How Do We Answer Our Children?

On Friday March 15, 2019 children all over the world walked away from school and joined organized marches to raise their voices in favor of combatting global warming. 

It’s estimated that around the world about one million marchers joined this protest, according to its organizers.  They gathered in over 1,600 cities in more than 100 countries.

This movement was started in 2018 by Greta Thunberg, a Swedish high school student, now 16 years old.  Her tweeted message from the March 15 protest is shown here:

She told the gathered marchers in Sweden “We are facing the greatest existential crisis humanity has ever faced. And yet it has been ignored. You who have ignored it know who you are.” 

In Africa, Isaac Oindo, from NGO Power Shift Africa, said:  “Some people think climate change is only a future problem but here in Africa we know that it is happening now. We're living through it. However we know that it is going to affect the next generation even more severely which is why it's no surprise to see school children here in Africa and around the world going on strike to demand action.”


In Berlin, Luis Anzolin, age 15, declared “We’re here because it’s important, it’s about our future. Because let’s face it, those sitting in Parliament will probably not be there in the future and it’s going to affect us.”

A 2018 Pew Research Poll conducted in 26 countries found that climate change is viewed as the main international threat in 13 of them.  Young people are more worried about the threats that climate change poses than are those over 50, in the U.S., France, Australia and the Philippines.

These youths, presently in their mid- to late-teen years, realize that within their lifetimes the world’s climate will wreak severe harm on our planet if humanity continues its present profligate energy habits. This was already foreseen in the United Nations’ 5^th Assessment Report (5AR) issued 2013-2014 by the Intergovernmental Panel on Climate Change (IPCC).The report models the future climate expected under four scenarios of greenhouse gas (GHG) emission rates. It finds that for an unconstrained scenario by 2100 the long-term global average surface temperature could reach as high as about 4.6°C (8.3°F) above the average for the two-decade period from 1861-1880, as seen in the image below. 

In this graphic the total accumulated amount of extra carbon dioxide (CO₂) added to the atmosphere since the industrial revolution began, arising from burning fossil fuels, is given on the upper horizontal axis.  The resulting increase in long-term global average temperature, arising from modeling the four emission scenarios, is shown on the vertical axis, referenced to the 1861-1880 average.  The four scenarios range from most stringent (falling to zero emissions at about 2040) shown in dark blue, giving a temperature increase of about 1.8°C (3.2°F) by 2100; passing on through the progressively less stringent scenarios shown in light blue and orange; and ending on the scenario that continues present trends of largely unconstrained emissions (red) mentioned earlier.

The black line in the lower left represent actual historical data, with each decadal year given by a dot, some of which show the year.  It’s seen that this historical “hindcast” reproduces the historical data very well, giving credence that the modeling is correct.  The four successive emissions scenarios follow almost a straight line toward the upper right, toward higher CO₂ levels and higher projected temperatures.

It’s already turning out that our children are right to be alarmed and frightened about their climate future.  In the five years since 5AR was issued, accumulated CO₂ in the atmosphere has continued to increase year by year, as has the long-term global average temperature.  The world has been afflicted with ever more severe bouts of extreme weather and extreme climate, just as the climate scientists writing 5AR foresaw.  These include, in differing regions of the planet, drought and reduced agricultural yield, heat waves and long-term hot temperatures also reducing agricultural yield, more extreme precipitation resulting in fresh water floods, more severe storms, fair weather tidal flooding along shorelines, and ocean warming resulting in displaced fisheries.  The science of attribution has made great progress in recent years; events such as listed here in many cases are deemed to have been made more severe because of global warming.  Our perceived sense of worsening weather and climate events is real, and is due to worsening warming.

Climate scientists have been calling for policies to mitigate global warming and to adapt to its consequences since at least the First Assessment Report almost three decades ago.  Policymakers in many countries, but especially in the U. S., have ignored or even sought to suppress these findings.

We must answer our children now.  Scant time remains for those in power the world over to act meaningfully to mitigate worsening warming and to implement adaptation measures to address effects that are already underway.  Being human, our policymakers themselves have children and grandchildren, or may have them soon.  Their children, like ours, call out for meaningful action.  Doing nothing is no longer an option, since it consigns all those in future generations to lives of misery and hardship.

Our children are waiting for us to act.  Their future calls for nothing less than decarbonizing our energy economy as completely as feasible, using existing and newly invented technologies.

 

 © 2019 Henry Auer

IPCC Fifth Assessment Report, Part 2: Impacts, Adaptation, and Vulnerability

Summary.  The Intergovernmental Panel on Climate Change issued  Part 2 of its Fifth Assessment Report, “Climate Change 2014: Impacts, Adaptation, and Vulnerability”, in March 2014.  Part 2 discusses the need for and implementation of adaptation strategies for coping with the adverse effects of global warming.

