Two aspects can be highlighted. On the one hand, life forms exist on earth due to the effect of greenhouse gases. On the other, the greenhouse effect depends on the concentration of a set of gases that occur, for the most part, naturally: water vapor, carbon dioxide and methane, all of which do not fit the notion of classical pollutants construed as substances that would not occur in nature without a human presence. The United Nations Framework Convention on Climate Change (UNFCCC) defines "greenhouse gases" (GHGs) as those atmospheric, natural and anthropogenic gases that absorb infrared radiation, primarily based on the following gases:
● Carbon dioxide (CO2)
● Methane (CH4)
● Nitrous oxide (N2O)
to which are added the following synthetic chemicals:
● Sulfur hexafluoride (SF6)
● Perfluorocarbons (PFCs)
● Hydrofluorocarbons (HFCs)
DESCARBONIZAR 2050
THE SCIENTIFIC BASIS OF CLIMATE CHANGE
The scientific community has been raising the warning level on climate change since 1988.
The greenhouse effect has long been known. The Swedish scientist Arrhenius published in 1896 in the Royal Swedish Academy of Sciences, a first attempt to quantify the greenhouse effect, specifically, the increase in the concentration of carbon dioxide in the atmosphere over the global temperature of the planet. Previously, the absorption property of infrared radiation from some gases had been experimentally confirmed in 1859 by John Tyndall. The Arrhenius quantification barely unveils the possibility of the global effect of increasing combustion of fossil fuels on the planet. Arrhenius believed that doubling greenhouse gases in the atmosphere would lead to an increase in global temperature of 5° Celsius. However, he also thought such levels would be reached over millennia. His conclusions were disputed by many physicists. His theory seemed simplistic and did not rely on many complex climatic effects, such as the role of the oceans or the albedo effect (the ability of surfaces to reflect sunlight (heat from the sun): light-coloured surfaces return a large part of the sunrays back to the atmosphere (high albedo) while dark surfaces absorb the rays from the sun (low albedo)”) Norwegian Polar Institute. The search for scientific data to clarify the exact dimension of this phenomenon had to wait for advances in meteorology as well as in the analysis of the composition of the gases. The controversy lasted decades.
Years later, Charles Keeling, while working with data from the Mauna Loa astronomical observatory in Hawaii and from Antarctica, conducted a series of observations indicating a marked increase in the concentration of greenhouse gases (carbon dioxide in particular) in the atmosphere. The graphic which Keeling produced then, is known today as one of the most supported arguments in favor of the existence of the effect of greenhouse gases:
Source: The Keeling Curve - Mauna Loa Observatory (https://www.esrl.noaa.gov/gmd/obop/mlo/)
The influence of these findings on climate theory is significant. Nevertheless, these results emerged at a time when the possibility of a new “ice age” was being discussed (temporary weather effects masked the evolution of the global climate during the 1940s and 1950s), and Keeling’s findings went relatively unnoticed.
The issue reemerges when a series of global temperature measurements finally confirms the prevalence of Arrhenius and Tyndall’s greenhouse effect.
THE DIFFERENCE BETWEEN THE GREENHOUSE EFFECT
AND ENHANCED GREENHOUSE EFFECT.
Source: http://css.snre.umich.edu/factsheets/climate-change-science-and-impacts-factsheet
GREENHOUSE GASES (GHG) AND THE POTENTIAL FOR GLOBAL WARMING
There are several gases that cause the greenhouse effect. It is fundamental to understand what their relative contribution to the problem is in order to tailor our response accordingly. To this end, several key metrics were developed to compare the effect of the different gases on global warming. It should also be noted that the effect of a given GHG emission depends on its ability to absorb energy (its "radioactive efficiency") and its permanence in the atmosphere. The latter factor is critical: a gas that is very potent but rapidly absorbed by natural processes would be less important than one that has a less potent emission in terms of climate change but would last many more years. Thus, the metric adopted by the United Nations Framework Convention on Climate Change and which has become the international benchmark, is the 100-year Global Warming Potential (GWP). The GWP is a measure of energy absorbed by 1 tonne of a specific gas, in relation to the emission of 1 tonne of carbon dioxide (CO2). The GWP, therefore, permits one to state that an emission of 1 tonne of methane (CH4) is equivalent, for the purposes of the impact on global warming, to the emission of 25 tonnes of CO2. In other words, methane’s GWP is 25. The UNFCCC sets fixed values for international accounting purposes. These values are revised periodically in light of new scientific advances.
