We Can No Longer Delay Minimizing Global Warming/Climate Change

Summary: The Intergovernmental Panel on Climate Change has issued six Assessment Reports over the past three decades.  This blog has presented three posts recently tabulating the effects of warming and the scientific need for reducing greenhouse gas (GHG) emissions that the Reports presented.  The posts focus on the unabated increase in man-made carbon dioxide emissions, the consequent increase in global average temperature, and the inexorable increase in sea level.  For each of these topics, from the beginning the Reports have declared the necessity of minimizing GHG emissions in order to avoid the worst harms and damages from continued warming.  Their warnings have become more urgent, and have been expressed with increasingly unambiguous certainty, as the series of Reports has been issued.

Harms and damages that were only hypothetical in the early Reports have now become commonplace, as sea levels have continued rising; droughts, famine and wildfires have ensued; and more intense, violent climate and weather events have unfolded with freakish intensity.  Even so, policymakers and commercial interests in the private realm have largely ignored these warnings throughout the three decades.  Now is the time energetically to combat further warming globally to make up for three decades of inaction, and to mitigate worsening climate change.  We have no alternative.

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Introduction – The Urgent Need to Minimize Greenhouse Gas (GHG) Emissions.  In three recent posts this blog has summarized aspects of the work of climate scientists over the last 30 years.  The first post is titled “What,Again? Greenhouse Gases Accumulate in the Atmosphere”, the second is “What, Again? Global Warming Continues Unabated”, and the third is “What, Again? Sea Level Will Continue Rising for Centuries”.

Each post summarizes the aspect of climate science reflected in its title, as presented by the U. N.’s Intergovernmental Panel on Climate Change (IPCC) in its series of six Assessment Reports (ARs) issued over the past 31 years up to the (first of three volumes of) the Sixth AR, which appeared in August 2021. Each post included a tabulation of the significant findings, and the suggested future policies, related to the title of the post, as found in each AR.  Significantly, the need to reduce GHG emissions was already expressed in the first AR in 1990 and has been reinforced in each report up to the present time in the Sixth AR.  What has changed is that the strength of the climate science underpinning those conclusions has increased dramatically over time.  The capabilities of gathering data and using more powerful computers to analyze them, and to develop more refined, detailed climate models, have all increased remarkably.

Sadly, the world’s policymakers and industries have not heeded these warnings, but have continued policies and practices leading to unabated, indeed increasing, GHGs emissions throughout these three decades, as shown in the graphic below.

 

 

Direct measurements of atmospheric carbon dioxide (smoothed over the 12 months of a year) taken atop the Mauna Loa volcano in Hawaii beginning in 1958.  The base level prior to the Industrial Revolution is 280 ppm.  Ppm, parts of carbon dioxide in 1 million parts of air. The vertical lines represent the dates of issue of the respective Assessment Reports, and the date of the U. N. Paris Climate Agreement (2015).    Adapted from the carbon dioxide data referenced in the URL at the bottom of the image.

 

In spite of the persistent urgings of the six teams of climate scientists writing the six ARs over three decades, and the agreement reached in Paris among virtually all GHG-emitting nations to begin reducing their emissions, the data in the graphic show no indication of slowing emission rates up to the present time.

Accumulated GHGs are directly responsible for increasing global temperatures.  Many man-made GHGs, including the extra carbon dioxide emitted by burning fossil fuels, are “long-lived” GHGs.  Once emitted into the atmosphere they remain there for hundreds or thousands of years without being destroyed or taken up by the earth system, so that they accumulate to ever higher levels with each passing year.  (A minor fraction of carbon dioxide is absorbed by photosynthesis and by dissolving into oceans and lakes.)  That is why the image above shows that carbon dioxide levels in the atmosphere keep increasing.  The increase from one year to the next represents the net amount added to the atmosphere during that year.  Indeed, the carbon dioxide level increased from about 353 ppm at the time of the First AR to about 416 ppm at the Sixth AR, the present.