Warming causes harms to human populations and natural environments around the globe.  Because of effects such as loss of water resources, lower crop yields, and exposure to extreme weather events, human wellbeing is severely affected. The world needs to adapt to these new climate realities.  Part 2 presents strategies for developing adaptation programs, emphasizing that this process depends importantly on risk management and the repetitive cycling of planning, implementation and assessment.  A major difficulty envisioned is procuring adequate funding for these endeavors. 

Introduction. The Intergovernmental Panel on Climate Change (IPCC) is established under the United Nations Framework Convention on Climate Change (UNFCCC).  Four Assessment Reports (ARs) have been issued previously beginning in 1990; they are summarized here.  Part 2 of the IPCC Fifth Assessment Report (5AR), “Climate Change 2014: Impacts, Adaptation, and Vulnerability”, was released on March 31, 2014 and is discussed here.  This post is based on its Summary for Policymakers (SPM) (Part 1 of the IPCC Fifth Assessment Report (5AR), “The Physical Science Basis”, was released on September 30, 2013, reported on here.  Part 3, “Mitigation of Climate Change”, is due in April, 2014.)

The IPCC Assessment Reports carry great weight among climate scientists and policymakers around the world.  Each part is assembled by a large group of researchers who are specialists in their respective fields, drawn from many of the UN member states.  The draft reports are subjected to two rounds of scientific review and approval by selected governments before being released (see Details at the end of this post.)  This process assures the most rigorous scientific validity and forms a sound basis for policy development.

Review of the Current Global Status Concerning Adaptation

Adaptation has grown to be an important topic because the world’s climate has already changed, inflicting harm on human populations and degrading the natural environment.  Worldwide impacts have already been felt across terrestrial and oceanic environments.  An extensive summary in SPM of global changes attributed largely to climate change already under way includes

receding mountain glaciers and decline in coral reefs in Africa;
receding mountain glaciers, and earlier leafing and fruit bearing of trees, in Europe;

permafrost degradation and decline in coral reefs in Asia;

shrinkage of mountain glaciers and reduced availability of water from mountain snowpack, and northward shifts of Atlantic fish in North America; and

shrinkage of mountain glaciers and increased Caribbean coral bleaching in Central and South America.

More generally, SPM states that both land species and water and ocean species are shifting their distribution ranges, migration patterns, abundances and ecological interactions in response to climate change.  Worldwide, climate change has caused crop yields to fall, especially for wheat and maize.

Socioeconomic effects of climate change depend importantly on the interplay of their vulnerability and their exposure.  Extreme events such as heat waves, droughts, floods, cyclones and wildfires can lead to altered ecosystems, disrupted food and water supplies, damage to infrastructure, morbidity, mortality, and poor mental health.  SPM states there is “a significant lack of preparedness for current climate variability….”

Adaptation is entering into the consciousness of the public and policymakers.  SPM states “adaptation is becoming embedded in some planning processes, with more limited implementation of responses”.  Both governments and private sector entities are developing adaptation plans and policies, including incorporating adaptation contingencies into broader development plans. Examples of adaptation planning include

disaster risk management;

coastal and water management;

early warning systems;

adapting to sea level rise;

protection of energy and public infrastructure; and

conservation and agricultural product shifts.

Planning future adaptation strategies involves dealing with significant climate uncertainties in a changing background.  Effectiveness of strategies cannot be presently determined because risk management is subject to many interacting factors, long time ranges, and persisting uncertainties.  Repeated cycles of planning, implementing and assessment of adaptive and mitigating strategies are central to this process going forward.

Mitigation of future climate change and adaptation to future harms are closely interacting activities.  Depending on the stringency of worldwide mitigation actions taken, future impacts of warming can vary significantly during the second half of this century.  The severity of these effects in turn impacts how much adaptation will be needed. 

Future Sources of Risk

“Dangerous [manmade] interference with the climate system” (SPM) adversely affects the hazards to and vulnerability of societies and natural systems.  Possible perils include death, injury, ill health or affected livelihoods, degraded coastal regions, pressures on urban populations, loss of infrastructure services, mortality and morbidity from excessive heat, food scarcity and food insecurity, and degradation of marine and terrestrial ecosystems.

The extent of future warming will determine how severe, pervasive and irreversible impacts will be.  Scenarios in which emissions continue at a moderate to high rate risk causing significant future adverse effects such as

on freshwater resources and drought;

terrestrial species extinctions;

submergence and flooding of coastlines;

loss of marine biodiversity and fisheries productivity;

reduced crop yields for wheat, rice and maize in most regions;

lowered economic activity; and

poor human health. 

There is furthermore the risk of population displacements, civil war and inter-regional war, and effects on national security policies due to climate effects on infrastructure.

