OK

heads in the sand for climate change
The Intergovernmental Panel on Climate Change released its Climate Change 2013: The Physical Science Basis Friday. The 2,000-page report of Working Group I's fifth assessment (AR5) since 1990 makes it clear that those who have denied and continue to deny that human-caused global warming is happening have accomplished just one thing in their lying attacks on science: slowed attempts to do something about the climate crisis. Scientists who reviewed a boat-load of peer-reviewed journal articles for the IPCC assessment raised their level of certainty that humans are causing global warming from the 90 percent of the fourth assessment published in 2007 to 95 percent now:
In their starkest warning yet, following nearly seven years of new research on the climate, the Intergovernmental Panel on Climate Change (IPCC) said it was "unequivocal" and that even if the world begins to moderate greenhouse gas emissions, warming is likely to cross the critical threshold of 2C by the end of this century. That would have serious consequences, including sea level rises, heatwaves and changes to rainfall meaning dry regions get less and already wet areas receive more.

In response to the report, the US secretary of state, John Kerry, said in a statement: "This is yet another wakeup call: 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 commonsense should be willing to even contemplate," he said.

Critics, of course, will not be persuaded. For example, Anthony Watts, a one-time television meteorologist who writes the oratorically aggressive blog Watts Up With That?, called the report “comical at best.” One might be tempted to think he was referring to himself. But the denial he and others continue to display in the face of ever more evidence is not at all funny. Neither is congressional failure to act laughable as a consequence of having 161 deniers in the U.S. House of Representatives. Their opposition is reckless and ultimately lethal.

The bottom line of the IPCC report is what its authors say about the continuing emission of carbon into the atmosphere. To keep the average global temperature from rising above 2°C (3.6°F), the scientists say, the world can only afford to add 800 to 880 billion tons of carbon dioxide to the atmosphere. We have already emitted 530 billion tons. In 2012, the world added another 31.6 billion tons to that total. The math is straightforward. At the current level CO2 emissions, that upper limit will be reached by 2025. Kids born today will only have reached the age of middle schoolers.

Some other critics have been saying in advance of the release of the IPCC assessment that it is too conservative in its pronouncements. Despite a flattening in temperature rise in the past 15 years, they say, the global average will hit 2°C well before the end of the century. Joe Romm of Climate Progress has repeatedly noted a key problem of the IPCC assessments is that they are obsolete before they are published. Given the process they must undergo to make it into print and pixels, that obsolescence is understandable.

U.N. Secretary General Ban Ki-moon announced last week that he wants a special summit of world leaders in 2014, a year ahead of the next round of talks at the 21st U.N. Conference on Climate Change (COP 21) in Paris. Getting together well in advance of the Paris talks is seen as crucial since the failure to come to substantial agreement in the Copenhagen talks of 2009 was blamed in great part on the fact that world leaders, including President Obama, more or less parachuted into Denmark at the last minute to salvage what they could. Which didn't work out. Indeed, in spite of efforts to put lipstick on the mess, the conference ended in discombobulation.

Please read below the fold for bullets condensed from the IPCC report.

Here are the condensed findings of the fifth assessment included in the summary for policymakers:

• Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.

• Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90 percent of the energy accumulated between 1971 and 2010. It is virtually certain that the upper ocean (0−700 meters) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971.

• Over the past two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.

Earth as ice cream cone
• 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 [0.17 to 0.21] meters.

• 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 percent since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30 percent of the emitted anthropogenic carbon dioxide, causing ocean acidification.

• Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750.

• Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.

• 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. This evidence for human influence
has grown since the fourth IPCC assessment. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

• Climate models have improved since the fourth IPCC assessment in 2007. Models reproduce observed continental-scale surface temperature patterns and trends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately following large volcanic eruptions.

• Observational and model studies of temperature change, climate feedbacks and changes in the Earth’s energy budget together provide confidence in the magnitude of global warming in response to past and future forcing.

• 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.

• Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all Representative Concentration Pathway (RCP) scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform.

• Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.

• The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.

• It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease.

• Global mean sea level will continue to rise during the 21st century. Under all RCP scenarios the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.

• Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will increase ocean acidification.

• Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond (see Figure SPM.10). 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.

Originally posted to Meteor Blades on Fri Sep 27, 2013 at 09:54 AM PDT.

Also republished by Climate Change SOS, DK GreenRoots, Climate Hawks, Holy $h*tters, and Daily Kos.

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