Greenhouse gases are called that because they retain a portion of the sun’s energy reaching the earth as heat energy, instead of having that heat be radiated from earth back into outer space.  This leads the temperature of the earth system to increase. The earth system mimics glass greenhouses in retaining heat.  Their glass enclosure captures outgoing heat energy, so that excess heat accumulates inside the greenhouse.  The interiors of cars in the summer sun heat up for the same reason.  Climate modeling of future warming, summarized in recent ARs, shows that the extent of incremental heating of the earth system depends on excess GHGs in the atmosphere (including excess carbon dioxide from fossil fuels) in almost a straight-line fashion.

It is critical to reduce the net annual GHG emission rate to near zero by midcentury, and optimally sooner.  The IPCC released “Global warming of 1.5°C [2.7°F]. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels, V. Masson-Delmotte, and coworkers (eds.)” in 2018.

As emphasized above, the world’s policymakers had ample time to implement GHG reduction technologies in orderly fashion had they heeded climate scientists’ warnings beginning with the First AR.  These urgings have been ignored or rejected in the three decades since, with the result that future weather and climate extremes that scientists warned of at the outset have actually come to pass ferociously in recent years.  In addition, the goal of limiting warming to 2.0°C [3.6°F] above pre-industrial levels, proposed in earlier reports, has been replaced in the Special Report by a more stringent limit, 1.5°C.  Climate action has to be undertaken urgently from this time onward, to make up for the lower revised limit and the time lost in past decades. The IPCC Special Report lays out this case in great detail. 

Conclusion.  Climate scientists have been characterizing the harms and damages they expected from continued unabated burning of fossil fuels, and from other GHG sources, for more than three decades.  Throughout that period policymakers have not acted meaningfully on the scientists’ urgings to reduce use of fossil fuels, nor to reduce other GHG sources.  And now, in recent years those harms and damages are coming to pass around the globe with increasing frequency and severity.

This post presents the urgent, critical case that ambitious, aggressive, effective actions need to be taken starting now to reduce annual GHG emission rates toward zero by midcentury or preferably earlier.  Policymakers can no longer ignore the inexorable action of the physical laws governing global warming.  Industries providing fossil fuels and those using that energy seek to preserve their business models indefinitely.  This is now clearly untenable.  They must change the way they do business or get out of the way.  We all must act internationally, at the national level, at the state and provincial level, and locally; global warming originates across our planet and must be addressed by all nations and citizens of the world in concert. As many have said, “There is no Planet B!”

© 2021 Henry E. Auer

What, Again? Greenhouse Gases Accumulate in the Atmosphere

Summary: This post tabulates important findings from the six Assessment Reports (ARs) that the United Nations Intergovernmental Panel on Climate Change (IPCC) has released since 1990.  As shown here, climate scientists have recognized, as of the date of each AR, that a) man-made GHGs continue to be emitted and accumulate further in the atmosphere, b) predicted emissions risk accumulating climatically dangerous levels of GHGs, and c) principles are proposed to minimize further emissions so as to keep accumulated GHG levels to as low a level as possible.

 Here attention is restricted to three topics, a historical review of accumulated atmospheric GHGs, projections of future emission rates and accumulated totals, and ways to stabilize accumulated atmospheric GHGs. Coming posts will consider other aspects of climate, presented over the three decades that ARs have been issued, resulting from the projected accumulated GHG levels.

Some may feel this and the coming posts sound like broken records; they may suffer from “climate fatigue”.  Humanity, however, has not responded to the worsening climate documented in the AR series. The critical, dire climate projections summarized here should provide powerful incentives to take meaningful action at this time.

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The United Nations Intergovernmental Panel on Climate Change (IPCC) released the first of three volumes of its Sixth Assessment Report (AR6) in August 2021.  ARs have been issued at intervals of 6-7 years since 1990. They document the history of the annual rate of global GHG emissions, due to human activity, of the principal greenhouse gases (GHGs) and of the total amount of GHGs accumulated in the atmosphere since the industrial revolution (Ind. Rev.) began.  Using climate models and a range of scenarios of GHG emission rates they present projections for each scenario of future climate characteristics to the end of this century.  They also discuss general principles (but not specific policies) for limiting future emission rates.