Adaptive measures should increase resilience to the harms of climate change.  Cross-disciplinary mechanisms for planning and implementation of adaptation measures are needed, at the international, national, regional, and local levels.  Potential problems can arise from constraints including insufficient funding, poor planning, and allocating investments between mitigation and adaptation.

Ideally successful planning will lead to climate-resilience and transformation.  Climate resilience results from combined implementation of adaptation and mitigation measures.  The process will rely on the repeated cycles of assessment and implementation described above, providing effective risk management over time.   Insufficient mitigation measures will result in the inability of adaptation measures to ward off the effects of warming.  The needed transformations include promoting human development (education, housing, etc.), reducing poverty, expanding social safety nets, enhancing ecosystem management, improving infrastructure and technology, implementing effective national policies for adaptation, and political and cultural actions to promote awareness.

Analysis

 

The IPCC Assessment Reports have been warning of the need for mitigation since 1990.  Each of the four earlier assessment reports presented the case for mitigating emissions of greenhouse gases (GHGs) with successively greater urgency, and with increasing confidence arising from better information and advancing technology.  The resulting enhancements in climate science are reflected in the successive ARs.  This trend continues with 5AR; for example Part 2 considered here cites twice as many publications as its predecessor 7 years ago. 

The urgings in successive assessment reports to begin meaningful reductions in annual rates of emission of greenhouse gases reflect perfectly the meaning of the old saying, “a stitch in time saves nine”.  In other words, early repair of a (tailoring or climatic) defect involving minimal effort avoids the need for later extensive repair of the worsening defect that was left untended.

For example, the prominent climate scientist Thomas F. Stocker concluded in 2013  “…every year counts….  [The longer] the starting time of [a global mitigation program] is delayed, the [more] low [limiting temperature] targets are progressively lost.  The door for these climate targets closes irreversibly.”

As SPM makes clear, early potential mitigation steps not pursued inevitably lead to a need for adaptation to be undertaken, a need that would be far less urgent had mitigation been begun early.

An opportunity for effective global mitigation policy with the Kyoto Protocol (KP) was missed.  KP, setting achievable mitigation goals, was negotiated in 1997 under the UNFCCC; it entered into force in 2005 and expired in 2012.  The treaty crucially excludes developing countries from coverage, retaining only developed countries under its terms.  For this and other reasons the U. S. Senate did not ratify the treaty, so the U. S., the country with the highest GHG emission rate at the time, was not bound by its terms.  Covered nations pledged to reduce their annual emission rates by stated percentages by 2012.  Developing countries and the U. S., on the other hand, were free to continue unconstrained emissions.  During this interval China, now the nation with the highest annual emission rate, and India each increased their emission rates by about 160%, while the rate for the U. S. increased only 30%.

It is clear in hindsight that a critical opportunity for mitigating global GHG emissions was missed.  As a result the reasoned investments in mitigation urged by the IPCC assessment reports, and by Stocker and others, must now be made at a far more intense, and more demanding, rate of expenditure.

Such investments, considered at a global or regional economic scale, largely represent shifting of funds from new fossil fuel development into establishing new infrastructure for renewable energy.  In other words, these investments should be considered to involve funding that had been previously planned.

Adaptation strategies now must find new investment funding from scarce resources.  In contrast to shifting preexisting investment resources for mitigation, funding for adaptation indeed must be found from new, previously unallocated sources.  Consider Hurricane Sandy that struck the New Jersey-New York region in October 2012.  The damage estimate was US$71 billion.  The public ultimately pays this cost in the form of higher insurance premiums and higher taxes, both of which are expenses that previously did not exist and were not planned for.

New York City is responding to the damage caused by the hurricane by undertaking a massive adaptation program to enhance its resilience, valued at US$19.5 billion. An interactive map of cities and states of the U. S. shows their progress toward planning for adaptation. The United Nations estimates that globally adaptation expenditures could be  US$49 billion to US$171 billion a year through 2030.

Adaptation was recognized as an important aspect of the global warming issue at the UNFCCC conference in Cancun in 2010.  The conference established an adaptation fund to assist poorer nations of the world facing harms from global warming.  It was to achieve a contribution amount of US$100 billion/yr by 2020.  Of this, the U. S. was expected to contribute US$20-30 billion/yr. Unfortunately the U. S. has contributed only about US$2.5 billion/yr since 2010.

 

Conclusion

Worsening of planetary warming due to manmade emissions of GHGs is causing  the world to recognize that in addition to mitigation of emissions, adaptation to our changing climate is now needed.  Warming adversely affects human populations and natural ecosystems in ways that negatively impact human wellbeing.  These harms are expected to worsen as warming becomes more pronounced in coming decades.

