Yasna Palmeiro-Silva introduces us to the links between global warming, human health, and sustainability. In this first instalment, we learn about the anthropogenic effects on climate change over the last couple of centuries.
For millennia, human beings have been in a close relationship with the environment. That is because the environment has provided us several resources that we need to survive; for instance, we have used ‘natural’ caves as shelter, rivers as a source of fresh water, land for agricultural purposes, and natural resources for manufacturing. Nevertheless, this relationship has not just been unidirectional, because human actions have had important consequences for the environment. A significant example of this relationship is the Industrial Revolution.
This revolution allowed humans to enhance and accelerate the processes of industrialization and manufacturing of goods. The technological advances of the time had several positive impacts on human development, such as; better transportation and communication systems, more energy sources, economic growth, healthcare, and agricultural improvements, amongst others. However, these improvements occurred not just because the intelligence of human being, but also because the environment provided us with important resources such as coal, water, petroleum, fertile lands, etc. As mentioned before, one of the many negative consequences of this human-mediated revolution was environmental pollution because the use of fossil fuels as a source of energy.
Fossil fuels, such as coal, crude oil and, natural gas, have a high carbon content; consequently, when these fuels are used for manufacturing or industrial processes, they release huge amounts of carbon dioxide (CO2) into the atmosphere, which is a significant source of greenhouse gas.
Figure 1 shows the concentration of atmospheric CO2 in parts per million (ppm) from 400,000 years ago. As you can see, carbon dioxide concentration has moved cyclically between 170 and 300 ppm; however, by 1950, this concentration had increased dramatically, and the last measurement of atmospheric CO2 was a whopping 410 ppm in January 2019.
Figure 1. Levels of atmospheric CO2 concentration.
Now, the question is what is the problem with CO2? Well, first we should understand the greenhouse effect.
In very simple terms, the temperature on Earth is, on average, 15°C, and this is because the Earth is surrounded by the atmosphere, which contains greenhouse gases (GHGs), such as water vapour, Carbon dioxide, Methane, Nitrous dioxide, Ozone, etc. Figure 2 explains how the greenhouse effect is produced, and enhanced by increased CO2 levels. Solar radiation comes from the Sun to the Earth, and part of it warms the Earth. Then, some of the absorbed energy by the Earth is re-radiated into space; but GHGs trap part of this heat that is re-emitted into the Earth, allowing global temperature of 15°C.
However, the problem with CO2 starts when its concentration increases; therefore, the GHG layer becomes thicker. The same amount of solar radiation comes to the Earth, and almost the same amount of energy is re-radiated. However, this thicker layer of GHG traps more heat and less escapes into space. As a result, the Earth becomes warmer, a phenomenon that is called global warming.
Figure 2. Greenhouse Effect [left] modified by GHGs [right]. Adapted from C2ES. 2018.
According to the National Oceanic and Atmospheric Administration (NOAA) and NASA’s Goddard Institute for Space Studies (GISS), surface temperatures on Earth have increased 0.99 degrees Celsius from 1850 to 2016. Figure 3 show the global surface temperature anomalies averaged from 1900-1904 and 2012-2016. Orange-tone colours and red-tone colours mean an increment of the temperature from 0.5 to 2 degrees Celsius.
Figure 3. Global temperature anomalies averaged from 1900-1904 [left] and 2012-2016 [right]. NASA’s Scientific Visualization Studio, public domain.
According to paleoclimate studies, the rise in Earth’s surface temperatures has been linked directly to the amount of atmospheric CO2. However, all of the heat trapped in the atmosphere is affecting the entire climate system (atmosphere, hydrosphere, lithosphere, cryosphere, and biosphere), but also, higher concentrations of CO2 have been promoting the acidification of oceans, acid rain, crop yields changes, etc.
Figures 4 and 5 show that the temperature on land and ocean surface have increased (a); the sea ice extent has decreased by 4 million km2 in the Arctic (c); the global mean sea level has risen (d); and the annual precipitation over land has decreased in some part of the world (brown dots), but increased in others (light-blue dots).
Figure 4. Evolution of land and ocean surface temperature anomaly, sea ice extent, global mean sea level. IPCC 2014. Synthesis Report. p 41.
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