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This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Thursday, January 21, 2016

A Global Agreement on Reduction of Greenhouse Gas Emissions

The member nations of the U.N. gathered in Paris in December 2015, and concluded a dramatic new agreement to reduce worldwide greenhouse gas emissions.  The agreement differs from earlier failed attempts to negotiate a climate treaty.  First, all member nations are covered by its terms, rather than being segregated into two groups only one of which is to be bound.  And second, each member nation generates its own voluntary pledge for mitigation based on its domestic situation and its view of the seriousness of global warming.

In the time leading up to the Paris meeting, extremes of global weather and climate had been felt all around the world.  Many of these have been recognized to be causative factors in climate disasters.   Recognition of these events likely contributed to the successful negotiation of the agreement. A month after the meeting scientists announced that global average temperatures in 2015 broke all historical records for the hottest year. The world is now on a path to limiting the rise in global temperatures and its consequences.


We have been experiencing a variety of unusual climate effects and extreme weather events in recent years.  2015 was the warmest year on record, using temperatures measured over the entire year on both land and ocean surfaces .  The high temperatures averaged worldwide have produced large numbers of extreme weather events, especially heat waves, over the last five years; they have been “influenced by climate change”, the World Meteorological Organization reports .

Extreme events.  Climate extremes due to, or made worse by, global warming have contributed to the vast political and social unrest in Syria, leading to a major refugee crisis extending as far as Europe; agricultural losses in regions of Europe; and the extreme drought in California and the American Southwest, as examples.   Record rainfall and severe flooding afflicted England and Wales leading up to Christmas 2015.  In the summer of 2015 extremely intense rainfall during the monsoon season caused hundreds of deaths and displaced millions of people in India, Bangla Desh, Pakistan and Myanmar.  In Myanmar, the World Food Program Director, Dom Scalpelli, said "…people have lost homes, livelihoods, crops and existing food and seed stocks. Food security will be seriously affected."  

The total accumulated level of greenhouse gases (GHGs) in the air determines the extent of global warming.  Carbon dioxide (CO2) is a long-lived GHG; it remains in the atmosphere for centuries once it emerges into the air.  Mankind’s burning of fossil fuels generates the excess CO2 that has led to the global warming of the past century or more as the concentration of this gas has increased from about 280 parts per million (ppm; volumes of CO2 per million volumes of air) to about 400 ppm at the present.  There is currently no known technology available to remove CO2 from the atmosphere on the industrial scale needed to compensate for our industrialized modes of burning fossil fuels for energy.  The global average temperature is directly related to the total GHG content of the atmosphere.  Continued emission of CO2 serves only to increase the atmospheric burden of this GHG, leading to a stronger greenhouse effect and higher worldwide average temperatures. 

These are facts which cannot be altered or dismissed.  They underlie the stark conclusions first, that even if humanity were to cease burning all fossil fuels “today” we could not realistically lower the CO2 concentration in the atmosphere.  And second, that we can not return to a lower average temperature that prevailed in earlier decades.  At best, we can only strive to keep further warming as low as possible by limiting further GHG emissions as stringently as we can.  Ambitious decarbonization of the global energy economy is needed to accomplish this goal.  The anecdotes in the opening section provide excellent examples of why the people of the world need to act.

The December 2015 Paris Agreement of the United Nations member states is a major advance toward reducing worldwide emissions.  The earlier treaty, the Kyoto Protocol (KP) of 1997 divided the negotiating nations into two groups, developed (already industrialized) nations and developing countries.  Only the developed countries were included under its terms.  KP also imposed binding goals for emission reductions, assigned to each covered nation.  The U.S. Senate opposed KP so that the U.S. was never constrained by its terms.  KP expired in 2012. 

The Paris Climate Agreement.  The agreement negotiated in Paris in December 2015 codified a radically different approach than that provided by KP.  First, all 193 subscribing U.N. member nations are to be uniformly constrained by its terms, eliminating the division of nations into two groups.  And second, rather than imposing numerical emission rate reductions assigned from within the United Nations framework, each nation voluntarily submits its own domestically-generated emission reduction goals to the U.N.  Mechanisms for measuring, reporting and validating each nation’s emission rates are to be developed under the treaty.  Other aspects of the Agreement deal with finance, and land use change and reforestation.