Adaptation requires the investment of new money not previously allocated for this purpose.  The planning and implementing of adaptation measures explores uncharted paths, since the world has no previous experience in these matters.  Risks arise from uncertainties concerning effects of future warming and undetermined effects that adaptation measures will have.  Risk management therefore will require repeated cycles of planning and implementing adaptation measures, and assessing the efficacy of the resulting projects.  Conclusions drawn from the assessments will then be used to start the cycle over.  Effective adaptations should alleviate the harms from warming that affect human populations and our natural world.

 

Details

 

Significance of IPCC Assessment Reports.  The 5AR, like its predecessors, is produced by a large, ecumenical group of hundreds of experts in their fields, and subjected to review by other experts and by appropriate governmental bodies before it is approved and accepted for release.  Technical details in the ARs are based only on peer-reviewed journal articles and reports produced by renowned nongovernmental organizations or government agencies.  The exhaustive review assures that the released report both represents the current state of scientific and technical expertise, on the one hand, and the points of view of governments of the IPCC, on the other. 

The steps involved in preparing the reports are summarized here, including details for the 30 chapters in Part 2 :

1. Governments and organizations nominate authors, who are then selected by the organizers of the Working Groups (here called “Parts”)
2. 745 authors and reviewers from over 100 countries were selected to prepare a first draft of Part 2, considering over 12,000 peer-reviewed scientific articles;
3. The first draft was reviewed by 1,774 other experts who considered 19,598 comments;
4. 2,631 expert reviewers prepared a second draft considering 28,544 comments;
5. The second draft was reviewed by 1,271 experts from 67 countries, and by 33 governments;
6. The final draft of the Summary for Policymakers was prepared by 241 reviewers from 45 governments, considering 2,350 comments; and
7. The final draft was approved and accepted by the IPCC, and released.

As a result of this thorough drafting and review process, the ARs are rigorously objective.  The reader cannot seriously believe that the ARs offer prejudiced or directed findings or opinions. Indeed, the approval and acceptance process likely leads to consensus positions on unresolved or contentious issues while minimizing the importance granted outlying results or evaluations.

 
© 2014 Henry Auer

IPCC Fifth Assessment Report, Part 1: The Physical Science Basis

Summary.  The Intergovernmental Panel on Climate Change issued Part 1 of its Fifth Assessment Report, “The Physical Science Basis”, on September 30, 2013.  The Report first summarizes past changes in the climate system.  It states that the recent warming of the earth/s climate is “unequivocal”.  Since the 1950s changes in many climate parameters including concentrations of greenhouse gases; temperature; loss of snow cover, glaciers and ice sheets; and rising sea levels are “unprecedented” considering the last decades to thousands of years.  There are many recognized contributions to these effects but by far greatest single factor is the increase in the atmospheric concentration of the greenhouse gas carbon dioxide.

A variety of climate models of lesser or greater complexity successfully reproduce the earth’s recent climate history on global and regional scales and over longer periods of time, showing that the models adequately account for the major processes involved in evolving climate change. 

These same models are then employed together with four scenarios of decreasing stringency concerning greenhouse gas emissions. Imposing rigorous emission constraints will limit further warming to a low, but still more elevated, level than the present by 2100; whereas continuing “business as usual”, an essentially unconstrained scenario, will lead to drastic increases in temperature by 2100 and induce severe changes in climate and the consequences thereof.

Furthermore, since carbon dioxide remains in the atmosphere for centuries or thousands of years, humanity’s actions today and in the near future will lead to irreversible and persistently higher global average temperatures for long time periods, affecting the lives and wellbeing of mankind’s progeny for generations.  For this reason this writer believes it is now time for the member states of the United Nations to coalesce around a meaningful agreement to reduce GHG emissions toward zero in order to stabilize the climate at the lowest level possible of its  new, higher greenhouse-mediated temperature.

 

Introduction.  The Intergovernmental Panel on Climate Change (IPCC) is established under the United Nations Framework Convention on Climate Change.  Four Assessment Reports (ARs) have been issued previously beginning in 1990; they are summarized here. Part 1 of the IPCC Fifth Assessment Report (5AR), “The Physical Science Basis”, was released on September 30, 2013.  This post is based on the Summary for Policymakers. 

(Part 2,  “Impacts, Adaptation and Vulnerability”, is due in late March 2014; and Part 3, “Mitigation of Climate Change”, is due in early April, 2014.)

As explained below in the Details section, IPCC ARs are prepared by hundreds of eminent climate scientists selected from among all member nations of the U. N.  First and second drafts are prepared in succession, each reviewed by others before moving to the next stage, and finally reviewed by selected government officials.  For this reason the 5AR meets every reasonable standard for scientific rigor, objectivity and validity.  It represents a worldwide consensus on the current status of climate science and projections of future effects as the world continues to warm, and merits serious consideration by all in view of the process outlined here and in expanded form below.

