Thoughts on the ocean, the environment, the universe and everything from nearly a mile high.

Panorama of The Grand Tetons From the top of Table Mountain, Wyoming © Alan Holyoak, 2011

Sunday, September 29, 2013

Highlights from the IPCC 5th Assessment Report - Summary for Policy Makers - Humans are driving climate change!

The Intergovernmental Panel on Climate Change released a draft of its Summary for Policy Makers report on Friday 9/28/2013.

This posting is a summary of the main points from that document.  The parts in bold font below are direct quotes from that document.  I inserted some additional comments clarifying or commenting on those quotes in the text in brackets below each quote.

You can read the entire document by clicking this link - it's about 30pp long:

Point #1 - Overall state of the climate:
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.

(In other words, the climate is changing, and not for the better - an observation, not a prediction, not a model)

Point #2 - State of the Atmosphere:
Each of the last three decades has been successively warmer at the Earth’s surface than any  preceding decade since 1850

(Not only is the Earth's surface temperature warmer than it used to be, decade by decade it's getting even warmer - an observation, not a prediction, not a model)

Point #3 - State of the Ocean:
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 (high confidence). It is virtually certain (=99-100% confidence) that the upper ocean (0−700 m) warmed from 1971 to 2010 

(The upper ocean is warmer than it used to be - an observation, not a prediction, not a model)

Point #4 - State of the Cryosphere (frozen regions):
Over the last 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.

(Ice is melting and ice masses are in decling everywhere - an observation, not a prediction, not a model.)

Point #5 - Sea Level:
The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901–2010, global mean sea level rose by 0.19 [0.17 to 0.21] m 

(Sea level has risen 10" - so far - since 1901 - an observation, not a prediction, not a model)

Point #6 - Carbon and other Geochemical Cycles:
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% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification. 

(Burning fossil fuels together with land use changes produced unprecedented levels of CO2 compared to its levels over the past 800K years - an observation, not a prediction, not a model)

Point #7 - Drivers of Climate Change
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.

(Radiative forcing is the term used to determine whether climate is warming or cooling.  Positive forcing is warming, negative forcing is cooling.  So, the largest contributor to current climate change is CO2 emissions - a conclusion based on many observations.)

Point #8 - Understanding the Climate and its Recent Changes
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.

(What humans have done and are doing affects climate.)

Point #9 - Evaluation of Climate Models
Climate models have improved since the AR4 (4th assessment report - 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 (very high confidence)

(Climate models are better than they used to be, and are now quite good at modeling observed climate history and observed current trends in climate change)

Point #10 - 2 Quantification of Climate System Responses:
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.

(In other words, the accumulated mass of observations collected so far, together with improved climate models increase our confidence that what we think is happening [i.e., human-driven global warming] really is happening.)

Point #11 - Detection and Attribution of Climate Change
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 AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid 20th century.

(The term "extremely likely" correlates with a statistical significance of 95% confidence, which is about the same degree of scientific confidence we have about the link between tobacco use and cancer.  So, the data now show that we are in the realm of scientific certainty that human activities have been the dominant cause of recent observed climate change.  Bottom line - HUMANS ARE CAUSING GLOBAL WARMING.)

Point #12 - Future Global and Regional Climate Change
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.

(Translation - if we just keep doing what we're doing, pumping CO2 into the atmosphere with reckless abandon, things will just keep getting worse.  The only way to mitigate the climate change problem is to cut back, way back, on carbon emissions.)

Point #13 - Future of Atmospheric Temperature
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 RCP (modeled) 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.

(No matter what we do, the atmosphere is already on a warming trend that will continue for some time to come, even if we cut carbon emissions to zero immediately.)

Point #14 - Future of the Atmosphere: Water Cycle
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.

(Most likely wet areas will get wetter, and dry areas will get drier, with some exceptions.  Get ready!)

Point #15 - Future of the Ocean
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.

(The ocean will continue to warm, no matter what we do - this will affect the movement of water, and consequently of heat around the planet)

Point #16 - Future of the Cyrosphere (ice regions)
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.

(There will be less ice on average, everywhere.)

Point #17 - Future of Sea Level
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.

(No matter what we do, sea level will continue to rise for a prolonged period of time.  All we can do now is limit how fast and how high it will rise - this is linked to carbon emissions.)

Point #18 - Carbon and Other Geochemical Cycles
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.

(Emitting even more carbon will make things progressively worse, and will drive ocean acidification - a change that will almost certainly affect marine ecosystems and probably cause the extinction of many marine species)

Point #19 - Climate Stabilization, Climate Change Commitment and Irreversibility
Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. 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.

(There is no stopping anthropgenic climate change now, our actions from this point though will determine how far it will go.  It's our call.)

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