Recognizing that initial pledges may be inadequate (see Analysis) the Agreement further suggests that nations submit updated, more robust goals for reductions of emission rates in future years.  It includes the objective from 2009 of seeking to keep the increase in the global average temperature above preindustrial times to 2ºC (3.6ºF), but for the first time further encourages striving toward the more ambitious goal of keeping the temperature rise below 1.5ºC (2.7ºF).


The U. N. Paris climate agreement covers all 193 member nations of the organization.  It is a highly significant accord, for it excuses no member from coverage under its terms, and because no numerical goals for emissions reduction were imposed on members by the negotiators.

Most nations submitted their pledges of voluntary reductions in GHG emissions before the Paris conference convened.  Climate scientists evaluated the pledges right away, and it became clear that the anticipated reductions in GHG emissions were too small to put the world on the path toward limiting the rise in global temperatures to less than 2ºC. 

The International Energy Agency’s World Energy Outlook warns that plans currently being discussed for limiting emission rates may be too slow.  Another report discloses that China’s accounting of its historical use of coal, and thus its emissions as well, may have underestimated the actual amount by 17%.  Yet another account discusses the difficulties that India will face as it seeks to reduce emission rates while still accommodating the needs of its growing population, expected to reach 1.5 billion by 2030.

In an additional example (Fawcett and coworkers, Science, 2015, Vol. 350, pp. 1168-1169) climate model calculations show that the current voluntary pledges will keep the annual

Actual (up to 2010) and projected annual rates of emission of CO2 from energy and major industrial sources from 1990 to 2100.  The heavy lines are summary representations for four emissions scenarios.  Top to bottom these are the reference case of no emissions mitigation policy in place; no mitigation policy up to 2030, then a 2% per year reduction in emissions; implementation of only the current voluntary pledges through 2030, continued unchanged to 2100 (curve labeled INDCs); and the current voluntary pledges to 2030, then mitigation by at least 5% per year to 2100.  The individual thin lines are actual modeling runs repeated many times.
Source: Fawcett and coworkers, Science, 2015, Vol. 350, pp. 1168-1169; .

rate of CO2 emissions level at their present rates, about 40 gigatons CO2/year, up to 2100 (curve labeled INDCs in the graphic above).  Since these are annual rates, the emissions will continue to raise the total accumulated CO2 level throughout this period leading to a steady rise in global average temperature to 2100.  Only the lowest heavy blue curve shows a decreased rate of annual emissions after 2030, reaching about 7 gigatons/year by 2100, accomplished in the model by imposing a stringent reduction in annual emissions rate of 5% per year.  The accumulation of CO2 in the atmosphere continues, admittedly at lower rates, throughout this period, so that the global average temperature will still rise from its present (unprecedented high) value at a slow but measurable pace.

The Paris Agreement is highly significant because it is the first time that negotiators from all over the world have come together and approved a treaty that applies to them all.  This is a truly dramatic shift because, for example, China and India only a few years ago refused to consider adopting mitigation policies of any kind to address global warming.  Recently though, many cities in China and other Asian countries have been struggling with the threats to public health from unprecedented levels of smog, much of which originates from the burning of fossil fuels.  Domestic pressures arising from the smog problem may have contributed to the policy change in these, and other, nations.

Each member nation now considers the agreement for approval or ratification according to its own domestic procedures.  Importantly, public opinion in 39 of 40 countries surveyed, except Pakistan, agrees that global GHG emissions need to be reduced, according to a poll by the Pew Research Center.  About 70% of polled people in the U.S. and China supported this view. 

The U.S. historically has never enacted a national policy on global warming by legislative procedures.  The Senate refused to consider KP because it was argued that the distinction between developed and developing countries puts the U.S. at a competitive disadvantage on the world economic stage.  Now, with the Paris Agreement, this argument is no longer valid.  All nations of the world agree to the same terms, bound by the same requirements.  Voluntary pledges toward reduction of emissions make it more acceptable to conform.  Most, if not all, other major emitting countries have undertaken to reduce emission rates in coming decades.  Now is the time for the U.S. to enact meaningful mitigation legislation that places the country on equal footing with other nations of the world, both those already advanced economically and those developing their economies. 

© 2015 Henry Auer

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