Part 1 of 5AR is presented in four sections: a summary of data characterizing past and present trends, the sources for the heat energy that is warming the planet, providing an understanding of past climate patterns using models, and projections of possible future warming depending on assumptions of humanity’s behavior.  These are summarized here and expanded in the Details section.

Observed Changes in the Climate System.  The Summary characterizes the warming of the earth’s climate to date as “unequivocal”.  Since the 1950’s many climate parameters have changed to an extent that is “unprecedented” with respect to historical patterns going back from decades to thousands of years.  Particular findings include increased concentrations of greenhouse gases (GHGs) in the atmosphere, warming of the atmosphere and the waters of the oceans, decreased amounts of snow (such as found in high mountain regions) and ice (such as land-based glaciers and sea ice), and a higher average sea level.

Properties of the Earth System That Contribute to Global Warming.  Contributions from many climatic features must be considered in arriving at a final value for the rate that the earth absorbs energy from the sun or releases it back into space.  The result shows that the overall rate of energy absorption per unit area of the earth’s surface is in fact a warming contribution.  This rate of absorption was 43% higher in 2011 than the value given for 2005 presented in the IPCC Fourth Assessment Report (4AR).  The largest contributing factor is the increase in atmospheric concentration of CO₂.

Providing an Understanding of Past Climate Patterns Using Models.  Humanity’s activities have been the dominant factor impacting global warming, both atmospheric and oceanic; changes in the global water cycle; reductions in snow and ice amounts; and the global mean sea level (95-100% likelihood).  Human activities affecting the earth’s climate are well understood, including adding to the atmospheric burden of GHGs. 

Historical data for the climate are well reproduced using climate models.  These have been improved greatly since 4AR.  More, and better quality, data have been acquired since then.  Computing power has greatly expanded.  Comprehensive models permit assessing effects with higher spatial and time resolution.  The Summary states with “very high confidence” that models now in use successfully provide temperature patterns at a continental scale of resolution and provide trends over many decades, capturing the dramatic warming since the middle of the 20^th century as well as transient cooling effects of large volcanic eruptions.

Projections of Possible Future Warming.  An ensemble of climate models, all of which successfully reproduce past climate behavior, was used to project future trends.  Four possible pathways (termed RCPs) are considered, characterized by increasing rates of heating the planet due to continued manmade emissions of GHGs, up to the year 2100.  Based on these models and pathways, the Summary concludes that if humanity continues emitting GHGs the earth will warm further, and the other climate responses discussed above will likewise continue worsening along paths already under way.  Limiting further climate change, beyond the level already established, depends on “substantial and sustained” reductions of GHG emissions.  The extent and severity of most further changes foreseen in 5AR differ little from those already characterized in 4AR; sea level rise, however, is projected to be more pronounced.

Conclusion

The Summary ends by stating

“Cumulative emissions of CO₂ largely determine global mean surface warming by the late 21^st 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.”

The global average temperature increases essentially linearly with the amount of CO₂ emitted into the atmosphere from 1870, through the historical period ending at 2010, and on into the projected emissions-temperature pathways through 2100.  The only difference in the projections for the four RCP cases is that for RCP 2.6 the trajectory ends in 2100 at a low level of total accumulated CO₂, with an overall increase in temperature under 2ºC (3.6ºF); the intermediate RCPs extend to higher total accumulated emissions and correspondingly higher temperatures projected for 2100; and ending with RCP 8.5 at the highest level of total accumulated CO₂ emitted by 2100 corresponding to a total temperature increase from 1870 of about 4.6ºC (8.3ºF).

Additional contributors to the rate of energy increase of the earth arise from sources other than CO₂ such as other GHGs, warming feedbacks that affect the rate of energy accumulation and sources such as melting permafrost which emits new methane.  Accounting for these additional factors leads to lowering the projected amounts of manmade CO₂ emissions permissible in order to remain below any given level of global warming.

The Summary further states “A large fraction of anthropogenic climate change resulting from CO₂ emissions is irreversible on a multi-century to millennial time scale” for the portion not absorbed into the ocean or taken up by photosynthetic plants.  There is no natural process operating within this time scale that removes CO₂ from the atmosphere.  It is projected that 15 to 40% of emitted CO₂ will remain in the atmosphere longer than 1,000 years.  Therefore the resulting warming of the earth will likewise persist at the higher temperatures projected in the models for many centuries, even after all new emissions of CO₂ will have come to an end. At least partly for this reason global sea levels will continue rising beyond 2100, due to further thermal expansion and continued melting of ice sheets and glaciers.  Melting continues as long as the air temperature at the ice sheet surface remains above the melting point.  By 2300 the sea level could rise by 1 m (3.3 ft) under the RCP 2.6 scenario, or by as much as 1 m to more than 3 m (10 ft) under the RCP 8.5 scenario.  Sustained warm temperatures are thought to lead to complete loss of the Greenland ice sheet over 1,000 years, producing a sea level rise of up to 7 m (23 ft).

