nights has increased on the global scale. It is likely that the frequency of heat waves has increased in large parts of Europe, Asia, and Australia. There are likely more land regions where the number of heavy precipitation events has increased than where it has decreased. The frequency or intensity of heavy precipitation events has likely increased in North America and Europe." The report made no mention of tornadoes and severe thunderstorms, since the uncertainties of how they have behaved in the past and how climate change might affect them in the future are too great.

Q: What does the IPCC say about a "Day After Tomorrow" scenario?
A: In the disaster movie "The Day After Tomorrow", the Atlantic Meridional Overturning Circulation (AMOC)--the ocean current system of which the Gulf Stream Current is a part of--collapses, causing a rapid and extreme change in climate. A collapse of the AMOC is very unlikely (0 - 10% chance) before 2100 according to the report, but cannot be ruled out beyond the 21st century. A weakening of the AMOC by about 11 - 34% by 2100 is expected in the moderate RCP4.5 scenario, where CO2 levels reach 538 ppm in 2100. However, these odds assume that Greenland will dump a relatively modest amount of fresh water into the North Atlantic by 2100. If the higher-end sea level rise estimates that the IPCC did not consider as plausible come true, the AMOC will likely slow down much more, with a higher chance of collapse this century. No slow-down in the AMOC has been observed yet, according to the report.

Commentary
As I read though the report, digesting the exhaustive list of changes to Earth's atmosphere, oceans, and ice that have occurred over the past few decades, I was struck by how the IPCC report reads like lab results from a sick hospital patient. The natural systems that civilization depends upon to thrive have been profoundly disturbed, and the forecast for the future reads like a medical diagnosis for an overweight smoker with a heart condition: unless the patient makes major lifestyle changes, the illness will grow far worse, with severe debilitation or death distinct possibilities. We can and we must make the huge effort to turn things around. Oil and natural gas are the energy technologies of the 20th century. Coal is the energy technology of the 19th century. We have countless innovative and dedicated people ready to move us to the energy technology of the 21st century; I heard three of them speak last night at the Climate Week event I am at, and they really gave me some needed hope that we can turn things around. We must elect new leaders and pressure our existing leaders to take the strong actions needed to advance us into a new, 21st century energy economy. You can all help make it so!

Jeff Masters


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