GLOBAL WARMING POTENTIALS (100-YEAR TIME HORIZON)
Source: IPCC Fifth Assessment Report, WGIII, Introductory chapter.
HOW DO DISTINCT GASES CONTRIBUTE TO GLOBAL WARMING?
It is possible to determine the relative contribution of the distinct gases to global warming by knowing the GWP and the global emissions of each gas.
Carbon dioxide is by far the major culprit, with 73% of emissions measured by its effect on global warming. Methane is second at approximately 20% and nitrous oxide at 5% is third. Despite the very high GWP of some chemical gases, their overall contribution to global warming is relatively small.
THE RELATIONSHIP BETWEEN GLOBAL WARMING AND
THE DEPLETION OF THE OZONE LAYER
The answer to a question about global warming in a survey carried out in Portugal years ago showed the prevailing confusion between global warming/climate change and the depletion of the ozone layer. What is the relationship between these two problems?
Ozone (chemical formula: O3) is an oxygen gas that occurs naturally in the atmosphere. At the highest level of the atmosphere, at about 10-30 km in altitude, a relatively thin layer of this gas plays a vital role for life on the planet. Stratospheric ozone, as it is called, prevents certain types of ultraviolet radiation from reaching the earth's surface. Emissions of substances that act on this layer consequently cause an increased risk of diseases like skin cancers or cataracts. In the event of total ozone depletion, life on Earth would be impossible. This ozone layer is affected by the emission of a number of chemical compounds. Additionally, the same naturally occurring gas in the stratosphere becomes an important pollutant when found in the troposphere ("at our level") impacting our health.”
Ferreira de Almeida et al., “II Inquérito Nacional sobre Representações e Práticas dos Portugueses sobre Ambiente”, Observa, ISCTE-IUL. Celta Editora (2004).
None of this is directly related to the phenomenon of global warming. Unfortunately, there is a serious problem at the intersection of these two phenomena. The Montreal Protocol on the Ozone Layer mandates the phase-out of ozone-depleting gases mandated by international agreements, the famous CFCs (chlorofluorocarbons present, for example, in refrigerators and in refrigeration systems). These have been replaced by gases such as hydroclorofluorocarbons (HCFCs). The production of the latter led to an exponential increase in the emission of HFCs (hydrofluorocarbons). In turn, these gases are among those with the greatest potential for global warming. In our attempt to solve the problem of the ozone layer we have inadvertently increased the problem of global warming.
CLIMATE CHANGE
OR GLOBAL WARMING?
WHY DO WE SOMETIMES TALK ABOUT “GLOBAL WARMING” AND OTHER TIMES OF “CLIMATE CHANGE”?
The term "global warming" refers to the progressive increase in temperature since the beginning of the 20th century, especially since the 1970s. This tendency is due, in large part, to the increase in emissions from burning fossil fuels (oil and derivatives, natural gas, coal). It has been estimated that the global temperature has risen by approximately 0.8° Celsius since the 1880s.
Climate change encompasses a wide array of global phenomena generated by emissions from burning fossil fuels. These changes in climate obviously include global warming. Nonetheless, other phenomena are also included such as mean sea level rise, loss of ice in polar caps and glaciers around the world, changes in plant cycles and extreme climate events.
CLIMATE CHANGE AND THE "INTERNALIZATION OF EXTERNALITIES"
Lord Nicholas Stern, a renowned economist, wrote in an influential report that climate change is "the biggest global market failure" (STERN, N. H. (2007). The economics of climate change: The Stern review. Cambridge, UK, Cambridge University Press).
For economists, a "market failure" occurs when the market does not value an asset properly and does not give it a price reflective of its scarcity. In the case of climate change, the global services of the Earth's atmosphere are not appreciated, as no cost is incurred by using the atmosphere. In this sense, there is no cost associated with the degradation of the atmosphere and its capacity to sustain the ecosystems we know. The solution is to "internalize" the problem in the market, creating a cost or price for the emission of greenhouse gases. Alternatively, the control of emissions with quantified emission targets ("quotas") also serves to create a cost for companies.