 

Analysis

 

The IPCC, starting in 1990, has concluded that our planet is warming as the result of manmade emissions of GHGs including CO₂.  In its First AR and thereafter, it has urged the nations of the world to reduce emissions drastically in order to minimize anticipated increases in the long-term average global temperature. Recent ARs corroborated the earlier ones as more, and more sophisticated, data has been accumulated and analyzed, and more robust modeling has permitted more detailed projections of future climate trajectories to be made.   As a result statements of the likelihood of potential outcomes have become more certain.

The present 5AR continues this progression, benefiting from robust newly gathered data and analysis, and elaboration of climate models of increasing sophistication, regional and spatial resolution, and time development.  It continues the trend of the earlier reports, presenting data analysis and projections that have not changed significantly in substance, but that are now presented with higher degrees of certainty in view of the newly acquired information and the specificity of new modeling forecasts.

If meaningful abatement steps were not undertaken, the ARs have warned, serious consequences to human welfare would occur.  These include rising sea levels carrying the danger of unprecedented storm surges, and region-dependent increases in heat and drought in certain areas or heavier precipitation and river flooding in others.  All these eventualities impact negatively on the socioeconomic wellbeing of affected populations.

These warnings are actually coming to pass with increasing regularity and ferocity in recent years; global warming contributes significantly to such extreme events.

 

Global warming is “unequivocal”; it is under way at the present time.  Climatic changes are due to manmade emissions of GHGs including CO₂ released when fossil fuels are burned.  The harms arising from greenhouse effects, such as record high temperatures and heat waves, more and more intense storms including flooding, and sea level rise, cause widespread damage and human suffering.  Ultimately society pays for these emergencies through relief and adaptation measures.  Now is the time for the member states of the United Nations to coalesce around a meaningful agreement to reduce GHG emissions toward zero in order to stabilize the climate at its new, higher greenhouse-mediated temperature.

 

Details

 

Significance of IPCC Assessment Reports.  The 5AR, like its predecessors, is produced by a large, ecumenical group of hundreds of  experts in their fields, and subjected to review by other experts and by appropriate governmental bodies before it is approved and accepted for release.  Technical details are based only on peer-reviewed journal articles and reports produced by renowned nongovernmental organizations or government agencies.  The exhaustive review assures that the released report both represents the current state of scientific and technical expertise, on the one hand, and the points of view of governments of the IPCC, on the other. 

The steps involved in preparing the reports are summarized here:

1. Governments and organizations nominate authors, who are then selected by the organizers of the Working Groups (here called “Parts”)
2. The selected authors prepare a first draft of the Part;
3. The first draft is reviewed by others;
4. Authors prepare a second draft considering reviewers’ comments;
5. The second draft is reviewed by governments and experts
6. A final draft is prepared considering reviewers’ comments;
7. Governments review the final draft; and
8. The final draft is approved and accepted by the IPCC, and released.

As a result of this thorough drafting and review process, the ARs are rigorously objective.  The reader cannot seriously believe that the ARs offer prejudiced or directed findings or opinions. Indeed, the approval and acceptance process likely leads to consensus positions on unresolved or contentious issues while minimizing the importance granted outlying results or evaluations.

Preparation of the first draft of Part 1 of the 5AR involved 659 experts and considered 21,400 comments; the second draft involved 800 experts and 26 governments, and considered 31,422 comments.

The following sections expand on the summaries outlined above.

Observed Changes in the Climate System.  As dates of observation advance from 1880 to the present, more data sets covering much of or all the globe have become available.   In recent decades satellite measurements have become significant. 

Considering 10-year averages, the last three decades have been successively warmer at the Earth’s surface than before, and warmer than any earlier decade going back as far as 1850.  For the period 1880 to 2012 the earth has warmed by 0.85ºC (1.5ºF), with a 90% confidence interval of 0.65 to 1.06ºC.   For the period 1901 to 2012, for which adequate regional data exist (this excludes the Arctic and Antarctica, and regions in the Amazon, central Africa and central China), a global map of temperature trends shows almost all regions on the earth’s surface of experienced warming (only a region of the North Atlantic south of Greenland became cooler).

The troposphere, the lowest part of the atmosphere closest to the earth’s surface, has warmed since the 1950’s (stated with virtual certainty, i.e. 99-100% likelihood).

The Summary specifically points out that short-term patterns are highly variable (speaking of periods as long as 10 to 15 years).  Variations on such a time scale cannot be taken to represent a change in long-term (periods of up to 60 years) trends.  It calls this phenomenon “natural variability”.  Short-term trends depend critically on the years that an interested observer might choose for the beginning and end of the period.  For example, the Summary cites the low rate of increase in temperature over the period 1998 to 2012, which began with a strong cyclical oceanic El Niño phase (warming of the ocean and atmosphere), was only 0.05ºC (0.09ºF) per decade.  The longer-term heating rate, however, from 1951-2012 was 0.12 ºC (0.22ºF) per decade. 

