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Although climate change is the center of many political debates, the warming of Earth’s climate system is a widely accepted fact in the scientific world. Ninety-seven percent of “actively publishing climate scientists” agree that Earth’s climate is changing as a result of human activities (NASA 2018). The atmosphere’s current CO2 levels (as of March 2019) are 410 parts per million (ppm), which is the highest measurement in the past 800,000 years (NASA 2018). Before the industrial revolution, Earth’s CO2 levels fluctuated between roughly 180 ppm during ice age periods and 280 ppm during interglacial periods (NASA 2018). These rising and falling levels are considered within the normal spectrum of the Earth’s temperature cycles, which has a frequency of about 100,000 years. In a glacial cycle, temperatures and CO2 levels fluctuate up and down, and about every 15,000 years the temperatures spike, and then rapidly fall soon after. In comparison, the current level of over 410 ppm represents uncharted territory. Because of the unprecedented levels of CO2, scientists do not know exactly how these high CO2 levels will affect humanity and other life that lives on this planet. However, scientists do know that throughout climate history, temperature is directly correlated with atmospheric CO2 levels (NOAA 2008). When graphed, temperature and carbon dioxide follow each other closely.

CO2 is just one of the GHGs in Earth’s atmosphere that contributes to warming Earth. GHGs have a warming effect due to their ability to trap heat in the atmosphere. GHGs in Earth’s atmosphere absorb infrared radiation emitted from Earth’s surface and also re-emit infrared radiation, commonly known as heat. The greenhouse effect refers to the natural process of infrared radiation being absorbed by GHG molecules, and then re-emitted in all directions, some of which is directed back towards Earth. “Without naturally occurring greenhouse gases, Earth's average temperature would be near 0°F (or -18°C) instead of the much warmer 59°F (15°C)” (NASA 1998).

However, since the Industrial Revolution, the burning of fossil fuels and other human activities has led to a dramatic increase in the concentration of GHGs in the atmosphere. GHGs that have high global warming potentials have a long residence time in the atmosphere, absorb effectively in the infrared part of the electromagnetic spectrum, and have a relatively high concentration in the troposphere (lowest layer of the atmosphere). Once GHG molecules absorb infrared radiation, they collide with and transfer kinetic energy to other molecules in the atmosphere such as nitrogen and oxygen, which increases the temperature of the atmosphere. As the concentration of GHG molecules in the atmosphere increases, more energy is trapped.In this way, GHGs act as a “blanket” and prevent heat energy from escaping back out to space.

Scientific research published in peer-reviewed journals shows that the current CO2 levels in Earth’s atmosphere have been rising since the industrial revolution (Scripps Institution of Oceanography UC San Diego 2017). Human activity is also responsible for the release of methane, nitrous oxide, and other potent GHGs (Keeling 1997). Humans are already experiencing the effects of a warmer climate through more extreme weather events, increases in pests and disease, devastation to wildlife habitat, and perhaps most directly relevant to HHS, increased costs (Keeling 1997).

Arguably, the most concerning part of global climate change is that it is extremely difficult to reverse. Now that there is momentum in warming Earth, the extent of sea ice is diminishing, sea levels are rising, oceans are warming, and glaciers around the world are melting. Further, these events lead to positive feedback loops that amplify warming. Due to climate momentum, it will take hundreds of years for GHG concentrations in the atmosphere to return to preindustrial concentrations. For these reasons, we need to take responsibility for emissions coming from the HHS community and implement this CAP immediately.