Hello friends! Today on the blog we are chatting about CO2, and going to answer the question: “How does CO2 contribute to increasing temperatures?”
Rising levels of CO2 are frequently mentioned in news articles and media clips, but what does rising CO2 mean, and how exactly, does this lead to increased global temperatures? Read on for more!
First of all, what is CO2?
CO2, or carbon dioxide, is a colorless gas that consists of a carbon atom paired with 2 oxygen atoms, and occurs naturally in the Earth’s atmosphere as a trace gas, and is absorbed by plants for photosynthesis.
CO2 is a natural greenhouse gas. Greenhouse gasses (GHG) selectively absorb some of earth’s outgoing infrared radiation. GHG usually selectively absorb and emit radiation at longer wave radiation (infrared) lengths, emitted from earth, and let shorter wave radiation (emitted from the sun) to pass through.
Without the presence of greenhouse gases, radiation would go out to space, and the earth would be about 33℃ cooler than it is today.
Where does CO2 come from?
CO2 is emitted from natural sources like volcanoes, hot springs, and carbonate rocks. CO2 is also emitted in large amounts my human activities, including fossil fuel combustion.
Before the industrial revolution, the global average CO2 was about 280 parts per million (ppm). In 2018, the average ppm was 407.4 ppm, which is higher than it has been at any point in at least the last 800,000 years.
In 2017, CO2 emissions from burning fossil fuels made up for 93% of the total CO2 emissions in the US, and about 76% of the country’s total GHG emissions. Put another way, burning fossil fuels is a major contributor to increasing levels of CO2.
Although levels of CO2 have historically cycled through highs and lows, they have never gone above 300ppm in recorded history. Furthermore, the rate at which CO2 is rising today is unprecedented; the annual rate of increase in atmospheric CO2 over the past 60 years is about 100 times faster than previous naturally occurring increases in CO2 levels (such as those during the last ice age).
How does CO2 contribute to increasing temperatures?
Before we can discuss global temperatures increasing, it is first important to understand what happens under normal atmospheric conditions.
The earth has an energy budget. According to the First Law of Thermodynamics, energy can neither be created, nor destroyed. The amount of energy entering from the top of the atmosphere must equal the amount leaving the top of the atmosphere back into space. This is known as radiative equilibrium.
Energy that enters the atmosphere from the sun is called incoming solar radiation. The radiation is shorter wave radiation, and bounces off the surface of the earth, heading back out into space. Energy leaving the atmosphere is known as outgoing solar radiation. This radiation is longer wavelength radiation, making it ideal for preferential absorption by GHGs, including CO2.
If more energy enters the atmosphere than leaves it, the amount of energy within the earth’s system increases, and thus, the temperature of the earth increases. If more energy leaves than enters, the amount of energy in the earth’s system decreases, and thus, so does the temperature.
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