Heat energy is stored in the waters of the oceans to a far greater extent than on the surface of the earth or in the atmosphere.  Warming of the ocean accounts for more than 90% of the increase in heat energy experienced by the earth between 1971 and 2010, stored mostly in the upper 700 m (2,296 ft).  The upper 75 m (246 ft) warmed by 0.11ºC (0.20ºF) per decade over this interval.

The Greenland and Antarctic ice sheets and glaciers worldwide have decreased significantly.  The rates of loss due to melting have increased considerably over the past 20-30 years.  Arctic sea ice refers to permanent ice and peripheral seasonal ice frozen out of the Arctic Ocean.  The area of Arctic sea ice has decreased by 3.5 to 4.1% per decade over the period 1979 to 2012, and the summer minimum decreased by 9.4 to 13.6% (90-100% probability).  Northern hemisphere snow cover has decreased since the mid 20^th century.  Areas of permafrost have experienced surface temperatures warmer by 2-3ºC (3.6-5.4ºF).

The rate of rise of sea level has increased since the mid 19^th century to a rate larger than has been found for the last 2,000 years.  This rate of increase itself has grown from the late 1800’s and early 1900’s to considerably stronger increases since the early 20^th century.  Sea level rise originates largely from contributions of a) the expansion of the volume occupied by ocean water as it warms, b) melting of glaciers and the polar ice sheets, and c) changes in storage of water by land areas.

Atmospheric concentrations of GHGs have increased to levels unseen in the geological record for at least the last 800,000 years.  These include carbon dioxide (CO₂), methane (natural gas) and nitrous oxide.  Their atmospheric concentrations have increased since 1750 because of human activity associated with the Industrial Revolution.  CO₂ has increased by 40% in this time, mostly from burning fossil fuels and cement production, and somewhat from emissions arising from changes in land use.  About 30% of atmospheric CO₂ is absorbed by the waters of the oceans; since CO₂ is an acid the increase from human activity has caused a surface zone of the oceans to become more acidic by 0.1 pH unit; this translates to an increase in the concentration of acid in the water by 26%. 

Properties of the Earth System That Contribute to Global Warming.  Processes affecting the energy balance of the earth are measured in terms of the rates of energy exchange per unit surface area. In order of decreasing rates  of heating the earth, the contributors are CO₂, methane, ozone, fluorine-containing hydrocarbons (which originate from manufacture and recycling of refrigerators and air conditioners), nitrous oxide, carbon monoxide, and other lesser contributors. 

The role of aerosols has become better understood since 4AR.  Black carbon aerosols (originating from incomplete burning of fuels) contribute to net energy absorption, while white or light colored aerosols (from volcanic eruptions and byproducts of emanations from green plants) are negative, acting to reflect incoming sunlight back into space.  Aerosols figure importantly in the secondary effects of cloud droplet formation, and are evaluated here as having a net effect of increasing reflection of incoming sunlight back into space.  (Aerosols from volcanic eruptions and changes in net intensity of sunlight impinging on the earth are evaluated as being very small.  Volcanic aerosols are very transitory; even large eruptions, while having a cooling effect, last only a few years.)

Overall, the sum of the effects considered here result in a large increased rate of energy absorption per unit area by earth, almost double the rate evaluated in 1980.  The rate for 1980 in turn was more than double the rate evaluated for 1950.  (See the graphic below.)

Increase in the net rate of absorption of energy per unit area of the earth (Radiative Forcing, in watts per square meter) due to humanity’s activities for the years 1950, 1980 and 2011, relative to the value for 1750.  The horizontal black lines extending left and right from the tips of the red bars are estimates of the error in each value.  Values for the mean increase, and the lower and upper extents of the error (inside square brackets) are shown to the right of each bar in red.  These results are the sums of the contributions, positive and negative, described in the paragraph preceding this graphic.

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

Providing an Understanding of Past Climate Patterns Using Models.  Models successfully reproduce observed temperature trends over the long term from 1951 to 2012 with “very high confidence”.  But more short term effects are not matched in models.  For example, the reduced warming rate between 1998 and 2012, compared to the long-term trend from 1951 to 2012, is thought to arise equally from lower overall heating of the earth system, arising from volcanic eruptions and a weakening portion of the 11-year solar cycle, and a cooling contribution from internal variability such as larger removal of heat from the surface by the waters of the oceans.

Modeling global trends in extreme weather and extreme climate events has improved, as has continental scale modeling of precipitation.  Cyclical global patterns such as monsoons and the El Niño-Southern Oscillation have improved.