The general results and projections presented in ARs 1-6 are broadly consistent with each other across the AR series.  They record the profound increase, due to human activity, in accumulated atmospheric GHGs across the years, emphasizing the results for the most significant GHG, carbon dioxide (CO₂).  Accumulated CO₂ is shown in the graphic below, adapted here by adding vertical lines for the years in which the various ARs were released, as well as the additional red line corresponding to the date of the Paris Climate

Direct measurements of atmospheric carbon dioxide (smoothed over the 12 months of a year) taken atop the Mauna Loa volcano in Hawaii beginning in 1958.  The base level prior to the Ind. Rev. is 280 ppm.  Ppm, parts of carbon dioxide in 1 million parts of air. The vertical lines represent the dates of issue of the respective Assessment Report (AR), and the date of the Paris Agreement.

 

Agreement of 2015.  The principal goal of the Paris Agreement is to reduce emissions sufficiently to keep the increase in the global average temperature to below 2.0°C (3.8°F), and preferably 1.5°C (2.7°F) by 2100.  It is seen in the graphic that there is a consistent increase in CO₂ emission rate beginning with the first measurements in 1958 and continuing throughout the three decades following AR1. 

The topics selected for this post are tabulated below in the Details section.  The authors of AR1 recognized already in 1990 that atmospheric accumulation of man-made GHGs was increasing.  As the graphic above and the entries for the successive ARs in the table show, the growth in accumulated levels continued unabated up to the present (AR6).  Furthermore, projected future trends for various emission scenarios were generally comparable throughout the series.  Finally, the need to reduce annual emissions was recognized from the beginning and reiterated, with increasing urgency, throughout the series.

 Whereas the need to reduce emissions begins in AR1 and extends up to the present in AR6, the strength of climate science underpinning those conclusions has increased dramatically.  For example this first of the three volumes of AR6 was compiled by 234 climate scientists chosen from among all the nations of the IPCC.  They reviewed over 14,000 research articles published since AR5.  The capabilities of gathering data and using more powerful computers to analyze them, and to develop more refined, detailed climate models, have all increased dramatically. 

 Drafts of the chapters in AR6 were reviewed by other scientists as well as by national governments.  We can feel assured that the final text represents scientific and political consensus views.

 Conclusion

In the table given below in the Details section the column “Actions to Stabilize Atmospheric GHGs” summarizes the increasing urgency of acting to reduce annual emission rates essentially to zero as the AR series progresses.  For AR1 and AR2 ambitious reduction goals were already stated, but planetary manifestations of the effects of global warming were not yet readily distinguishable.  By the time of AR6, 2021, extreme weather and climate events have become the subjects of frequent headlines, distributed across heat waves and droughts, famine, uncontrolled wildfires across the globe, intense precipitation events and flooding, and melting of glaciers and ice sheets leading to sea level rise.  Also, by AR6 the science of attribution of extreme climate events has progressed dramatically, and permits ascribing the severity, if not the actual occurrence or not, of events to the effects of global warming.

As noted in the Actions column of the table, early action could have been taken at moderate levels of effort and expense, to avert future, if not yet apparent, hazards.  Such opportunities were not seized.  By 2021 hazardous events are now current, requiring immediate action.  Necessarily these current actions must be far more aggressive, pervasive and expensive.  They also require fundamental and comprehensive changes in social and cultural approaches to the problem.

We must encourage our political, corporate and civic leaders to accept these challenges and overcome them without further delay.

 Details

This writer collated the entries in the following table from either the Summary for Policymakers, a “Headline” document or a press release, all issued by the IPCC in conjunction with each AR.  The entries are necessarily selective rather than comprehensive, and have been edited for brevity.

 

© 2021 Henry Auer