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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".

Monday, September 22, 2014

Record Greenhouse Gases Continue to Accumulate in the Atmosphere

We experience weather at the local or regional level.  Here, one person may be in a heavy rainstorm, while there, somewhere else in the world, another could be in an uncomfortable heat wave.  Daily or weekly weather, however, is not the same as long-term regional or global climate; climate relates to yearly, multi-year, and even decade-long behavior. 

The world’s climate is affected by the atmospheric accumulation of greenhouse gases (GHGs), which continued unabated during 2013.  GHGs in the atmosphere preferentially retain heat radiating from the earth’s surface and prevent its escape to space. 

Record High Levels of Carbon Dioxide.  The World Meteorological Organization (WMO), an agency of the United Nations, reported recently that the global average concentration of carbon dioxide (CO2), a major GHG, reached a record level of 396 parts per million (ppm; volume of CO2 gas in 1 million volumes of air) in 2013 (see the graphic below). 

 
 
Atmospheric concentration of CO2 in ppm, reported monthly from 1984 to the present.
 
The WMO evaluates observations gathered from many land-based stations, ship-based observatories and aircraft.  The increase in CO2 from 2012, 2.9 ppm, was the largest yearly change since 1984.  The present CO2 concentration is 42% higher than that before the industrial revolution began during the century between 1750 and 1850.  The dramatic increase in CO2 emissions in the last 160 years, coinciding with the increasing role that fossil fuels have played in powering the world’s economic growth during that period, is shown below.

Annual rates of emission of CO2 (evaluated on the basis of the carbon portion of the carbon dioxide molecule) from the three main fossil fuels, plus the production of cement from limestone.  The amounts shown represent about 80% of all human-derived carbon, with most of the remainder arising from human-induced deforestation.
Source: The Third U. S. National Climate Assessment (data from Boden et al. 2012); www.nca2014.globalchange.gov
 

Even more recently the New York Times reported that another international group of climate scientists likewise found that GHG emissions in 2013 reached record levels.  Worldwide this group found that the increase from the previous year was 2.3%, while in the U. S. the increase was 2.9%, opposing a decreasing trend in earlier years.

Why should we care about this pattern in CO2 levels?

As atmospheric CO2 levels trend higher the long-term worldwide average temperature of the earth’s atmosphere has also been increasing, in concert with the increasing concentration of CO2 (see the graphic below).  This has been happening because of the greenhouse effect of CO2 and other greenhouse gases (also reported by the WMO).

Correlation between global temperature and atmospheric CO2 concentration from 1880 to 2012.  The thick black line gives the yearly CO2 concentration in parts per million (volumes of CO2 present in 1 million volumes of air) with values along the right vertical axis.  The ends of the blue and red lines show the temperature with values along the left vertical axis.  The horizontal line shows the average temperature across this time span.  The ends of the blue lines show the temperature values for years in which the temperature was below the average, and the ends of the red lines show the temperature values for years in which the temperature was above the average.
Source: The Third U. S. National Climate Assessment; www.nca2014.globalchange.gov.

 
The global average temperature has increased by about 0.7-0.8ºC (1.3-1.4ºF) over pre-industrial temperatures.  As a current example, U. S. government scientists report that each of the months June, July and August 2014 were the hottest on record, when averaged over the entire globe.  These temperatures exceeded the previous monthly records set in 1998. 

The increased CO2 levels arise directly as a result of humanity’s burning of fossil fuels for energy, and not from natural causes (see also the U. S. National Climate Assessment (a U. S. government interagency report) issued May 2014).

There have been many reports over the past several months documenting increasing GHG emissions and warmer long-term global average temperatures.  These include the Fifth Assessment Report of the United Nations-sponsored Intergovernmental Panel on Climate Change, the Third U. S. National Climate Assessment, and the two reports mentioned here.  The persistent drumbeat of reports on global warming emphasize the conclusion that the increase in atmospheric CO2 and the resulting increase in global average temperature are manmade: they originate from humanity’s burning of fossil fuels for energy to drive economic development. 

Higher worldwide temperatures are leading to more, and more extreme, climate and weather events.  For example, warmer temperatures permit the atmosphere to hold more water vapor, so that many regions will likely experience heavier rain and snow, leading to flooding.  In other areas, higher temperatures will likely increase evaporation of moisture from the land leading to drought.  Both flooding and drought can reduce crop yields, leading to higher prices or famine.  Sea levels are rising as land-based ice sheets and glaciers melt, with the runoff entering the ocean.  All these trends lead to physical and socioeconomic harm to humanity as extreme patterns and catastrophes inflict more damage than in earlier times.

Human health is likewise significantly harmed, as air quality is degraded and as warmer conditions make it easier for disease-bearing microorganisms to flourish and infect the population.

Increased emission of GHGs is a worldwide problem requiring a worldwide solution.  The international community is currently beginning final negotiations on a worldwide treaty to reduce GHG emissions, undertake adaptation measures and assist those nations most adversely affected by global warming.  The participating nations must approach these negotiations in good faith, with an eye to the future, so they can agree to meaningful abatement and adaptation policies.  Our wellbeing, and that of future generations to follow, demands no less.

© 2014 Henry Auer