Modeling of positive and negative climate feedbacks has improved.  Surface warming, its effect on atmospheric content of water vapor, and dynamics of cloud formation are better.  The net feedback from these effects is “extremely likely” (95-100%) to be positive, amplifying warming effects on climate.

Climate sensitivity measures the extent of warming for a given change in overall energy absorption by the earth.  It is frequently characterized by the extent of warming expected from a doubling in atmospheric concentration of CO₂.  A lower number means the earth warms only weakly with increases in GHGs, while a high number indicates stronger warming with increased GHGs.  In 5AR climate sensitivity is likely (66-100%) in the range 1.5 to 4.5ºC (2.7 to 8.1ºF).  The lower limit of 1.5ºC represents a decrease from the 2ºC lower limit in 4AR, but the upper limit is the same.  

More than half of the increase in global surface temperature from 1951 to 2010 is due to human emissions of GHGs and other manmade contributors to warming effects (95-100% likelihood). 

It is “very likely” (90-100%) that manmade contributions have led to increased heat content in the upper 700 m (2,296 ft) of the oceans.  They have also contributed to increased atmospheric moisture content, and consequent changes in precipitation including intensification of heavy precipitation over land. 

It is “very likely” (90-100%) that manmade effects have increased the frequency and intensity of extremes of temperature across the globe, probably doubling the occurrence of heat waves.  It is also “very likely” that manmade influences have contributed to loss of Arctic sea ice and the global rise in sea level.

Projections of possible future warming were carried out using a variety of models, ranging from simple climate models, to models of intermediate complexity, to comprehensive climate models, and Earth System Models.  These were run with four emissions scenarios termed RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5.  (The numbers refer to the rate of energy increase per unit area at the surface of the earth, in watts per square meter.)  RCP2.6 is intended to project a pathway to warming equilibrium within the guideline established earlier by the IPCC to limit global warming to 2ºC (3.6ºF) above the level before industrial times.  The remaining RCP scenarios reflect worsening, more severe warming originating from increasing rates of emission of GHGs.  RCP 8.5 approximates a “business as usual” pathway in which no significant policies are implemented to limit GHG emissions through 2100.

(Temperature changes in AR5 shown below are referenced to the starting period 1986-2005.  These are 0.61ºC (1.10ºF) above the preindustrial level.  This amount should be added to all values mentioned here to arrive at the full change since the beginning of the Industrial Revolution.)

The following table shows projected temperature increases over the 1986-2005 reference, and projected increases in global mean sea level over the 1986-2005 reference.

Changes in global mean surface temperature in ºC (top) and global mean sea level rise in m (bottom) for the two time periods shown, referenced to the period 1986-2005.  The “likely range” gives confidence limits for a 5%-95% interval. 
For temperature, corresponding values for ºF are exemplified as 1ºC =1.8ºF, 2.0ºC = 3.6ºF, and 3.7ºC = 6.7ºF.

For sea level, corresponding values for feet are exemplified as 0.24 m = 0.79 ft, 0.30 m = 1.0 ft, 0.40 m = 1.3 ft, and 0.63 m = 2.1 ft.

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

Global maps of warming are shown below for the mildest scenario, RCP 2.6, and the most severe scenario, RCP 8.5, referenced to the period 1986-2005.

Global grid of projected temperature changes by 2081-2100 referenced to the period 1986-2005.  The changes are color coded in ºC according to the heat bar at the bottom.  The number of models used is shown at the upper right of each map.  The stippling (dot pattern) is used to show high significance of the result for the given map location above internal variation (exceeds 13-87% deviation from the mean).

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

It is seen that temperatures are projected to be higher over land masses than over oceans.  Also, the size of the temperature increase is highest over the Arctic in both scenarios.  The changes in the Arctic would give rise to significant losses in sea ice and ice sheet masses, and would melt permafrost.

It is “virtually certain” (99-100% likelihood) that the frequency of hot temperature extremes on both daily and seasonal timescales will increase, and that of cold temperatures will diminish.

The models project regional changes in precipitation amount over the globe.  The range of differences between wetter and dryer regions will grow, and the contrast between wet and dry seasons will increase.  Extreme precipitation events are “very likely” (90-100%) to become more frequent and more intense.

It is “very likely” that Arctic sea ice will continue to decrease, that Northern hemisphere snow cover will be reduced, and the amount of glacier ice will decrease.  Permafrost will continue melting, and large fractions will be lost, depending on the scenario.

Global mean sea level will continue rising due to increased ocean temperature (thermal expansion, 30-55%) and increased melting from glaciers (15-35%) and the Greenland ice sheet.

Oceans will continue warming.  Heat absorbed from the atmosphere will be redistributed to greater depths, affecting the long-term ocean circulation. 

© 2013 Henry Auer